The "random" regression test uses a function called oidrand(), which
takes two parameters, an OID x and an integer y, and returns "true" with probability 1/y (the OID argument is ignored). This can be useful -- for example, it can be used to select a random sampling of the rows in a table (which is what the "random" regression test uses it for). This patch removes that function, because it was old and messy. The old function had the following problems: - it was undocumented - it was poorly named - it was designed to workaround an optimizer bug that no longer exists (the OID argument is to ensure that the optimizer won't optimize away calls to the function; AFAIK marking the function as 'volatile' suffices nowadays) - it used a different random-number generation technique than the other PSRNG-related functions in the backend do (it called random() like they do, but it had its own logic for setting a set and deciding when to reseed the RNG). Ok, this patch removes oidrand(), oidsrand(), and userfntest(), and improves the SGML docs a little bit (un-commenting the setseed() documentation). Neil Conway
This commit is contained in:
Bruce Momjian
parent
8195f8f042
commit
6cb1f4fe44
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@ -1,5 +1,5 @@
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<!--
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$Header: /cvsroot/pgsql/doc/src/sgml/func.sgml,v 1.138 2003/02/06 20:25:31 tgl Exp $
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$Header: /cvsroot/pgsql/doc/src/sgml/func.sgml,v 1.139 2003/02/13 05:24:01 momjian Exp $
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PostgreSQL documentation
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-->
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@ -682,14 +682,15 @@ PostgreSQL documentation
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<entry><literal>round(42.4382, 2)</literal></entry>
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<entry>42.44</entry>
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</row>
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<!--
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<row>
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<entry><function>setseed</function>(<replaceable>new-seed</replaceable>)</entry>
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<entry>set seed for subsequent random() calls</entry>
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<entry><literal>setseed(0.54823)</literal></entry>
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<entry></entry>
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</row>
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-->
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<row>
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<entry><function>setseed</function>(<type>dp</type>)</entry>
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<entry><type>int32</type></entry>
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<entry>set seed for subsequent random() calls</entry>
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<entry><literal>setseed(0.54823)</literal></entry>
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<entry>1177314959</entry>
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</row>
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<row>
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<entry><function>sign</function>(<type>dp</type> or <type>numeric</type>)</entry>
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<entry>(same as input)</entry>
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@ -955,7 +956,8 @@ PostgreSQL documentation
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<entry><function>substring</function>(<parameter>string</parameter> from <replaceable>pattern</replaceable> for <replaceable>escape</replaceable>)</entry>
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<entry><type>text</type></entry>
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<entry>
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Extract substring matching SQL regular expression
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Extract substring matching <acronym>SQL</acronym> regular
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expression
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<indexterm>
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<primary>substring</primary>
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</indexterm>
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@ -1168,7 +1170,7 @@ PostgreSQL documentation
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<entry><type>text</type></entry>
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<entry>
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Return the given string suitably quoted to be used as an identifier
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in an SQL query string.
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in an <acronym>SQL</acronym> query string.
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Quotes are added only if necessary (i.e., if the string contains
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non-identifier characters or would be case-folded).
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Embedded quotes are properly doubled.
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@ -1182,7 +1184,7 @@ PostgreSQL documentation
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<entry><type>text</type></entry>
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<entry>
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Return the given string suitably quoted to be used as a literal
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in an SQL query string.
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in an <acronym>SQL</acronym> query string.
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Embedded quotes and backslashes are properly doubled.
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</entry>
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<entry><literal>quote_literal('O\'Reilly')</literal></entry>
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@ -2511,14 +2513,15 @@ PostgreSQL documentation
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<function>SUBSTRING(<parameter>string</parameter> FROM
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<replaceable>pattern</replaceable> FOR
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<replaceable>escape</replaceable>)</function>, provides
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extraction of a substring that matches a SQL99 regular expression
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pattern. As with <literal>SIMILAR TO</>, the specified pattern
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must match to the entire data string, else the function fails and
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returns null. To indicate the part of the pattern that should be
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returned on success, SQL99 specifies that the pattern must
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contain two occurrences of the escape character followed by
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double quote (<literal>"</>). The text matching the portion of
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the pattern between these markers is returned.
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extraction of a substring that matches a <acronym>SQL99</acronym>
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regular expression pattern. As with <literal>SIMILAR TO</>, the
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specified pattern must match to the entire data string, else the
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function fails and returns null. To indicate the part of the
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pattern that should be returned on success,
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<acronym>SQL99</acronym> specifies that the pattern must contain
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two occurrences of the escape character followed by double quote
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(<literal>"</>). The text matching the portion of the pattern
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between these markers is returned.
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</para>
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<para>
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@ -6025,11 +6028,11 @@ SELECT TIMESTAMP 'now';
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</table>
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<para>
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For largely historical reasons, the sequence to be operated on by
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a sequence-function call is specified by a text-string argument.
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To achieve some compatibility with the handling of ordinary SQL
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names, the sequence functions convert their argument to lower case
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unless the string is double-quoted. Thus
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For largely historical reasons, the sequence to be operated on by a
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sequence-function call is specified by a text-string argument. To
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achieve some compatibility with the handling of ordinary
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<acronym>SQL</acronym> names, the sequence functions convert their
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argument to lower case unless the string is double-quoted. Thus
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<programlisting>
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nextval('foo') <lineannotation>operates on sequence <literal>foo</literal></>
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nextval('FOO') <lineannotation>operates on sequence <literal>foo</literal></>
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@ -6480,7 +6483,8 @@ SELECT NULLIF(value, '(none)') ...
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<para>
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The <function>current_setting</function> is used to obtain the current
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value of the <parameter>setting_name</parameter> setting, as a query
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result. It is the equivalent to the SQL <command>SHOW</command> command.
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result. It is the equivalent to the <acronym>SQL</acronym>
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<command>SHOW</command> command.
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For example:
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<programlisting>
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select current_setting('DateStyle');
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@ -6497,8 +6501,8 @@ select current_setting('DateStyle');
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If <parameter>is_local</parameter> is set to <literal>true</literal>,
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the new value will only apply to the current transaction. If you want
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the new value to apply for the current session, use
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<literal>false</literal> instead. It is the equivalent to the SQL
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<command>SET</command> command. For example:
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<literal>false</literal> instead. It is the equivalent to the
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<acronym>SQL</acronym> <command>SET</command> command. For example:
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<programlisting>
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select set_config('show_statement_stats','off','f');
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set_config
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@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/utils/adt/misc.c,v 1.27 2002/09/04 20:31:28 momjian Exp $
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* $Header: /cvsroot/pgsql/src/backend/utils/adt/misc.c,v 1.28 2003/02/13 05:24:02 momjian Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -43,75 +43,6 @@ nonnullvalue(PG_FUNCTION_ARGS)
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PG_RETURN_BOOL(true);
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}
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/*
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* oidrand (oid o, int4 X)-
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* Takes in an oid and a int4 X, and will return 'true' about 1/X of
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* the time. If X == 0, this will always return true.
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* Useful for doing random sampling or subsetting.
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*
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* Example use:
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* select * from TEMP where oidrand(TEMP.oid, 10)
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* will return about 1/10 of the tuples in TEMP
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*
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* NOTE: the OID input is not used at all. It is there just because of
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* an old optimizer bug: a qual expression containing no variables was
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* mistakenly assumed to be a constant. Pretending to access the row's OID
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* prevented the optimizer from treating the oidrand() result as constant.
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*/
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static bool random_initialized = false;
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Datum
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oidrand(PG_FUNCTION_ARGS)
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{
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#ifdef NOT_USED
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Oid o = PG_GETARG_OID(0);
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#endif
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int32 X = PG_GETARG_INT32(1);
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bool result;
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if (X == 0)
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PG_RETURN_BOOL(true);
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/*
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* We do this because the cancel key is actually a random, so we don't
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* want them to be able to request random numbers using our postmaster
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* seeded value.
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*/
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if (!random_initialized)
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{
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srandom((unsigned int) time(NULL));
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random_initialized = true;
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}
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result = (random() % X == 0);
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PG_RETURN_BOOL(result);
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}
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/*
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oidsrand(int32 X) -
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seeds the random number generator
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always returns true
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*/
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Datum
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oidsrand(PG_FUNCTION_ARGS)
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{
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int32 X = PG_GETARG_INT32(0);
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srandom((unsigned int) X);
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random_initialized = true;
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PG_RETURN_BOOL(true);
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}
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Datum
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userfntest(PG_FUNCTION_ARGS)
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{
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int32 i = PG_GETARG_INT32(0);
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PG_RETURN_INT32(i);
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}
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/*
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* current_database()
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* Expose the current database to the user
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@ -37,7 +37,7 @@
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* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $Id: catversion.h,v 1.175 2003/02/03 21:15:44 tgl Exp $
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* $Id: catversion.h,v 1.176 2003/02/13 05:24:02 momjian Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -53,6 +53,6 @@
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*/
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/* yyyymmddN */
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#define CATALOG_VERSION_NO 200302031
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#define CATALOG_VERSION_NO 200302131
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#endif
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@ -7,7 +7,7 @@
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* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $Id: pg_proc.h,v 1.282 2003/01/28 22:13:36 tgl Exp $
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* $Id: pg_proc.h,v 1.283 2003/02/13 05:24:02 momjian Exp $
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*
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* NOTES
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* The script catalog/genbki.sh reads this file and generates .bki
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@ -944,12 +944,6 @@ DESCR("greater-than");
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/* OIDS 700 - 799 */
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DATA(insert OID = 710 ( getpgusername PGNSP PGUID 12 f f t f s 0 19 "" current_user - _null_ ));
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DESCR("deprecated -- use current_user");
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DATA(insert OID = 711 ( userfntest PGNSP PGUID 12 f f t f i 1 23 "23" userfntest - _null_ ));
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DESCR("");
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DATA(insert OID = 713 ( oidrand PGNSP PGUID 12 f f t f v 2 16 "26 23" oidrand - _null_ ));
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DESCR("random");
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DATA(insert OID = 715 ( oidsrand PGNSP PGUID 12 f f t f v 1 16 "23" oidsrand - _null_ ));
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DESCR("seed random number generator");
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DATA(insert OID = 716 ( oidlt PGNSP PGUID 12 f f t f i 2 16 "26 26" oidlt - _null_ ));
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DESCR("less-than");
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DATA(insert OID = 717 ( oidle PGNSP PGUID 12 f f t f i 2 16 "26 26" oidle - _null_ ));
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@ -7,7 +7,7 @@
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* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $Id: builtins.h,v 1.207 2003/02/06 20:25:33 tgl Exp $
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* $Id: builtins.h,v 1.208 2003/02/13 05:24:04 momjian Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -315,9 +315,6 @@ extern Datum float84ge(PG_FUNCTION_ARGS);
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/* misc.c */
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extern Datum nullvalue(PG_FUNCTION_ARGS);
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extern Datum nonnullvalue(PG_FUNCTION_ARGS);
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extern Datum oidrand(PG_FUNCTION_ARGS);
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extern Datum oidsrand(PG_FUNCTION_ARGS);
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extern Datum userfntest(PG_FUNCTION_ARGS);
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extern Datum current_database(PG_FUNCTION_ARGS);
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/* not_in.c */
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@ -15,11 +15,11 @@ SELECT count(*) FROM onek;
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-- have a regression test which can pass/fail
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-- - thomas 1998-08-17
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SELECT count(*) AS random INTO RANDOM_TBL
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FROM onek WHERE oidrand(onek.oid, 10);
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FROM onek WHERE random() < 1.0/10;
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-- select again, the count should be different
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INSERT INTO RANDOM_TBL (random)
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SELECT count(*)
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FROM onek WHERE oidrand(onek.oid, 10);
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FROM onek WHERE random() < 1.0/10;
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-- now test the results for randomness in the correct range
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SELECT random, count(random) FROM RANDOM_TBL
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GROUP BY random HAVING count(random) > 1;
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@ -12,12 +12,12 @@ SELECT count(*) FROM onek;
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-- have a regression test which can pass/fail
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-- - thomas 1998-08-17
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SELECT count(*) AS random INTO RANDOM_TBL
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FROM onek WHERE oidrand(onek.oid, 10);
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FROM onek WHERE random() < 1.0/10;
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-- select again, the count should be different
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INSERT INTO RANDOM_TBL (random)
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SELECT count(*)
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FROM onek WHERE oidrand(onek.oid, 10);
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FROM onek WHERE random() < 1.0/10;
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-- now test the results for randomness in the correct range
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SELECT random, count(random) FROM RANDOM_TBL
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Loading…
Reference in New Issue