diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml index ce33df9e58..8854bda05f 100644 --- a/doc/src/sgml/catalogs.sgml +++ b/doc/src/sgml/catalogs.sgml @@ -6,6 +6,23 @@ System Catalogs + + Overview + + + The term system catalog is a widely used + synonym for the schema pg_catalog and + its tables. They are listed in + with links to more detailed documentation. + + + + Most system catalogs are copied from the template database during + database creation and are thereafter database-specific. A few + catalogs are physically shared across all databases in a cluster; + these are noted in the descriptions of the individual catalogs. + + The system catalogs are the place where a relational database management system stores schema metadata, such as information about @@ -23,21 +40,6 @@ of the system catalogs is ever decreasing. - - Overview - - - lists the system catalogs. - More detailed documentation of each catalog follows below. - - - - Most system catalogs are copied from the template database during - database creation and are thereafter database-specific. A few - catalogs are physically shared across all databases in a cluster; - these are noted in the descriptions of the individual catalogs. - - System Catalogs diff --git a/doc/src/sgml/information_schema.sgml b/doc/src/sgml/information_schema.sgml index 7a995a1b64..ea8561d9e5 100644 --- a/doc/src/sgml/information_schema.sgml +++ b/doc/src/sgml/information_schema.sgml @@ -7,46 +7,8 @@ information schema - - The information schema consists of a set of views that contain - information about the objects defined in the current database. The - information schema is defined in the SQL standard and can therefore - be expected to be portable and remain stable — unlike the system - catalogs, which are specific to - PostgreSQL and are modeled after - implementation concerns. The information schema views do not, - however, contain information about - PostgreSQL-specific features; to inquire - about those you need to query the system catalogs or other - PostgreSQL-specific views. - - - - - When querying the database for constraint information, it is possible - for a standard-compliant query that expects to return one row to - return several. This is because the SQL standard requires constraint - names to be unique within a schema, but - PostgreSQL does not enforce this - restriction. PostgreSQL - automatically-generated constraint names avoid duplicates in the - same schema, but users can specify such duplicate names. - - - - This problem can appear when querying information schema views such - as check_constraint_routine_usage, - check_constraints, domain_constraints, and - referential_constraints. Some other views have similar - issues but contain the table name to help distinguish duplicate - rows, e.g., constraint_column_usage, - constraint_table_usage, table_constraints. - - - - - The Schema + Overview The information schema itself is a schema named @@ -57,6 +19,44 @@ the space savings achieved by that are minuscule). + + The information schema consists of a set of views to tables + in the schema pg_catalog, so it contains + information about the objects defined in the current database. The + information schema is defined in the SQL standard and can therefore + be expected to be portable and remain stable — unlike the system + catalogs, which are specific to + PostgreSQL and are modeled after + implementation concerns. The information schema views do not, + however, contain information about + PostgreSQL-specific features; to inquire + about those you need to query the system catalogs or other + PostgreSQL-specific views. + + + + + When querying the database for constraint information, it is possible + for a standard-compliant query that expects to return one row to + return several. This is because the SQL standard requires constraint + names to be unique within a schema, but + PostgreSQL does not enforce this + restriction. PostgreSQL + automatically-generated constraint names avoid duplicates in the + same schema, but users can specify such duplicate names. + + + + This problem can appear when querying information schema views such + as check_constraint_routine_usage, + check_constraints, domain_constraints, and + referential_constraints. Some other views have similar + issues but contain the table name to help distinguish duplicate + rows, e.g., constraint_column_usage, + constraint_table_usage, table_constraints. + + + By default, the information schema is not in the schema search path, so you need to access all objects in it through qualified @@ -65,6 +65,7 @@ should be careful if you want to put the information schema in the path. +