On 2020-Apr-02, Corey Huinker wrote: > On Thu, Apr 2, 2020 at 8:44 AM Jürgen Purtz <juer...@purtz.de> wrote: > > > +1 and many thanks to Alvaros edits. > > > > > I did some of the grunt work Alvaro alluded to in v6, and the results are > attached and they build, which means there are no invalid links.
Thank you! I had been working on some other changes myself, and merged most of your changes. I give you v8. > * renamed id glossary-temporary-tables to glossary-temporary-table Good. > * temporarily re-added an id for glossary-row as we have many references to > that. unsure if we should use the term Tuple in all those places or say Row > while linking to glossary-tuple, or something else I changed these to link to glossary-tuple; that entry already explains these two other terms, so this seems acceptable. > * temporarily re-added an id for glossary-segment, glossary-wal-segment, > glossary-analytic-function, as those were also referenced and will need > similar decisions made Ditto. > * added a stub entry for glossary-unique-index, unsure if it should have a > definition on it's own, or we split it into unique and index. I changed Unique Index into Unique Constraint, which is supposed to be the overarching concept. Used that in the definition of primary key. > * I noticed several cases where a glossterm is used twice in a definition, > but didn't de-term them Did that for most I found, but I expect that some remain. > * I'm curious about how we should tag a term when using it in its own > definition. same as anywhere else? I think we should not tag those. I fixed the definition of global object as mentioned previously. Also added "client", made "connection" have less importance compared to "session", and removed "window frame" (made "window function" refer to "partition" instead). If you (or anybody) have suggestions for the definition of "client" and "session", I'm all ears. I'm quite liking the result of this now. Thanks for all your efforts. -- Álvaro Herrera https://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
diff --git a/doc/src/sgml/filelist.sgml b/doc/src/sgml/filelist.sgml index 1043d0f7ab..cf21ef857e 100644 --- a/doc/src/sgml/filelist.sgml +++ b/doc/src/sgml/filelist.sgml @@ -170,6 +170,7 @@ <!ENTITY limits SYSTEM "limits.sgml"> <!ENTITY acronyms SYSTEM "acronyms.sgml"> +<!ENTITY glossary SYSTEM "glossary.sgml"> <!ENTITY color SYSTEM "color.sgml"> <!ENTITY features-supported SYSTEM "features-supported.sgml"> diff --git a/doc/src/sgml/glossary.sgml b/doc/src/sgml/glossary.sgml new file mode 100644 index 0000000000..7d981a9223 --- /dev/null +++ b/doc/src/sgml/glossary.sgml @@ -0,0 +1,1692 @@ +<appendix id="glossary"> + <title>Glossary</title> + <para> + This is a list of terms and their meaning in the context of + <productname>PostgreSQL</productname> and relational database + systems in general. + </para> + + <glosslist> + <glossentry id="glossary-aggregate"> + <glossterm>Aggregate Function</glossterm> + <glossdef> + <para> + A <glossterm linkend="glossary-function">function</glossterm> that + combines (<firstterm>aggregates</firstterm>) multiple input values, + for example by counting, averaging or adding, + yielding a single output value. + </para> + <para> + For more information, see + <xref linkend="functions-aggregate"/>. + </para> + <glossseealso otherterm="glossary-window-function" /> + </glossdef> + </glossentry> + + <glossentry id="glossary-analyze"> + <glossterm>Analyze (operation)</glossterm> + <glossdef> + <para> + The process of collecting statistics from data in + <glossterm linkend="glossary-table">tables</glossterm> + and other <glossterm linkend="glossary-relation">relations</glossterm> + to help the <glossterm linkend="glossary-planner">query planner</glossterm> + to make decisions about how to execute + <glossterm linkend="glossary-query">queries</glossterm>. + </para> + </glossdef> + </glossentry> + + <glossentry> + <glossterm>Analytic Function</glossterm> + <glosssee otherterm="glossary-window-function" /> + </glossentry> + + <glossentry id="glossary-atomic"> + <glossterm>Atomic</glossterm> + <glossdef> + <para> + In reference to a <glossterm linkend="glossary-datum">datum</glossterm>: + the fact that its value that cannot be broken down into smaller + components. + </para> + </glossdef> + <glossdef> + <para> + In reference to a + <glossterm linkend="glossary-transaction">database transaction</glossterm>: + see <glossterm linkend="glossary-atomicity">atomicity</glossterm>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-atomicity"> + <glossterm>Atomicity</glossterm> + <glossdef> + <para> + The property of a <glossterm linkend="glossary-transaction">transaction</glossterm> + that either all its operations complete as a single unit or none do. + In addition, if a system failure occurs during the execution of a + transaction, no partial results are visible after recovery. + This is one of the <acronym>ACID</acronym> properties. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-attribute"> + <glossterm>Attribute</glossterm> + <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>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-autovacuum"> + <glossterm>Autovacuum (process)</glossterm> + <glossdef> + <para> + A set of background processes that routinely perform + <glossterm linkend="glossary-vacuum">vacuum</glossterm> + and <glossterm linkend="glossary-analyze">analyze</glossterm> + operations. + </para> + <para> + For more information, see + <xref linkend="autovacuum"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-backend"> + <glossterm>Backend (process)</glossterm> + <glossdef> + <para> + Processes of an <glossterm linkend="glossary-instance">instance</glossterm> + which act on behalf of client <glossterm linkend="glossary-session">sessions</glossterm> + and handle their requests. + </para> + <para> + (Don't confuse this term with the similar terms + <glossterm linkend="glossary-background-worker">Background Worker</glossterm> or + <glossterm linkend="glossary-background-writer">Background Writer</glossterm>). + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-background-worker"> + <glossterm>Background Worker (process)</glossterm> + <glossdef> + <para> + Individual processes within an <glossterm linkend="glossary-instance">instance</glossterm>, + which run system- or user-supplied code. + They provide infrastructure for several features in + <productname>PostgreSQL</productname>, such as + <glossterm linkend="glossary-replication">logical replication</glossterm> + and <glossterm linkend="glossary-parallel-query">parallel queries</glossterm>. + <glossterm linkend="glossary-extension">Extensions</glossterm> can add + custom background worker processes, as well. + </para> + <para> + For more information, see + <xref linkend="bgworker"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-background-writer"> + <glossterm>Background Writer (process)</glossterm> + <glossdef> + <para> + A process that continuously writes dirty pages from + <glossterm linkend="glossary-shared-memory">Shared Memory</glossterm> to + the file system. It wakes up periodically, but works only for a short + period in order to distribute its expensive <acronym>I/O</acronym> + activity over time, instead of generating fewer larger + <acronym>I/O</acronym> peaks which could block other processes. + </para> + <para> + For more information, see + <xref linkend="runtime-config-resource"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-cast"> + <glossterm>Cast</glossterm> + <glossdef> + <para> + A conversion of a <glossterm linkend="glossary-datum">Datum</glossterm> + from its current data type to another data type. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-catalog"> + <glossterm>Catalog</glossterm> + <glossdef> + <para> + The <acronym>SQL</acronym> standard uses this term to + indicate what is called a + <glossterm linkend="glossary-database">Database</glossterm> in + <productname>PostgreSQL</productname>'s terminology. + </para> + <para> + This should not be confused with the + <glossterm linkend="glossary-system-catalog">System Catalog</glossterm>. + </para> + <para> + For more information, see + <xref linkend="manage-ag-overview"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-check-constraint"> + <glossterm>Check Constraint</glossterm> + <glossdef> + <para> + A type of <glossterm linkend="glossary-constraint">constraint</glossterm> + defined on a <glossterm linkend="glossary-relation">relation</glossterm> + which restricts the values allowed in one or more + <glossterm linkend="glossary-attribute">attributes</glossterm>. The + check constraint can make reference to any attribute of the same row in + the relation, but cannot reference other rows of the same relation or + other relations. + </para> + <para> + For more information, see + <xref linkend="ddl-constraints"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-checkpointer"> + <glossterm>Checkpointer (process)</glossterm> + <glossdef> + <para> + A process that writes dirty pages to the file system and creates a special + checkpoint WAL record. This process is initiated when predefined + conditions are met, such as a specified amount of time has passed, or + a certain volume of records has been written. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-checkpoint"> + <glossterm>Checkpoint</glossterm> + <glossdef> + <para> + A point in the <glossterm linkend="glossary-wal">WAL</glossterm> sequence + at which it is guaranteed that the heap and index data files have been + updated with all information from + <glossterm linkend="glossary-shared-memory">Shared Memory</glossterm> + modified before that checkpoint; + a <firstterm>checkpoint record</firstterm> is written and flushed to WAL + to mark that point. + </para> + <para> + For more information, see + <xref linkend="wal-configuration"/>. + </para> + </glossdef> + </glossentry> + + <glossentry> + <glossterm>Class (archaic)</glossterm> + <glosssee otherterm="glossary-relation" /> + </glossentry> + + <glossentry id="glossary-client"> + <glossterm>Client (process)</glossterm> + <glossdef> + <para> + Any process, possibly remote, that establishes a + <glossterm linkend="glossary-session">session</glossterm> + by <glossterm linkend="glossary-connection">connecting</glossterm> to an + <glossterm linkend="glossary-instance">instance</glossterm> + to interact with a <glossterm linkend="glossary-database">database</glossterm>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-cluster"> + <glossterm>Cluster</glossterm> + <glossdef> + <para> + A group of <glossterm linkend="glossary-database">Databases</glossterm> plus their + <glossterm linkend="glossary-global-sql-object">Global SQL Objects</glossterm>. The + <firstterm>cluster</firstterm> is managed by exactly one + <glossterm linkend="glossary-instance">Instance</glossterm>. A newly created + Cluster will have three databases created automatically. They are + <literal>template0</literal>, <literal>template1</literal>, and + <literal>postgres</literal>. It is expected that an application will + create one or more additional database aside from these three. + </para> + <para> + Don't confuse the <productname>PostgreSQL</productname>-specific term + <glossterm linkend="glossary-cluster">Cluster</glossterm> with the SQL + command <command>CLUSTER</command>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-column"> + <glossterm>Column</glossterm> + <glossdef> + <para> + An <glossterm linkend="glossary-attribute">Attribute</glossterm> found in + a <glossterm linkend="glossary-table">Table</glossterm> or + <glossterm linkend="glossary-view">View</glossterm>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-commit"> + <glossterm>Commit</glossterm> + <glossdef> + <para> + The act of finalizing a + <glossterm linkend="glossary-transaction">transaction</glossterm> within + the <glossterm linkend="glossary-database">Database</glossterm>, which + makes it visible to other transactions and assures its + <glossterm linkend="glossary-durability">durability</glossterm>. + </para> + <para> + For more information, see + <xref linkend="sql-commit"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-concurrency"> + <glossterm>Concurrency</glossterm> + <glossdef> + <para> + The concept that multiple independent operations happen within the + <glossterm linkend="glossary-database">Database</glossterm> at the same time. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-connection"> + <glossterm>Connection</glossterm> + <glossdef> + <para> + An established line of communication between a client process and a + <glossterm linkend="glossary-backend">backend</glossterm> process, + usually over a network, supporting a + <glossterm linkend="glossary-session">session</glossterm>. This term is + sometimes used as a synonym for session. + </para> + <para> + For more information, see + <xref linkend="runtime-config-connection"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-consistency"> + <glossterm>Consistency</glossterm> + <glossdef> + <para> + The property that the data in the + <glossterm linkend="glossary-database">database</glossterm> + is always in compliance with + <glossterm linkend="glossary-constraint">integrity constraints</glossterm>. + Transactions may be allowed to violate some of the constraints + transiently before it commits, but if such violations are not fixed + by the time it commits, such transaction is automatically + <glossterm linkend="glossary-rollback">rolled back</glossterm>. + This is one of the <acronym>ACID</acronym> properties. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-constraint"> + <glossterm>Constraint</glossterm> + <glossdef> + <para> + A restriction on the values of data allowed within a + <glossterm linkend="glossary-table">Table</glossterm>. + </para> + <para> + For more information, see + <xref linkend="ddl-constraints"/>. + </para> + </glossdef> + </glossentry> + + <glossentry> + <glossterm>Data Area</glossterm> + <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 a + <glossterm linkend="glossary-cluster">Cluster</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 Object</glossterm>s. + </para> + <para> + For more information, see + <xref linkend="manage-ag-overview"/>. + </para> + </glossdef> + </glossentry> + + <glossentry> + <glossterm>Database Server</glossterm> + <glosssee otherterm="glossary-instance" /> + </glossentry> + + <glossentry id="glossary-datum"> + <glossterm>Datum</glossterm> + <glossdef> + <para> + The internal representation of one value of a <acronym>SQL</acronym> + data type. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-delete"> + <glossterm>Delete</glossterm> + <glossdef> + <para> + A <acronym>SQL</acronym> command which removes + <glossterm linkend="glossary-tuple">Row</glossterm>s from a given + <glossterm linkend="glossary-table">Table</glossterm> + or <glossterm linkend="glossary-relation">Relation</glossterm>. + </para> + <para> + For more information, see + <xref linkend="sql-delete"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-durability"> + <glossterm>Durability</glossterm> + <glossdef> + <para> + The assurance that once a + <glossterm linkend="glossary-transaction">transaction</glossterm> has + been <glossterm linkend="glossary-commit">Committed</glossterm>, the + changes remain even after a system failure or crash. + This is one of the <acronym>ACID</acronym> properties. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-extension"> + <glossterm>Extension</glossterm> + <glossdef> + <para> + A software add-on package that can be installed on an + <glossterm linkend="glossary-instance">instance</glossterm> to + get extra features. + </para> + <para> + For more information, see + <xref linkend="extend-extensions" />. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-file-segment"> + <glossterm>File Segment</glossterm> + <glossdef> + <para> + A physical file which stores data for a given + <glossterm linkend="glossary-heap">Heap</glossterm> or + <glossterm linkend="glossary-index">Index</glossterm> object. + <glossterm linkend="glossary-file-segment">File Segment</glossterm>s are + limited in size by a configuration value and if that size is exceeded, it + will be split into multiple physical files. + </para> + <para> + For more information, see + <xref linkend="storage-file-layout"/>. + </para> + <para> + (Don't confuse this term with the similar term + <glossterm linkend="glossary-wal-file">WAL Segment</glossterm>). + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-foreign-data-wrapper"> + <glossterm>Foreign Data Wrapper</glossterm> + <glossdef> + <para> + A means of representing data that is not contained in the local + <glossterm linkend="glossary-database">Database</glossterm> so that it appears as if were in local + <glossterm linkend="glossary-table">Table</glossterm>(s). With a Foreign Data Wrapper it is + possible to define a <glossterm linkend="glossary-foreign-server">Foreign Server</glossterm> and + <glossterm linkend="glossary-foreign-table">Foreign Table</glossterm>s. + </para> + <para> + For more information, see + <xref linkend="sql-createforeigndatawrapper"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-foreign-key"> + <glossterm>Foreign Key</glossterm> + <glossdef> + <para> + A type of <glossterm linkend="glossary-constraint">Constraint</glossterm> + defined on one or more <glossterm linkend="glossary-column">Column</glossterm>s + in a <glossterm linkend="glossary-table">Table</glossterm> which + requires the value(s) in those <glossterm linkend="glossary-column">Column</glossterm>s to + identify zero or one <glossterm linkend="glossary-tuple">Row</glossterm> + in another (or, infrequently, the same) + <glossterm linkend="glossary-table">Table</glossterm>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-foreign-server"> + <glossterm>Foreign Server</glossterm> + <glossdef> + <para> + A named collection of + <glossterm linkend="glossary-foreign-table">Foreign Table</glossterm>s which + all use the same + <glossterm linkend="glossary-foreign-data-wrapper">Foreign Data Wrapper</glossterm> + and have other configuration values in common. + </para> + <para> + For more information, see + <xref linkend="sql-createserver"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-foreign-table"> + <glossterm>Foreign Table</glossterm> + <glossdef> + <para> + A <glossterm linkend="glossary-relation">Relation</glossterm> which appears to have + <glossterm linkend="glossary-tuple">rows</glossterm> and + <glossterm linkend="glossary-column">columns</glossterm> similar to a + regular <glossterm linkend="glossary-table">Table</glossterm>, but will forward + requests for data through its + <glossterm linkend="glossary-foreign-data-wrapper">Foreign Data Wrapper</glossterm>, + which will return <glossterm linkend="glossary-result-set">Result Sets</glossterm> + structured according to the definition of the + <glossterm linkend="glossary-foreign-table">Foreign Table</glossterm>. + </para> + <para> + For more information, see + <xref linkend="sql-createforeigntable"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-function"> + <glossterm>Function</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. + </para> + <para> + For more information, see + <xref linkend="sql-createfunction"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-global-sql-object"> + <glossterm>Global SQL Object</glossterm> + <glossdef> + <para> + <glossterm linkend="glossary-sql-object">SQL Object</glossterm>s which do + not belong to a specific + <glossterm linkend="glossary-database">database</glossterm>. + </para> + <para> + These objects are + <glossterm linkend="glossary-role">roles</glossterm>, + <glossterm linkend="glossary-tablespace">tablespaces</glossterm>, + replication origins, and subscriptions for logical replication. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-grant"> + <glossterm>Grant</glossterm> + <glossdef> + <para> + A <acronym>SQL</acronym> command that is used to allow + <glossterm linkend="glossary-user">User</glossterm>s or <glossterm linkend="glossary-role">Role</glossterm>s to access + specific objects within the <glossterm linkend="glossary-database">Database</glossterm>. + </para> + <para> + For more information, see + <xref linkend="sql-grant"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-heap"> + <glossterm>Heap</glossterm> + <glossdef> + <para> + Contains the values of <glossterm linkend="glossary-tuple">Row</glossterm> + attributes (i.e. the data). The <glossterm linkend="glossary-heap">Heap</glossterm> + is realized within <glossterm linkend="glossary-database">Database</glossterm> files. + </para> + </glossdef> + </glossentry> + + <glossentry> + <glossterm>Host</glossterm> + <glosssee otherterm="glossary-server" /> + </glossentry> + + <glossentry id="glossary-index"> + <glossterm>Index</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>). + Its internal structure supports fast retrieval of and access to the original + data. + </para> + <para> + For more information, see + <xref linkend="sql-createindex"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-insert"> + <glossterm>Insert</glossterm> + <glossdef> + <para> + A <acronym>SQL</acronym> command used to add new data into a + <glossterm linkend="glossary-table">Table</glossterm>. + </para> + <para> + For more information, see + <xref linkend="sql-insert"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-instance"> + <glossterm>Instance</glossterm> + <glossdef> + <para> + An <glossterm>Instance</glossterm> is a group of processes, + its supporting <glossterm linkend="glossary-data-directory">storage space</glossterm>, + plus their + common <glossterm linkend="glossary-shared-memory">Shared Memory</glossterm>, + running on a single <glossterm linkend="glossary-server">Server</glossterm>. + The <glossterm linkend="glossary-instance">Instance</glossterm> + handles all key features of a <acronym>DBMS</acronym>: read and write + access to files and shared memory, assurance of + the <acronym>ACID</acronym> paradigm, <acronym>MVCC</acronym>, + <glossterm linkend="glossary-connection">Connection</glossterm>s to client programs, backup, + recovery, replication, privileges, etc. + </para> + <para> + An <glossterm>Instance</glossterm> manages exactly one + <glossterm linkend="glossary-cluster">Cluster</glossterm>. + </para> + <para> + Many <glossterm>Instance</glossterm>s can run on the same server as + long as their <acronym>TCP/IP</acronym> ports do not conflict. + Different instances on a server may use the + same or different versions of <productname>PostgreSQL</productname>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-isolation"> + <glossterm>Isolation</glossterm> + <glossdef> + <para> + The property that the effects of a transaction are not visible to + <glossterm linkend="glossary-concurrency">concurrent transactions</glossterm> + before it commits. + This is one of the <acronym>ACID</acronym> properties. + </para> + <para> + For more information, see <xref linkend="transaction-iso" />. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-join"> + <glossterm>Join</glossterm> + <glossdef> + <para> + A <acronym>SQL</acronym> keyword used in <command>SELECT</command> statements for + combining data from multiple <glossterm linkend="glossary-relation">Relation</glossterm>s. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-key"> + <glossterm>Key</glossterm> + <glossdef> + <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 + values contained within one or more <glossterm linkend="glossary-attribute">Attribute</glossterm>s + in that <glossterm linkend="glossary-table">Table</glossterm>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-lock"> + <glossterm>Lock</glossterm> + <glossdef> + <para> + A mechanism that allows a process to limit or prevent simultaneous + access to a resource. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-log-file"> + <glossterm>Log File</glossterm> + <glossdef> + <para> + <glossterm>Log File</glossterm>s contain human-readable text lines about + events. Examples include login failures, long-running queries, etc. + </para> + <para> + For more information, see + <xref linkend="logfile-maintenance"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-logger"> + <glossterm>Logger (process)</glossterm> + <glossdef> + <para> + If activated, the + <glossterm linkend="glossary-logger">Logger</glossterm> process + writes information about database events into the current + <glossterm linkend="glossary-log-file">Log File</glossterm>. When reaching certain time- or + volume-dependent criteria, a new log file is created. + Also called <firstterm>syslogger</firstterm>. + </para> + <para> + For more information, see + <xref linkend="runtime-config-logging"/>. + </para> + </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> + <para> + A <glossterm linkend="glossary-table">Table</glossterm> is considered + <glossterm linkend="glossary-logged">Logged</glossterm> if changes to it are sent to the + <glossterm linkend="glossary-wal">WAL</glossterm>. By default, all regular + <glossterm linkend="glossary-table">Table</glossterm>s are <glossterm linkend="glossary-logged">Logged</glossterm>. A + table can be specified as <glossterm linkend="glossary-unlogged">Unlogged</glossterm> either at + creation time or via the <command>ALTER TABLE</command> command. + </para> + </glossdef> + </glossentry> + + <glossentry> + <glossterm>Master (server)</glossterm> + <glosssee otherterm="glossary-primary-server" /> + </glossentry> + + <glossentry id="glossary-materialized"> + <glossterm>Materialized</glossterm> + <glossdef> + <para> + The act of storing information rather than just the method of accessing + the information. This term is used in <glossterm linkend="glossary-materialized-view">Materialized + View</glossterm>s, meaning that the data derived from the + <glossterm linkend="glossary-view">View</glossterm> is actually stored on disk separately from + the sources of that data. When using the term + <glossterm linkend="glossary-materialized">Materialized</glossterm> to refer to + multi-step queries, it means that the data of a given step is stored + in memory, but that storage may spill over onto disk. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-materialized-view"> + <glossterm>Materialized View</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 <glossterm linkend="glossary-table">Table</glossterm> does. It cannot be modified via + <command>INSERT</command>, <command>UPDATE</command>, or + <command>DELETE</command> operations. + </para> + <para> + For more information, see + <xref linkend="sql-creatematerializedview"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-mvcc"> + <glossterm>Multi-version concurrency control (MVCC)</glossterm> + <glossdef> + <para> + A mechanism designed to allow several + <glossterm linkend="glossary-transaction">transactions</glossterm> to be + reading and writing the same rows without one process causing other + processes to stall. + In <productname>PostgreSQL</productname>, MVCC is implemented by + creating copies (<firstterm>versions</firstterm>) of + <glossterm linkend="glossary-tuple">tuples</glossterm> as they are + modified; after transactions that can see the old versions terminate, + those old versions need to be removed. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-null"> + <glossterm>Null</glossterm> + <glossdef> + <para> + A concept of non-existence that is a central tenet of Relational + Database Theory. It represents the absence of value. + </para> + </glossdef> + </glossentry> + + <glossentry> + <glossterm>Optimizer</glossterm> + <glosssee otherterm="glossary-planner" /> + </glossentry> + + <glossentry id="glossary-parallel-query"> + <glossterm>Parallel Query</glossterm> + <glossdef> + <para> + The ability to handle parts of executing a + <glossterm linkend="glossary-query">query</glossterm> to take advantage + of parallel processes on servers with multiple <acronym>CPU</acronym>s. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-partition"> + <glossterm>Partition</glossterm> + <glossdef> + <para> + In reference to a <glossterm linkend="glossary-table">Table</glossterm>: + A <glossterm linkend="glossary-table">Table</glossterm> that can be queried directly, + or via a partitioned table, which is a collection of + sub-tables, each capable of holding one defined + subset of information that does not overlap with any other + table in the collection. + </para> + </glossdef> + <glossdef> + <para> + In reference to a <glossterm linkend="glossary-window-function">window function</glossterm>: + a partition is a definition that identifies which neighboring + <glossterm linkend="glossary-tuple">Row</glossterm>s can be considered by the + function. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-postmaster"> + <glossterm>Postmaster (process)</glossterm> + <glossdef> + <para> + The very first process of an <glossterm linkend="glossary-instance">Instance</glossterm>. It + starts and manages the other auxiliary processes and creates + <glossterm linkend="glossary-backend">backend processes</glossterm> + on demand. + </para> + <para> + For more information, see + <xref linkend="server-start"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-primary-server"> + <glossterm>Primary (server)</glossterm> + <glossdef> + <para> + When two or more <glossterm linkend="glossary-database">Database</glossterm>s 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> + <para> + A special case of a + <glossterm linkend="glossary-unique-constraint">unique constraint</glossterm> + defined on a + <glossterm linkend="glossary-table">Table</glossterm> or other + <glossterm linkend="glossary-relation">Relation</glossterm> that also + guarantees that all of the + <glossterm linkend="glossary-attribute">Attribute</glossterm>s + within the <glossterm linkend="glossary-primary-key">Primary Key</glossterm> + do not have <glossterm linkend="glossary-null">Null</glossterm> values. + As the name implies, there can be only one + primary key per table, though it is possible to have multiple unique + constraints that also have no null-capable attributes. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-procedure"> + <glossterm>Procedure</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 may seem + 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 + as <command>COMMIT</command> and <command>ROLLBACK</command>. + </para> + <para> + For more information, see + <xref linkend="sql-createprocedure"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-query"> + <glossterm>Query</glossterm> + <glossdef> + <para> + A request sent by a client to a <glossterm linkend="glossary-backend">backend</glossterm>, + usually to return results or to modify data on the database. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-planner"> + <glossterm>Query Planner</glossterm> + <glossdef> + <para> + The part of <productname>PostgreSQL</productname> that is devoted to + determining (<firstterm>planning</firstterm>) the most efficient way to + execute <glossterm linkend="glossary-query">queries</glossterm>. + Also known as <firstterm>query optimizer</firstterm>, + <firstterm>optimizer</firstterm>, or simply <firstterm>planner</firstterm>. + </para> + </glossdef> + </glossentry> + + <glossentry> + <glossterm>Record</glossterm> + <glosssee otherterm="glossary-tuple" /> + </glossentry> + + <glossentry> + <glossterm>Recycling</glossterm> + <glosssee otherterm="glossary-wal-file" /> + </glossentry> + + <glossentry id="glossary-referential-integrity"> + <glossterm>Referential Integrity</glossterm> + <glossdef> + <para> + A means of restricting data in one <glossterm linkend="glossary-relation">Relation</glossterm> + by a <glossterm linkend="glossary-foreign-key">Foreign Key</glossterm> + so that it must have matching data in another + <glossterm linkend="glossary-relation">Relation</glossterm>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-relation"> + <glossterm>Relation</glossterm> + <glossdef> + <para> + The generic term for all objects in a <glossterm linkend="glossary-database">Database</glossterm> + that have a name and a list of <glossterm linkend="glossary-attribute">Attribute</glossterm>s + defined in a specific order. <glossterm linkend="glossary-table">Table</glossterm>s, + <glossterm linkend="glossary-view">View</glossterm>s, <glossterm linkend="glossary-foreign-table">Foreign Table</glossterm>s, + <glossterm linkend="glossary-materialized-view">Materialized View</glossterm>s, and + <glossterm linkend="glossary-index">Index</glossterm>es are all relations. + </para> + <para> + <firstterm>Class</firstterm> is an archaic synonym for + <firstterm>relation</firstterm>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-replica"> + <glossterm>Replica</glossterm> + <glossdef> + <para> + A <glossterm linkend="glossary-database">Database</glossterm> that is paired with a + <glossterm linkend="glossary-primary-server">primary</glossterm> + database and is maintaining a copy of some or + all of the primary <glossterm linkend="glossary-database">Database</glossterm>'s data. The foremost + reasons for doing this are to allow for greater access to that data, + and to maintain availability of the data in the event that the + <glossterm linkend="glossary-primary-server">primary</glossterm> becomes unavailable. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-replication"> + <glossterm>Replication</glossterm> + <glossdef> + <para> + The act of reproducing data on one <glossterm linkend="glossary-server">Server</glossterm> onto + another server called a <glossterm linkend="glossary-replica">Replica</glossterm>. This can take the + form of <firstterm>physical replication</firstterm>, where all file + changes from one server are copied verbatim, + or <firstterm>logical replication</firstterm> where a defined subset + of data changes are conveyed using a higher-level representation. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-result-set"> + <glossterm>Result Set</glossterm> + <glossdef> + <para> + A data structure transmitted from a <glossterm linkend="glossary-backend">Backend Process</glossterm> to + client program upon the completion of a <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">Row</glossterm>s with the same ordered set of + <glossterm linkend="glossary-attribute">Attribute</glossterm>s. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-revoke"> + <glossterm>Revoke</glossterm> + <glossdef> + <para> + A command to prevent access to a named set of + <glossterm linkend="glossary-database">Database</glossterm> objects for a named list of + <glossterm linkend="glossary-user">User</glossterm>s and <glossterm linkend="glossary-role">Role</glossterm>s. + </para> + <para> + For more information, see + <xref linkend="sql-revoke"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-role"> + <glossterm>Role</glossterm> + <glossdef> + <para> + A collection of access privileges to the + <glossterm linkend="glossary-database">Database</glossterm>. <glossterm linkend="glossary-role">Role</glossterm>s are + themselves a privilege that can be granted to other roles. This is + often done for convenience or to ensure completeness when multiple + <glossterm linkend="glossary-user">User</glossterm>s need the same privileges. + </para> + <para> + For more information, see + <xref linkend="sql-createrole"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-rollback"> + <glossterm>Rollback</glossterm> + <glossdef> + <para> + A command to undo all of the operations performed since the beginning + of a <glossterm linkend="glossary-transaction">Transaction</glossterm>. + </para> + <para> + For more information, see + <xref linkend="sql-rollback"/>. + </para> + </glossdef> + </glossentry> + + <glossentry> + <glossterm>Row</glossterm> + <glosssee otherterm="glossary-tuple" /> + </glossentry> + + <glossentry id="glossary-savepoint"> + <glossterm>Savepoint</glossterm> + <glossdef> + <para> + A special mark inside the sequence of steps in a + <glossterm linkend="glossary-transaction">Transaction</glossterm>. Data modifications after this + point in time may be reverted to the time of the savepoint. + </para> + <para> + For more information, see + <xref linkend="sql-savepoint"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-schema"> + <glossterm>Schema</glossterm> + <glossdef> + <para> + A <glossterm linkend="glossary-schema">Schema</glossterm> is a namespace for + <glossterm linkend="glossary-sql-object">SQL object</glossterm>s, which all reside in the same + <glossterm linkend="glossary-database">database</glossterm>. Each + <glossterm linkend="glossary-sql-object">SQL object</glossterm> must reside in exactly one + <glossterm linkend="glossary-schema">Schema</glossterm>. + </para> + <para> + The names of <glossterm linkend="glossary-sql-object">SQL Objects</glossterm> + of the same type in the same schema are enforced unique. There is no + restriction on reusing a name in multiple schemas. + </para> + <para> + Many <glossterm linkend="glossary-sql-object">SQL Object</glossterm>s reside in the default + <glossterm linkend="glossary-schema">Schema</glossterm> <literal>public</literal>, but it is + expected that more schemas are created to hold application-specific + <glossterm linkend="glossary-sql-object">SQL Object</glossterm>s. + </para> + </glossdef> + <glossdef> + <para> + More generically, the term <firstterm>Schema</firstterm> is used to mean all data descriptions + (<glossterm linkend="glossary-table">Table</glossterm> definitions, + <glossterm linkend="glossary-constraint">Constraint</glossterm>s, comments, etc) + for a given <glossterm linkend="glossary-database">Database</glossterm> or + subset thereof. + </para> + <para> + For more information, see + <xref linkend="ddl-schemas"/>. + </para> + </glossdef> + </glossentry> + + <glossentry> + <glossterm>Segment</glossterm> + <glosssee otherterm="glossary-file-segment" /> + </glossentry> + + <glossentry id="glossary-select"> + <glossterm>Select</glossterm> + <glossdef> + <para> + The <acronym>SQL</acronym> command used to query a <glossterm linkend="glossary-database">Database</glossterm>. + Normally, <command>SELECT</command>s are not expected to modify the + <glossterm linkend="glossary-database">Database</glossterm> in any way, but it is possible that + <glossterm linkend="glossary-function">Function</glossterm>s invoked within the query could have + side effects that do modify data. + </para> + <para> + For more information, see + <xref linkend="sql-select"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-serializable"> + <glossterm>Serializable</glossterm> + <glossdef> + <para> + Transactions defined as <literal>SERIALIZABLE</literal> are unable to + see changes made within other transactions. In effect, for the + initializing session the entire <glossterm linkend="glossary-database">Database</glossterm> + appears to be frozen for the duration of the + <glossterm linkend="glossary-transaction">Transaction</glossterm>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-server"> + <glossterm>Server</glossterm> + <glossdef> + <para> + A computer on which <productname>PostgreSQL</productname> + <glossterm linkend="glossary-instance">instances</glossterm> run. + The term <firstterm>server</firstterm> denotes real hardware, a + container, or a Virtual Machine. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-session"> + <glossterm>Session</glossterm> + <glossdef> + <para> + A state that allows a client and a backend to interact, + communicating over a <glossterm linkend="glossary-connection">connection</glossterm>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-sequence"> + <glossterm>Sequence</glossterm> + <glossdef> + <para> + A <glossterm linkend="glossary-database">Database</glossterm> object which + represents the mathematical concept of a numerical integral sequence. + It can be thought of as a <glossterm linkend="glossary-table">Table</glossterm> + with exactly one <glossterm linkend="glossary-tuple">Row</glossterm> and + one <glossterm linkend="glossary-column">Column</glossterm>. The + value stored is known as the current value. A + <glossterm linkend="glossary-sequence">Sequence</glossterm> has a defined + direction (usually increasing) and an interval step (usually 1). + Whenever the <literal>NEXTVAL</literal> pseudo-column of a + <glossterm linkend="glossary-sequence">Sequence</glossterm> is accessed, + the current value is moved in the defined direction by the defined + interval step, that value is returned to the invoking query, + and the current value of the sequence is updated to reflect the new value. + The value can be updated multiple times in a single query, + the net effect being that each row selected will have a different value. + Values taken from a + <glossterm linkend="glossary-sequence">Sequence</glossterm> are never + reverted, even in the case of a + <glossterm linkend="glossary-rollback">Rollback</glossterm>, which means + that the <glossterm linkend="glossary-sequence">Sequence</glossterm> + will never generate the same number twice, which makes it useful for + generating + <glossterm linkend="glossary-primary-key">Primary Key</glossterm> values. + </para> + <para> + For more information, see + <xref linkend="sql-createsequence"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-shared-memory"> + <glossterm>Shared Memory</glossterm> + <glossdef> + <para> + <acronym>RAM</acronym> which is used by the processes common to an + <glossterm linkend="glossary-instance">Instance</glossterm>. It mirrors parts of + <glossterm linkend="glossary-database">Database</glossterm> files, provides an area for + <glossterm linkend="glossary-wal-record">WAL Record</glossterm>s, and stores additional common + information. Note that <glossterm linkend="glossary-shared-memory">Shared Memory</glossterm> belongs to + the complete <glossterm linkend="glossary-instance">Instance</glossterm>, not to a single + <glossterm linkend="glossary-database">Database</glossterm>. + </para> + <para> + <glossterm linkend="glossary-shared-memory">Shared Memory</glossterm> is organized into pages. If a + page is modified, it is called a dirty page until it is written back + to the file system. + </para> + <para> + For more information, see + <xref linkend="runtime-config-resource-memory"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-sql-object"> + <glossterm>SQL Object</glossterm> + <glossdef> + <para> + A <glossterm linkend="glossary-table">table</glossterm>, + <glossterm linkend="glossary-view">view</glossterm>, + <glossterm linkend="glossary-materialized-view">materialized view</glossterm>, + <glossterm linkend="glossary-index">index</glossterm>, + <glossterm linkend="glossary-constraint">constraint</glossterm>, + <glossterm linkend="glossary-sequence">sequence</glossterm>, + <glossterm linkend="glossary-function">function</glossterm>, + <glossterm linkend="glossary-procedure">procedure</glossterm>, + <glossterm linkend="glossary-trigger">trigger</glossterm>, + data type, or operator. Every one of those SQL objects + belong to exactly one <glossterm linkend="glossary-schema">Schema</glossterm>. + </para> + <para> + There also exist SQL objects that do not belong to schemas; those include + <glossterm linkend="glossary-extension">extensions</glossterm>, + <glossterm linkend="glossary-cast">data type cases</glossterm>, + and + <glossterm linkend="glossary-foreign-data-wrapper">foreign data wrappers</glossterm>. + </para> + <para> + For more information, see + <xref linkend="manage-ag-overview"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-stats-collector"> + <glossterm>Stats Collector</glossterm> + <glossdef> + <para> + This process collects statistical information about the + <glossterm linkend="glossary-cluster">Cluster</glossterm>'s activities. + </para> + <para> + For more information, see + <xref linkend="monitoring-stats"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-system-catalog"> + <glossterm>System Catalog</glossterm> + <glossdef> + <para> + A collection of <glossterm linkend="glossary-table">Table</glossterm>s and + <glossterm linkend="glossary-view">View</glossterm>s which describe the structure of all + <acronym>SQL</acronym> objects of the <glossterm linkend="glossary-database">Database</glossterm> + and the <glossterm linkend="glossary-global-sql-object">Global SQL Object</glossterm>s of the + <glossterm linkend="glossary-cluster">Cluster</glossterm>. The <glossterm linkend="glossary-system-catalog">System + Catalog</glossterm> resides in the schema + <literal>pg_catalog</literal>. Main parts are mirrored as + <glossterm linkend="glossary-view">View</glossterm>s in the <glossterm linkend="glossary-schema">Schema</glossterm> + <literal>information_schema</literal>. + </para> + <para> + For more information, see + <xref linkend="ddl-schemas"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-table"> + <glossterm>Table</glossterm> + <glossdef> + <para> + A collection of <glossterm linkend="glossary-tuple">tuples</glossterm> having + a common data structure (the same number of + <glossterm linkend="glossary-attribute">attributes</glossterm>, in the same + order, having the same name and type per position). + A table is the most common form of + <glossterm linkend="glossary-relation">Relation</glossterm> in + <productname>PostgreSQL</productname>. + </para> + <para> + For more information, see + <xref linkend="sql-createtable"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-tablespace"> + <glossterm>Tablespace</glossterm> + <glossdef> + <para> + A named location on the server filesystem. All <glossterm linkend="glossary-sql-object">SQL Object</glossterm>s + which require storage beyond their definition in the + <glossterm linkend="glossary-system-catalog">System Catalog</glossterm> + must belong to a single tablespace. + </para> + <para> + For more information, see + <xref linkend="manage-ag-tablespaces"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-temporary-table"> + <glossterm>Temporary Table</glossterm> + <glossdef> + <para> + <glossterm linkend="glossary-table">Table</glossterm>s that exist either + for the lifetime of a + <glossterm linkend="glossary-session">Session</glossterm> or a + <glossterm linkend="glossary-transaction">Transaction</glossterm>, as + specified at the time of creation. The data in them is not visible to + other sessions, and is not + <glossterm linkend="glossary-logged">Logged</glossterm>. + Temporary tables are often used to store intermediate data for a + multi-step operation. + </para> + <para> + For more information, see + <xref linkend="sql-createtable"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-transaction"> + <glossterm>Transaction</glossterm> + <glossdef> + <para> + A combination of commands that must act as a single + <glossterm linkend="glossary-atomic">Atomic</glossterm> command: they all + succeed or all fail as a single unit, and their effects are not visible to + other <glossterm linkend="glossary-session">Session</glossterm>s until + the transaction is complete. + </para> + <para> + For more information, see + <xref linkend="transaction-iso"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-trigger"> + <glossterm>Trigger</glossterm> + <glossdef> + <para> + A <glossterm linkend="glossary-function">Function</glossterm> which can be defined to execute + whenever a certain operation (<command>INSERT</command>, + <command>UPDATE</command>, <command>DELETE</command>, + <command>TRUNCATE</command>) is applied to a <glossterm linkend="glossary-relation">Relation</glossterm>. + A <glossterm linkend="glossary-trigger">Trigger</glossterm> + executes within the same <glossterm linkend="glossary-transaction">Transaction</glossterm> as the + statement which invoked it, and if the <glossterm linkend="glossary-function">Function</glossterm> + fails, then the invoking statement also fails. + </para> + <para> + For more information, see + <xref linkend="sql-createtrigger"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-tuple"> + <glossterm>Tuple</glossterm> + <glossdef> + <para> + A collection of <glossterm linkend="glossary-attribute">Attribute</glossterm>s in a fixed order. + That order may be defined by the <glossterm linkend="glossary-table">Table</glossterm> where + the <glossterm linkend="glossary-tuple">Tuple</glossterm> is found, in which case the + <glossterm linkend="glossary-tuple">Tuple</glossterm> is often called a + row or record. + It may also be defined by the structure of a + <glossterm linkend="glossary-result-set">Result Set</glossterm>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-unique-constraint"> + <glossterm>Unique Constraint</glossterm> + <glossdef> + <para> + A type of <glossterm linkend="glossary-constraint">constraint</glossterm> + defined on a <glossterm linkend="glossary-relation">relation</glossterm> + which restricts the values allowed in one or a combination of columns + so that each value or combination of values can only appear once in the + relation — that is, no other row in the relation contains values + that are equal to those. + </para> + <para> + Because <glossterm linkend="glossary-null">null values</glossterm> are + not considered equal to each other, multiple rows with null values are + allowed to exist without violating the unique constraint. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-unlogged"> + <glossterm>Unlogged</glossterm> + <glossdef> + <para> + Changes to an unlogged <glossterm linkend="glossary-relation">Relation</glossterm> + are not reflected in the <glossterm linkend="glossary-wal">WAL</glossterm>. + This disables replication and crash recovery for these relations. + </para> + <para> + The primary use of unlogged tables is for storing + transient work data that must be shared across processes. + </para> + <para> + <glossterm linkend="glossary-temporary-table">Temporary Table</glossterm>s are always unlogged. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-update"> + <glossterm>Update</glossterm> + <glossdef> + <para> + A <acronym>SQL</acronym> command used to modify + <glossterm linkend="glossary-tuple">rows</glossterm> + that may already exist in a specified <glossterm linkend="glossary-table">Table</glossterm>. + It cannot create or remove rows. + </para> + <para> + For more information, see + <xref linkend="sql-update"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-user"> + <glossterm>User</glossterm> + <glossdef> + <para> + A <glossterm linkend="glossary-role">Role</glossterm> that has the <literal>LOGIN</literal> + privilege is said to be a <glossterm linkend="glossary-user">User</glossterm>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-user-mapping"> + <glossterm>User Mapping</glossterm> + <glossdef> + <para> + The translation of login credentials in the local + <glossterm linkend="glossary-database">Database</glossterm> to credentials + in a remote data system defined by a + <glossterm linkend="glossary-foreign-data-wrapper">Foreign Data Wrapper</glossterm>. + </para> + <para> + For more information, see + <xref linkend="sql-createusermapping"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-vacuum"> + <glossterm>Vacuum</glossterm> + <glossdef> + <para> + The process of removing outdated <glossterm linkend="glossary-tuple">tuple + versions</glossterm> from tables, and other closely related + garbage-collection-like processing required by <productname>PostgreSQL</productname>'s + implementation of <glossterm linkend="glossary-mvcc">MVCC</glossterm>. + This can be initiated through the use of + the <command>VACUUM</command> command, but can also be handled automatically + via <glossterm linkend="glossary-autovacuum">Autovacuum</glossterm> processes. + </para> + <para> + For more information, see + <xref linkend="routine-vacuuming"/> . + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-view"> + <glossterm>View</glossterm> + <glossdef> + <para> + A <glossterm linkend="glossary-relation">Relation</glossterm> that is defined by a + <command>SELECT</command> statement, but has no storage of its own. + Any time a query references a <glossterm linkend="glossary-view">View</glossterm>, the + definition of the <glossterm linkend="glossary-view">View</glossterm> is substituted into the + query as if the user had typed that subquery instead of the name of + the <glossterm linkend="glossary-view">View</glossterm>. + </para> + <para> + For more information, see + <xref linkend="sql-createview"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-wal-archiver"> + <glossterm>WAL Archiver (process)</glossterm> + <glossdef> + <para> + A process that saves copies of <glossterm linkend="glossary-wal-file">WAL File</glossterm>s + for the purposes of creating backups or keeping + <glossterm linkend="glossary-replica">Replica</glossterm>s current. + </para> + <para> + For more information, see + <xref linkend="continuous-archiving"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-wal-file"> + <glossterm>WAL File</glossterm> + <glossdef> + <para> + Also known as <firstterm>WAL segment</firstterm> or + <firstterm>WAL segment file</firstterm>. + Each of the numerically-numbered files that provide storage space for + <glossterm linkend="glossary-wal">WAL</glossterm>. + The files are all of the same predefined size + and are written in sequential order, interspersing changes + as they occur in multiple simultaneous sessions. + If the system crashes, the files are read in order, and each of the + changes are replayed to restore the system to the state as it was + before the crash. + </para> + <para> + Each WAL file can be released after a + <glossterm linkend="glossary-checkpoint">checkpoint</glossterm> + writes all the changes in it to the corresponding data files. + Releasing the file can be done either by deleting it, or by changing its + name so that it will be used in the future, which is called + <firstterm>recycling</firstterm>. + </para> + <para> + For more information, see + <xref linkend="wal-internals"/>. + </para> + </glossdef> + </glossentry> + + <glossentry> + <glossterm>WAL</glossterm> + <glosssee otherterm="glossary-wal" /> + </glossentry> + + <glossentry id="glossary-wal-record"> + <glossterm>WAL Record</glossterm> + <glossdef> + <para> + A low-level description of an individual data change. + It contains sufficient information for the data change to be + re-executed (<firstterm>replayed</firstterm>) in case a system failure + causes the change to be lost. + WAL records use a non-printable binary format. + </para> + <para> + For more information, see + <xref linkend="wal-internals"/>. + </para> + </glossdef> + </glossentry> + + <glossentry> + <glossterm>WAL Segment</glossterm> + <glosssee otherterm="glossary-wal-file" /> + </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 id="linkend-shared-memory">shared memory</glossterm> to + <glossterm id="linkend-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> + <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>. + 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. + Also known as <firstterm>analytic functions</firstterm>. + </para> + <para> + For more information, see + <xref linkend="tutorial-window"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-wal"> + <glossterm>Write-Ahead Log</glossterm> + <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. It comprises many individual + <glossterm linkend="glossary-wal-record">WAL records</glossterm> written + sequentially to <glossterm linkend="glossary-wal-file">WAL files</glossterm>. + </para> + </glossdef> + </glossentry> + </glosslist> +</appendix> diff --git a/doc/src/sgml/postgres.sgml b/doc/src/sgml/postgres.sgml index 1f7bd32878..ba3d626102 100644 --- a/doc/src/sgml/postgres.sgml +++ b/doc/src/sgml/postgres.sgml @@ -278,6 +278,7 @@ &docguide; &limits; &acronyms; + &glossary; &color; </part>
