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Adjust some glossary terms 

Mostly in response to Jürgen Purtz critique of previous definitions,
though I added many other changes.

Author: Álvaro Herrera <alvherre@alvh.no-ip.org>
Reviewed-by: Jürgen Purtz <juergen@purtz.de>
Reviewed-by: Justin Pryzby <pryzby@telsasoft.com>
Reviewed-by: Erik Rijkers <er@xs4all.nl>
Discussion: https://postgr.es/m/c1e06008-2132-30f4-9b38-877e8683d418@purtz.de
This commit is contained in:
Alvaro Herrera 2020-06-19 12:55:43 -04:00
parent dedb92d4a3
commit 91a890bd7f
1 changed files with 246 additions and 165 deletions
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doc/src/sgml/glossary.sgml
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@ -23,7 +23,7 @@
</glossentry>
<glossentry id="glossary-aggregate">
<glossterm>Aggregate function</glossterm>
<glossterm>Aggregate function (routine)</glossterm>
<glossdef>
<para>
A <glossterm linkend="glossary-function">function</glossterm> that
@ -39,6 +39,11 @@
</glossdef>
</glossentry>
<glossentry>
<glossterm>Analytic function</glossterm>
<glosssee otherterm="glossary-window-function" />
</glossentry>
<glossentry id="glossary-analyze">
<glossterm>Analyze (operation)</glossterm>
<glossdef>
@ -54,14 +59,13 @@
(Don't confuse this term with the <literal>ANALYZE</literal> option
to the <xref linkend="sql-explain"/> command.)
</para>
<para>
For more information, see
<xref linkend="sql-analyze"/>.
</para>
</glossdef>
</glossentry>
<glossentry>
<glossterm>Analytic function</glossterm>
<glosssee otherterm="glossary-window-function" />
</glossentry>
<glossentry id="glossary-atomic">
<glossterm>Atomic</glossterm>
<glossdef>
@ -98,8 +102,7 @@
<glossdef>
<para>
An element with a certain name and data type found within a
<glossterm linkend="glossary-tuple">tuple</glossterm> or
<glossterm linkend="glossary-table">table</glossterm>.
<glossterm linkend="glossary-tuple">tuple</glossterm>.
</para>
</glossdef>
</glossentry>
@ -389,36 +392,12 @@
<glosssee otherterm="glossary-data-directory" />
</glossentry>
<glossentry id="glossary-data-directory">
<glossterm>Data directory</glossterm>
<glossdef>
<para>
The base directory on the filesystem of a
<glossterm linkend="glossary-server">server</glossterm> that contains all
data files and subdirectories associated with an
<glossterm linkend="glossary-instance">instance</glossterm> (with the
exception of <glossterm linkend="glossary-tablespace">tablespaces</glossterm>).
The environment variable <literal>PGDATA</literal> is commonly used to
refer to the
<glossterm linkend="glossary-data-directory">data directory</glossterm>.
</para>
<para>
An <glossterm linkend="glossary-instance">instance</glossterm>'s storage
space comprises the data directory plus any additional tablespaces.
</para>
<para>
For more information, see
<xref linkend="storage-file-layout"/>.
</para>
</glossdef>
</glossentry>
<glossentry id="glossary-database">
<glossterm>Database</glossterm>
<glossdef>
<para>
A named collection of
<glossterm linkend="glossary-sql-object">SQL objects</glossterm>.
<glossterm linkend="glossary-sql-object">local SQL objects</glossterm>.
</para>
<para>
For more information, see
@ -427,11 +406,53 @@
</glossdef>
</glossentry>
<glossentry id="glossary-db-cluster">
<glossterm>Database cluster</glossterm>
<glossdef>
<para>
A collection of databases and global SQL objects,
and their common static and dynamic metadata.
Sometimes referred to as a
<firstterm>cluster</firstterm>.
</para>
<para>
In <productname>PostgreSQL</productname>, the term
<firstterm>cluster</firstterm> is also sometimes used to refer to an instance.
(Don't confuse this term with the SQL command <command>CLUSTER</command>.)
</para>
</glossdef>
</glossentry>
<glossentry>
<glossterm>Database server</glossterm>
<glosssee otherterm="glossary-instance" />
</glossentry>
<glossentry id="glossary-data-directory">
<glossterm>Data directory</glossterm>
<glossdef>
<para>
The base directory on the filesystem of a
<glossterm linkend="glossary-server">server</glossterm> that contains all
data files and subdirectories associated with a
<glossterm linkend="glossary-db-cluster">database cluster</glossterm>
(with the exception of
<glossterm linkend="glossary-tablespace">tablespaces</glossterm>,
and optionally <glossterm linkend="glossary-wal">WAL</glossterm>).
The environment variable <literal>PGDATA</literal> is commonly used to
refer to the data directory.
</para>
<para>
A <glossterm linkend="glossary-db-cluster">cluster</glossterm>'s storage
space comprises the data directory plus any additional tablespaces.
</para>
<para>
For more information, see
<xref linkend="storage-file-layout"/>.
</para>
</glossdef>
</glossentry>
<glossentry id="glossary-data-page">
<glossterm>Data page</glossterm>
<glossdef>
@ -578,7 +599,7 @@
</glossentry>
<glossentry id="glossary-foreign-table">
<glossterm>Foreign table</glossterm>
<glossterm>Foreign table (relation)</glossterm>
<glossdef>
<para>
A <glossterm linkend="glossary-relation">relation</glossterm> which appears to have
@ -631,12 +652,20 @@
</glossentry>
<glossentry id="glossary-function">
<glossterm>Function</glossterm>
<glossterm>Function (routine)</glossterm>
<glossdef>
<para>
Any defined transformation of data. Many functions are already defined
within <productname>PostgreSQL</productname> itself, but user-defined
ones can also be added.
A type of routine that receives zero or more arguments, returns zero or more
output values, and is constrained to run within one transaction.
Functions are invoked as part of a query, for example via
<command>SELECT</command>.
Certain functions can return
<glossterm linkend="glossary-result-set">sets</glossterm>; those are
called <firstterm>set-returning functions</firstterm>.
</para>
<para>
Functions can also be used for
<glossterm linkend="glossary-trigger">triggers</glossterm> to invoke.
</para>
<para>
For more information, see
@ -689,13 +718,12 @@
</glossentry>
<glossentry id="glossary-index">
<glossterm>Index</glossterm>
<glossterm>Index (relation)</glossterm>
<glossdef>
<para>
A <glossterm linkend="glossary-relation">relation</glossterm> that contains
data derived from a <glossterm linkend="glossary-table">table</glossterm>
(or <glossterm linkend="glossary-relation">relation</glossterm> types
such as a <glossterm linkend="glossary-materialized-view">materialized view</glossterm>).
or <glossterm linkend="glossary-materialized-view">materialized view</glossterm>.
Its internal structure supports fast retrieval of and access to the original
data.
</para>
@ -724,14 +752,12 @@
<glossterm>Instance</glossterm>
<glossdef>
<para>
A set of databases and accompanying global SQL objects that are stored in
the same <glossterm linkend="glossary-data-directory">data directory</glossterm>
in a single <glossterm linkend="glossary-server">server</glossterm>.
If running, one
A group of backend and auxiliary processes that communicate using
a common shared memory area. One
<glossterm linkend="glossary-postmaster">postmaster process</glossterm>
manages a group of backend and auxiliary processes that communicate
using a common <glossterm linkend="glossary-shared-memory">shared memory</glossterm>
area. Many instances can run on the same
manages the instance; one instance manages exactly one
<glossterm linkend="glossary-db-cluster">database cluster</glossterm>
with all its databases. Many instances can run on the same
<glossterm linkend="glossary-server">server</glossterm>
as long as their <acronym>TCP</acronym> ports do not conflict.
</para>
@ -739,14 +765,10 @@
The instance handles all key features of a <acronym>DBMS</acronym>:
read and write access to files and shared memory,
assurance of the <acronym>ACID</acronym> properties,
<glossterm linkend="glossary-connection">connections</glossterm> to client processes,
<glossterm linkend="glossary-connection">connections</glossterm> to
<glossterm linkend="glossary-client">client processes</glossterm>,
privilege verification, crash recovery, replication, etc.
</para>
<para>
In <productname>PostgreSQL</productname>, the term
<firstterm>cluster</firstterm> is also sometimes used to refer to an instance.
(Don't confuse this term with the SQL command <command>CLUSTER</command>.)
</para>
</glossdef>
</glossentry>
@ -769,8 +791,10 @@
<glossterm>Join</glossterm>
<glossdef>
<para>
An <acronym>SQL</acronym> keyword used in <command>SELECT</command> statements for
combining data from multiple <glossterm linkend="glossary-relation">relations</glossterm>.
An operation and <acronym>SQL</acronym> keyword used in
<glossterm linkend="glossary-query">queries</glossterm>
for combining data from multiple
<glossterm linkend="glossary-relation">relations</glossterm>.
</para>
</glossdef>
</glossentry>
@ -781,10 +805,10 @@
<para>
A means of identifying a <glossterm linkend="glossary-tuple">row</glossterm> within a
<glossterm linkend="glossary-table">table</glossterm> or
<glossterm linkend="glossary-relation">relation</glossterm> by
other <glossterm linkend="glossary-relation">relation</glossterm> by
values contained within one or more
<glossterm linkend="glossary-attribute">attributes</glossterm>
in that table.
in that relation.
</para>
</glossdef>
</glossentry>
@ -813,15 +837,6 @@
</glossdef>
</glossentry>
<glossentry id="glossary-log-record">
<glossterm>Log record</glossterm>
<glossdef>
<para>
Archaic term for a <glossterm linkend="glossary-wal-record">WAL record</glossterm>.
</para>
</glossdef>
</glossentry>
<glossentry id="glossary-logged">
<glossterm>Logged</glossterm>
<glossdef>
@ -855,6 +870,15 @@
</glossdef>
</glossentry>
<glossentry id="glossary-log-record">
<glossterm>Log record</glossterm>
<glossdef>
<para>
Archaic term for a <glossterm linkend="glossary-wal-record">WAL record</glossterm>.
</para>
</glossdef>
</glossentry>
<glossentry>
<glossterm>Master (server)</glossterm>
<glosssee otherterm="glossary-primary-server" />
@ -883,12 +907,13 @@
</glossentry>
<glossentry id="glossary-materialized-view">
<glossterm>Materialized view</glossterm>
<glossterm>Materialized view (relation)</glossterm>
<glossdef>
<para>
A <glossterm linkend="glossary-relation">relation</glossterm> that is
defined in the same way that a <glossterm linkend="glossary-view">view</glossterm>
is, but stores data in the same way that a
defined by a <command>SELECT</command> statement
(just like a <glossterm linkend="glossary-view">view</glossterm>),
but stores data in the same way that a
<glossterm linkend="glossary-table">table</glossterm> does. It cannot be
modified via <command>INSERT</command>, <command>UPDATE</command>, or
<command>DELETE</command> operations.
@ -949,6 +974,8 @@
<para>
One of several disjoint (not overlapping) subsets of a larger set.
</para>
</glossdef>
<glossdef>
<para>
In reference to a
<glossterm linkend="glossary-partitioned-table">partitioned table</glossterm>:
@ -961,16 +988,18 @@
</glossdef>
<glossdef>
<para>
In reference to a <glossterm linkend="glossary-window-function">window function</glossterm>:
In reference to a <glossterm linkend="glossary-window-function">window function</glossterm>
in a <glossterm linkend="glossary-query">query</glossterm>,
a partition is a user-defined criterion that identifies which neighboring
<glossterm linkend="glossary-tuple">rows</glossterm> can be considered by the
function.
<glossterm linkend="glossary-tuple">rows</glossterm>
of the <glossterm linkend="glossary-result-set">query's result set</glossterm>
can be considered by the function.
</para>
</glossdef>
</glossentry>
<glossentry id="glossary-partitioned-table">
<glossterm>Partitioned table</glossterm>
<glossterm>Partitioned table (relation)</glossterm>
<glossdef>
<para>
A <glossterm linkend="glossary-relation">relation</glossterm> that is
@ -997,20 +1026,6 @@
</glossdef>
</glossentry>
<glossentry id="glossary-primary-server">
<glossterm>Primary (server)</glossterm>
<glossdef>
<para>
When two or more <glossterm linkend="glossary-database">databases</glossterm>
are linked via <glossterm linkend="glossary-replication">replication</glossterm>,
the <glossterm linkend="glossary-server">server</glossterm>
that is considered the authoritative source of information is called
the <firstterm>primary</firstterm>,
also known as a <firstterm>master</firstterm>.
</para>
</glossdef>
</glossentry>
<glossentry id="glossary-primary-key">
<glossterm>Primary key</glossterm>
<glossdef>
@ -1031,19 +1046,29 @@
</glossdef>
</glossentry>
<glossentry id="glossary-procedure">
<glossterm>Procedure</glossterm>
<glossentry id="glossary-primary-server">
<glossterm>Primary (server)</glossterm>
<glossdef>
<para>
A defined set of instructions for manipulating data within a
<glossterm linkend="glossary-database">database</glossterm>.
A <glossterm linkend="glossary-procedure">procedure</glossterm> can
be written in a variety of programming languages. They are
similar to <glossterm linkend="glossary-function">functions</glossterm>,
but are different in that they must be invoked via the <command>CALL</command>
command rather than the <command>SELECT</command> or <command>PERFORM</command>
commands, and they are allowed to make transactional statements such
When two or more <glossterm linkend="glossary-database">databases</glossterm>
are linked via <glossterm linkend="glossary-replication">replication</glossterm>,
the <glossterm linkend="glossary-server">server</glossterm>
that is considered the authoritative source of information is called
the <firstterm>primary</firstterm>,
also known as a <firstterm>master</firstterm>.
</para>
</glossdef>
</glossentry>
<glossentry id="glossary-procedure">
<glossterm>Procedure (routine)</glossterm>
<glossdef>
<para>
A type of routine.
Their distinctive qualities are that they do not return values,
and that they are allowed to make transactional statements such
as <command>COMMIT</command> and <command>ROLLBACK</command>.
They are invoked via the <command>CALL</command> command.
</para>
<para>
For more information, see
@ -1115,6 +1140,11 @@
<glossterm linkend="glossary-index">indexes</glossterm> are all relations.
</para>
<para>
More generically, a relation is a set of tuples; for example,
the result of a query is also a relation.
</para>
<para>
In <productname>PostgreSQL</productname>,
<firstterm>Class</firstterm> is an archaic synonym for
<firstterm>relation</firstterm>.
</para>
@ -1155,16 +1185,23 @@
<glossterm>Result set</glossterm>
<glossdef>
<para>
A data structure transmitted from a
<glossterm linkend="glossary-backend">backend process</glossterm> to
a <glossterm linkend="glossary-client">client</glossterm> upon the
completion of an <acronym>SQL</acronym>
command, usually a <command>SELECT</command> but it can be an
A <glossterm linkend="glossary-relation">relation</glossterm> transmitted
from a <glossterm linkend="glossary-backend">backend process</glossterm>
to a <glossterm linkend="glossary-client">client</glossterm> upon the
completion of an <acronym>SQL</acronym> command, usually a
<command>SELECT</command> but it can be an
<command>INSERT</command>, <command>UPDATE</command>, or
<command>DELETE</command> command if the <literal>RETURNING</literal>
clause is specified. The data structure consists of zero or more
<glossterm linkend="glossary-tuple">rows</glossterm> with the same ordered set of
<glossterm linkend="glossary-attribute">attributes</glossterm>.
clause is specified.
</para>
<para>
The fact that a result set is a relation means that a query can be used
in the definition of another query, becoming a
<firstterm>subquery</firstterm>.
</para>
</glossdef>
<glossdef>
<para>
</para>
</glossdef>
</glossentry>
@ -1216,6 +1253,27 @@
</glossdef>
</glossentry>
<glossentry id="glossary-routine">
<glossterm>Routine</glossterm>
<glossdef>
<para>
A defined set of instructions stored in the database system
that can be invoked for execution.
A routine can be written in a variety of programming
languages. Routines can be
<glossterm linkend="glossary-function">functions</glossterm>
(including set-returning functions and
<glossterm linkend="glossary-trigger">trigger functions</glossterm>),
<glossterm linkend="glossary-aggregate">aggregate functions</glossterm>,
and <glossterm linkend="glossary-procedure">procedures</glossterm>.
</para>
<para>
Many routines are already defined within <productname>PostgreSQL</productname>
itself, but user-defined ones can also be added.
</para>
</glossdef>
</glossentry>
<glossentry>
<glossterm>Row</glossterm>
<glosssee otherterm="glossary-tuple" />
@ -1248,16 +1306,7 @@
Each SQL object must reside in exactly one schema.
</para>
<para>
The names of SQL objects of the same type in the same schema are enforced
to be unique.
There is no restriction on reusing a name in multiple schemas.
</para>
<para>
All system-defined SQL objects reside in schema <literal>pg_catalog</literal>,
and commonly many user-defined SQL objects reside in the default schema
<literal>public</literal>,
but it is common and recommended that other schemas are created to hold
application-specific SQL objects.
All system-defined SQL objects reside in schema <literal>pg_catalog</literal>.
</para>
</glossdef>
<glossdef>
@ -1299,6 +1348,19 @@
</glossdef>
</glossentry>
<glossentry id="glossary-sequence">
<glossterm>Sequence (relation)</glossterm>
<glossdef>
<para>
A type of relation that is used to generate values.
Typically the generated values are sequential non-repeating numbers.
They are commonly used to generate surrogate
<glossterm linkend="glossary-primary-key">primary key</glossterm>
values.
</para>
</glossdef>
</glossentry>
<!-- XXX should define all other isolation levels (and improve this definition)
<glossentry id="glossary-serializable">
<glossterm>Serializable (isolation level)</glossterm>
@ -1339,19 +1401,6 @@
</glossdef>
</glossentry>
<glossentry id="glossary-sequence">
<glossterm>Sequence</glossterm>
<glossdef>
<para>
A type of relation that is used to generate values.
Typically the generated values are sequential non-repeating numbers.
They are commonly used to generate surrogate
<glossterm linkend="glossary-primary-key">primary key</glossterm>
values.
</para>
</glossdef>
</glossentry>
<glossentry id="glossary-shared-memory">
<glossterm>Shared memory</glossterm>
<glossdef>
@ -1378,33 +1427,43 @@
</glossdef>
</glossentry>
<glossentry>
<glossterm>Standby (server)</glossterm>
<glosssee otherterm="glossary-replica" />
</glossentry>
<glossentry id="glossary-sql-object">
<glossterm>SQL Object</glossterm>
<glossterm>SQL object</glossterm>
<glossdef>
<para>
Any object that can be created with a <command>CREATE</command>
command. Most objects are specific to one database, and are commonly
known as <firstterm>local objects</firstterm>.
<glossterm linkend="glossary-role">Roles</glossterm>,
</para>
<para>
Most local objects belong to a specific
<glossterm linkend="glossary-schema">schema</glossterm> in their
containing database, such as
<glossterm linkend="glossary-relation">relations</glossterm> (all types),
<glossterm linkend="glossary-function">routines</glossterm> (all types),
data types, etc.
The names of such objects of the same type in the same schema
are enforced to be unique.
</para>
<para>
There also exist local objects that do not belong to schemas; some examples are
<glossterm linkend="glossary-extension">extensions</glossterm>,
<glossterm linkend="glossary-cast">data type casts</glossterm>, and
<glossterm linkend="glossary-foreign-data-wrapper">foreign data wrappers</glossterm>.
The names of such objects of the same type are enforced to be unique
within the database.
</para>
<para>
Other object types, such as
<glossterm linkend="glossary-role">roles</glossterm>,
<glossterm linkend="glossary-tablespace">tablespaces</glossterm>,
replication origins, subscriptions for logical replication, and
databases themselves are not local SQL objects since they exist
entirely outside of any specific database;
they are called <firstterm>global objects</firstterm>.
The names of such objects are enforced to be unique within the whole
database cluster.
</para>
<para>
Most local objects belong to a specific
<glossterm linkend="glossary-schema">schema</glossterm> in their containing database.
There also exist local objects that do not belong to schemas; some examples are
<glossterm linkend="glossary-extension">extensions</glossterm>,
<glossterm linkend="glossary-cast">data type casts</glossterm>, and
<glossterm linkend="glossary-foreign-data-wrapper">foreign data wrappers</glossterm>.
</para>
<para>
For more information, see
<xref linkend="manage-ag-overview"/>.
@ -1421,6 +1480,11 @@
</glossdef>
</glossentry>
<glossentry>
<glossterm>Standby (server)</glossterm>
<glosssee otherterm="glossary-replica" />
</glossentry>
<glossentry id="glossary-stats-collector">
<glossterm>Stats collector</glossterm>
<glossdef>
@ -1489,8 +1553,8 @@
which require storage beyond their definition in the
<glossterm linkend="glossary-system-catalog">system catalog</glossterm>
must belong to a single tablespace.
Initially, an instance contains a single usable tablespace which is
used as the default one for all SQL objects, called <literal>pg_default</literal>.
Initially, a database cluster contains a single usable tablespace which is
used as the default for all SQL objects, called <literal>pg_default</literal>.
</para>
<para>
For more information, see
@ -1577,6 +1641,18 @@
</glossdef>
</glossentry>
<glossentry id="glossary-tps">
<glossterm>Transactions per second (TPS)</glossterm>
<glossdef>
<para>
Average number of transactions that are executed per second,
totalled across all sessions active for a measured run.
This is used as a measure of the performance characteristics of
an instance.
</para>
</glossdef>
</glossentry>
<glossentry id="glossary-trigger">
<glossterm>Trigger</glossterm>
<glossdef>
@ -1605,6 +1681,7 @@
A collection of <glossterm linkend="glossary-attribute">attributes</glossterm>
in a fixed order.
That order may be defined by the <glossterm linkend="glossary-table">table</glossterm>
(or other <glossterm linkend="glossary-relation">relation</glossterm>)
where the tuple is contained, in which case the tuple is often called a
<firstterm>row</firstterm>. It may also be defined by the structure of a
result set, in which case it is sometimes called a <firstterm>record</firstterm>.
@ -1818,28 +1895,32 @@
</glossentry>
<glossentry id="glossary-wal-writer">
<glossterm>WAL writer (process)</glossterm>
<glossdef>
<para>
A process that writes <glossterm linkend="glossary-wal-record">WAL records</glossterm>
from <glossterm linkend="glossary-shared-memory">shared memory</glossterm> to
<glossterm linkend="glossary-wal-file">WAL files</glossterm>.
</para>
<para>
For more information, see
<xref linkend="runtime-config-wal"/>.
</para>
</glossdef>
<glossterm>WAL writer (process)</glossterm>
<glossdef>
<para>
A process that writes <glossterm linkend="glossary-wal-record">WAL records</glossterm>
from <glossterm linkend="glossary-shared-memory">shared memory</glossterm> to
<glossterm linkend="glossary-wal-file">WAL files</glossterm>.
</para>
<para>
For more information, see
<xref linkend="runtime-config-wal"/>.
</para>
</glossdef>
</glossentry>
<glossentry id="glossary-window-function">
<glossterm>Window function</glossterm>
<glossterm>Window function (routine)</glossterm>
<glossdef>
<para>
A type of <glossterm linkend="glossary-function">function</glossterm> whose
result is based on values found in
<glossterm linkend="glossary-tuple">rows</glossterm> of the same
<glossterm linkend="glossary-partition">partition</glossterm>.
A type of <glossterm linkend="glossary-function">function</glossterm>
used in a <glossterm linkend="glossary-query">query</glossterm>
that applies to a <glossterm linkend="glossary-partition">partition</glossterm>
of the query's <glossterm linkend="glossary-result-set">result set</glossterm>;
the function's result is based on values found in
<glossterm linkend="glossary-tuple">rows</glossterm> of the same partition or frame.
</para>
<para>
All <glossterm linkend="glossary-aggregate">aggregate functions</glossterm>
can be used as window functions, but window functions can also be
used to, for example, give ranks to each of the rows in the partition.
@ -1857,8 +1938,8 @@
<glossdef>
<para>
The journal that keeps track of the changes in the
<glossterm linkend="glossary-instance">instance</glossterm> as user- and
system-invoked operations take place.
<glossterm linkend="glossary-db-cluster">database cluster</glossterm>
as user- and system-invoked operations take place.
It comprises many individual
<glossterm linkend="glossary-wal-record">WAL records</glossterm> written
sequentially to <glossterm linkend="glossary-wal-file">WAL files</glossterm>.