mirror of
https://git.postgresql.org/git/postgresql.git
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The new format accepts exactly the same data as the json type. However, it is stored in a format that does not require reparsing the orgiginal text in order to process it, making it much more suitable for indexing and other operations. Insignificant whitespace is discarded, and the order of object keys is not preserved. Neither are duplicate object keys kept - the later value for a given key is the only one stored. The new type has all the functions and operators that the json type has, with the exception of the json generation functions (to_json, json_agg etc.) and with identical semantics. In addition, there are operator classes for hash and btree indexing, and two classes for GIN indexing, that have no equivalent in the json type. This feature grew out of previous work by Oleg Bartunov and Teodor Sigaev, which was intended to provide similar facilities to a nested hstore type, but which in the end proved to have some significant compatibility issues. Authors: Oleg Bartunov, Teodor Sigaev, Peter Geoghegan and Andrew Dunstan. Review: Andres Freund
4703 lines
161 KiB
Plaintext
4703 lines
161 KiB
Plaintext
<!-- doc/src/sgml/datatype.sgml -->
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<chapter id="datatype">
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<title>Data Types</title>
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<indexterm zone="datatype">
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<primary>data type</primary>
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</indexterm>
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<indexterm>
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<primary>type</primary>
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<see>data type</see>
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</indexterm>
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<para>
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<productname>PostgreSQL</productname> has a rich set of native data
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types available to users. Users can add new types to
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<productname>PostgreSQL</productname> using the <xref
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linkend="sql-createtype"> command.
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</para>
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<para>
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<xref linkend="datatype-table"> shows all the built-in general-purpose data
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types. Most of the alternative names listed in the
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<quote>Aliases</quote> column are the names used internally by
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<productname>PostgreSQL</productname> for historical reasons. In
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addition, some internally used or deprecated types are available,
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but are not listed here.
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</para>
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<table id="datatype-table">
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<title>Data Types</title>
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<tgroup cols="3">
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<thead>
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<row>
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<entry>Name</entry>
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<entry>Aliases</entry>
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<entry>Description</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry><type>bigint</type></entry>
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<entry><type>int8</type></entry>
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<entry>signed eight-byte integer</entry>
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</row>
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<row>
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<entry><type>bigserial</type></entry>
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<entry><type>serial8</type></entry>
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<entry>autoincrementing eight-byte integer</entry>
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</row>
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<row>
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<entry><type>bit [ (<replaceable>n</replaceable>) ]</type></entry>
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<entry></entry>
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<entry>fixed-length bit string</entry>
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</row>
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<row>
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<entry><type>bit varying [ (<replaceable>n</replaceable>) ]</type></entry>
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<entry><type>varbit</type></entry>
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<entry>variable-length bit string</entry>
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</row>
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<row>
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<entry><type>boolean</type></entry>
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<entry><type>bool</type></entry>
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<entry>logical Boolean (true/false)</entry>
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</row>
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<row>
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<entry><type>box</type></entry>
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<entry></entry>
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<entry>rectangular box on a plane</entry>
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</row>
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<row>
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<entry><type>bytea</type></entry>
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<entry></entry>
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<entry>binary data (<quote>byte array</>)</entry>
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</row>
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<row>
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<entry><type>character [ (<replaceable>n</replaceable>) ]</type></entry>
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<entry><type>char [ (<replaceable>n</replaceable>) ]</type></entry>
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<entry>fixed-length character string</entry>
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</row>
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<row>
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<entry><type>character varying [ (<replaceable>n</replaceable>) ]</type></entry>
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<entry><type>varchar [ (<replaceable>n</replaceable>) ]</type></entry>
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<entry>variable-length character string</entry>
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</row>
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<row>
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<entry><type>cidr</type></entry>
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<entry></entry>
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<entry>IPv4 or IPv6 network address</entry>
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</row>
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<row>
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<entry><type>circle</type></entry>
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<entry></entry>
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<entry>circle on a plane</entry>
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</row>
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<row>
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<entry><type>date</type></entry>
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<entry></entry>
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<entry>calendar date (year, month, day)</entry>
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</row>
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<row>
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<entry><type>double precision</type></entry>
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<entry><type>float8</type></entry>
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<entry>double precision floating-point number (8 bytes)</entry>
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</row>
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<row>
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<entry><type>inet</type></entry>
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<entry></entry>
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<entry>IPv4 or IPv6 host address</entry>
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</row>
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<row>
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<entry><type>integer</type></entry>
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<entry><type>int</type>, <type>int4</type></entry>
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<entry>signed four-byte integer</entry>
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</row>
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<row>
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<entry><type>interval [ <replaceable>fields</replaceable> ] [ (<replaceable>p</replaceable>) ]</type></entry>
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<entry></entry>
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<entry>time span</entry>
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</row>
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<row>
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<entry><type>json</type></entry>
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<entry></entry>
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<entry>textual JSON data</entry>
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</row>
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<row>
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<entry><type>jsonb</type></entry>
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<entry></entry>
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<entry>binary JSON data, decomposed</entry>
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</row>
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<row>
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<entry><type>line</type></entry>
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<entry></entry>
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<entry>infinite line on a plane</entry>
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</row>
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<row>
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<entry><type>lseg</type></entry>
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<entry></entry>
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<entry>line segment on a plane</entry>
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</row>
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<row>
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<entry><type>macaddr</type></entry>
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<entry></entry>
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<entry>MAC (Media Access Control) address</entry>
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</row>
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<row>
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<entry><type>money</type></entry>
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<entry></entry>
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<entry>currency amount</entry>
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</row>
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<row>
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<entry><type>numeric [ (<replaceable>p</replaceable>,
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<replaceable>s</replaceable>) ]</type></entry>
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<entry><type>decimal [ (<replaceable>p</replaceable>,
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<replaceable>s</replaceable>) ]</type></entry>
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<entry>exact numeric of selectable precision</entry>
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</row>
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<row>
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<entry><type>path</type></entry>
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<entry></entry>
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<entry>geometric path on a plane</entry>
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</row>
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<row>
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<entry><type>pg_lsn</type></entry>
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<entry></entry>
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<entry><productname>PostgreSQL</productname> Log Sequence Number</entry>
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</row>
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<row>
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<entry><type>point</type></entry>
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<entry></entry>
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<entry>geometric point on a plane</entry>
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</row>
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<row>
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<entry><type>polygon</type></entry>
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<entry></entry>
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<entry>closed geometric path on a plane</entry>
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</row>
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<row>
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<entry><type>real</type></entry>
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<entry><type>float4</type></entry>
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<entry>single precision floating-point number (4 bytes)</entry>
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</row>
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<row>
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<entry><type>smallint</type></entry>
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<entry><type>int2</type></entry>
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<entry>signed two-byte integer</entry>
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</row>
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<row>
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<entry><type>smallserial</type></entry>
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<entry><type>serial2</type></entry>
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<entry>autoincrementing two-byte integer</entry>
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</row>
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<row>
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<entry><type>serial</type></entry>
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<entry><type>serial4</type></entry>
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<entry>autoincrementing four-byte integer</entry>
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</row>
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<row>
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<entry><type>text</type></entry>
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<entry></entry>
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<entry>variable-length character string</entry>
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</row>
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<row>
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<entry><type>time [ (<replaceable>p</replaceable>) ] [ without time zone ]</type></entry>
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<entry></entry>
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<entry>time of day (no time zone)</entry>
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</row>
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<row>
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<entry><type>time [ (<replaceable>p</replaceable>) ] with time zone</type></entry>
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<entry><type>timetz</type></entry>
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<entry>time of day, including time zone</entry>
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</row>
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<row>
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<entry><type>timestamp [ (<replaceable>p</replaceable>) ] [ without time zone ]</type></entry>
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<entry></entry>
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<entry>date and time (no time zone)</entry>
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</row>
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<row>
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<entry><type>timestamp [ (<replaceable>p</replaceable>) ] with time zone</type></entry>
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<entry><type>timestamptz</type></entry>
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<entry>date and time, including time zone</entry>
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</row>
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<row>
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<entry><type>tsquery</type></entry>
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<entry></entry>
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<entry>text search query</entry>
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</row>
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<row>
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<entry><type>tsvector</type></entry>
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<entry></entry>
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<entry>text search document</entry>
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</row>
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<row>
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<entry><type>txid_snapshot</type></entry>
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<entry></entry>
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<entry>user-level transaction ID snapshot</entry>
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</row>
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<row>
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<entry><type>uuid</type></entry>
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<entry></entry>
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<entry>universally unique identifier</entry>
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</row>
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<row>
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<entry><type>xml</type></entry>
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<entry></entry>
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<entry>XML data</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<note>
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<title>Compatibility</title>
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<para>
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The following types (or spellings thereof) are specified by
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<acronym>SQL</acronym>: <type>bigint</type>, <type>bit</type>, <type>bit
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varying</type>, <type>boolean</type>, <type>char</type>,
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<type>character varying</type>, <type>character</type>,
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<type>varchar</type>, <type>date</type>, <type>double
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precision</type>, <type>integer</type>, <type>interval</type>,
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<type>numeric</type>, <type>decimal</type>, <type>real</type>,
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<type>smallint</type>, <type>time</type> (with or without time zone),
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<type>timestamp</type> (with or without time zone),
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<type>xml</type>.
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</para>
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</note>
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<para>
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Each data type has an external representation determined by its input
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and output functions. Many of the built-in types have
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obvious external formats. However, several types are either unique
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to <productname>PostgreSQL</productname>, such as geometric
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paths, or have several possible formats, such as the date
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and time types.
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Some of the input and output functions are not invertible, i.e.,
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the result of an output function might lose accuracy when compared to
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the original input.
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</para>
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<sect1 id="datatype-numeric">
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<title>Numeric Types</title>
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<indexterm zone="datatype-numeric">
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<primary>data type</primary>
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<secondary>numeric</secondary>
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</indexterm>
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<para>
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Numeric types consist of two-, four-, and eight-byte integers,
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four- and eight-byte floating-point numbers, and selectable-precision
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decimals. <xref linkend="datatype-numeric-table"> lists the
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available types.
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</para>
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<table id="datatype-numeric-table">
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<title>Numeric Types</title>
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<tgroup cols="4">
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<thead>
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<row>
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<entry>Name</entry>
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<entry>Storage Size</entry>
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<entry>Description</entry>
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<entry>Range</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry><type>smallint</></entry>
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<entry>2 bytes</entry>
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<entry>small-range integer</entry>
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<entry>-32768 to +32767</entry>
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</row>
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<row>
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<entry><type>integer</></entry>
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<entry>4 bytes</entry>
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<entry>typical choice for integer</entry>
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<entry>-2147483648 to +2147483647</entry>
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</row>
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<row>
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<entry><type>bigint</></entry>
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<entry>8 bytes</entry>
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<entry>large-range integer</entry>
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<entry>-9223372036854775808 to +9223372036854775807</entry>
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</row>
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<row>
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<entry><type>decimal</></entry>
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<entry>variable</entry>
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<entry>user-specified precision, exact</entry>
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<entry>up to 131072 digits before the decimal point; up to 16383 digits after the decimal point</entry>
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</row>
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<row>
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<entry><type>numeric</></entry>
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<entry>variable</entry>
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<entry>user-specified precision, exact</entry>
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<entry>up to 131072 digits before the decimal point; up to 16383 digits after the decimal point</entry>
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</row>
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<row>
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<entry><type>real</></entry>
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<entry>4 bytes</entry>
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<entry>variable-precision, inexact</entry>
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<entry>6 decimal digits precision</entry>
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</row>
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<row>
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<entry><type>double precision</></entry>
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<entry>8 bytes</entry>
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<entry>variable-precision, inexact</entry>
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<entry>15 decimal digits precision</entry>
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</row>
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<row>
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<entry><type>smallserial</type></entry>
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<entry>2 bytes</entry>
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<entry>small autoincrementing integer</entry>
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<entry>1 to 32767</entry>
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</row>
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<row>
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<entry><type>serial</></entry>
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<entry>4 bytes</entry>
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<entry>autoincrementing integer</entry>
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<entry>1 to 2147483647</entry>
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</row>
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<row>
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<entry><type>bigserial</type></entry>
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<entry>8 bytes</entry>
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<entry>large autoincrementing integer</entry>
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<entry>1 to 9223372036854775807</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<para>
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The syntax of constants for the numeric types is described in
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<xref linkend="sql-syntax-constants">. The numeric types have a
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full set of corresponding arithmetic operators and
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functions. Refer to <xref linkend="functions"> for more
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information. The following sections describe the types in detail.
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</para>
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<sect2 id="datatype-int">
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<title>Integer Types</title>
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<indexterm zone="datatype-int">
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<primary>integer</primary>
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</indexterm>
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<indexterm zone="datatype-int">
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<primary>smallint</primary>
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</indexterm>
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<indexterm zone="datatype-int">
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<primary>bigint</primary>
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</indexterm>
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<indexterm>
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<primary>int4</primary>
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<see>integer</see>
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</indexterm>
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<indexterm>
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<primary>int2</primary>
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<see>smallint</see>
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</indexterm>
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<indexterm>
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<primary>int8</primary>
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<see>bigint</see>
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</indexterm>
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<para>
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The types <type>smallint</type>, <type>integer</type>, and
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<type>bigint</type> store whole numbers, that is, numbers without
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fractional components, of various ranges. Attempts to store
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values outside of the allowed range will result in an error.
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</para>
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<para>
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The type <type>integer</type> is the common choice, as it offers
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the best balance between range, storage size, and performance.
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The <type>smallint</type> type is generally only used if disk
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space is at a premium. The <type>bigint</type> type is designed to be
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used when the range of the <type>integer</type> type is insufficient.
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</para>
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<para>
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<acronym>SQL</acronym> only specifies the integer types
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<type>integer</type> (or <type>int</type>),
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<type>smallint</type>, and <type>bigint</type>. The
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type names <type>int2</type>, <type>int4</type>, and
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<type>int8</type> are extensions, which are also used by some
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other <acronym>SQL</acronym> database systems.
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</para>
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</sect2>
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<sect2 id="datatype-numeric-decimal">
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<title>Arbitrary Precision Numbers</title>
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<indexterm>
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<primary>numeric (data type)</primary>
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</indexterm>
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<indexterm>
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<primary>arbitrary precision numbers</primary>
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</indexterm>
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<indexterm>
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<primary>decimal</primary>
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<see>numeric</see>
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</indexterm>
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<para>
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The type <type>numeric</type> can store numbers with a
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very large number of digits and perform calculations exactly. It is
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especially recommended for storing monetary amounts and other
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quantities where exactness is required. However, arithmetic on
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<type>numeric</type> values is very slow compared to the integer
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|
types, or to the floating-point types described in the next section.
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</para>
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<para>
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We use the following terms below: The
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<firstterm>scale</firstterm> of a <type>numeric</type> is the
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count of decimal digits in the fractional part, to the right of
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the decimal point. The <firstterm>precision</firstterm> of a
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<type>numeric</type> is the total count of significant digits in
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the whole number, that is, the number of digits to both sides of
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the decimal point. So the number 23.5141 has a precision of 6
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and a scale of 4. Integers can be considered to have a scale of
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zero.
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|
</para>
|
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<para>
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|
Both the maximum precision and the maximum scale of a
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<type>numeric</type> column can be
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configured. To declare a column of type <type>numeric</type> use
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the syntax:
|
|
<programlisting>
|
|
NUMERIC(<replaceable>precision</replaceable>, <replaceable>scale</replaceable>)
|
|
</programlisting>
|
|
The precision must be positive, the scale zero or positive.
|
|
Alternatively:
|
|
<programlisting>
|
|
NUMERIC(<replaceable>precision</replaceable>)
|
|
</programlisting>
|
|
selects a scale of 0. Specifying:
|
|
<programlisting>
|
|
NUMERIC
|
|
</programlisting>
|
|
without any precision or scale creates a column in which numeric
|
|
values of any precision and scale can be stored, up to the
|
|
implementation limit on precision. A column of this kind will
|
|
not coerce input values to any particular scale, whereas
|
|
<type>numeric</type> columns with a declared scale will coerce
|
|
input values to that scale. (The <acronym>SQL</acronym> standard
|
|
requires a default scale of 0, i.e., coercion to integer
|
|
precision. We find this a bit useless. If you're concerned
|
|
about portability, always specify the precision and scale
|
|
explicitly.)
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
The maximum allowed precision when explicitly specified in the
|
|
type declaration is 1000; <type>NUMERIC</type> without a specified
|
|
precision is subject to the limits described in <xref
|
|
linkend="datatype-numeric-table">.
|
|
</para>
|
|
</note>
|
|
|
|
<para>
|
|
If the scale of a value to be stored is greater than the declared
|
|
scale of the column, the system will round the value to the specified
|
|
number of fractional digits. Then, if the number of digits to the
|
|
left of the decimal point exceeds the declared precision minus the
|
|
declared scale, an error is raised.
|
|
</para>
|
|
|
|
<para>
|
|
Numeric values are physically stored without any extra leading or
|
|
trailing zeroes. Thus, the declared precision and scale of a column
|
|
are maximums, not fixed allocations. (In this sense the <type>numeric</>
|
|
type is more akin to <type>varchar(<replaceable>n</>)</type>
|
|
than to <type>char(<replaceable>n</>)</type>.) The actual storage
|
|
requirement is two bytes for each group of four decimal digits,
|
|
plus three to eight bytes overhead.
|
|
</para>
|
|
|
|
<indexterm>
|
|
<primary>NaN</primary>
|
|
<see>not a number</see>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>not a number</primary>
|
|
<secondary>numeric (data type)</secondary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
In addition to ordinary numeric values, the <type>numeric</type>
|
|
type allows the special value <literal>NaN</>, meaning
|
|
<quote>not-a-number</quote>. Any operation on <literal>NaN</>
|
|
yields another <literal>NaN</>. When writing this value
|
|
as a constant in an SQL command, you must put quotes around it,
|
|
for example <literal>UPDATE table SET x = 'NaN'</>. On input,
|
|
the string <literal>NaN</> is recognized in a case-insensitive manner.
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
In most implementations of the <quote>not-a-number</> concept,
|
|
<literal>NaN</> is not considered equal to any other numeric
|
|
value (including <literal>NaN</>). In order to allow
|
|
<type>numeric</> values to be sorted and used in tree-based
|
|
indexes, <productname>PostgreSQL</> treats <literal>NaN</>
|
|
values as equal, and greater than all non-<literal>NaN</>
|
|
values.
|
|
</para>
|
|
</note>
|
|
|
|
<para>
|
|
The types <type>decimal</type> and <type>numeric</type> are
|
|
equivalent. Both types are part of the <acronym>SQL</acronym>
|
|
standard.
|
|
</para>
|
|
</sect2>
|
|
|
|
|
|
<sect2 id="datatype-float">
|
|
<title>Floating-Point Types</title>
|
|
|
|
<indexterm zone="datatype-float">
|
|
<primary>real</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-float">
|
|
<primary>double precision</primary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>float4</primary>
|
|
<see>real</see>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>float8</primary>
|
|
<see>double precision</see>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-float">
|
|
<primary>floating point</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
The data types <type>real</type> and <type>double
|
|
precision</type> are inexact, variable-precision numeric types.
|
|
In practice, these types are usually implementations of
|
|
<acronym>IEEE</acronym> Standard 754 for Binary Floating-Point
|
|
Arithmetic (single and double precision, respectively), to the
|
|
extent that the underlying processor, operating system, and
|
|
compiler support it.
|
|
</para>
|
|
|
|
<para>
|
|
Inexact means that some values cannot be converted exactly to the
|
|
internal format and are stored as approximations, so that storing
|
|
and retrieving a value might show slight discrepancies.
|
|
Managing these errors and how they propagate through calculations
|
|
is the subject of an entire branch of mathematics and computer
|
|
science and will not be discussed here, except for the
|
|
following points:
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>
|
|
If you require exact storage and calculations (such as for
|
|
monetary amounts), use the <type>numeric</type> type instead.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
If you want to do complicated calculations with these types
|
|
for anything important, especially if you rely on certain
|
|
behavior in boundary cases (infinity, underflow), you should
|
|
evaluate the implementation carefully.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
Comparing two floating-point values for equality might not
|
|
always work as expected.
|
|
</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
|
|
<para>
|
|
On most platforms, the <type>real</type> type has a range of at least
|
|
1E-37 to 1E+37 with a precision of at least 6 decimal digits. The
|
|
<type>double precision</type> type typically has a range of around
|
|
1E-307 to 1E+308 with a precision of at least 15 digits. Values that
|
|
are too large or too small will cause an error. Rounding might
|
|
take place if the precision of an input number is too high.
|
|
Numbers too close to zero that are not representable as distinct
|
|
from zero will cause an underflow error.
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
The <xref linkend="guc-extra-float-digits"> setting controls the
|
|
number of extra significant digits included when a floating point
|
|
value is converted to text for output. With the default value of
|
|
<literal>0</literal>, the output is the same on every platform
|
|
supported by PostgreSQL. Increasing it will produce output that
|
|
more accurately represents the stored value, but may be unportable.
|
|
</para>
|
|
</note>
|
|
|
|
<indexterm>
|
|
<primary>not a number</primary>
|
|
<secondary>double precision</secondary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
In addition to ordinary numeric values, the floating-point types
|
|
have several special values:
|
|
<literallayout>
|
|
<literal>Infinity</literal>
|
|
<literal>-Infinity</literal>
|
|
<literal>NaN</literal>
|
|
</literallayout>
|
|
These represent the IEEE 754 special values
|
|
<quote>infinity</quote>, <quote>negative infinity</quote>, and
|
|
<quote>not-a-number</quote>, respectively. (On a machine whose
|
|
floating-point arithmetic does not follow IEEE 754, these values
|
|
will probably not work as expected.) When writing these values
|
|
as constants in an SQL command, you must put quotes around them,
|
|
for example <literal>UPDATE table SET x = 'Infinity'</>. On input,
|
|
these strings are recognized in a case-insensitive manner.
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
IEEE754 specifies that <literal>NaN</> should not compare equal
|
|
to any other floating-point value (including <literal>NaN</>).
|
|
In order to allow floating-point values to be sorted and used
|
|
in tree-based indexes, <productname>PostgreSQL</> treats
|
|
<literal>NaN</> values as equal, and greater than all
|
|
non-<literal>NaN</> values.
|
|
</para>
|
|
</note>
|
|
|
|
<para>
|
|
<productname>PostgreSQL</productname> also supports the SQL-standard
|
|
notations <type>float</type> and
|
|
<type>float(<replaceable>p</replaceable>)</type> for specifying
|
|
inexact numeric types. Here, <replaceable>p</replaceable> specifies
|
|
the minimum acceptable precision in <emphasis>binary</> digits.
|
|
<productname>PostgreSQL</productname> accepts
|
|
<type>float(1)</type> to <type>float(24)</type> as selecting the
|
|
<type>real</type> type, while
|
|
<type>float(25)</type> to <type>float(53)</type> select
|
|
<type>double precision</type>. Values of <replaceable>p</replaceable>
|
|
outside the allowed range draw an error.
|
|
<type>float</type> with no precision specified is taken to mean
|
|
<type>double precision</type>.
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
The assumption that <type>real</type> and
|
|
<type>double precision</type> have exactly 24 and 53 bits in the
|
|
mantissa respectively is correct for IEEE-standard floating point
|
|
implementations. On non-IEEE platforms it might be off a little, but
|
|
for simplicity the same ranges of <replaceable>p</replaceable> are used
|
|
on all platforms.
|
|
</para>
|
|
</note>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="datatype-serial">
|
|
<title>Serial Types</title>
|
|
|
|
<indexterm zone="datatype-serial">
|
|
<primary>smallserial</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-serial">
|
|
<primary>serial</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-serial">
|
|
<primary>bigserial</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-serial">
|
|
<primary>serial2</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-serial">
|
|
<primary>serial4</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-serial">
|
|
<primary>serial8</primary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>auto-increment</primary>
|
|
<see>serial</see>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>sequence</primary>
|
|
<secondary>and serial type</secondary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
The data types <type>smallserial</type>, <type>serial</type> and
|
|
<type>bigserial</type> are not true types, but merely
|
|
a notational convenience for creating unique identifier columns
|
|
(similar to the <literal>AUTO_INCREMENT</literal> property
|
|
supported by some other databases). In the current
|
|
implementation, specifying:
|
|
|
|
<programlisting>
|
|
CREATE TABLE <replaceable class="parameter">tablename</replaceable> (
|
|
<replaceable class="parameter">colname</replaceable> SERIAL
|
|
);
|
|
</programlisting>
|
|
|
|
is equivalent to specifying:
|
|
|
|
<programlisting>
|
|
CREATE SEQUENCE <replaceable class="parameter">tablename</replaceable>_<replaceable class="parameter">colname</replaceable>_seq;
|
|
CREATE TABLE <replaceable class="parameter">tablename</replaceable> (
|
|
<replaceable class="parameter">colname</replaceable> integer NOT NULL DEFAULT nextval('<replaceable class="parameter">tablename</replaceable>_<replaceable class="parameter">colname</replaceable>_seq')
|
|
);
|
|
ALTER SEQUENCE <replaceable class="parameter">tablename</replaceable>_<replaceable class="parameter">colname</replaceable>_seq OWNED BY <replaceable class="parameter">tablename</replaceable>.<replaceable class="parameter">colname</replaceable>;
|
|
</programlisting>
|
|
|
|
Thus, we have created an integer column and arranged for its default
|
|
values to be assigned from a sequence generator. A <literal>NOT NULL</>
|
|
constraint is applied to ensure that a null value cannot be
|
|
inserted. (In most cases you would also want to attach a
|
|
<literal>UNIQUE</> or <literal>PRIMARY KEY</> constraint to prevent
|
|
duplicate values from being inserted by accident, but this is
|
|
not automatic.) Lastly, the sequence is marked as <quote>owned by</>
|
|
the column, so that it will be dropped if the column or table is dropped.
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
Because <type>smallserial</type>, <type>serial</type> and
|
|
<type>bigserial</type> are implemented using sequences, there may
|
|
be "holes" or gaps in the sequence of values which appears in the
|
|
column, even if no rows are ever deleted. A value allocated
|
|
from the sequence is still "used up" even if a row containing that
|
|
value is never successfully inserted into the table column. This
|
|
may happen, for example, if the inserting transaction rolls back.
|
|
See <literal>nextval()</literal> in <xref linkend="functions-sequence">
|
|
for details.
|
|
</para>
|
|
</note>
|
|
|
|
<para>
|
|
To insert the next value of the sequence into the <type>serial</type>
|
|
column, specify that the <type>serial</type>
|
|
column should be assigned its default value. This can be done
|
|
either by excluding the column from the list of columns in
|
|
the <command>INSERT</command> statement, or through the use of
|
|
the <literal>DEFAULT</literal> key word.
|
|
</para>
|
|
|
|
<para>
|
|
The type names <type>serial</type> and <type>serial4</type> are
|
|
equivalent: both create <type>integer</type> columns. The type
|
|
names <type>bigserial</type> and <type>serial8</type> work
|
|
the same way, except that they create a <type>bigint</type>
|
|
column. <type>bigserial</type> should be used if you anticipate
|
|
the use of more than 2<superscript>31</> identifiers over the
|
|
lifetime of the table. The type names <type>smallserial</type> and
|
|
<type>serial2</type> also work the same way, except that they
|
|
create a <type>smallint</type> column.
|
|
</para>
|
|
|
|
<para>
|
|
The sequence created for a <type>serial</type> column is
|
|
automatically dropped when the owning column is dropped.
|
|
You can drop the sequence without dropping the column, but this
|
|
will force removal of the column default expression.
|
|
</para>
|
|
</sect2>
|
|
</sect1>
|
|
|
|
<sect1 id="datatype-money">
|
|
<title>Monetary Types</title>
|
|
|
|
<para>
|
|
The <type>money</type> type stores a currency amount with a fixed
|
|
fractional precision; see <xref
|
|
linkend="datatype-money-table">. The fractional precision is
|
|
determined by the database's <xref linkend="guc-lc-monetary"> setting.
|
|
The range shown in the table assumes there are two fractional digits.
|
|
Input is accepted in a variety of formats, including integer and
|
|
floating-point literals, as well as typical
|
|
currency formatting, such as <literal>'$1,000.00'</literal>.
|
|
Output is generally in the latter form but depends on the locale.
|
|
</para>
|
|
|
|
<table id="datatype-money-table">
|
|
<title>Monetary Types</title>
|
|
<tgroup cols="4">
|
|
<thead>
|
|
<row>
|
|
<entry>Name</entry>
|
|
<entry>Storage Size</entry>
|
|
<entry>Description</entry>
|
|
<entry>Range</entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry>money</entry>
|
|
<entry>8 bytes</entry>
|
|
<entry>currency amount</entry>
|
|
<entry>-92233720368547758.08 to +92233720368547758.07</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
Since the output of this data type is locale-sensitive, it might not
|
|
work to load <type>money</> data into a database that has a different
|
|
setting of <varname>lc_monetary</>. To avoid problems, before
|
|
restoring a dump into a new database make sure <varname>lc_monetary</> has
|
|
the same or equivalent value as in the database that was dumped.
|
|
</para>
|
|
|
|
<para>
|
|
Values of the <type>numeric</type>, <type>int</type>, and
|
|
<type>bigint</type> data types can be cast to <type>money</type>.
|
|
Conversion from the <type>real</type> and <type>double precision</type>
|
|
data types can be done by casting to <type>numeric</type> first, for
|
|
example:
|
|
<programlisting>
|
|
SELECT '12.34'::float8::numeric::money;
|
|
</programlisting>
|
|
However, this is not recommended. Floating point numbers should not be
|
|
used to handle money due to the potential for rounding errors.
|
|
</para>
|
|
|
|
<para>
|
|
A <type>money</type> value can be cast to <type>numeric</type> without
|
|
loss of precision. Conversion to other types could potentially lose
|
|
precision, and must also be done in two stages:
|
|
<programlisting>
|
|
SELECT '52093.89'::money::numeric::float8;
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
When a <type>money</type> value is divided by another <type>money</type>
|
|
value, the result is <type>double precision</type> (i.e., a pure number,
|
|
not money); the currency units cancel each other out in the division.
|
|
</para>
|
|
</sect1>
|
|
|
|
|
|
<sect1 id="datatype-character">
|
|
<title>Character Types</title>
|
|
|
|
<indexterm zone="datatype-character">
|
|
<primary>character string</primary>
|
|
<secondary>data types</secondary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>string</primary>
|
|
<see>character string</see>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-character">
|
|
<primary>character</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-character">
|
|
<primary>character varying</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-character">
|
|
<primary>text</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-character">
|
|
<primary>char</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-character">
|
|
<primary>varchar</primary>
|
|
</indexterm>
|
|
|
|
<table id="datatype-character-table">
|
|
<title>Character Types</title>
|
|
<tgroup cols="2">
|
|
<thead>
|
|
<row>
|
|
<entry>Name</entry>
|
|
<entry>Description</entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry><type>character varying(<replaceable>n</>)</type>, <type>varchar(<replaceable>n</>)</type></entry>
|
|
<entry>variable-length with limit</entry>
|
|
</row>
|
|
<row>
|
|
<entry><type>character(<replaceable>n</>)</type>, <type>char(<replaceable>n</>)</type></entry>
|
|
<entry>fixed-length, blank padded</entry>
|
|
</row>
|
|
<row>
|
|
<entry><type>text</type></entry>
|
|
<entry>variable unlimited length</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
<xref linkend="datatype-character-table"> shows the
|
|
general-purpose character types available in
|
|
<productname>PostgreSQL</productname>.
|
|
</para>
|
|
|
|
<para>
|
|
<acronym>SQL</acronym> defines two primary character types:
|
|
<type>character varying(<replaceable>n</>)</type> and
|
|
<type>character(<replaceable>n</>)</type>, where <replaceable>n</>
|
|
is a positive integer. Both of these types can store strings up to
|
|
<replaceable>n</> characters (not bytes) in length. An attempt to store a
|
|
longer string into a column of these types will result in an
|
|
error, unless the excess characters are all spaces, in which case
|
|
the string will be truncated to the maximum length. (This somewhat
|
|
bizarre exception is required by the <acronym>SQL</acronym>
|
|
standard.) If the string to be stored is shorter than the declared
|
|
length, values of type <type>character</type> will be space-padded;
|
|
values of type <type>character varying</type> will simply store the
|
|
shorter
|
|
string.
|
|
</para>
|
|
|
|
<para>
|
|
If one explicitly casts a value to <type>character
|
|
varying(<replaceable>n</>)</type> or
|
|
<type>character(<replaceable>n</>)</type>, then an over-length
|
|
value will be truncated to <replaceable>n</> characters without
|
|
raising an error. (This too is required by the
|
|
<acronym>SQL</acronym> standard.)
|
|
</para>
|
|
|
|
<para>
|
|
The notations <type>varchar(<replaceable>n</>)</type> and
|
|
<type>char(<replaceable>n</>)</type> are aliases for <type>character
|
|
varying(<replaceable>n</>)</type> and
|
|
<type>character(<replaceable>n</>)</type>, respectively.
|
|
<type>character</type> without length specifier is equivalent to
|
|
<type>character(1)</type>. If <type>character varying</type> is used
|
|
without length specifier, the type accepts strings of any size. The
|
|
latter is a <productname>PostgreSQL</> extension.
|
|
</para>
|
|
|
|
<para>
|
|
In addition, <productname>PostgreSQL</productname> provides the
|
|
<type>text</type> type, which stores strings of any length.
|
|
Although the type <type>text</type> is not in the
|
|
<acronym>SQL</acronym> standard, several other SQL database
|
|
management systems have it as well.
|
|
</para>
|
|
|
|
<para>
|
|
Values of type <type>character</type> are physically padded
|
|
with spaces to the specified width <replaceable>n</>, and are
|
|
stored and displayed that way. However, trailing spaces are treated as
|
|
semantically insignificant and disregarded when comparing two values
|
|
of type <type>character</type>. In collations where whitespace
|
|
is significant, this behavior can produce unexpected results,
|
|
e.g. <command>SELECT 'a '::CHAR(2) collate "C" <
|
|
'a\n'::CHAR(2)</command> returns true.
|
|
Trailing spaces are removed when converting a <type>character</type> value
|
|
to one of the other string types. Note that trailing spaces
|
|
<emphasis>are</> semantically significant in
|
|
<type>character varying</type> and <type>text</type> values, and
|
|
when using pattern matching, e.g. <literal>LIKE</>,
|
|
regular expressions.
|
|
</para>
|
|
|
|
<para>
|
|
The storage requirement for a short string (up to 126 bytes) is 1 byte
|
|
plus the actual string, which includes the space padding in the case of
|
|
<type>character</type>. Longer strings have 4 bytes of overhead instead
|
|
of 1. Long strings are compressed by the system automatically, so
|
|
the physical requirement on disk might be less. Very long values are also
|
|
stored in background tables so that they do not interfere with rapid
|
|
access to shorter column values. In any case, the longest
|
|
possible character string that can be stored is about 1 GB. (The
|
|
maximum value that will be allowed for <replaceable>n</> in the data
|
|
type declaration is less than that. It wouldn't be useful to
|
|
change this because with multibyte character encodings the number of
|
|
characters and bytes can be quite different. If you desire to
|
|
store long strings with no specific upper limit, use
|
|
<type>text</type> or <type>character varying</type> without a length
|
|
specifier, rather than making up an arbitrary length limit.)
|
|
</para>
|
|
|
|
<tip>
|
|
<para>
|
|
There is no performance difference among these three types,
|
|
apart from increased storage space when using the blank-padded
|
|
type, and a few extra CPU cycles to check the length when storing into
|
|
a length-constrained column. While
|
|
<type>character(<replaceable>n</>)</type> has performance
|
|
advantages in some other database systems, there is no such advantage in
|
|
<productname>PostgreSQL</productname>; in fact
|
|
<type>character(<replaceable>n</>)</type> is usually the slowest of
|
|
the three because of its additional storage costs. In most situations
|
|
<type>text</type> or <type>character varying</type> should be used
|
|
instead.
|
|
</para>
|
|
</tip>
|
|
|
|
<para>
|
|
Refer to <xref linkend="sql-syntax-strings"> for information about
|
|
the syntax of string literals, and to <xref linkend="functions">
|
|
for information about available operators and functions. The
|
|
database character set determines the character set used to store
|
|
textual values; for more information on character set support,
|
|
refer to <xref linkend="multibyte">.
|
|
</para>
|
|
|
|
<example>
|
|
<title>Using the Character Types</title>
|
|
|
|
<programlisting>
|
|
CREATE TABLE test1 (a character(4));
|
|
INSERT INTO test1 VALUES ('ok');
|
|
SELECT a, char_length(a) FROM test1; -- <co id="co.datatype-char">
|
|
<computeroutput>
|
|
a | char_length
|
|
------+-------------
|
|
ok | 2
|
|
</computeroutput>
|
|
|
|
CREATE TABLE test2 (b varchar(5));
|
|
INSERT INTO test2 VALUES ('ok');
|
|
INSERT INTO test2 VALUES ('good ');
|
|
INSERT INTO test2 VALUES ('too long');
|
|
<computeroutput>ERROR: value too long for type character varying(5)</computeroutput>
|
|
INSERT INTO test2 VALUES ('too long'::varchar(5)); -- explicit truncation
|
|
SELECT b, char_length(b) FROM test2;
|
|
<computeroutput>
|
|
b | char_length
|
|
-------+-------------
|
|
ok | 2
|
|
good | 5
|
|
too l | 5
|
|
</computeroutput>
|
|
</programlisting>
|
|
<calloutlist>
|
|
<callout arearefs="co.datatype-char">
|
|
<para>
|
|
The <function>char_length</function> function is discussed in
|
|
<xref linkend="functions-string">.
|
|
</para>
|
|
</callout>
|
|
</calloutlist>
|
|
</example>
|
|
|
|
<para>
|
|
There are two other fixed-length character types in
|
|
<productname>PostgreSQL</productname>, shown in <xref
|
|
linkend="datatype-character-special-table">. The <type>name</type>
|
|
type exists <emphasis>only</emphasis> for the storage of identifiers
|
|
in the internal system catalogs and is not intended for use by the general user. Its
|
|
length is currently defined as 64 bytes (63 usable characters plus
|
|
terminator) but should be referenced using the constant
|
|
<symbol>NAMEDATALEN</symbol> in <literal>C</> source code.
|
|
The length is set at compile time (and
|
|
is therefore adjustable for special uses); the default maximum
|
|
length might change in a future release. The type <type>"char"</type>
|
|
(note the quotes) is different from <type>char(1)</type> in that it
|
|
only uses one byte of storage. It is internally used in the system
|
|
catalogs as a simplistic enumeration type.
|
|
</para>
|
|
|
|
<table id="datatype-character-special-table">
|
|
<title>Special Character Types</title>
|
|
<tgroup cols="3">
|
|
<thead>
|
|
<row>
|
|
<entry>Name</entry>
|
|
<entry>Storage Size</entry>
|
|
<entry>Description</entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry><type>"char"</type></entry>
|
|
<entry>1 byte</entry>
|
|
<entry>single-byte internal type</entry>
|
|
</row>
|
|
<row>
|
|
<entry><type>name</type></entry>
|
|
<entry>64 bytes</entry>
|
|
<entry>internal type for object names</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
</sect1>
|
|
|
|
<sect1 id="datatype-binary">
|
|
<title>Binary Data Types</title>
|
|
|
|
<indexterm zone="datatype-binary">
|
|
<primary>binary data</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-binary">
|
|
<primary>bytea</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
The <type>bytea</type> data type allows storage of binary strings;
|
|
see <xref linkend="datatype-binary-table">.
|
|
</para>
|
|
|
|
<table id="datatype-binary-table">
|
|
<title>Binary Data Types</title>
|
|
<tgroup cols="3">
|
|
<thead>
|
|
<row>
|
|
<entry>Name</entry>
|
|
<entry>Storage Size</entry>
|
|
<entry>Description</entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry><type>bytea</type></entry>
|
|
<entry>1 or 4 bytes plus the actual binary string</entry>
|
|
<entry>variable-length binary string</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
A binary string is a sequence of octets (or bytes). Binary
|
|
strings are distinguished from character strings in two
|
|
ways. First, binary strings specifically allow storing
|
|
octets of value zero and other <quote>non-printable</quote>
|
|
octets (usually, octets outside the range 32 to 126).
|
|
Character strings disallow zero octets, and also disallow any
|
|
other octet values and sequences of octet values that are invalid
|
|
according to the database's selected character set encoding.
|
|
Second, operations on binary strings process the actual bytes,
|
|
whereas the processing of character strings depends on locale settings.
|
|
In short, binary strings are appropriate for storing data that the
|
|
programmer thinks of as <quote>raw bytes</>, whereas character
|
|
strings are appropriate for storing text.
|
|
</para>
|
|
|
|
<para>
|
|
The <type>bytea</type> type supports two external formats for
|
|
input and output: <productname>PostgreSQL</productname>'s historical
|
|
<quote>escape</quote> format, and <quote>hex</quote> format. Both
|
|
of these are always accepted on input. The output format depends
|
|
on the configuration parameter <xref linkend="guc-bytea-output">;
|
|
the default is hex. (Note that the hex format was introduced in
|
|
<productname>PostgreSQL</productname> 9.0; earlier versions and some
|
|
tools don't understand it.)
|
|
</para>
|
|
|
|
<para>
|
|
The <acronym>SQL</acronym> standard defines a different binary
|
|
string type, called <type>BLOB</type> or <type>BINARY LARGE
|
|
OBJECT</type>. The input format is different from
|
|
<type>bytea</type>, but the provided functions and operators are
|
|
mostly the same.
|
|
</para>
|
|
|
|
<sect2>
|
|
<title><type>bytea</> Hex Format</title>
|
|
|
|
<para>
|
|
The <quote>hex</> format encodes binary data as 2 hexadecimal digits
|
|
per byte, most significant nibble first. The entire string is
|
|
preceded by the sequence <literal>\x</literal> (to distinguish it
|
|
from the escape format). In some contexts, the initial backslash may
|
|
need to be escaped by doubling it, in the same cases in which backslashes
|
|
have to be doubled in escape format; details appear below.
|
|
The hexadecimal digits can
|
|
be either upper or lower case, and whitespace is permitted between
|
|
digit pairs (but not within a digit pair nor in the starting
|
|
<literal>\x</literal> sequence).
|
|
The hex format is compatible with a wide
|
|
range of external applications and protocols, and it tends to be
|
|
faster to convert than the escape format, so its use is preferred.
|
|
</para>
|
|
|
|
<para>
|
|
Example:
|
|
<programlisting>
|
|
SELECT E'\\xDEADBEEF';
|
|
</programlisting>
|
|
</para>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title><type>bytea</> Escape Format</title>
|
|
|
|
<para>
|
|
The <quote>escape</quote> format is the traditional
|
|
<productname>PostgreSQL</productname> format for the <type>bytea</type>
|
|
type. It
|
|
takes the approach of representing a binary string as a sequence
|
|
of ASCII characters, while converting those bytes that cannot be
|
|
represented as an ASCII character into special escape sequences.
|
|
If, from the point of view of the application, representing bytes
|
|
as characters makes sense, then this representation can be
|
|
convenient. But in practice it is usually confusing because it
|
|
fuzzes up the distinction between binary strings and character
|
|
strings, and also the particular escape mechanism that was chosen is
|
|
somewhat unwieldy. So this format should probably be avoided
|
|
for most new applications.
|
|
</para>
|
|
|
|
<para>
|
|
When entering <type>bytea</type> values in escape format,
|
|
octets of certain
|
|
values <emphasis>must</emphasis> be escaped, while all octet
|
|
values <emphasis>can</emphasis> be escaped. In
|
|
general, to escape an octet, convert it into its three-digit
|
|
octal value and precede it
|
|
by a backslash (or two backslashes, if writing the value as a
|
|
literal using escape string syntax).
|
|
Backslash itself (octet value 92) can alternatively be represented by
|
|
double backslashes.
|
|
<xref linkend="datatype-binary-sqlesc">
|
|
shows the characters that must be escaped, and gives the alternative
|
|
escape sequences where applicable.
|
|
</para>
|
|
|
|
<table id="datatype-binary-sqlesc">
|
|
<title><type>bytea</> Literal Escaped Octets</title>
|
|
<tgroup cols="5">
|
|
<thead>
|
|
<row>
|
|
<entry>Decimal Octet Value</entry>
|
|
<entry>Description</entry>
|
|
<entry>Escaped Input Representation</entry>
|
|
<entry>Example</entry>
|
|
<entry>Output Representation</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry>0</entry>
|
|
<entry>zero octet</entry>
|
|
<entry><literal>E'\\000'</literal></entry>
|
|
<entry><literal>SELECT E'\\000'::bytea;</literal></entry>
|
|
<entry><literal>\000</literal></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry>39</entry>
|
|
<entry>single quote</entry>
|
|
<entry><literal>''''</literal> or <literal>E'\\047'</literal></entry>
|
|
<entry><literal>SELECT E'\''::bytea;</literal></entry>
|
|
<entry><literal>'</literal></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry>92</entry>
|
|
<entry>backslash</entry>
|
|
<entry><literal>E'\\\\'</literal> or <literal>E'\\134'</literal></entry>
|
|
<entry><literal>SELECT E'\\\\'::bytea;</literal></entry>
|
|
<entry><literal>\\</literal></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry>0 to 31 and 127 to 255</entry>
|
|
<entry><quote>non-printable</quote> octets</entry>
|
|
<entry><literal>E'\\<replaceable>xxx'</></literal> (octal value)</entry>
|
|
<entry><literal>SELECT E'\\001'::bytea;</literal></entry>
|
|
<entry><literal>\001</literal></entry>
|
|
</row>
|
|
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
The requirement to escape <emphasis>non-printable</emphasis> octets
|
|
varies depending on locale settings. In some instances you can get away
|
|
with leaving them unescaped. Note that the result in each of the examples
|
|
in <xref linkend="datatype-binary-sqlesc"> was exactly one octet in
|
|
length, even though the output representation is sometimes
|
|
more than one character.
|
|
</para>
|
|
|
|
<para>
|
|
The reason multiple backslashes are required, as shown
|
|
in <xref linkend="datatype-binary-sqlesc">, is that an input
|
|
string written as a string literal must pass through two parse
|
|
phases in the <productname>PostgreSQL</productname> server.
|
|
The first backslash of each pair is interpreted as an escape
|
|
character by the string-literal parser (assuming escape string
|
|
syntax is used) and is therefore consumed, leaving the second backslash of the
|
|
pair. (Dollar-quoted strings can be used to avoid this level
|
|
of escaping.) The remaining backslash is then recognized by the
|
|
<type>bytea</type> input function as starting either a three
|
|
digit octal value or escaping another backslash. For example,
|
|
a string literal passed to the server as <literal>E'\\001'</literal>
|
|
becomes <literal>\001</literal> after passing through the
|
|
escape string parser. The <literal>\001</literal> is then sent
|
|
to the <type>bytea</type> input function, where it is converted
|
|
to a single octet with a decimal value of 1. Note that the
|
|
single-quote character is not treated specially by <type>bytea</type>,
|
|
so it follows the normal rules for string literals. (See also
|
|
<xref linkend="sql-syntax-strings">.)
|
|
</para>
|
|
|
|
<para>
|
|
<type>Bytea</type> octets are sometimes escaped when output. In general, each
|
|
<quote>non-printable</quote> octet is converted into
|
|
its equivalent three-digit octal value and preceded by one backslash.
|
|
Most <quote>printable</quote> octets are represented by their standard
|
|
representation in the client character set. The octet with decimal
|
|
value 92 (backslash) is doubled in the output.
|
|
Details are in <xref linkend="datatype-binary-resesc">.
|
|
</para>
|
|
|
|
<table id="datatype-binary-resesc">
|
|
<title><type>bytea</> Output Escaped Octets</title>
|
|
<tgroup cols="5">
|
|
<thead>
|
|
<row>
|
|
<entry>Decimal Octet Value</entry>
|
|
<entry>Description</entry>
|
|
<entry>Escaped Output Representation</entry>
|
|
<entry>Example</entry>
|
|
<entry>Output Result</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
|
|
<row>
|
|
<entry>92</entry>
|
|
<entry>backslash</entry>
|
|
<entry><literal>\\</literal></entry>
|
|
<entry><literal>SELECT E'\\134'::bytea;</literal></entry>
|
|
<entry><literal>\\</literal></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry>0 to 31 and 127 to 255</entry>
|
|
<entry><quote>non-printable</quote> octets</entry>
|
|
<entry><literal>\<replaceable>xxx</></literal> (octal value)</entry>
|
|
<entry><literal>SELECT E'\\001'::bytea;</literal></entry>
|
|
<entry><literal>\001</literal></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry>32 to 126</entry>
|
|
<entry><quote>printable</quote> octets</entry>
|
|
<entry>client character set representation</entry>
|
|
<entry><literal>SELECT E'\\176'::bytea;</literal></entry>
|
|
<entry><literal>~</literal></entry>
|
|
</row>
|
|
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
Depending on the front end to <productname>PostgreSQL</> you use,
|
|
you might have additional work to do in terms of escaping and
|
|
unescaping <type>bytea</type> strings. For example, you might also
|
|
have to escape line feeds and carriage returns if your interface
|
|
automatically translates these.
|
|
</para>
|
|
</sect2>
|
|
</sect1>
|
|
|
|
|
|
<sect1 id="datatype-datetime">
|
|
<title>Date/Time Types</title>
|
|
|
|
<indexterm zone="datatype-datetime">
|
|
<primary>date</primary>
|
|
</indexterm>
|
|
<indexterm zone="datatype-datetime">
|
|
<primary>time</primary>
|
|
</indexterm>
|
|
<indexterm zone="datatype-datetime">
|
|
<primary>time without time zone</primary>
|
|
</indexterm>
|
|
<indexterm zone="datatype-datetime">
|
|
<primary>time with time zone</primary>
|
|
</indexterm>
|
|
<indexterm zone="datatype-datetime">
|
|
<primary>timestamp</primary>
|
|
</indexterm>
|
|
<indexterm zone="datatype-datetime">
|
|
<primary>timestamptz</primary>
|
|
</indexterm>
|
|
<indexterm zone="datatype-datetime">
|
|
<primary>timestamp with time zone</primary>
|
|
</indexterm>
|
|
<indexterm zone="datatype-datetime">
|
|
<primary>timestamp without time zone</primary>
|
|
</indexterm>
|
|
<indexterm zone="datatype-datetime">
|
|
<primary>interval</primary>
|
|
</indexterm>
|
|
<indexterm zone="datatype-datetime">
|
|
<primary>time span</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
<productname>PostgreSQL</productname> supports the full set of
|
|
<acronym>SQL</acronym> date and time types, shown in <xref
|
|
linkend="datatype-datetime-table">. The operations available
|
|
on these data types are described in
|
|
<xref linkend="functions-datetime">.
|
|
Dates are counted according to the Gregorian calendar, even in
|
|
years before that calendar was introduced (see <xref
|
|
linkend="datetime-units-history"> for more information).
|
|
</para>
|
|
|
|
<table id="datatype-datetime-table">
|
|
<title>Date/Time Types</title>
|
|
<tgroup cols="6">
|
|
<thead>
|
|
<row>
|
|
<entry>Name</entry>
|
|
<entry>Storage Size</entry>
|
|
<entry>Description</entry>
|
|
<entry>Low Value</entry>
|
|
<entry>High Value</entry>
|
|
<entry>Resolution</entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry><type>timestamp [ (<replaceable>p</replaceable>) ] [ without time zone ]</type></entry>
|
|
<entry>8 bytes</entry>
|
|
<entry>both date and time (no time zone)</entry>
|
|
<entry>4713 BC</entry>
|
|
<entry>294276 AD</entry>
|
|
<entry>1 microsecond / 14 digits</entry>
|
|
</row>
|
|
<row>
|
|
<entry><type>timestamp [ (<replaceable>p</replaceable>) ] with time zone</type></entry>
|
|
<entry>8 bytes</entry>
|
|
<entry>both date and time, with time zone</entry>
|
|
<entry>4713 BC</entry>
|
|
<entry>294276 AD</entry>
|
|
<entry>1 microsecond / 14 digits</entry>
|
|
</row>
|
|
<row>
|
|
<entry><type>date</type></entry>
|
|
<entry>4 bytes</entry>
|
|
<entry>date (no time of day)</entry>
|
|
<entry>4713 BC</entry>
|
|
<entry>5874897 AD</entry>
|
|
<entry>1 day</entry>
|
|
</row>
|
|
<row>
|
|
<entry><type>time [ (<replaceable>p</replaceable>) ] [ without time zone ]</type></entry>
|
|
<entry>8 bytes</entry>
|
|
<entry>time of day (no date)</entry>
|
|
<entry>00:00:00</entry>
|
|
<entry>24:00:00</entry>
|
|
<entry>1 microsecond / 14 digits</entry>
|
|
</row>
|
|
<row>
|
|
<entry><type>time [ (<replaceable>p</replaceable>) ] with time zone</type></entry>
|
|
<entry>12 bytes</entry>
|
|
<entry>times of day only, with time zone</entry>
|
|
<entry>00:00:00+1459</entry>
|
|
<entry>24:00:00-1459</entry>
|
|
<entry>1 microsecond / 14 digits</entry>
|
|
</row>
|
|
<row>
|
|
<entry><type>interval [ <replaceable>fields</replaceable> ] [ (<replaceable>p</replaceable>) ]</type></entry>
|
|
<entry>16 bytes</entry>
|
|
<entry>time interval</entry>
|
|
<entry>-178000000 years</entry>
|
|
<entry>178000000 years</entry>
|
|
<entry>1 microsecond / 14 digits</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<note>
|
|
<para>
|
|
The SQL standard requires that writing just <type>timestamp</type>
|
|
be equivalent to <type>timestamp without time
|
|
zone</type>, and <productname>PostgreSQL</productname> honors that
|
|
behavior. <type>timestamptz</type> is accepted as an
|
|
abbreviation for <type>timestamp with time zone</type>; this is a
|
|
<productname>PostgreSQL</productname> extension.
|
|
</para>
|
|
</note>
|
|
|
|
<para>
|
|
<type>time</type>, <type>timestamp</type>, and
|
|
<type>interval</type> accept an optional precision value
|
|
<replaceable>p</replaceable> which specifies the number of
|
|
fractional digits retained in the seconds field. By default, there
|
|
is no explicit bound on precision. The allowed range of
|
|
<replaceable>p</replaceable> is from 0 to 6 for the
|
|
<type>timestamp</type> and <type>interval</type> types.
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
When <type>timestamp</> values are stored as eight-byte integers
|
|
(currently the default), microsecond precision is available over
|
|
the full range of values. When <type>timestamp</> values are
|
|
stored as double precision floating-point numbers instead (a
|
|
deprecated compile-time option), the effective limit of precision
|
|
might be less than 6. <type>timestamp</type> values are stored as
|
|
seconds before or after midnight 2000-01-01. When
|
|
<type>timestamp</type> values are implemented using floating-point
|
|
numbers, microsecond precision is achieved for dates within a few
|
|
years of 2000-01-01, but the precision degrades for dates further
|
|
away. Note that using floating-point datetimes allows a larger
|
|
range of <type>timestamp</type> values to be represented than
|
|
shown above: from 4713 BC up to 5874897 AD.
|
|
</para>
|
|
|
|
<para>
|
|
The same compile-time option also determines whether
|
|
<type>time</type> and <type>interval</type> values are stored as
|
|
floating-point numbers or eight-byte integers. In the
|
|
floating-point case, large <type>interval</type> values degrade in
|
|
precision as the size of the interval increases.
|
|
</para>
|
|
</note>
|
|
|
|
<para>
|
|
For the <type>time</type> types, the allowed range of
|
|
<replaceable>p</replaceable> is from 0 to 6 when eight-byte integer
|
|
storage is used, or from 0 to 10 when floating-point storage is used.
|
|
</para>
|
|
|
|
<para>
|
|
The <type>interval</type> type has an additional option, which is
|
|
to restrict the set of stored fields by writing one of these phrases:
|
|
<literallayout class="monospaced">
|
|
YEAR
|
|
MONTH
|
|
DAY
|
|
HOUR
|
|
MINUTE
|
|
SECOND
|
|
YEAR TO MONTH
|
|
DAY TO HOUR
|
|
DAY TO MINUTE
|
|
DAY TO SECOND
|
|
HOUR TO MINUTE
|
|
HOUR TO SECOND
|
|
MINUTE TO SECOND
|
|
</literallayout>
|
|
Note that if both <replaceable>fields</replaceable> and
|
|
<replaceable>p</replaceable> are specified, the
|
|
<replaceable>fields</replaceable> must include <literal>SECOND</>,
|
|
since the precision applies only to the seconds.
|
|
</para>
|
|
|
|
<para>
|
|
The type <type>time with time zone</type> is defined by the SQL
|
|
standard, but the definition exhibits properties which lead to
|
|
questionable usefulness. In most cases, a combination of
|
|
<type>date</type>, <type>time</type>, <type>timestamp without time
|
|
zone</type>, and <type>timestamp with time zone</type> should
|
|
provide a complete range of date/time functionality required by
|
|
any application.
|
|
</para>
|
|
|
|
<para>
|
|
The types <type>abstime</type>
|
|
and <type>reltime</type> are lower precision types which are used internally.
|
|
You are discouraged from using these types in
|
|
applications; these internal types
|
|
might disappear in a future release.
|
|
</para>
|
|
|
|
<sect2 id="datatype-datetime-input">
|
|
<title>Date/Time Input</title>
|
|
|
|
<para>
|
|
Date and time input is accepted in almost any reasonable format, including
|
|
ISO 8601, <acronym>SQL</acronym>-compatible,
|
|
traditional <productname>POSTGRES</productname>, and others.
|
|
For some formats, ordering of day, month, and year in date input is
|
|
ambiguous and there is support for specifying the expected
|
|
ordering of these fields. Set the <xref linkend="guc-datestyle"> parameter
|
|
to <literal>MDY</> to select month-day-year interpretation,
|
|
<literal>DMY</> to select day-month-year interpretation, or
|
|
<literal>YMD</> to select year-month-day interpretation.
|
|
</para>
|
|
|
|
<para>
|
|
<productname>PostgreSQL</productname> is more flexible in
|
|
handling date/time input than the
|
|
<acronym>SQL</acronym> standard requires.
|
|
See <xref linkend="datetime-appendix">
|
|
for the exact parsing rules of date/time input and for the
|
|
recognized text fields including months, days of the week, and
|
|
time zones.
|
|
</para>
|
|
|
|
<para>
|
|
Remember that any date or time literal input needs to be enclosed
|
|
in single quotes, like text strings. Refer to
|
|
<xref linkend="sql-syntax-constants-generic"> for more
|
|
information.
|
|
<acronym>SQL</acronym> requires the following syntax
|
|
<synopsis>
|
|
<replaceable>type</replaceable> [ (<replaceable>p</replaceable>) ] '<replaceable>value</replaceable>'
|
|
</synopsis>
|
|
where <replaceable>p</replaceable> is an optional precision
|
|
specification giving the number of
|
|
fractional digits in the seconds field. Precision can be
|
|
specified for <type>time</type>, <type>timestamp</type>, and
|
|
<type>interval</type> types. The allowed values are mentioned
|
|
above. If no precision is specified in a constant specification,
|
|
it defaults to the precision of the literal value.
|
|
</para>
|
|
|
|
<sect3>
|
|
<title>Dates</title>
|
|
|
|
<indexterm>
|
|
<primary>date</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
<xref linkend="datatype-datetime-date-table"> shows some possible
|
|
inputs for the <type>date</type> type.
|
|
</para>
|
|
|
|
<table id="datatype-datetime-date-table">
|
|
<title>Date Input</title>
|
|
<tgroup cols="2">
|
|
<thead>
|
|
<row>
|
|
<entry>Example</entry>
|
|
<entry>Description</entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry>1999-01-08</entry>
|
|
<entry>ISO 8601; January 8 in any mode
|
|
(recommended format)</entry>
|
|
</row>
|
|
<row>
|
|
<entry>January 8, 1999</entry>
|
|
<entry>unambiguous in any <varname>datestyle</varname> input mode</entry>
|
|
</row>
|
|
<row>
|
|
<entry>1/8/1999</entry>
|
|
<entry>January 8 in <literal>MDY</> mode;
|
|
August 1 in <literal>DMY</> mode</entry>
|
|
</row>
|
|
<row>
|
|
<entry>1/18/1999</entry>
|
|
<entry>January 18 in <literal>MDY</> mode;
|
|
rejected in other modes</entry>
|
|
</row>
|
|
<row>
|
|
<entry>01/02/03</entry>
|
|
<entry>January 2, 2003 in <literal>MDY</> mode;
|
|
February 1, 2003 in <literal>DMY</> mode;
|
|
February 3, 2001 in <literal>YMD</> mode
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry>1999-Jan-08</entry>
|
|
<entry>January 8 in any mode</entry>
|
|
</row>
|
|
<row>
|
|
<entry>Jan-08-1999</entry>
|
|
<entry>January 8 in any mode</entry>
|
|
</row>
|
|
<row>
|
|
<entry>08-Jan-1999</entry>
|
|
<entry>January 8 in any mode</entry>
|
|
</row>
|
|
<row>
|
|
<entry>99-Jan-08</entry>
|
|
<entry>January 8 in <literal>YMD</> mode, else error</entry>
|
|
</row>
|
|
<row>
|
|
<entry>08-Jan-99</entry>
|
|
<entry>January 8, except error in <literal>YMD</> mode</entry>
|
|
</row>
|
|
<row>
|
|
<entry>Jan-08-99</entry>
|
|
<entry>January 8, except error in <literal>YMD</> mode</entry>
|
|
</row>
|
|
<row>
|
|
<entry>19990108</entry>
|
|
<entry>ISO 8601; January 8, 1999 in any mode</entry>
|
|
</row>
|
|
<row>
|
|
<entry>990108</entry>
|
|
<entry>ISO 8601; January 8, 1999 in any mode</entry>
|
|
</row>
|
|
<row>
|
|
<entry>1999.008</entry>
|
|
<entry>year and day of year</entry>
|
|
</row>
|
|
<row>
|
|
<entry>J2451187</entry>
|
|
<entry>Julian date</entry>
|
|
</row>
|
|
<row>
|
|
<entry>January 8, 99 BC</entry>
|
|
<entry>year 99 BC</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
</sect3>
|
|
|
|
<sect3>
|
|
<title>Times</title>
|
|
|
|
<indexterm>
|
|
<primary>time</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>time without time zone</primary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>time with time zone</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
The time-of-day types are <type>time [
|
|
(<replaceable>p</replaceable>) ] without time zone</type> and
|
|
<type>time [ (<replaceable>p</replaceable>) ] with time
|
|
zone</type>. <type>time</type> alone is equivalent to
|
|
<type>time without time zone</type>.
|
|
</para>
|
|
|
|
<para>
|
|
Valid input for these types consists of a time of day followed
|
|
by an optional time zone. (See <xref
|
|
linkend="datatype-datetime-time-table">
|
|
and <xref linkend="datatype-timezone-table">.) If a time zone is
|
|
specified in the input for <type>time without time zone</type>,
|
|
it is silently ignored. You can also specify a date but it will
|
|
be ignored, except when you use a time zone name that involves a
|
|
daylight-savings rule, such as
|
|
<literal>America/New_York</literal>. In this case specifying the date
|
|
is required in order to determine whether standard or daylight-savings
|
|
time applies. The appropriate time zone offset is recorded in the
|
|
<type>time with time zone</type> value.
|
|
</para>
|
|
|
|
<table id="datatype-datetime-time-table">
|
|
<title>Time Input</title>
|
|
<tgroup cols="2">
|
|
<thead>
|
|
<row>
|
|
<entry>Example</entry>
|
|
<entry>Description</entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry><literal>04:05:06.789</literal></entry>
|
|
<entry>ISO 8601</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>04:05:06</literal></entry>
|
|
<entry>ISO 8601</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>04:05</literal></entry>
|
|
<entry>ISO 8601</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>040506</literal></entry>
|
|
<entry>ISO 8601</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>04:05 AM</literal></entry>
|
|
<entry>same as 04:05; AM does not affect value</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>04:05 PM</literal></entry>
|
|
<entry>same as 16:05; input hour must be <= 12</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>04:05:06.789-8</literal></entry>
|
|
<entry>ISO 8601</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>04:05:06-08:00</literal></entry>
|
|
<entry>ISO 8601</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>04:05-08:00</literal></entry>
|
|
<entry>ISO 8601</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>040506-08</literal></entry>
|
|
<entry>ISO 8601</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>04:05:06 PST</literal></entry>
|
|
<entry>time zone specified by abbreviation</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>2003-04-12 04:05:06 America/New_York</literal></entry>
|
|
<entry>time zone specified by full name</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<table tocentry="1" id="datatype-timezone-table">
|
|
<title>Time Zone Input</title>
|
|
<tgroup cols="2">
|
|
<thead>
|
|
<row>
|
|
<entry>Example</entry>
|
|
<entry>Description</entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry><literal>PST</literal></entry>
|
|
<entry>Abbreviation (for Pacific Standard Time)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>America/New_York</literal></entry>
|
|
<entry>Full time zone name</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>PST8PDT</literal></entry>
|
|
<entry>POSIX-style time zone specification</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>-8:00</literal></entry>
|
|
<entry>ISO-8601 offset for PST</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>-800</literal></entry>
|
|
<entry>ISO-8601 offset for PST</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>-8</literal></entry>
|
|
<entry>ISO-8601 offset for PST</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>zulu</literal></entry>
|
|
<entry>Military abbreviation for UTC</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>z</literal></entry>
|
|
<entry>Short form of <literal>zulu</literal></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
Refer to <xref linkend="datatype-timezones"> for more information on how
|
|
to specify time zones.
|
|
</para>
|
|
</sect3>
|
|
|
|
<sect3>
|
|
<title>Time Stamps</title>
|
|
|
|
<indexterm>
|
|
<primary>timestamp</primary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>timestamp with time zone</primary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>timestamp without time zone</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
Valid input for the time stamp types consists of the concatenation
|
|
of a date and a time, followed by an optional time zone,
|
|
followed by an optional <literal>AD</literal> or <literal>BC</literal>.
|
|
(Alternatively, <literal>AD</literal>/<literal>BC</literal> can appear
|
|
before the time zone, but this is not the preferred ordering.)
|
|
Thus:
|
|
|
|
<programlisting>
|
|
1999-01-08 04:05:06
|
|
</programlisting>
|
|
and:
|
|
<programlisting>
|
|
1999-01-08 04:05:06 -8:00
|
|
</programlisting>
|
|
|
|
are valid values, which follow the <acronym>ISO</acronym> 8601
|
|
standard. In addition, the common format:
|
|
<programlisting>
|
|
January 8 04:05:06 1999 PST
|
|
</programlisting>
|
|
is supported.
|
|
</para>
|
|
|
|
<para>
|
|
The <acronym>SQL</acronym> standard differentiates
|
|
<type>timestamp without time zone</type>
|
|
and <type>timestamp with time zone</type> literals by the presence of a
|
|
<quote>+</quote> or <quote>-</quote> symbol and time zone offset after
|
|
the time. Hence, according to the standard,
|
|
|
|
<programlisting>TIMESTAMP '2004-10-19 10:23:54'</programlisting>
|
|
|
|
is a <type>timestamp without time zone</type>, while
|
|
|
|
<programlisting>TIMESTAMP '2004-10-19 10:23:54+02'</programlisting>
|
|
|
|
is a <type>timestamp with time zone</type>.
|
|
<productname>PostgreSQL</productname> never examines the content of a
|
|
literal string before determining its type, and therefore will treat
|
|
both of the above as <type>timestamp without time zone</type>. To
|
|
ensure that a literal is treated as <type>timestamp with time
|
|
zone</type>, give it the correct explicit type:
|
|
|
|
<programlisting>TIMESTAMP WITH TIME ZONE '2004-10-19 10:23:54+02'</programlisting>
|
|
|
|
In a literal that has been determined to be <type>timestamp without time
|
|
zone</type>, <productname>PostgreSQL</productname> will silently ignore
|
|
any time zone indication.
|
|
That is, the resulting value is derived from the date/time
|
|
fields in the input value, and is not adjusted for time zone.
|
|
</para>
|
|
|
|
<para>
|
|
For <type>timestamp with time zone</type>, the internally stored
|
|
value is always in UTC (Universal
|
|
Coordinated Time, traditionally known as Greenwich Mean Time,
|
|
<acronym>GMT</>). An input value that has an explicit
|
|
time zone specified is converted to UTC using the appropriate offset
|
|
for that time zone. If no time zone is stated in the input string,
|
|
then it is assumed to be in the time zone indicated by the system's
|
|
<xref linkend="guc-timezone"> parameter, and is converted to UTC using the
|
|
offset for the <varname>timezone</> zone.
|
|
</para>
|
|
|
|
<para>
|
|
When a <type>timestamp with time
|
|
zone</type> value is output, it is always converted from UTC to the
|
|
current <varname>timezone</> zone, and displayed as local time in that
|
|
zone. To see the time in another time zone, either change
|
|
<varname>timezone</> or use the <literal>AT TIME ZONE</> construct
|
|
(see <xref linkend="functions-datetime-zoneconvert">).
|
|
</para>
|
|
|
|
<para>
|
|
Conversions between <type>timestamp without time zone</type> and
|
|
<type>timestamp with time zone</type> normally assume that the
|
|
<type>timestamp without time zone</type> value should be taken or given
|
|
as <varname>timezone</> local time. A different time zone can
|
|
be specified for the conversion using <literal>AT TIME ZONE</>.
|
|
</para>
|
|
</sect3>
|
|
|
|
<sect3>
|
|
<title>Special Values</title>
|
|
|
|
<indexterm>
|
|
<primary>time</primary>
|
|
<secondary>constants</secondary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>date</primary>
|
|
<secondary>constants</secondary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
<productname>PostgreSQL</productname> supports several
|
|
special date/time input values for convenience, as shown in <xref
|
|
linkend="datatype-datetime-special-table">. The values
|
|
<literal>infinity</literal> and <literal>-infinity</literal>
|
|
are specially represented inside the system and will be displayed
|
|
unchanged; but the others are simply notational shorthands
|
|
that will be converted to ordinary date/time values when read.
|
|
(In particular, <literal>now</> and related strings are converted
|
|
to a specific time value as soon as they are read.)
|
|
All of these values need to be enclosed in single quotes when used
|
|
as constants in SQL commands.
|
|
</para>
|
|
|
|
<table id="datatype-datetime-special-table">
|
|
<title>Special Date/Time Inputs</title>
|
|
<tgroup cols="3">
|
|
<thead>
|
|
<row>
|
|
<entry>Input String</entry>
|
|
<entry>Valid Types</entry>
|
|
<entry>Description</entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry><literal>epoch</literal></entry>
|
|
<entry><type>date</type>, <type>timestamp</type></entry>
|
|
<entry>1970-01-01 00:00:00+00 (Unix system time zero)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>infinity</literal></entry>
|
|
<entry><type>date</type>, <type>timestamp</type></entry>
|
|
<entry>later than all other time stamps</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>-infinity</literal></entry>
|
|
<entry><type>date</type>, <type>timestamp</type></entry>
|
|
<entry>earlier than all other time stamps</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>now</literal></entry>
|
|
<entry><type>date</type>, <type>time</type>, <type>timestamp</type></entry>
|
|
<entry>current transaction's start time</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>today</literal></entry>
|
|
<entry><type>date</type>, <type>timestamp</type></entry>
|
|
<entry>midnight today</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>tomorrow</literal></entry>
|
|
<entry><type>date</type>, <type>timestamp</type></entry>
|
|
<entry>midnight tomorrow</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>yesterday</literal></entry>
|
|
<entry><type>date</type>, <type>timestamp</type></entry>
|
|
<entry>midnight yesterday</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>allballs</literal></entry>
|
|
<entry><type>time</type></entry>
|
|
<entry>00:00:00.00 UTC</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
The following <acronym>SQL</acronym>-compatible functions can also
|
|
be used to obtain the current time value for the corresponding data
|
|
type:
|
|
<literal>CURRENT_DATE</literal>, <literal>CURRENT_TIME</literal>,
|
|
<literal>CURRENT_TIMESTAMP</literal>, <literal>LOCALTIME</literal>,
|
|
<literal>LOCALTIMESTAMP</literal>. The latter four accept an
|
|
optional subsecond precision specification. (See <xref
|
|
linkend="functions-datetime-current">.) Note that these are
|
|
SQL functions and are <emphasis>not</> recognized in data input strings.
|
|
</para>
|
|
|
|
</sect3>
|
|
</sect2>
|
|
|
|
<sect2 id="datatype-datetime-output">
|
|
<title>Date/Time Output</title>
|
|
|
|
<indexterm>
|
|
<primary>date</primary>
|
|
<secondary>output format</secondary>
|
|
<seealso>formatting</seealso>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>time</primary>
|
|
<secondary>output format</secondary>
|
|
<seealso>formatting</seealso>
|
|
</indexterm>
|
|
|
|
<para>
|
|
The output format of the date/time types can be set to one of the four
|
|
styles ISO 8601,
|
|
<acronym>SQL</acronym> (Ingres), traditional <productname>POSTGRES</>
|
|
(Unix <application>date</> format), or
|
|
German. The default
|
|
is the <acronym>ISO</acronym> format. (The
|
|
<acronym>SQL</acronym> standard requires the use of the ISO 8601
|
|
format. The name of the <quote>SQL</quote> output format is a
|
|
historical accident.) <xref
|
|
linkend="datatype-datetime-output-table"> shows examples of each
|
|
output style. The output of the <type>date</type> and
|
|
<type>time</type> types is generally only the date or time part
|
|
in accordance with the given examples. However, the
|
|
<productname>POSTGRES</> style outputs date-only values in
|
|
<acronym>ISO</acronym> format.
|
|
</para>
|
|
|
|
<table id="datatype-datetime-output-table">
|
|
<title>Date/Time Output Styles</title>
|
|
<tgroup cols="3">
|
|
<thead>
|
|
<row>
|
|
<entry>Style Specification</entry>
|
|
<entry>Description</entry>
|
|
<entry>Example</entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry><literal>ISO</literal></entry>
|
|
<entry>ISO 8601, SQL standard</entry>
|
|
<entry><literal>1997-12-17 07:37:16-08</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>SQL</literal></entry>
|
|
<entry>traditional style</entry>
|
|
<entry><literal>12/17/1997 07:37:16.00 PST</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>Postgres</literal></entry>
|
|
<entry>original style</entry>
|
|
<entry><literal>Wed Dec 17 07:37:16 1997 PST</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>German</literal></entry>
|
|
<entry>regional style</entry>
|
|
<entry><literal>17.12.1997 07:37:16.00 PST</literal></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<note>
|
|
<para>
|
|
ISO 8601 specifies the use of uppercase letter <literal>T</> to separate
|
|
the date and time. <productname>PostgreSQL</> accepts that format on
|
|
input, but on output it uses a space rather than <literal>T</>, as shown
|
|
above. This is for readability and for consistency with RFC 3339 as
|
|
well as some other database systems.
|
|
</para>
|
|
</note>
|
|
|
|
<para>
|
|
In the <acronym>SQL</acronym> and POSTGRES styles, day appears before
|
|
month if DMY field ordering has been specified, otherwise month appears
|
|
before day.
|
|
(See <xref linkend="datatype-datetime-input">
|
|
for how this setting also affects interpretation of input values.)
|
|
<xref linkend="datatype-datetime-output2-table"> shows examples.
|
|
</para>
|
|
|
|
<table id="datatype-datetime-output2-table">
|
|
<title>Date Order Conventions</title>
|
|
<tgroup cols="3">
|
|
<thead>
|
|
<row>
|
|
<entry><varname>datestyle</varname> Setting</entry>
|
|
<entry>Input Ordering</entry>
|
|
<entry>Example Output</entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry><literal>SQL, DMY</></entry>
|
|
<entry><replaceable>day</replaceable>/<replaceable>month</replaceable>/<replaceable>year</replaceable></entry>
|
|
<entry><literal>17/12/1997 15:37:16.00 CET</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>SQL, MDY</></entry>
|
|
<entry><replaceable>month</replaceable>/<replaceable>day</replaceable>/<replaceable>year</replaceable></entry>
|
|
<entry><literal>12/17/1997 07:37:16.00 PST</literal></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>Postgres, DMY</></entry>
|
|
<entry><replaceable>day</replaceable>/<replaceable>month</replaceable>/<replaceable>year</replaceable></entry>
|
|
<entry><literal>Wed 17 Dec 07:37:16 1997 PST</literal></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
The date/time style can be selected by the user using the
|
|
<command>SET datestyle</command> command, the <xref
|
|
linkend="guc-datestyle"> parameter in the
|
|
<filename>postgresql.conf</filename> configuration file, or the
|
|
<envar>PGDATESTYLE</envar> environment variable on the server or
|
|
client.
|
|
</para>
|
|
|
|
<para>
|
|
The formatting function <function>to_char</function>
|
|
(see <xref linkend="functions-formatting">) is also available as
|
|
a more flexible way to format date/time output.
|
|
</para>
|
|
</sect2>
|
|
|
|
<sect2 id="datatype-timezones">
|
|
<title>Time Zones</title>
|
|
|
|
<indexterm zone="datatype-timezones">
|
|
<primary>time zone</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
Time zones, and time-zone conventions, are influenced by
|
|
political decisions, not just earth geometry. Time zones around the
|
|
world became somewhat standardized during the 1900's,
|
|
but continue to be prone to arbitrary changes, particularly with
|
|
respect to daylight-savings rules.
|
|
<productname>PostgreSQL</productname> uses the widely-used
|
|
<literal>zoneinfo</> (Olson) time zone database for information about
|
|
historical time zone rules. For times in the future, the assumption
|
|
is that the latest known rules for a given time zone will
|
|
continue to be observed indefinitely far into the future.
|
|
</para>
|
|
|
|
<para>
|
|
<productname>PostgreSQL</productname> endeavors to be compatible with
|
|
the <acronym>SQL</acronym> standard definitions for typical usage.
|
|
However, the <acronym>SQL</acronym> standard has an odd mix of date and
|
|
time types and capabilities. Two obvious problems are:
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>
|
|
Although the <type>date</type> type
|
|
cannot have an associated time zone, the
|
|
<type>time</type> type can.
|
|
Time zones in the real world have little meaning unless
|
|
associated with a date as well as a time,
|
|
since the offset can vary through the year with daylight-saving
|
|
time boundaries.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
The default time zone is specified as a constant numeric offset
|
|
from <acronym>UTC</>. It is therefore impossible to adapt to
|
|
daylight-saving time when doing date/time arithmetic across
|
|
<acronym>DST</acronym> boundaries.
|
|
</para>
|
|
</listitem>
|
|
|
|
</itemizedlist>
|
|
</para>
|
|
|
|
<para>
|
|
To address these difficulties, we recommend using date/time types
|
|
that contain both date and time when using time zones. We
|
|
do <emphasis>not</> recommend using the type <type>time with
|
|
time zone</type> (though it is supported by
|
|
<productname>PostgreSQL</productname> for legacy applications and
|
|
for compliance with the <acronym>SQL</acronym> standard).
|
|
<productname>PostgreSQL</productname> assumes
|
|
your local time zone for any type containing only date or time.
|
|
</para>
|
|
|
|
<para>
|
|
All timezone-aware dates and times are stored internally in
|
|
<acronym>UTC</acronym>. They are converted to local time
|
|
in the zone specified by the <xref linkend="guc-timezone"> configuration
|
|
parameter before being displayed to the client.
|
|
</para>
|
|
|
|
<para>
|
|
<productname>PostgreSQL</productname> allows you to specify time zones in
|
|
three different forms:
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>
|
|
A full time zone name, for example <literal>America/New_York</>.
|
|
The recognized time zone names are listed in the
|
|
<literal>pg_timezone_names</literal> view (see <xref
|
|
linkend="view-pg-timezone-names">).
|
|
<productname>PostgreSQL</productname> uses the widely-used
|
|
<literal>zoneinfo</> time zone data for this purpose, so the same
|
|
names are also recognized by much other software.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
A time zone abbreviation, for example <literal>PST</>. Such a
|
|
specification merely defines a particular offset from UTC, in
|
|
contrast to full time zone names which can imply a set of daylight
|
|
savings transition-date rules as well. The recognized abbreviations
|
|
are listed in the <literal>pg_timezone_abbrevs</> view (see <xref
|
|
linkend="view-pg-timezone-abbrevs">). You cannot set the
|
|
configuration parameters <xref linkend="guc-timezone"> or
|
|
<xref linkend="guc-log-timezone"> to a time
|
|
zone abbreviation, but you can use abbreviations in
|
|
date/time input values and with the <literal>AT TIME ZONE</>
|
|
operator.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
In addition to the timezone names and abbreviations,
|
|
<productname>PostgreSQL</productname> will accept POSIX-style time zone
|
|
specifications of the form <replaceable>STD</><replaceable>offset</> or
|
|
<replaceable>STD</><replaceable>offset</><replaceable>DST</>, where
|
|
<replaceable>STD</> is a zone abbreviation, <replaceable>offset</> is a
|
|
numeric offset in hours west from UTC, and <replaceable>DST</> is an
|
|
optional daylight-savings zone abbreviation, assumed to stand for one
|
|
hour ahead of the given offset. For example, if <literal>EST5EDT</>
|
|
were not already a recognized zone name, it would be accepted and would
|
|
be functionally equivalent to United States East Coast time. In this
|
|
syntax, a zone abbreviation can be a string of letters, or an
|
|
arbitrary string surrounded by angle brackets (<literal><></>).
|
|
When a daylight-savings zone abbreviation is present,
|
|
it is assumed to be used
|
|
according to the same daylight-savings transition rules used in the
|
|
<literal>zoneinfo</> time zone database's <filename>posixrules</> entry.
|
|
In a standard <productname>PostgreSQL</productname> installation,
|
|
<filename>posixrules</> is the same as <literal>US/Eastern</>, so
|
|
that POSIX-style time zone specifications follow USA daylight-savings
|
|
rules. If needed, you can adjust this behavior by replacing the
|
|
<filename>posixrules</> file.
|
|
</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
In short, this is the difference between abbreviations
|
|
and full names: abbreviations always represent a fixed offset from
|
|
UTC, whereas most of the full names imply a local daylight-savings time
|
|
rule, and so have two possible UTC offsets.
|
|
</para>
|
|
|
|
<para>
|
|
One should be wary that the POSIX-style time zone feature can
|
|
lead to silently accepting bogus input, since there is no check on the
|
|
reasonableness of the zone abbreviations. For example, <literal>SET
|
|
TIMEZONE TO FOOBAR0</> will work, leaving the system effectively using
|
|
a rather peculiar abbreviation for UTC.
|
|
Another issue to keep in mind is that in POSIX time zone names,
|
|
positive offsets are used for locations <emphasis>west</> of Greenwich.
|
|
Everywhere else, <productname>PostgreSQL</productname> follows the
|
|
ISO-8601 convention that positive timezone offsets are <emphasis>east</>
|
|
of Greenwich.
|
|
</para>
|
|
|
|
<para>
|
|
In all cases, timezone names are recognized case-insensitively.
|
|
(This is a change from <productname>PostgreSQL</productname> versions
|
|
prior to 8.2, which were case-sensitive in some contexts but not others.)
|
|
</para>
|
|
|
|
<para>
|
|
Neither full names nor abbreviations are hard-wired into the server;
|
|
they are obtained from configuration files stored under
|
|
<filename>.../share/timezone/</> and <filename>.../share/timezonesets/</>
|
|
of the installation directory
|
|
(see <xref linkend="datetime-config-files">).
|
|
</para>
|
|
|
|
<para>
|
|
The <xref linkend="guc-timezone"> configuration parameter can
|
|
be set in the file <filename>postgresql.conf</>, or in any of the
|
|
other standard ways described in <xref linkend="runtime-config">.
|
|
There are also some special ways to set it:
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>
|
|
The <acronym>SQL</acronym> command <command>SET TIME ZONE</command>
|
|
sets the time zone for the session. This is an alternative spelling
|
|
of <command>SET TIMEZONE TO</> with a more SQL-spec-compatible syntax.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
The <envar>PGTZ</envar> environment variable is used by
|
|
<application>libpq</application> clients
|
|
to send a <command>SET TIME ZONE</command>
|
|
command to the server upon connection.
|
|
</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
</sect2>
|
|
|
|
<sect2 id="datatype-interval-input">
|
|
<title>Interval Input</title>
|
|
|
|
<indexterm>
|
|
<primary>interval</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
<type>interval</type> values can be written using the following
|
|
verbose syntax:
|
|
|
|
<synopsis>
|
|
<optional>@</> <replaceable>quantity</> <replaceable>unit</> <optional><replaceable>quantity</> <replaceable>unit</>...</> <optional><replaceable>direction</></optional>
|
|
</synopsis>
|
|
|
|
where <replaceable>quantity</> is a number (possibly signed);
|
|
<replaceable>unit</> is <literal>microsecond</literal>,
|
|
<literal>millisecond</literal>, <literal>second</literal>,
|
|
<literal>minute</literal>, <literal>hour</literal>, <literal>day</literal>,
|
|
<literal>week</literal>, <literal>month</literal>, <literal>year</literal>,
|
|
<literal>decade</literal>, <literal>century</literal>, <literal>millennium</literal>,
|
|
or abbreviations or plurals of these units;
|
|
<replaceable>direction</> can be <literal>ago</literal> or
|
|
empty. The at sign (<literal>@</>) is optional noise. The amounts
|
|
of the different units are implicitly added with appropriate
|
|
sign accounting. <literal>ago</literal> negates all the fields.
|
|
This syntax is also used for interval output, if
|
|
<xref linkend="guc-intervalstyle"> is set to
|
|
<literal>postgres_verbose</>.
|
|
</para>
|
|
|
|
<para>
|
|
Quantities of days, hours, minutes, and seconds can be specified without
|
|
explicit unit markings. For example, <literal>'1 12:59:10'</> is read
|
|
the same as <literal>'1 day 12 hours 59 min 10 sec'</>. Also,
|
|
a combination of years and months can be specified with a dash;
|
|
for example <literal>'200-10'</> is read the same as <literal>'200 years
|
|
10 months'</>. (These shorter forms are in fact the only ones allowed
|
|
by the <acronym>SQL</acronym> standard, and are used for output when
|
|
<varname>IntervalStyle</> is set to <literal>sql_standard</literal>.)
|
|
</para>
|
|
|
|
<para>
|
|
Interval values can also be written as ISO 8601 time intervals, using
|
|
either the <quote>format with designators</> of the standard's section
|
|
4.4.3.2 or the <quote>alternative format</> of section 4.4.3.3. The
|
|
format with designators looks like this:
|
|
<synopsis>
|
|
P <replaceable>quantity</> <replaceable>unit</> <optional> <replaceable>quantity</> <replaceable>unit</> ...</optional> <optional> T <optional> <replaceable>quantity</> <replaceable>unit</> ...</optional></optional>
|
|
</synopsis>
|
|
The string must start with a <literal>P</>, and may include a
|
|
<literal>T</> that introduces the time-of-day units. The
|
|
available unit abbreviations are given in <xref
|
|
linkend="datatype-interval-iso8601-units">. Units may be
|
|
omitted, and may be specified in any order, but units smaller than
|
|
a day must appear after <literal>T</>. In particular, the meaning of
|
|
<literal>M</> depends on whether it is before or after
|
|
<literal>T</>.
|
|
</para>
|
|
|
|
<table id="datatype-interval-iso8601-units">
|
|
<title>ISO 8601 Interval Unit Abbreviations</title>
|
|
<tgroup cols="2">
|
|
<thead>
|
|
<row>
|
|
<entry>Abbreviation</entry>
|
|
<entry>Meaning</entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry>Y</entry>
|
|
<entry>Years</entry>
|
|
</row>
|
|
<row>
|
|
<entry>M</entry>
|
|
<entry>Months (in the date part)</entry>
|
|
</row>
|
|
<row>
|
|
<entry>W</entry>
|
|
<entry>Weeks</entry>
|
|
</row>
|
|
<row>
|
|
<entry>D</entry>
|
|
<entry>Days</entry>
|
|
</row>
|
|
<row>
|
|
<entry>H</entry>
|
|
<entry>Hours</entry>
|
|
</row>
|
|
<row>
|
|
<entry>M</entry>
|
|
<entry>Minutes (in the time part)</entry>
|
|
</row>
|
|
<row>
|
|
<entry>S</entry>
|
|
<entry>Seconds</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
In the alternative format:
|
|
<synopsis>
|
|
P <optional> <replaceable>years</>-<replaceable>months</>-<replaceable>days</> </optional> <optional> T <replaceable>hours</>:<replaceable>minutes</>:<replaceable>seconds</> </optional>
|
|
</synopsis>
|
|
the string must begin with <literal>P</literal>, and a
|
|
<literal>T</> separates the date and time parts of the interval.
|
|
The values are given as numbers similar to ISO 8601 dates.
|
|
</para>
|
|
|
|
<para>
|
|
When writing an interval constant with a <replaceable>fields</>
|
|
specification, or when assigning a string to an interval column that was
|
|
defined with a <replaceable>fields</> specification, the interpretation of
|
|
unmarked quantities depends on the <replaceable>fields</>. For
|
|
example <literal>INTERVAL '1' YEAR</> is read as 1 year, whereas
|
|
<literal>INTERVAL '1'</> means 1 second. Also, field values
|
|
<quote>to the right</> of the least significant field allowed by the
|
|
<replaceable>fields</> specification are silently discarded. For
|
|
example, writing <literal>INTERVAL '1 day 2:03:04' HOUR TO MINUTE</>
|
|
results in dropping the seconds field, but not the day field.
|
|
</para>
|
|
|
|
<para>
|
|
According to the <acronym>SQL</> standard all fields of an interval
|
|
value must have the same sign, so a leading negative sign applies to all
|
|
fields; for example the negative sign in the interval literal
|
|
<literal>'-1 2:03:04'</> applies to both the days and hour/minute/second
|
|
parts. <productname>PostgreSQL</> allows the fields to have different
|
|
signs, and traditionally treats each field in the textual representation
|
|
as independently signed, so that the hour/minute/second part is
|
|
considered positive in this example. If <varname>IntervalStyle</> is
|
|
set to <literal>sql_standard</literal> then a leading sign is considered
|
|
to apply to all fields (but only if no additional signs appear).
|
|
Otherwise the traditional <productname>PostgreSQL</> interpretation is
|
|
used. To avoid ambiguity, it's recommended to attach an explicit sign
|
|
to each field if any field is negative.
|
|
</para>
|
|
|
|
<para>
|
|
Internally <type>interval</> values are stored as months, days,
|
|
and seconds. This is done because the number of days in a month
|
|
varies, and a day can have 23 or 25 hours if a daylight savings
|
|
time adjustment is involved. The months and days fields are integers
|
|
while the seconds field can store fractions. Because intervals are
|
|
usually created from constant strings or <type>timestamp</> subtraction,
|
|
this storage method works well in most cases. Functions
|
|
<function>justify_days</> and <function>justify_hours</> are
|
|
available for adjusting days and hours that overflow their normal
|
|
ranges.
|
|
</para>
|
|
|
|
<para>
|
|
In the verbose input format, and in some fields of the more compact
|
|
input formats, field values can have fractional parts; for example
|
|
<literal>'1.5 week'</> or <literal>'01:02:03.45'</>. Such input is
|
|
converted to the appropriate number of months, days, and seconds
|
|
for storage. When this would result in a fractional number of
|
|
months or days, the fraction is added to the lower-order fields
|
|
using the conversion factors 1 month = 30 days and 1 day = 24 hours.
|
|
For example, <literal>'1.5 month'</> becomes 1 month and 15 days.
|
|
Only seconds will ever be shown as fractional on output.
|
|
</para>
|
|
|
|
<para>
|
|
<xref linkend="datatype-interval-input-examples"> shows some examples
|
|
of valid <type>interval</> input.
|
|
</para>
|
|
|
|
<table id="datatype-interval-input-examples">
|
|
<title>Interval Input</title>
|
|
<tgroup cols="2">
|
|
<thead>
|
|
<row>
|
|
<entry>Example</entry>
|
|
<entry>Description</entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry>1-2</entry>
|
|
<entry>SQL standard format: 1 year 2 months</entry>
|
|
</row>
|
|
<row>
|
|
<entry>3 4:05:06</entry>
|
|
<entry>SQL standard format: 3 days 4 hours 5 minutes 6 seconds</entry>
|
|
</row>
|
|
<row>
|
|
<entry>1 year 2 months 3 days 4 hours 5 minutes 6 seconds</entry>
|
|
<entry>Traditional Postgres format: 1 year 2 months 3 days 4 hours 5 minutes 6 seconds</entry>
|
|
</row>
|
|
<row>
|
|
<entry>P1Y2M3DT4H5M6S</entry>
|
|
<entry>ISO 8601 <quote>format with designators</>: same meaning as above</entry>
|
|
</row>
|
|
<row>
|
|
<entry>P0001-02-03T04:05:06</entry>
|
|
<entry>ISO 8601 <quote>alternative format</>: same meaning as above</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="datatype-interval-output">
|
|
<title>Interval Output</title>
|
|
|
|
<indexterm>
|
|
<primary>interval</primary>
|
|
<secondary>output format</secondary>
|
|
<seealso>formatting</seealso>
|
|
</indexterm>
|
|
|
|
<para>
|
|
The output format of the interval type can be set to one of the
|
|
four styles <literal>sql_standard</>, <literal>postgres</>,
|
|
<literal>postgres_verbose</>, or <literal>iso_8601</>,
|
|
using the command <literal>SET intervalstyle</literal>.
|
|
The default is the <literal>postgres</> format.
|
|
<xref linkend="interval-style-output-table"> shows examples of each
|
|
output style.
|
|
</para>
|
|
|
|
<para>
|
|
The <literal>sql_standard</> style produces output that conforms to
|
|
the SQL standard's specification for interval literal strings, if
|
|
the interval value meets the standard's restrictions (either year-month
|
|
only or day-time only, with no mixing of positive
|
|
and negative components). Otherwise the output looks like a standard
|
|
year-month literal string followed by a day-time literal string,
|
|
with explicit signs added to disambiguate mixed-sign intervals.
|
|
</para>
|
|
|
|
<para>
|
|
The output of the <literal>postgres</> style matches the output of
|
|
<productname>PostgreSQL</> releases prior to 8.4 when the
|
|
<xref linkend="guc-datestyle"> parameter was set to <literal>ISO</>.
|
|
</para>
|
|
|
|
<para>
|
|
The output of the <literal>postgres_verbose</> style matches the output of
|
|
<productname>PostgreSQL</> releases prior to 8.4 when the
|
|
<varname>DateStyle</> parameter was set to non-<literal>ISO</> output.
|
|
</para>
|
|
|
|
<para>
|
|
The output of the <literal>iso_8601</> style matches the <quote>format
|
|
with designators</> described in section 4.4.3.2 of the
|
|
ISO 8601 standard.
|
|
</para>
|
|
|
|
<table id="interval-style-output-table">
|
|
<title>Interval Output Style Examples</title>
|
|
<tgroup cols="4">
|
|
<thead>
|
|
<row>
|
|
<entry>Style Specification</entry>
|
|
<entry>Year-Month Interval</entry>
|
|
<entry>Day-Time Interval</entry>
|
|
<entry>Mixed Interval</entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry><literal>sql_standard</></entry>
|
|
<entry>1-2</entry>
|
|
<entry>3 4:05:06</entry>
|
|
<entry>-1-2 +3 -4:05:06</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>postgres</></entry>
|
|
<entry>1 year 2 mons</entry>
|
|
<entry>3 days 04:05:06</entry>
|
|
<entry>-1 year -2 mons +3 days -04:05:06</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>postgres_verbose</></entry>
|
|
<entry>@ 1 year 2 mons</entry>
|
|
<entry>@ 3 days 4 hours 5 mins 6 secs</entry>
|
|
<entry>@ 1 year 2 mons -3 days 4 hours 5 mins 6 secs ago</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>iso_8601</></entry>
|
|
<entry>P1Y2M</entry>
|
|
<entry>P3DT4H5M6S</entry>
|
|
<entry>P-1Y-2M3DT-4H-5M-6S</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
</sect2>
|
|
|
|
</sect1>
|
|
|
|
<sect1 id="datatype-boolean">
|
|
<title>Boolean Type</title>
|
|
|
|
<indexterm zone="datatype-boolean">
|
|
<primary>Boolean</primary>
|
|
<secondary>data type</secondary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-boolean">
|
|
<primary>true</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-boolean">
|
|
<primary>false</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
<productname>PostgreSQL</productname> provides the
|
|
standard <acronym>SQL</acronym> type <type>boolean</type>;
|
|
see <xref linkend="datatype-boolean-table">.
|
|
The <type>boolean</type> type can have several states:
|
|
<quote>true</quote>, <quote>false</quote>, and a third state,
|
|
<quote>unknown</quote>, which is represented by the
|
|
<acronym>SQL</acronym> null value.
|
|
</para>
|
|
|
|
<table id="datatype-boolean-table">
|
|
<title>Boolean Data Type</title>
|
|
<tgroup cols="3">
|
|
<thead>
|
|
<row>
|
|
<entry>Name</entry>
|
|
<entry>Storage Size</entry>
|
|
<entry>Description</entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry><type>boolean</type></entry>
|
|
<entry>1 byte</entry>
|
|
<entry>state of true or false</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
Valid literal values for the <quote>true</quote> state are:
|
|
<simplelist>
|
|
<member><literal>TRUE</literal></member>
|
|
<member><literal>'t'</literal></member>
|
|
<member><literal>'true'</literal></member>
|
|
<member><literal>'y'</literal></member>
|
|
<member><literal>'yes'</literal></member>
|
|
<member><literal>'on'</literal></member>
|
|
<member><literal>'1'</literal></member>
|
|
</simplelist>
|
|
For the <quote>false</quote> state, the following values can be
|
|
used:
|
|
<simplelist>
|
|
<member><literal>FALSE</literal></member>
|
|
<member><literal>'f'</literal></member>
|
|
<member><literal>'false'</literal></member>
|
|
<member><literal>'n'</literal></member>
|
|
<member><literal>'no'</literal></member>
|
|
<member><literal>'off'</literal></member>
|
|
<member><literal>'0'</literal></member>
|
|
</simplelist>
|
|
Leading or trailing whitespace is ignored, and case does not matter.
|
|
The key words
|
|
<literal>TRUE</literal> and <literal>FALSE</literal> are the preferred
|
|
(<acronym>SQL</acronym>-compliant) usage.
|
|
</para>
|
|
|
|
<para>
|
|
<xref linkend="datatype-boolean-example"> shows that
|
|
<type>boolean</type> values are output using the letters
|
|
<literal>t</literal> and <literal>f</literal>.
|
|
</para>
|
|
|
|
<example id="datatype-boolean-example">
|
|
<title>Using the <type>boolean</type> Type</title>
|
|
|
|
<programlisting>
|
|
CREATE TABLE test1 (a boolean, b text);
|
|
INSERT INTO test1 VALUES (TRUE, 'sic est');
|
|
INSERT INTO test1 VALUES (FALSE, 'non est');
|
|
SELECT * FROM test1;
|
|
a | b
|
|
---+---------
|
|
t | sic est
|
|
f | non est
|
|
|
|
SELECT * FROM test1 WHERE a;
|
|
a | b
|
|
---+---------
|
|
t | sic est
|
|
</programlisting>
|
|
</example>
|
|
</sect1>
|
|
|
|
<sect1 id="datatype-enum">
|
|
<title>Enumerated Types</title>
|
|
|
|
<indexterm zone="datatype-enum">
|
|
<primary>data type</primary>
|
|
<secondary>enumerated (enum)</secondary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-enum">
|
|
<primary>enumerated types</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
Enumerated (enum) types are data types that
|
|
comprise a static, ordered set of values.
|
|
They are equivalent to the <type>enum</type>
|
|
types supported in a number of programming languages. An example of an enum
|
|
type might be the days of the week, or a set of status values for
|
|
a piece of data.
|
|
</para>
|
|
|
|
<sect2>
|
|
<title>Declaration of Enumerated Types</title>
|
|
|
|
<para>
|
|
Enum types are created using the <xref
|
|
linkend="sql-createtype"> command,
|
|
for example:
|
|
|
|
<programlisting>
|
|
CREATE TYPE mood AS ENUM ('sad', 'ok', 'happy');
|
|
</programlisting>
|
|
|
|
Once created, the enum type can be used in table and function
|
|
definitions much like any other type:
|
|
<programlisting>
|
|
CREATE TYPE mood AS ENUM ('sad', 'ok', 'happy');
|
|
CREATE TABLE person (
|
|
name text,
|
|
current_mood mood
|
|
);
|
|
INSERT INTO person VALUES ('Moe', 'happy');
|
|
SELECT * FROM person WHERE current_mood = 'happy';
|
|
name | current_mood
|
|
------+--------------
|
|
Moe | happy
|
|
(1 row)
|
|
</programlisting>
|
|
</para>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>Ordering</title>
|
|
|
|
<para>
|
|
The ordering of the values in an enum type is the
|
|
order in which the values were listed when the type was created.
|
|
All standard comparison operators and related
|
|
aggregate functions are supported for enums. For example:
|
|
|
|
<programlisting>
|
|
INSERT INTO person VALUES ('Larry', 'sad');
|
|
INSERT INTO person VALUES ('Curly', 'ok');
|
|
SELECT * FROM person WHERE current_mood > 'sad';
|
|
name | current_mood
|
|
-------+--------------
|
|
Moe | happy
|
|
Curly | ok
|
|
(2 rows)
|
|
|
|
SELECT * FROM person WHERE current_mood > 'sad' ORDER BY current_mood;
|
|
name | current_mood
|
|
-------+--------------
|
|
Curly | ok
|
|
Moe | happy
|
|
(2 rows)
|
|
|
|
SELECT name
|
|
FROM person
|
|
WHERE current_mood = (SELECT MIN(current_mood) FROM person);
|
|
name
|
|
-------
|
|
Larry
|
|
(1 row)
|
|
</programlisting>
|
|
</para>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>Type Safety</title>
|
|
|
|
<para>
|
|
Each enumerated data type is separate and cannot
|
|
be compared with other enumerated types. See this example:
|
|
|
|
<programlisting>
|
|
CREATE TYPE happiness AS ENUM ('happy', 'very happy', 'ecstatic');
|
|
CREATE TABLE holidays (
|
|
num_weeks integer,
|
|
happiness happiness
|
|
);
|
|
INSERT INTO holidays(num_weeks,happiness) VALUES (4, 'happy');
|
|
INSERT INTO holidays(num_weeks,happiness) VALUES (6, 'very happy');
|
|
INSERT INTO holidays(num_weeks,happiness) VALUES (8, 'ecstatic');
|
|
INSERT INTO holidays(num_weeks,happiness) VALUES (2, 'sad');
|
|
ERROR: invalid input value for enum happiness: "sad"
|
|
SELECT person.name, holidays.num_weeks FROM person, holidays
|
|
WHERE person.current_mood = holidays.happiness;
|
|
ERROR: operator does not exist: mood = happiness
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
If you really need to do something like that, you can either
|
|
write a custom operator or add explicit casts to your query:
|
|
|
|
<programlisting>
|
|
SELECT person.name, holidays.num_weeks FROM person, holidays
|
|
WHERE person.current_mood::text = holidays.happiness::text;
|
|
name | num_weeks
|
|
------+-----------
|
|
Moe | 4
|
|
(1 row)
|
|
|
|
</programlisting>
|
|
</para>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>Implementation Details</title>
|
|
|
|
<para>
|
|
An enum value occupies four bytes on disk. The length of an enum
|
|
value's textual label is limited by the <symbol>NAMEDATALEN</symbol>
|
|
setting compiled into <productname>PostgreSQL</productname>; in standard
|
|
builds this means at most 63 bytes.
|
|
</para>
|
|
|
|
<para>
|
|
Enum labels are case sensitive, so
|
|
<type>'happy'</type> is not the same as <type>'HAPPY'</type>.
|
|
White space in the labels is significant too.
|
|
</para>
|
|
|
|
<para>
|
|
The translations from internal enum values to textual labels are
|
|
kept in the system catalog
|
|
<link linkend="catalog-pg-enum"><structname>pg_enum</structname></link>.
|
|
Querying this catalog directly can be useful.
|
|
</para>
|
|
|
|
</sect2>
|
|
</sect1>
|
|
|
|
<sect1 id="datatype-geometric">
|
|
<title>Geometric Types</title>
|
|
|
|
<para>
|
|
Geometric data types represent two-dimensional spatial
|
|
objects. <xref linkend="datatype-geo-table"> shows the geometric
|
|
types available in <productname>PostgreSQL</productname>.
|
|
</para>
|
|
|
|
<table id="datatype-geo-table">
|
|
<title>Geometric Types</title>
|
|
<tgroup cols="4">
|
|
<thead>
|
|
<row>
|
|
<entry>Name</entry>
|
|
<entry>Storage Size</entry>
|
|
<entry>Description</entry>
|
|
<entry>Representation</entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry><type>point</type></entry>
|
|
<entry>16 bytes</entry>
|
|
<entry>Point on a plane</entry>
|
|
<entry>(x,y)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><type>line</type></entry>
|
|
<entry>32 bytes</entry>
|
|
<entry>Infinite line</entry>
|
|
<entry>{A,B,C}</entry>
|
|
</row>
|
|
<row>
|
|
<entry><type>lseg</type></entry>
|
|
<entry>32 bytes</entry>
|
|
<entry>Finite line segment</entry>
|
|
<entry>((x1,y1),(x2,y2))</entry>
|
|
</row>
|
|
<row>
|
|
<entry><type>box</type></entry>
|
|
<entry>32 bytes</entry>
|
|
<entry>Rectangular box</entry>
|
|
<entry>((x1,y1),(x2,y2))</entry>
|
|
</row>
|
|
<row>
|
|
<entry><type>path</type></entry>
|
|
<entry>16+16n bytes</entry>
|
|
<entry>Closed path (similar to polygon)</entry>
|
|
<entry>((x1,y1),...)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><type>path</type></entry>
|
|
<entry>16+16n bytes</entry>
|
|
<entry>Open path</entry>
|
|
<entry>[(x1,y1),...]</entry>
|
|
</row>
|
|
<row>
|
|
<entry><type>polygon</type></entry>
|
|
<entry>40+16n bytes</entry>
|
|
<entry>Polygon (similar to closed path)</entry>
|
|
<entry>((x1,y1),...)</entry>
|
|
</row>
|
|
<row>
|
|
<entry><type>circle</type></entry>
|
|
<entry>24 bytes</entry>
|
|
<entry>Circle</entry>
|
|
<entry><(x,y),r> (center point and radius)</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
A rich set of functions and operators is available to perform various geometric
|
|
operations such as scaling, translation, rotation, and determining
|
|
intersections. They are explained in <xref linkend="functions-geometry">.
|
|
</para>
|
|
|
|
<sect2>
|
|
<title>Points</title>
|
|
|
|
<indexterm>
|
|
<primary>point</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
Points are the fundamental two-dimensional building block for geometric
|
|
types. Values of type <type>point</type> are specified using either of
|
|
the following syntaxes:
|
|
|
|
<synopsis>
|
|
( <replaceable>x</replaceable> , <replaceable>y</replaceable> )
|
|
<replaceable>x</replaceable> , <replaceable>y</replaceable>
|
|
</synopsis>
|
|
|
|
where <replaceable>x</> and <replaceable>y</> are the respective
|
|
coordinates, as floating-point numbers.
|
|
</para>
|
|
|
|
<para>
|
|
Points are output using the first syntax.
|
|
</para>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>Lines</title>
|
|
|
|
<indexterm>
|
|
<primary>line</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
Lines (<type>line</type>) are represented by the linear equation Ax + By
|
|
+ C = 0, where A and B are not both zero. Values of
|
|
type <type>line</type> is input and output in the following form:
|
|
<synopsis>
|
|
{ <replaceable>A</replaceable>, <replaceable>B</replaceable>, <replaceable>C</replaceable> }
|
|
</synopsis>
|
|
|
|
Alternatively, any of the following forms can be used for input:
|
|
|
|
<synopsis>
|
|
[ ( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ( <replaceable>x2</replaceable> , <replaceable>y2</replaceable> ) ]
|
|
( ( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ( <replaceable>x2</replaceable> , <replaceable>y2</replaceable> ) )
|
|
( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ( <replaceable>x2</replaceable> , <replaceable>y2</replaceable> )
|
|
<replaceable>x1</replaceable> , <replaceable>y1</replaceable> , <replaceable>x2</replaceable> , <replaceable>y2</replaceable>
|
|
</synopsis>
|
|
|
|
where
|
|
<literal>(<replaceable>x1</replaceable>,<replaceable>y1</replaceable>)</literal>
|
|
and
|
|
<literal>(<replaceable>x2</replaceable>,<replaceable>y2</replaceable>)</literal>
|
|
are two (different) points on the line.
|
|
</para>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>Line Segments</title>
|
|
|
|
<indexterm>
|
|
<primary>lseg</primary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>line segment</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
Line segments (<type>lseg</type>) are represented by pairs of points.
|
|
Values of type <type>lseg</type> are specified using any of the following
|
|
syntaxes:
|
|
|
|
<synopsis>
|
|
[ ( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ( <replaceable>x2</replaceable> , <replaceable>y2</replaceable> ) ]
|
|
( ( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ( <replaceable>x2</replaceable> , <replaceable>y2</replaceable> ) )
|
|
( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ( <replaceable>x2</replaceable> , <replaceable>y2</replaceable> )
|
|
<replaceable>x1</replaceable> , <replaceable>y1</replaceable> , <replaceable>x2</replaceable> , <replaceable>y2</replaceable>
|
|
</synopsis>
|
|
|
|
where
|
|
<literal>(<replaceable>x1</replaceable>,<replaceable>y1</replaceable>)</literal>
|
|
and
|
|
<literal>(<replaceable>x2</replaceable>,<replaceable>y2</replaceable>)</literal>
|
|
are the end points of the line segment.
|
|
</para>
|
|
|
|
<para>
|
|
Line segments are output using the first syntax.
|
|
</para>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>Boxes</title>
|
|
|
|
<indexterm>
|
|
<primary>box (data type)</primary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>rectangle</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
Boxes are represented by pairs of points that are opposite
|
|
corners of the box.
|
|
Values of type <type>box</type> are specified using any of the following
|
|
syntaxes:
|
|
|
|
<synopsis>
|
|
( ( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ( <replaceable>x2</replaceable> , <replaceable>y2</replaceable> ) )
|
|
( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ( <replaceable>x2</replaceable> , <replaceable>y2</replaceable> )
|
|
<replaceable>x1</replaceable> , <replaceable>y1</replaceable> , <replaceable>x2</replaceable> , <replaceable>y2</replaceable>
|
|
</synopsis>
|
|
|
|
where
|
|
<literal>(<replaceable>x1</replaceable>,<replaceable>y1</replaceable>)</literal>
|
|
and
|
|
<literal>(<replaceable>x2</replaceable>,<replaceable>y2</replaceable>)</literal>
|
|
are any two opposite corners of the box.
|
|
</para>
|
|
|
|
<para>
|
|
Boxes are output using the second syntax.
|
|
</para>
|
|
|
|
<para>
|
|
Any two opposite corners can be supplied on input, but the values
|
|
will be reordered as needed to store the
|
|
upper right and lower left corners, in that order.
|
|
</para>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>Paths</title>
|
|
|
|
<indexterm>
|
|
<primary>path (data type)</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
Paths are represented by lists of connected points. Paths can be
|
|
<firstterm>open</firstterm>, where
|
|
the first and last points in the list are considered not connected, or
|
|
<firstterm>closed</firstterm>,
|
|
where the first and last points are considered connected.
|
|
</para>
|
|
|
|
<para>
|
|
Values of type <type>path</type> are specified using any of the following
|
|
syntaxes:
|
|
|
|
<synopsis>
|
|
[ ( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ... , ( <replaceable>xn</replaceable> , <replaceable>yn</replaceable> ) ]
|
|
( ( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ... , ( <replaceable>xn</replaceable> , <replaceable>yn</replaceable> ) )
|
|
( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ... , ( <replaceable>xn</replaceable> , <replaceable>yn</replaceable> )
|
|
( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> , ... , <replaceable>xn</replaceable> , <replaceable>yn</replaceable> )
|
|
<replaceable>x1</replaceable> , <replaceable>y1</replaceable> , ... , <replaceable>xn</replaceable> , <replaceable>yn</replaceable>
|
|
</synopsis>
|
|
|
|
where the points are the end points of the line segments
|
|
comprising the path. Square brackets (<literal>[]</>) indicate
|
|
an open path, while parentheses (<literal>()</>) indicate a
|
|
closed path. When the outermost parentheses are omitted, as
|
|
in the third through fifth syntaxes, a closed path is assumed.
|
|
</para>
|
|
|
|
<para>
|
|
Paths are output using the first or second syntax, as appropriate.
|
|
</para>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>Polygons</title>
|
|
|
|
<indexterm>
|
|
<primary>polygon</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
Polygons are represented by lists of points (the vertexes of the
|
|
polygon). Polygons are very similar to closed paths, but are
|
|
stored differently and have their own set of support routines.
|
|
</para>
|
|
|
|
<para>
|
|
Values of type <type>polygon</type> are specified using any of the
|
|
following syntaxes:
|
|
|
|
<synopsis>
|
|
( ( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ... , ( <replaceable>xn</replaceable> , <replaceable>yn</replaceable> ) )
|
|
( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ... , ( <replaceable>xn</replaceable> , <replaceable>yn</replaceable> )
|
|
( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> , ... , <replaceable>xn</replaceable> , <replaceable>yn</replaceable> )
|
|
<replaceable>x1</replaceable> , <replaceable>y1</replaceable> , ... , <replaceable>xn</replaceable> , <replaceable>yn</replaceable>
|
|
</synopsis>
|
|
|
|
where the points are the end points of the line segments
|
|
comprising the boundary of the polygon.
|
|
</para>
|
|
|
|
<para>
|
|
Polygons are output using the first syntax.
|
|
</para>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>Circles</title>
|
|
|
|
<indexterm>
|
|
<primary>circle</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
Circles are represented by a center point and radius.
|
|
Values of type <type>circle</type> are specified using any of the
|
|
following syntaxes:
|
|
|
|
<synopsis>
|
|
< ( <replaceable>x</replaceable> , <replaceable>y</replaceable> ) , <replaceable>r</replaceable> >
|
|
( ( <replaceable>x</replaceable> , <replaceable>y</replaceable> ) , <replaceable>r</replaceable> )
|
|
( <replaceable>x</replaceable> , <replaceable>y</replaceable> ) , <replaceable>r</replaceable>
|
|
<replaceable>x</replaceable> , <replaceable>y</replaceable> , <replaceable>r</replaceable>
|
|
</synopsis>
|
|
|
|
where
|
|
<literal>(<replaceable>x</replaceable>,<replaceable>y</replaceable>)</>
|
|
is the center point and <replaceable>r</replaceable> is the radius of the
|
|
circle.
|
|
</para>
|
|
|
|
<para>
|
|
Circles are output using the first syntax.
|
|
</para>
|
|
</sect2>
|
|
|
|
</sect1>
|
|
|
|
<sect1 id="datatype-net-types">
|
|
<title>Network Address Types</title>
|
|
|
|
<indexterm zone="datatype-net-types">
|
|
<primary>network</primary>
|
|
<secondary>data types</secondary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
<productname>PostgreSQL</> offers data types to store IPv4, IPv6, and MAC
|
|
addresses, as shown in <xref linkend="datatype-net-types-table">. It
|
|
is better to use these types instead of plain text types to store
|
|
network addresses, because
|
|
these types offer input error checking and specialized
|
|
operators and functions (see <xref linkend="functions-net">).
|
|
</para>
|
|
|
|
<table tocentry="1" id="datatype-net-types-table">
|
|
<title>Network Address Types</title>
|
|
<tgroup cols="3">
|
|
<thead>
|
|
<row>
|
|
<entry>Name</entry>
|
|
<entry>Storage Size</entry>
|
|
<entry>Description</entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
|
|
<row>
|
|
<entry><type>cidr</type></entry>
|
|
<entry>7 or 19 bytes</entry>
|
|
<entry>IPv4 and IPv6 networks</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><type>inet</type></entry>
|
|
<entry>7 or 19 bytes</entry>
|
|
<entry>IPv4 and IPv6 hosts and networks</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><type>macaddr</type></entry>
|
|
<entry>6 bytes</entry>
|
|
<entry>MAC addresses</entry>
|
|
</row>
|
|
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
When sorting <type>inet</type> or <type>cidr</type> data types,
|
|
IPv4 addresses will always sort before IPv6 addresses, including
|
|
IPv4 addresses encapsulated or mapped to IPv6 addresses, such as
|
|
::10.2.3.4 or ::ffff:10.4.3.2.
|
|
</para>
|
|
|
|
|
|
<sect2 id="datatype-inet">
|
|
<title><type>inet</type></title>
|
|
|
|
<indexterm>
|
|
<primary>inet (data type)</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
The <type>inet</type> type holds an IPv4 or IPv6 host address, and
|
|
optionally its subnet, all in one field.
|
|
The subnet is represented by the number of network address bits
|
|
present in the host address (the
|
|
<quote>netmask</quote>). If the netmask is 32 and the address is IPv4,
|
|
then the value does not indicate a subnet, only a single host.
|
|
In IPv6, the address length is 128 bits, so 128 bits specify a
|
|
unique host address. Note that if you
|
|
want to accept only networks, you should use the
|
|
<type>cidr</type> type rather than <type>inet</type>.
|
|
</para>
|
|
|
|
<para>
|
|
The input format for this type is
|
|
<replaceable class="parameter">address/y</replaceable>
|
|
where
|
|
<replaceable class="parameter">address</replaceable>
|
|
is an IPv4 or IPv6 address and
|
|
<replaceable class="parameter">y</replaceable>
|
|
is the number of bits in the netmask. If the
|
|
<replaceable class="parameter">/y</replaceable>
|
|
portion is missing, the
|
|
netmask is 32 for IPv4 and 128 for IPv6, so the value represents
|
|
just a single host. On display, the
|
|
<replaceable class="parameter">/y</replaceable>
|
|
portion is suppressed if the netmask specifies a single host.
|
|
</para>
|
|
</sect2>
|
|
|
|
<sect2 id="datatype-cidr">
|
|
<title><type>cidr</></title>
|
|
|
|
<indexterm>
|
|
<primary>cidr</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
The <type>cidr</type> type holds an IPv4 or IPv6 network specification.
|
|
Input and output formats follow Classless Internet Domain Routing
|
|
conventions.
|
|
The format for specifying networks is <replaceable
|
|
class="parameter">address/y</> where <replaceable
|
|
class="parameter">address</> is the network represented as an
|
|
IPv4 or IPv6 address, and <replaceable
|
|
class="parameter">y</> is the number of bits in the netmask. If
|
|
<replaceable class="parameter">y</> is omitted, it is calculated
|
|
using assumptions from the older classful network numbering system, except
|
|
it will be at least large enough to include all of the octets
|
|
written in the input. It is an error to specify a network address
|
|
that has bits set to the right of the specified netmask.
|
|
</para>
|
|
|
|
<para>
|
|
<xref linkend="datatype-net-cidr-table"> shows some examples.
|
|
</para>
|
|
|
|
<table id="datatype-net-cidr-table">
|
|
<title><type>cidr</> Type Input Examples</title>
|
|
<tgroup cols="3">
|
|
<thead>
|
|
<row>
|
|
<entry><type>cidr</type> Input</entry>
|
|
<entry><type>cidr</type> Output</entry>
|
|
<entry><literal><function>abbrev(<type>cidr</type>)</function></literal></entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry>192.168.100.128/25</entry>
|
|
<entry>192.168.100.128/25</entry>
|
|
<entry>192.168.100.128/25</entry>
|
|
</row>
|
|
<row>
|
|
<entry>192.168/24</entry>
|
|
<entry>192.168.0.0/24</entry>
|
|
<entry>192.168.0/24</entry>
|
|
</row>
|
|
<row>
|
|
<entry>192.168/25</entry>
|
|
<entry>192.168.0.0/25</entry>
|
|
<entry>192.168.0.0/25</entry>
|
|
</row>
|
|
<row>
|
|
<entry>192.168.1</entry>
|
|
<entry>192.168.1.0/24</entry>
|
|
<entry>192.168.1/24</entry>
|
|
</row>
|
|
<row>
|
|
<entry>192.168</entry>
|
|
<entry>192.168.0.0/24</entry>
|
|
<entry>192.168.0/24</entry>
|
|
</row>
|
|
<row>
|
|
<entry>128.1</entry>
|
|
<entry>128.1.0.0/16</entry>
|
|
<entry>128.1/16</entry>
|
|
</row>
|
|
<row>
|
|
<entry>128</entry>
|
|
<entry>128.0.0.0/16</entry>
|
|
<entry>128.0/16</entry>
|
|
</row>
|
|
<row>
|
|
<entry>128.1.2</entry>
|
|
<entry>128.1.2.0/24</entry>
|
|
<entry>128.1.2/24</entry>
|
|
</row>
|
|
<row>
|
|
<entry>10.1.2</entry>
|
|
<entry>10.1.2.0/24</entry>
|
|
<entry>10.1.2/24</entry>
|
|
</row>
|
|
<row>
|
|
<entry>10.1</entry>
|
|
<entry>10.1.0.0/16</entry>
|
|
<entry>10.1/16</entry>
|
|
</row>
|
|
<row>
|
|
<entry>10</entry>
|
|
<entry>10.0.0.0/8</entry>
|
|
<entry>10/8</entry>
|
|
</row>
|
|
<row>
|
|
<entry>10.1.2.3/32</entry>
|
|
<entry>10.1.2.3/32</entry>
|
|
<entry>10.1.2.3/32</entry>
|
|
</row>
|
|
<row>
|
|
<entry>2001:4f8:3:ba::/64</entry>
|
|
<entry>2001:4f8:3:ba::/64</entry>
|
|
<entry>2001:4f8:3:ba::/64</entry>
|
|
</row>
|
|
<row>
|
|
<entry>2001:4f8:3:ba:2e0:81ff:fe22:d1f1/128</entry>
|
|
<entry>2001:4f8:3:ba:2e0:81ff:fe22:d1f1/128</entry>
|
|
<entry>2001:4f8:3:ba:2e0:81ff:fe22:d1f1</entry>
|
|
</row>
|
|
<row>
|
|
<entry>::ffff:1.2.3.0/120</entry>
|
|
<entry>::ffff:1.2.3.0/120</entry>
|
|
<entry>::ffff:1.2.3/120</entry>
|
|
</row>
|
|
<row>
|
|
<entry>::ffff:1.2.3.0/128</entry>
|
|
<entry>::ffff:1.2.3.0/128</entry>
|
|
<entry>::ffff:1.2.3.0/128</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
</sect2>
|
|
|
|
<sect2 id="datatype-inet-vs-cidr">
|
|
<title><type>inet</type> vs. <type>cidr</type></title>
|
|
|
|
<para>
|
|
The essential difference between <type>inet</type> and <type>cidr</type>
|
|
data types is that <type>inet</type> accepts values with nonzero bits to
|
|
the right of the netmask, whereas <type>cidr</type> does not.
|
|
</para>
|
|
|
|
<tip>
|
|
<para>
|
|
If you do not like the output format for <type>inet</type> or
|
|
<type>cidr</type> values, try the functions <function>host</>,
|
|
<function>text</>, and <function>abbrev</>.
|
|
</para>
|
|
</tip>
|
|
</sect2>
|
|
|
|
<sect2 id="datatype-macaddr">
|
|
<title><type>macaddr</type></title>
|
|
|
|
<indexterm>
|
|
<primary>macaddr (data type)</primary>
|
|
</indexterm>
|
|
|
|
<indexterm>
|
|
<primary>MAC address</primary>
|
|
<see>macaddr</see>
|
|
</indexterm>
|
|
|
|
<para>
|
|
The <type>macaddr</> type stores MAC addresses, known for example
|
|
from Ethernet card hardware addresses (although MAC addresses are
|
|
used for other purposes as well). Input is accepted in the
|
|
following formats:
|
|
|
|
<simplelist>
|
|
<member><literal>'08:00:2b:01:02:03'</></member>
|
|
<member><literal>'08-00-2b-01-02-03'</></member>
|
|
<member><literal>'08002b:010203'</></member>
|
|
<member><literal>'08002b-010203'</></member>
|
|
<member><literal>'0800.2b01.0203'</></member>
|
|
<member><literal>'08002b010203'</></member>
|
|
</simplelist>
|
|
|
|
These examples would all specify the same address. Upper and
|
|
lower case is accepted for the digits
|
|
<literal>a</> through <literal>f</>. Output is always in the
|
|
first of the forms shown.
|
|
</para>
|
|
|
|
<para>
|
|
IEEE Std 802-2001 specifies the second shown form (with hyphens)
|
|
as the canonical form for MAC addresses, and specifies the first
|
|
form (with colons) as the bit-reversed notation, so that
|
|
08-00-2b-01-02-03 = 01:00:4D:08:04:0C. This convention is widely
|
|
ignored nowadays, and it is relevant only for obsolete network
|
|
protocols (such as Token Ring). PostgreSQL makes no provisions
|
|
for bit reversal, and all accepted formats use the canonical LSB
|
|
order.
|
|
</para>
|
|
|
|
<para>
|
|
The remaining four input formats are not part of any standard.
|
|
</para>
|
|
</sect2>
|
|
|
|
</sect1>
|
|
|
|
<sect1 id="datatype-bit">
|
|
<title>Bit String Types</title>
|
|
|
|
<indexterm zone="datatype-bit">
|
|
<primary>bit string</primary>
|
|
<secondary>data type</secondary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
Bit strings are strings of 1's and 0's. They can be used to store
|
|
or visualize bit masks. There are two SQL bit types:
|
|
<type>bit(<replaceable>n</replaceable>)</type> and <type>bit
|
|
varying(<replaceable>n</replaceable>)</type>, where
|
|
<replaceable>n</replaceable> is a positive integer.
|
|
</para>
|
|
|
|
<para>
|
|
<type>bit</type> type data must match the length
|
|
<replaceable>n</replaceable> exactly; it is an error to attempt to
|
|
store shorter or longer bit strings. <type>bit varying</type> data is
|
|
of variable length up to the maximum length
|
|
<replaceable>n</replaceable>; longer strings will be rejected.
|
|
Writing <type>bit</type> without a length is equivalent to
|
|
<literal>bit(1)</literal>, while <type>bit varying</type> without a length
|
|
specification means unlimited length.
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
If one explicitly casts a bit-string value to
|
|
<type>bit(<replaceable>n</>)</type>, it will be truncated or
|
|
zero-padded on the right to be exactly <replaceable>n</> bits,
|
|
without raising an error. Similarly,
|
|
if one explicitly casts a bit-string value to
|
|
<type>bit varying(<replaceable>n</>)</type>, it will be truncated
|
|
on the right if it is more than <replaceable>n</> bits.
|
|
</para>
|
|
</note>
|
|
|
|
<para>
|
|
Refer to <xref
|
|
linkend="sql-syntax-bit-strings"> for information about the syntax
|
|
of bit string constants. Bit-logical operators and string
|
|
manipulation functions are available; see <xref
|
|
linkend="functions-bitstring">.
|
|
</para>
|
|
|
|
<example>
|
|
<title>Using the Bit String Types</title>
|
|
|
|
<programlisting>
|
|
CREATE TABLE test (a BIT(3), b BIT VARYING(5));
|
|
INSERT INTO test VALUES (B'101', B'00');
|
|
INSERT INTO test VALUES (B'10', B'101');
|
|
<computeroutput>
|
|
ERROR: bit string length 2 does not match type bit(3)
|
|
</computeroutput>
|
|
INSERT INTO test VALUES (B'10'::bit(3), B'101');
|
|
SELECT * FROM test;
|
|
<computeroutput>
|
|
a | b
|
|
-----+-----
|
|
101 | 00
|
|
100 | 101
|
|
</computeroutput>
|
|
</programlisting>
|
|
</example>
|
|
|
|
<para>
|
|
A bit string value requires 1 byte for each group of 8 bits, plus
|
|
5 or 8 bytes overhead depending on the length of the string
|
|
(but long values may be compressed or moved out-of-line, as explained
|
|
in <xref linkend="datatype-character"> for character strings).
|
|
</para>
|
|
</sect1>
|
|
|
|
<sect1 id="datatype-textsearch">
|
|
<title>Text Search Types</title>
|
|
|
|
<indexterm zone="datatype-textsearch">
|
|
<primary>full text search</primary>
|
|
<secondary>data types</secondary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-textsearch">
|
|
<primary>text search</primary>
|
|
<secondary>data types</secondary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
<productname>PostgreSQL</productname> provides two data types that
|
|
are designed to support full text search, which is the activity of
|
|
searching through a collection of natural-language <firstterm>documents</>
|
|
to locate those that best match a <firstterm>query</>.
|
|
The <type>tsvector</type> type represents a document in a form optimized
|
|
for text search; the <type>tsquery</type> type similarly represents
|
|
a text query.
|
|
<xref linkend="textsearch"> provides a detailed explanation of this
|
|
facility, and <xref linkend="functions-textsearch"> summarizes the
|
|
related functions and operators.
|
|
</para>
|
|
|
|
<sect2 id="datatype-tsvector">
|
|
<title><type>tsvector</type></title>
|
|
|
|
<indexterm>
|
|
<primary>tsvector (data type)</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
A <type>tsvector</type> value is a sorted list of distinct
|
|
<firstterm>lexemes</>, which are words that have been
|
|
<firstterm>normalized</> to merge different variants of the same word
|
|
(see <xref linkend="textsearch"> for details). Sorting and
|
|
duplicate-elimination are done automatically during input, as shown in
|
|
this example:
|
|
|
|
<programlisting>
|
|
SELECT 'a fat cat sat on a mat and ate a fat rat'::tsvector;
|
|
tsvector
|
|
----------------------------------------------------
|
|
'a' 'and' 'ate' 'cat' 'fat' 'mat' 'on' 'rat' 'sat'
|
|
</programlisting>
|
|
|
|
To represent
|
|
lexemes containing whitespace or punctuation, surround them with quotes:
|
|
|
|
<programlisting>
|
|
SELECT $$the lexeme ' ' contains spaces$$::tsvector;
|
|
tsvector
|
|
-------------------------------------------
|
|
' ' 'contains' 'lexeme' 'spaces' 'the'
|
|
</programlisting>
|
|
|
|
(We use dollar-quoted string literals in this example and the next one
|
|
to avoid the confusion of having to double quote marks within the
|
|
literals.) Embedded quotes and backslashes must be doubled:
|
|
|
|
<programlisting>
|
|
SELECT $$the lexeme 'Joe''s' contains a quote$$::tsvector;
|
|
tsvector
|
|
------------------------------------------------
|
|
'Joe''s' 'a' 'contains' 'lexeme' 'quote' 'the'
|
|
</programlisting>
|
|
|
|
Optionally, integer <firstterm>positions</>
|
|
can be attached to lexemes:
|
|
|
|
<programlisting>
|
|
SELECT 'a:1 fat:2 cat:3 sat:4 on:5 a:6 mat:7 and:8 ate:9 a:10 fat:11 rat:12'::tsvector;
|
|
tsvector
|
|
-------------------------------------------------------------------------------
|
|
'a':1,6,10 'and':8 'ate':9 'cat':3 'fat':2,11 'mat':7 'on':5 'rat':12 'sat':4
|
|
</programlisting>
|
|
|
|
A position normally indicates the source word's location in the
|
|
document. Positional information can be used for
|
|
<firstterm>proximity ranking</firstterm>. Position values can
|
|
range from 1 to 16383; larger numbers are silently set to 16383.
|
|
Duplicate positions for the same lexeme are discarded.
|
|
</para>
|
|
|
|
<para>
|
|
Lexemes that have positions can further be labeled with a
|
|
<firstterm>weight</>, which can be <literal>A</literal>,
|
|
<literal>B</literal>, <literal>C</literal>, or <literal>D</literal>.
|
|
<literal>D</literal> is the default and hence is not shown on output:
|
|
|
|
<programlisting>
|
|
SELECT 'a:1A fat:2B,4C cat:5D'::tsvector;
|
|
tsvector
|
|
----------------------------
|
|
'a':1A 'cat':5 'fat':2B,4C
|
|
</programlisting>
|
|
|
|
Weights are typically used to reflect document structure, for example
|
|
by marking title words differently from body words. Text search
|
|
ranking functions can assign different priorities to the different
|
|
weight markers.
|
|
</para>
|
|
|
|
<para>
|
|
It is important to understand that the
|
|
<type>tsvector</type> type itself does not perform any normalization;
|
|
it assumes the words it is given are normalized appropriately
|
|
for the application. For example,
|
|
|
|
<programlisting>
|
|
select 'The Fat Rats'::tsvector;
|
|
tsvector
|
|
--------------------
|
|
'Fat' 'Rats' 'The'
|
|
</programlisting>
|
|
|
|
For most English-text-searching applications the above words would
|
|
be considered non-normalized, but <type>tsvector</type> doesn't care.
|
|
Raw document text should usually be passed through
|
|
<function>to_tsvector</> to normalize the words appropriately
|
|
for searching:
|
|
|
|
<programlisting>
|
|
SELECT to_tsvector('english', 'The Fat Rats');
|
|
to_tsvector
|
|
-----------------
|
|
'fat':2 'rat':3
|
|
</programlisting>
|
|
|
|
Again, see <xref linkend="textsearch"> for more detail.
|
|
</para>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="datatype-tsquery">
|
|
<title><type>tsquery</type></title>
|
|
|
|
<indexterm>
|
|
<primary>tsquery (data type)</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
A <type>tsquery</type> value stores lexemes that are to be
|
|
searched for, and combines them honoring the Boolean operators
|
|
<literal>&</literal> (AND), <literal>|</literal> (OR), and
|
|
<literal>!</> (NOT). Parentheses can be used to enforce grouping
|
|
of the operators:
|
|
|
|
<programlisting>
|
|
SELECT 'fat & rat'::tsquery;
|
|
tsquery
|
|
---------------
|
|
'fat' & 'rat'
|
|
|
|
SELECT 'fat & (rat | cat)'::tsquery;
|
|
tsquery
|
|
---------------------------
|
|
'fat' & ( 'rat' | 'cat' )
|
|
|
|
SELECT 'fat & rat & ! cat'::tsquery;
|
|
tsquery
|
|
------------------------
|
|
'fat' & 'rat' & !'cat'
|
|
</programlisting>
|
|
|
|
In the absence of parentheses, <literal>!</> (NOT) binds most tightly,
|
|
and <literal>&</literal> (AND) binds more tightly than
|
|
<literal>|</literal> (OR).
|
|
</para>
|
|
|
|
<para>
|
|
Optionally, lexemes in a <type>tsquery</type> can be labeled with
|
|
one or more weight letters, which restricts them to match only
|
|
<type>tsvector</> lexemes with matching weights:
|
|
|
|
<programlisting>
|
|
SELECT 'fat:ab & cat'::tsquery;
|
|
tsquery
|
|
------------------
|
|
'fat':AB & 'cat'
|
|
</programlisting>
|
|
</para>
|
|
|
|
<para>
|
|
Also, lexemes in a <type>tsquery</type> can be labeled with <literal>*</>
|
|
to specify prefix matching:
|
|
<programlisting>
|
|
SELECT 'super:*'::tsquery;
|
|
tsquery
|
|
-----------
|
|
'super':*
|
|
</programlisting>
|
|
This query will match any word in a <type>tsvector</> that begins
|
|
with <quote>super</>. Note that prefixes are first processed by
|
|
text search configurations, which means this comparison returns
|
|
true:
|
|
<programlisting>
|
|
SELECT to_tsvector( 'postgraduate' ) @@ to_tsquery( 'postgres:*' );
|
|
?column?
|
|
----------
|
|
t
|
|
(1 row)
|
|
</programlisting>
|
|
because <literal>postgres</> gets stemmed to <literal>postgr</>:
|
|
<programlisting>
|
|
SELECT to_tsquery('postgres:*');
|
|
to_tsquery
|
|
------------
|
|
'postgr':*
|
|
(1 row)
|
|
</programlisting>
|
|
which then matches <literal>postgraduate</>.
|
|
</para>
|
|
|
|
<para>
|
|
Quoting rules for lexemes are the same as described previously for
|
|
lexemes in <type>tsvector</>; and, as with <type>tsvector</>,
|
|
any required normalization of words must be done before converting
|
|
to the <type>tsquery</> type. The <function>to_tsquery</>
|
|
function is convenient for performing such normalization:
|
|
|
|
<programlisting>
|
|
SELECT to_tsquery('Fat:ab & Cats');
|
|
to_tsquery
|
|
------------------
|
|
'fat':AB & 'cat'
|
|
</programlisting>
|
|
</para>
|
|
|
|
</sect2>
|
|
|
|
</sect1>
|
|
|
|
<sect1 id="datatype-uuid">
|
|
<title><acronym>UUID</acronym> Type</title>
|
|
|
|
<indexterm zone="datatype-uuid">
|
|
<primary>UUID</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
The data type <type>uuid</type> stores Universally Unique Identifiers
|
|
(UUID) as defined by RFC 4122, ISO/IEC 9834-8:2005, and related standards.
|
|
(Some systems refer to this data type as a globally unique identifier, or
|
|
GUID,<indexterm><primary>GUID</primary></indexterm> instead.) This
|
|
identifier is a 128-bit quantity that is generated by an algorithm chosen
|
|
to make it very unlikely that the same identifier will be generated by
|
|
anyone else in the known universe using the same algorithm. Therefore,
|
|
for distributed systems, these identifiers provide a better uniqueness
|
|
guarantee than sequence generators, which
|
|
are only unique within a single database.
|
|
</para>
|
|
|
|
<para>
|
|
A UUID is written as a sequence of lower-case hexadecimal digits,
|
|
in several groups separated by hyphens, specifically a group of 8
|
|
digits followed by three groups of 4 digits followed by a group of
|
|
12 digits, for a total of 32 digits representing the 128 bits. An
|
|
example of a UUID in this standard form is:
|
|
<programlisting>
|
|
a0eebc99-9c0b-4ef8-bb6d-6bb9bd380a11
|
|
</programlisting>
|
|
<productname>PostgreSQL</productname> also accepts the following
|
|
alternative forms for input:
|
|
use of upper-case digits, the standard format surrounded by
|
|
braces, omitting some or all hyphens, adding a hyphen after any
|
|
group of four digits. Examples are:
|
|
<programlisting>
|
|
A0EEBC99-9C0B-4EF8-BB6D-6BB9BD380A11
|
|
{a0eebc99-9c0b-4ef8-bb6d-6bb9bd380a11}
|
|
a0eebc999c0b4ef8bb6d6bb9bd380a11
|
|
a0ee-bc99-9c0b-4ef8-bb6d-6bb9-bd38-0a11
|
|
{a0eebc99-9c0b4ef8-bb6d6bb9-bd380a11}
|
|
</programlisting>
|
|
Output is always in the standard form.
|
|
</para>
|
|
|
|
<para>
|
|
<productname>PostgreSQL</productname> provides storage and comparison
|
|
functions for UUIDs, but the core database does not include any
|
|
function for generating UUIDs, because no single algorithm is well
|
|
suited for every application. The <xref
|
|
linkend="uuid-ossp"> module
|
|
provides functions that implement several standard algorithms.
|
|
The <xref linkend="pgcrypto"> module also provides a generation
|
|
function for random UUIDs.
|
|
Alternatively, UUIDs could be generated by client applications or
|
|
other libraries invoked through a server-side function.
|
|
</para>
|
|
</sect1>
|
|
|
|
<sect1 id="datatype-xml">
|
|
<title><acronym>XML</> Type</title>
|
|
|
|
<indexterm zone="datatype-xml">
|
|
<primary>XML</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
The <type>xml</type> data type can be used to store XML data. Its
|
|
advantage over storing XML data in a <type>text</type> field is that it
|
|
checks the input values for well-formedness, and there are support
|
|
functions to perform type-safe operations on it; see <xref
|
|
linkend="functions-xml">. Use of this data type requires the
|
|
installation to have been built with <command>configure
|
|
--with-libxml</>.
|
|
</para>
|
|
|
|
<para>
|
|
The <type>xml</type> type can store well-formed
|
|
<quote>documents</quote>, as defined by the XML standard, as well
|
|
as <quote>content</quote> fragments, which are defined by the
|
|
production <literal>XMLDecl? content</literal> in the XML
|
|
standard. Roughly, this means that content fragments can have
|
|
more than one top-level element or character node. The expression
|
|
<literal><replaceable>xmlvalue</replaceable> IS DOCUMENT</literal>
|
|
can be used to evaluate whether a particular <type>xml</type>
|
|
value is a full document or only a content fragment.
|
|
</para>
|
|
|
|
<sect2>
|
|
<title>Creating XML Values</title>
|
|
<para>
|
|
To produce a value of type <type>xml</type> from character data,
|
|
use the function
|
|
<function>xmlparse</function>:<indexterm><primary>xmlparse</primary></indexterm>
|
|
<synopsis>
|
|
XMLPARSE ( { DOCUMENT | CONTENT } <replaceable>value</replaceable>)
|
|
</synopsis>
|
|
Examples:
|
|
<programlisting><![CDATA[
|
|
XMLPARSE (DOCUMENT '<?xml version="1.0"?><book><title>Manual</title><chapter>...</chapter></book>')
|
|
XMLPARSE (CONTENT 'abc<foo>bar</foo><bar>foo</bar>')
|
|
]]></programlisting>
|
|
While this is the only way to convert character strings into XML
|
|
values according to the SQL standard, the PostgreSQL-specific
|
|
syntaxes:
|
|
<programlisting><![CDATA[
|
|
xml '<foo>bar</foo>'
|
|
'<foo>bar</foo>'::xml
|
|
]]></programlisting>
|
|
can also be used.
|
|
</para>
|
|
|
|
<para>
|
|
The <type>xml</type> type does not validate input values
|
|
against a document type declaration
|
|
(DTD),<indexterm><primary>DTD</primary></indexterm>
|
|
even when the input value specifies a DTD.
|
|
There is also currently no built-in support for validating against
|
|
other XML schema languages such as XML Schema.
|
|
</para>
|
|
|
|
<para>
|
|
The inverse operation, producing a character string value from
|
|
<type>xml</type>, uses the function
|
|
<function>xmlserialize</function>:<indexterm><primary>xmlserialize</primary></indexterm>
|
|
<synopsis>
|
|
XMLSERIALIZE ( { DOCUMENT | CONTENT } <replaceable>value</replaceable> AS <replaceable>type</replaceable> )
|
|
</synopsis>
|
|
<replaceable>type</replaceable> can be
|
|
<type>character</type>, <type>character varying</type>, or
|
|
<type>text</type> (or an alias for one of those). Again, according
|
|
to the SQL standard, this is the only way to convert between type
|
|
<type>xml</type> and character types, but PostgreSQL also allows
|
|
you to simply cast the value.
|
|
</para>
|
|
|
|
<para>
|
|
When a character string value is cast to or from type
|
|
<type>xml</type> without going through <type>XMLPARSE</type> or
|
|
<type>XMLSERIALIZE</type>, respectively, the choice of
|
|
<literal>DOCUMENT</literal> versus <literal>CONTENT</literal> is
|
|
determined by the <quote>XML option</quote>
|
|
<indexterm><primary>XML option</primary></indexterm>
|
|
session configuration parameter, which can be set using the
|
|
standard command:
|
|
<synopsis>
|
|
SET XML OPTION { DOCUMENT | CONTENT };
|
|
</synopsis>
|
|
or the more PostgreSQL-like syntax
|
|
<synopsis>
|
|
SET xmloption TO { DOCUMENT | CONTENT };
|
|
</synopsis>
|
|
The default is <literal>CONTENT</literal>, so all forms of XML
|
|
data are allowed.
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
With the default XML option setting, you cannot directly cast
|
|
character strings to type <type>xml</type> if they contain a
|
|
document type declaration, because the definition of XML content
|
|
fragment does not accept them. If you need to do that, either
|
|
use <literal>XMLPARSE</literal> or change the XML option.
|
|
</para>
|
|
</note>
|
|
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>Encoding Handling</title>
|
|
<para>
|
|
Care must be taken when dealing with multiple character encodings
|
|
on the client, server, and in the XML data passed through them.
|
|
When using the text mode to pass queries to the server and query
|
|
results to the client (which is the normal mode), PostgreSQL
|
|
converts all character data passed between the client and the
|
|
server and vice versa to the character encoding of the respective
|
|
end; see <xref linkend="multibyte">. This includes string
|
|
representations of XML values, such as in the above examples.
|
|
This would ordinarily mean that encoding declarations contained in
|
|
XML data can become invalid as the character data is converted
|
|
to other encodings while traveling between client and server,
|
|
because the embedded encoding declaration is not changed. To cope
|
|
with this behavior, encoding declarations contained in
|
|
character strings presented for input to the <type>xml</type> type
|
|
are <emphasis>ignored</emphasis>, and content is assumed
|
|
to be in the current server encoding. Consequently, for correct
|
|
processing, character strings of XML data must be sent
|
|
from the client in the current client encoding. It is the
|
|
responsibility of the client to either convert documents to the
|
|
current client encoding before sending them to the server, or to
|
|
adjust the client encoding appropriately. On output, values of
|
|
type <type>xml</type> will not have an encoding declaration, and
|
|
clients should assume all data is in the current client
|
|
encoding.
|
|
</para>
|
|
|
|
<para>
|
|
When using binary mode to pass query parameters to the server
|
|
and query results back to the client, no character set conversion
|
|
is performed, so the situation is different. In this case, an
|
|
encoding declaration in the XML data will be observed, and if it
|
|
is absent, the data will be assumed to be in UTF-8 (as required by
|
|
the XML standard; note that PostgreSQL does not support UTF-16).
|
|
On output, data will have an encoding declaration
|
|
specifying the client encoding, unless the client encoding is
|
|
UTF-8, in which case it will be omitted.
|
|
</para>
|
|
|
|
<para>
|
|
Needless to say, processing XML data with PostgreSQL will be less
|
|
error-prone and more efficient if the XML data encoding, client encoding,
|
|
and server encoding are the same. Since XML data is internally
|
|
processed in UTF-8, computations will be most efficient if the
|
|
server encoding is also UTF-8.
|
|
</para>
|
|
|
|
<caution>
|
|
<para>
|
|
Some XML-related functions may not work at all on non-ASCII data
|
|
when the server encoding is not UTF-8. This is known to be an
|
|
issue for <function>xpath()</> in particular.
|
|
</para>
|
|
</caution>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>Accessing XML Values</title>
|
|
|
|
<para>
|
|
The <type>xml</type> data type is unusual in that it does not
|
|
provide any comparison operators. This is because there is no
|
|
well-defined and universally useful comparison algorithm for XML
|
|
data. One consequence of this is that you cannot retrieve rows by
|
|
comparing an <type>xml</type> column against a search value. XML
|
|
values should therefore typically be accompanied by a separate key
|
|
field such as an ID. An alternative solution for comparing XML
|
|
values is to convert them to character strings first, but note
|
|
that character string comparison has little to do with a useful
|
|
XML comparison method.
|
|
</para>
|
|
|
|
<para>
|
|
Since there are no comparison operators for the <type>xml</type>
|
|
data type, it is not possible to create an index directly on a
|
|
column of this type. If speedy searches in XML data are desired,
|
|
possible workarounds include casting the expression to a
|
|
character string type and indexing that, or indexing an XPath
|
|
expression. Of course, the actual query would have to be adjusted
|
|
to search by the indexed expression.
|
|
</para>
|
|
|
|
<para>
|
|
The text-search functionality in PostgreSQL can also be used to speed
|
|
up full-document searches of XML data. The necessary
|
|
preprocessing support is, however, not yet available in the PostgreSQL
|
|
distribution.
|
|
</para>
|
|
</sect2>
|
|
</sect1>
|
|
|
|
&json;
|
|
|
|
&array;
|
|
|
|
&rowtypes;
|
|
|
|
&rangetypes;
|
|
|
|
<sect1 id="datatype-oid">
|
|
<title>Object Identifier Types</title>
|
|
|
|
<indexterm zone="datatype-oid">
|
|
<primary>object identifier</primary>
|
|
<secondary>data type</secondary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-oid">
|
|
<primary>oid</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-oid">
|
|
<primary>regproc</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-oid">
|
|
<primary>regprocedure</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-oid">
|
|
<primary>regoper</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-oid">
|
|
<primary>regoperator</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-oid">
|
|
<primary>regclass</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-oid">
|
|
<primary>regtype</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-oid">
|
|
<primary>regconfig</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-oid">
|
|
<primary>regdictionary</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-oid">
|
|
<primary>xid</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-oid">
|
|
<primary>cid</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-oid">
|
|
<primary>tid</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
Object identifiers (OIDs) are used internally by
|
|
<productname>PostgreSQL</productname> as primary keys for various
|
|
system tables. OIDs are not added to user-created tables, unless
|
|
<literal>WITH OIDS</literal> is specified when the table is
|
|
created, or the <xref linkend="guc-default-with-oids">
|
|
configuration variable is enabled. Type <type>oid</> represents
|
|
an object identifier. There are also several alias types for
|
|
<type>oid</>: <type>regproc</>, <type>regprocedure</>,
|
|
<type>regoper</>, <type>regoperator</>, <type>regclass</>,
|
|
<type>regtype</>, <type>regconfig</>, and <type>regdictionary</>.
|
|
<xref linkend="datatype-oid-table"> shows an overview.
|
|
</para>
|
|
|
|
<para>
|
|
The <type>oid</> type is currently implemented as an unsigned
|
|
four-byte integer. Therefore, it is not large enough to provide
|
|
database-wide uniqueness in large databases, or even in large
|
|
individual tables. So, using a user-created table's OID column as
|
|
a primary key is discouraged. OIDs are best used only for
|
|
references to system tables.
|
|
</para>
|
|
|
|
<para>
|
|
The <type>oid</> type itself has few operations beyond comparison.
|
|
It can be cast to integer, however, and then manipulated using the
|
|
standard integer operators. (Beware of possible
|
|
signed-versus-unsigned confusion if you do this.)
|
|
</para>
|
|
|
|
<para>
|
|
The OID alias types have no operations of their own except
|
|
for specialized input and output routines. These routines are able
|
|
to accept and display symbolic names for system objects, rather than
|
|
the raw numeric value that type <type>oid</> would use. The alias
|
|
types allow simplified lookup of OID values for objects. For example,
|
|
to examine the <structname>pg_attribute</> rows related to a table
|
|
<literal>mytable</>, one could write:
|
|
<programlisting>
|
|
SELECT * FROM pg_attribute WHERE attrelid = 'mytable'::regclass;
|
|
</programlisting>
|
|
rather than:
|
|
<programlisting>
|
|
SELECT * FROM pg_attribute
|
|
WHERE attrelid = (SELECT oid FROM pg_class WHERE relname = 'mytable');
|
|
</programlisting>
|
|
While that doesn't look all that bad by itself, it's still oversimplified.
|
|
A far more complicated sub-select would be needed to
|
|
select the right OID if there are multiple tables named
|
|
<literal>mytable</> in different schemas.
|
|
The <type>regclass</> input converter handles the table lookup according
|
|
to the schema path setting, and so it does the <quote>right thing</>
|
|
automatically. Similarly, casting a table's OID to
|
|
<type>regclass</> is handy for symbolic display of a numeric OID.
|
|
</para>
|
|
|
|
<table id="datatype-oid-table">
|
|
<title>Object Identifier Types</title>
|
|
<tgroup cols="4">
|
|
<thead>
|
|
<row>
|
|
<entry>Name</entry>
|
|
<entry>References</entry>
|
|
<entry>Description</entry>
|
|
<entry>Value Example</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
|
|
<row>
|
|
<entry><type>oid</></entry>
|
|
<entry>any</entry>
|
|
<entry>numeric object identifier</entry>
|
|
<entry><literal>564182</></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><type>regproc</></entry>
|
|
<entry><structname>pg_proc</></entry>
|
|
<entry>function name</entry>
|
|
<entry><literal>sum</></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><type>regprocedure</></entry>
|
|
<entry><structname>pg_proc</></entry>
|
|
<entry>function with argument types</entry>
|
|
<entry><literal>sum(int4)</></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><type>regoper</></entry>
|
|
<entry><structname>pg_operator</></entry>
|
|
<entry>operator name</entry>
|
|
<entry><literal>+</></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><type>regoperator</></entry>
|
|
<entry><structname>pg_operator</></entry>
|
|
<entry>operator with argument types</entry>
|
|
<entry><literal>*(integer,integer)</> or <literal>-(NONE,integer)</></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><type>regclass</></entry>
|
|
<entry><structname>pg_class</></entry>
|
|
<entry>relation name</entry>
|
|
<entry><literal>pg_type</></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><type>regtype</></entry>
|
|
<entry><structname>pg_type</></entry>
|
|
<entry>data type name</entry>
|
|
<entry><literal>integer</></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><type>regconfig</></entry>
|
|
<entry><structname>pg_ts_config</></entry>
|
|
<entry>text search configuration</entry>
|
|
<entry><literal>english</></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><type>regdictionary</></entry>
|
|
<entry><structname>pg_ts_dict</></entry>
|
|
<entry>text search dictionary</entry>
|
|
<entry><literal>simple</></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
All of the OID alias types accept schema-qualified names, and will
|
|
display schema-qualified names on output if the object would not
|
|
be found in the current search path without being qualified.
|
|
The <type>regproc</> and <type>regoper</> alias types will only
|
|
accept input names that are unique (not overloaded), so they are
|
|
of limited use; for most uses <type>regprocedure</> or
|
|
<type>regoperator</> are more appropriate. For <type>regoperator</>,
|
|
unary operators are identified by writing <literal>NONE</> for the unused
|
|
operand.
|
|
</para>
|
|
|
|
<para>
|
|
An additional property of the OID alias types is the creation of
|
|
dependencies. If a
|
|
constant of one of these types appears in a stored expression
|
|
(such as a column default expression or view), it creates a dependency
|
|
on the referenced object. For example, if a column has a default
|
|
expression <literal>nextval('my_seq'::regclass)</>,
|
|
<productname>PostgreSQL</productname>
|
|
understands that the default expression depends on the sequence
|
|
<literal>my_seq</>; the system will not let the sequence be dropped
|
|
without first removing the default expression.
|
|
</para>
|
|
|
|
<para>
|
|
Another identifier type used by the system is <type>xid</>, or transaction
|
|
(abbreviated <abbrev>xact</>) identifier. This is the data type of the system columns
|
|
<structfield>xmin</> and <structfield>xmax</>. Transaction identifiers are 32-bit quantities.
|
|
</para>
|
|
|
|
<para>
|
|
A third identifier type used by the system is <type>cid</>, or
|
|
command identifier. This is the data type of the system columns
|
|
<structfield>cmin</> and <structfield>cmax</>. Command identifiers are also 32-bit quantities.
|
|
</para>
|
|
|
|
<para>
|
|
A final identifier type used by the system is <type>tid</>, or tuple
|
|
identifier (row identifier). This is the data type of the system column
|
|
<structfield>ctid</>. A tuple ID is a pair
|
|
(block number, tuple index within block) that identifies the
|
|
physical location of the row within its table.
|
|
</para>
|
|
|
|
<para>
|
|
(The system columns are further explained in <xref
|
|
linkend="ddl-system-columns">.)
|
|
</para>
|
|
</sect1>
|
|
|
|
<sect1 id="datatype-pg-lsn">
|
|
<title><acronym>pg_lsn Type</acronym></title>
|
|
|
|
<indexterm zone="datatype-pg-lsn">
|
|
<primary>pg_lsn</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
The <type>pg_lsn</type> data type can be used to store LSN (Log Sequence
|
|
Number) data which is a pointer to a location in the XLOG. This type is a
|
|
representation of XLogRecPtr and an internal system type of
|
|
<productname>PostgreSQL</productname>.
|
|
</para>
|
|
|
|
<para>
|
|
Internally, an LSN is a 64-bit integer, representing a byte position in
|
|
the write-ahead log stream. It is printed as two hexadecimal numbers of
|
|
up to 8 digits each, separated by a slash; for example,
|
|
<literal>16/B374D848</>. The <type>pg_lsn</type> type supports the
|
|
standard comparison operators, like <literal>=</literal> and
|
|
<literal>></literal>. Two LSNs can be subtracted using the
|
|
<literal>-</literal> operator; the result is the number of bytes separating
|
|
those write-ahead log positions.
|
|
</para>
|
|
</sect1>
|
|
|
|
<sect1 id="datatype-pseudo">
|
|
<title>Pseudo-Types</title>
|
|
|
|
<indexterm zone="datatype-pseudo">
|
|
<primary>record</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-pseudo">
|
|
<primary>any</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-pseudo">
|
|
<primary>anyelement</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-pseudo">
|
|
<primary>anyarray</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-pseudo">
|
|
<primary>anynonarray</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-pseudo">
|
|
<primary>anyenum</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-pseudo">
|
|
<primary>anyrange</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-pseudo">
|
|
<primary>void</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-pseudo">
|
|
<primary>trigger</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-pseudo">
|
|
<primary>language_handler</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-pseudo">
|
|
<primary>fdw_handler</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-pseudo">
|
|
<primary>cstring</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-pseudo">
|
|
<primary>internal</primary>
|
|
</indexterm>
|
|
|
|
<indexterm zone="datatype-pseudo">
|
|
<primary>opaque</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
The <productname>PostgreSQL</productname> type system contains a
|
|
number of special-purpose entries that are collectively called
|
|
<firstterm>pseudo-types</>. A pseudo-type cannot be used as a
|
|
column data type, but it can be used to declare a function's
|
|
argument or result type. Each of the available pseudo-types is
|
|
useful in situations where a function's behavior does not
|
|
correspond to simply taking or returning a value of a specific
|
|
<acronym>SQL</acronym> data type. <xref
|
|
linkend="datatype-pseudotypes-table"> lists the existing
|
|
pseudo-types.
|
|
</para>
|
|
|
|
<table id="datatype-pseudotypes-table">
|
|
<title>Pseudo-Types</title>
|
|
<tgroup cols="2">
|
|
<thead>
|
|
<row>
|
|
<entry>Name</entry>
|
|
<entry>Description</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry><type>any</></entry>
|
|
<entry>Indicates that a function accepts any input data type.</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><type>anyelement</></entry>
|
|
<entry>Indicates that a function accepts any data type
|
|
(see <xref linkend="extend-types-polymorphic">).</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><type>anyarray</></entry>
|
|
<entry>Indicates that a function accepts any array data type
|
|
(see <xref linkend="extend-types-polymorphic">).</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><type>anynonarray</></entry>
|
|
<entry>Indicates that a function accepts any non-array data type
|
|
(see <xref linkend="extend-types-polymorphic">).</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><type>anyenum</></entry>
|
|
<entry>Indicates that a function accepts any enum data type
|
|
(see <xref linkend="extend-types-polymorphic"> and
|
|
<xref linkend="datatype-enum">).</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><type>anyrange</></entry>
|
|
<entry>Indicates that a function accepts any range data type
|
|
(see <xref linkend="extend-types-polymorphic"> and
|
|
<xref linkend="rangetypes">).</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><type>cstring</></entry>
|
|
<entry>Indicates that a function accepts or returns a null-terminated C string.</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><type>internal</></entry>
|
|
<entry>Indicates that a function accepts or returns a server-internal
|
|
data type.</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><type>language_handler</></entry>
|
|
<entry>A procedural language call handler is declared to return <type>language_handler</>.</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><type>fdw_handler</></entry>
|
|
<entry>A foreign-data wrapper handler is declared to return <type>fdw_handler</>.</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><type>record</></entry>
|
|
<entry>Identifies a function returning an unspecified row type.</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><type>trigger</></entry>
|
|
<entry>A trigger function is declared to return <type>trigger.</></entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><type>void</></entry>
|
|
<entry>Indicates that a function returns no value.</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><type>opaque</></entry>
|
|
<entry>An obsolete type name that formerly served all the above purposes.</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
Functions coded in C (whether built-in or dynamically loaded) can be
|
|
declared to accept or return any of these pseudo data types. It is up to
|
|
the function author to ensure that the function will behave safely
|
|
when a pseudo-type is used as an argument type.
|
|
</para>
|
|
|
|
<para>
|
|
Functions coded in procedural languages can use pseudo-types only as
|
|
allowed by their implementation languages. At present the procedural
|
|
languages all forbid use of a pseudo-type as argument type, and allow
|
|
only <type>void</> and <type>record</> as a result type (plus
|
|
<type>trigger</> when the function is used as a trigger). Some also
|
|
support polymorphic functions using the types <type>anyelement</>,
|
|
<type>anyarray</>, <type>anynonarray</>, <type>anyenum</>, and
|
|
<type>anyrange</>.
|
|
</para>
|
|
|
|
<para>
|
|
The <type>internal</> pseudo-type is used to declare functions
|
|
that are meant only to be called internally by the database
|
|
system, and not by direct invocation in an <acronym>SQL</acronym>
|
|
query. If a function has at least one <type>internal</>-type
|
|
argument then it cannot be called from <acronym>SQL</acronym>. To
|
|
preserve the type safety of this restriction it is important to
|
|
follow this coding rule: do not create any function that is
|
|
declared to return <type>internal</> unless it has at least one
|
|
<type>internal</> argument.
|
|
</para>
|
|
|
|
</sect1>
|
|
|
|
</chapter>
|