<!-- $Header: /cvsroot/pgsql/doc/src/sgml/information_schema.sgml,v 1.1 2003/05/18 20:55:56 petere Exp $ -->

<chapter id="information-schema">
 <title>The Information Schema</title>

 <indexterm zone="information-schema">
  <primary>information schema</primary>
 </indexterm>

 <para>
  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 modelled 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.
 </para>

 <sect1 id="infoschema-schema">
  <title>The Schema</title>

  <para>
   The information schema itself is a schema named
   <literal>information_schema</literal>.  This schema automatically
   exists in all databases.  The owner of this schema is the initial
   database user in the cluster, and that user naturally has all the
   privileges on this schema, including the ability to drop it (but
   the space savings achieved by this are minuscule).
  </para>

  <para>
   By default, the information schema is not in the schema search
   path, so you need to access all objects in it through qualified
   names.  Since the names of some of the objects in the information
   schema are generic names that might occur in user applications, you
   should be careful if you want to put the information schema in the
   path.
  </para>
 </sect1>

 <sect1 id="infoschema-datatypes">
  <title>Data Types</title>

  <para>
   The columns of the information schema views use special data types
   that are defined in the information schema.  These are defined as
   simple domains over ordinary built-in types.  You should not use
   these types for work outside the information schema, but your
   applications must be prepared for them if they select from the
   information schema.
  </para>

  <para>
   These types are:

   <variablelist>
    <varlistentry>
     <term><type>cardinal_number</type></term>
     <listitem>
      <para>
       A nonnegative integer.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><type>character_data</type></term>
     <listitem>
      <para>
       A character string (without specific maximum length).
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><type>sql_identifier</type></term>
     <listitem>
      <para>
       A character string.  This type is used for SQL identifiers, the
       type <type>character_data</type> is used for any other kind of
       text data.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><type>time_stamp</type></term>
     <listitem>
      <para>
       A domain over the type <type>timestamp</type>
      </para>
     </listitem>
    </varlistentry>
   </variablelist>

   Every column in the information schema has one of these four types.
  </para>

  <para>
   Boolean (true/false) data is represented in the information schema
   by a column of type <type>character_data</type> that contains
   either <literal>YES</literal> or <literal>NO</literal>.  (The
   information schema was invented before the type
   <type>boolean</type> was added to the SQL standard, so this
   convention is necessary to keep the information schema backward
   compatible.)
  </para>
 </sect1>

 <sect1 id="infoschema-information-schema-catalog-name">
  <title><literal>information_schema_catalog_name</literal></title>

  <para>
   <literal>information_schema_catalog_name</literal> is a table that
   always contains one row and one column containing the name of the
   current database (current catalog, in SQL terminology).
  </para>

  <table>
   <title><literal>information_schema_catalog_name</literal> Columns</title>

   <tgroup cols="3">
    <thead>
     <row>
      <entry>Name</entry>
      <entry>Data Type</entry>
      <entry>Description</entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry><literal>catalog_name</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the database that contains this information schema</entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>

 <sect1 id="infoschema-check-constraints">
  <title><literal>check_constraints</literal></title>

  <para>
   The view <literal>check_constraints</literal> contains all check
   constraints, either defined on a table or on a domain, that are
   owned by the current user.
  </para>

  <table>
   <title><literal>check_constraints</literal> Columns</title>

   <tgroup cols="3">
    <thead>
     <row>
      <entry>Name</entry>
      <entry>Data Type</entry>
      <entry>Description</entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry><literal>constraint_catalog</literal></entry>
      <entry><literal>sql_identifier</literal></entry>
      <entry>Name of the database containing the constraint (always the current database)</entry>
     </row>

     <row>
      <entry><literal>constraint_schema</literal></entry>
      <entry><literal>sql_identifier</literal></entry>
      <entry>Name of the schema containing the constraint</entry>
     </row>

     <row>
      <entry><literal>constraint_name</literal></entry>
      <entry><literal>sql_identifier</literal></entry>
      <entry>Name of the constraint</entry>
     </row>

     <row>
      <entry><literal>check_clause</literal></entry>
      <entry><literal>character_data</literal></entry>
      <entry>The check expression of the check constraint</entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>

 <sect1 id="infoschema-column-domain-usage">
  <title><literal>column_domain_usage</literal></title>

  <para>
   The view <literal>column_domain_usage</literal> identifies all
   columns (of a table or a view) that make use of some domain defined
   in the current database and owned by the current user.
  </para>

  <table>
   <title><literal>column_domain_usage</literal> Columns</title>

   <tgroup cols="3">
    <thead>
     <row>
      <entry>Name</entry>
      <entry>Data Type</entry>
      <entry>Description</entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry><literal>domain_catalog</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the database containing the domain (always the current database)</entry>
     </row>

     <row>
      <entry><literal>domain_schema</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the schema containing the domain</entry>
     </row>

     <row>
      <entry><literal>domain_name</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the domain</entry>
     </row>

     <row>
      <entry><literal>table_catalog</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the database containing the table (always the current database)</entry>
     </row>

     <row>
      <entry><literal>table_schema</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the schema containing the table</entry>
     </row>

     <row>
      <entry><literal>table_name</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the table</entry>
     </row>

     <row>
      <entry><literal>column_name</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the column</entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>

 <sect1 id="infoschema-columns">
  <title><literal>columns</literal></title>

  <para>
   The view <literal>columns</literal> contains information about all
   table columns (or view columns) in the database.  System columns
   (<literal>oid</>, etc.) are not included.
  </para>

  <table>
   <title><literal>columns</literal> Columns</title>

   <tgroup cols="3">
    <thead>
     <row>
      <entry>Name</entry>
      <entry>Data Type</entry>
      <entry>Description</entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry><literal>table_catalog</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the database containing the table (always the current database)</entry>
     </row>

     <row>
      <entry><literal>table_schema</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the schema containing the table</entry>
     </row>

     <row>
      <entry><literal>table_name</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the table</entry>
     </row>

     <row>
      <entry><literal>column_name</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the column</entry>
     </row>

     <row>
      <entry><literal>ordinal_position</literal></entry>
      <entry><type>cardinal_number</type></entry>
      <entry>Ordinal position of the column within the table (count starts at 1)</entry>
     </row>

     <row>
      <entry><literal>column_default</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>
       Default expression of the column (null if the current user is
       not the owner of the table containing the column)
      </entry>
     </row>

     <row>
      <entry><literal>is_nullable</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>
       <literal>YES</literal> if the column is possibly nullable,
       <literal>NO</literal> if it is known not nullable.  A not-null
       constraint is one way a column can be known not nullable, but
       there may be others.
      </entry>
     </row>

     <row>
      <entry><literal>data_type</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>Data type of the column</entry>
     </row>

     <row>
      <entry><literal>character_maximum_length</literal></entry>
      <entry><type>cardinal_number</type></entry>
      <entry>
       If the column has a character or bit string type, the declared
       maximum length; null for all other data types or if no maximum
       length was declared.
      </entry>
     </row>

     <row>
      <entry><literal>character_octet_length</literal></entry>
      <entry><type>cardinal_number</type></entry>
      <entry>
       If the column has a character type, the maximum possible length
       in octets (bytes) of a datum (this should not be of concern to
       PostgreSQL users); null for all other data types.
      </entry>
     </row>

     <row>
      <entry><literal>numeric_precision</literal></entry>
      <entry><type>cardinal_number</type></entry>
      <entry>
       If the column has a numeric type, this column contains the
       (declared or implicit) precision of the type for this column.
       The precision indicates the number of significant digits.  It
       may be expressed in decimal (base 10) or binary (base 2) terms,
       as specified in the column
       <literal>numeric_precision_radix</literal>.  For all other data
       types, this column is null.
      </entry>
     </row>

     <row>
      <entry><literal>numeric_precision_radix</literal></entry>
      <entry><type>cardinal_number</type></entry>
      <entry>
       If the column has a numeric type, this column indicates in
       which base the values in the columns
       <literal>numeric_precision</literal> and
       <literal>numeric_scale</literal> are expressed.  The value is
       either 2 or 10.  For all other data types, this column is null.
      </entry>
     </row>

     <row>
      <entry><literal>numeric_scale</literal></entry>
      <entry><type>cardinal_number</type></entry>
      <entry>
       If the column has an exact numeric type, this column contains
       the (declared or implicit) scale of the type for this column.
       The scale indicates the number of significant digits to the
       right of the decimal point.  It may be expressed in decimal
       (base 10) or binary (base 2) terms, as specified in the column
       <literal>numeric_precision_radix</literal>.  For all other data
       types, this column is null.
      </entry>
     </row>

     <row>
      <entry><literal>datetime_precision</literal></entry>
      <entry><type>cardinal_number</type></entry>
      <entry>
       If the column has a date, time, or interval type, the declared
       precision; null for all other data types or if no precision was
       declared.
      </entry>
     </row>

     <row>
      <entry><literal>interval_type</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>Not yet implemented</entry>
     </row>

     <row>
      <entry><literal>interval_precision</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>Not yet implemented</entry>
     </row>

     <row>
      <entry><literal>character_set_catalog</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>

     <row>
      <entry><literal>character_set_schema</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>

     <row>
      <entry><literal>character_set_name</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>

     <row>
      <entry><literal>collation_catalog</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>

     <row>
      <entry><literal>collation_schema</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>

     <row>
      <entry><literal>collation_name</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>

     <row>
      <entry><literal>domain_catalog</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>
       If the column has a domain type, the name of the database that
       the domain is defined in (always the current database), else
       null.
      </entry>
     </row>

     <row>
      <entry><literal>domain_schema</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>
       If the column has a domain type, the name of the schema that
       the domain is defined in, else null.
      </entry>
     </row>

     <row>
      <entry><literal>domain_name</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>If the column has a domain type, the name of the domain, else null.</entry>
     </row>

     <row>
      <entry><literal>udt_catalog</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>
       Name of the database that the column data type is defined in
       (always the current database), null if the column has a domain
       type.
      </entry>
     </row>

     <row>
      <entry><literal>udt_schema</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>
       Name of the schema that the column data type is defined in,
       null if the column has a domain type.
      </entry>
     </row>

     <row>
      <entry><literal>udt_name</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the column data type, null if the column has a domain type.</entry>
     </row>

     <row>
      <entry><literal>scope_catalog</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>

     <row>
      <entry><literal>scope_schema</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>

     <row>
      <entry><literal>scope_name</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>

     <row>
      <entry><literal>maximum_cardinality</literal></entry>
      <entry><type>cardinal_number</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>

     <row>
      <entry><literal>dtd_identifier</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>

     <row>
      <entry><literal>is_self_referencing</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>

 <sect1 id="infoschema-domain-constraints">
  <title><literal>domain_constraints</literal></title>

  <para>
   The view <literal>domain_constraints</literal> contains all
   constraints belonging to domains.
  </para>

  <table>
   <title><literal>domain_constraints</literal> Columns</title>

   <tgroup cols="3">
    <thead>
     <row>
      <entry>Name</entry>
      <entry>Data Type</entry>
      <entry>Description</entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry><literal>constraint_catalog</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the database that contains the constraint (always the current database)</entry>
     </row>

     <row>
      <entry><literal>constraint_schema</literal</entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the schema that contains the constraint</entry>
     </row>

     <row>
      <entry><literal>constraint_name</literal</entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the constraint</entry>
     </row>

     <row>
      <entry><literal>domain_catalog</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the database that contains the domain (always the current database)</entry>
     </row>

     <row>
      <entry><literal>domain_schema</literal</entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the schema that contains the domain</entry>
     </row>

     <row>
      <entry><literal>domain_name</literal</entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the domain</entry>
     </row>

     <row>
      <entry><literal>is_deferrable</literal></entry>
      <entry><type>character_data</type></entry>
      <entry><literal>YES</literal> if the constraint is deferrable, <literal>NO</literal> if not</entry>
     </row>

     <row>
      <entry><literal>initially_deferred</literal></entry>
      <entry><type>character_data</type></entry>
      <entry><literal>YES</literal> if the constraint is deferrable and initially deferred, <literal>NO</literal> if not</entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>

 <sect1 id="infoschema-domains">
  <title><literal>domains</literal></title>

  <para>
   The view <literal>domains</literal> contains all domains defined in
   the current database.
  </para>

  <table>
   <title><literal>domains</literal> Columns</title>

   <tgroup cols="3">
    <thead>
     <row>
      <entry>Name</entry>
      <entry>Data Type</entry>
      <entry>Description</entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry><literal>domain_catalog</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the database that contains the domain (always the current database)</entry>
     </row>

     <row>
      <entry><literal>domain_schema</literal</entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the schema that contains the domain</entry>
     </row>

     <row>
      <entry><literal>domain_name</literal</entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the domain</entry>
     </row>

     <row>
      <entry><literal>data_type</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>Data type of the domain</entry>
     </row>

     <row>
      <entry><literal>character_maximum_length</literal></entry>
      <entry><type>cardinal_number</type></entry>
      <entry>
       If the domain has a character or bit string type, the declared
       maximum length; null for all other data types or if no maximum
       length was declared.
      </entry>
     </row>

     <row>
      <entry><literal>character_octet_length</literal></entry>
      <entry><type>cardinal_number</type></entry>
      <entry>
       If the domain has a character type, the maximum possible length
       in octets (bytes) of a datum (this should not be of concern to
       PostgreSQL users); null for all other data types.
      </entry>
     </row>

     <row>
      <entry><literal>character_set_catalog</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>

     <row>
      <entry><literal>character_set_schema</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>

     <row>
      <entry><literal>character_set_name</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>

     <row>
      <entry><literal>collation_catalog</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>

     <row>
      <entry><literal>collation_schema</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>

     <row>
      <entry><literal>collation_name</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>

     <row>
      <entry><literal>numeric_precision</literal></entry>
      <entry><type>cardinal_number</type></entry>
      <entry>
       If the domain has a numeric type, this column contains the
       (declared or implicit) precision of the type for this column.
       The precision indicates the number of significant digits.  It
       may be expressed in decimal (base 10) or binary (base 2) terms,
       as specified in the column
       <literal>numeric_precision_radix</literal>.  For all other data
       types, this column is null.
      </entry>
     </row>

     <row>
      <entry><literal>numeric_precision_radix</literal></entry>
      <entry><type>cardinal_number</type></entry>
      <entry>
       If the domain has a numeric type, this column indicates in
       which base the values in the columns
       <literal>numeric_precision</literal> and
       <literal>numeric_scale</literal> are expressed.  The value is
       either 2 or 10.  For all other data types, this column is null.
      </entry>
     </row>

     <row>
      <entry><literal>numeric_scale</literal></entry>
      <entry><type>cardinal_number</type></entry>
      <entry>
       If the domain has an exact numeric type, this column contains
       the (declared or implicit) scale of the type for this column.
       The scale indicates the number of significant digits to the
       right of the decimal point.  It may be expressed in decimal
       (base 10) or binary (base 2) terms, as specified in the column
       <literal>numeric_precision_radix</literal>.  For all other data
       types, this column is null.
      </entry>
     </row>

     <row>
      <entry><literal>datetime_precision</literal></entry>
      <entry><type>cardinal_number</type></entry>
      <entry>
       If the domain has a date, time, or interval type, the declared
       precision; null for all other data types or if no precision was
       declared.
      </entry>
     </row>

     <row>
      <entry><literal>interval_type</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>Not yet implemented</entry>
     </row>

     <row>
      <entry><literal>interval_precision</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>Not yet implemented</entry>
     </row>

     <row>
      <entry><literal>domain_default</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>Default expression of the domain</entry>
     </row>

      <row>
      <entry><literal>udt_catalog</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the database that the domain data type is defined in (always the current database)</entry>
     </row>

     <row>
      <entry><literal>udt_schema</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the schema that the domain data type is defined in</entry>
     </row>

     <row>
      <entry><literal>udt_name</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the domain data type</entry>
     </row>

     <row>
      <entry><literal>scope_catalog</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>

     <row>
      <entry><literal>scope_schema</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>

     <row>
      <entry><literal>scope_name</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>

     <row>
      <entry><literal>maximum_cardinality</literal></entry>
      <entry><type>cardinal_number</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>

     <row>
      <entry><literal>dtd_identifier</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>

 <sect1 id="infoschema-referential-constraints">
  <title><literal>referential_constraints</literal></title>

  <para>
   The view <literal>referential_constraints</literal> contains all
   referential (foreign key) constraints in the current database that
   belong to a table owned by the current user.
  </para>

  <table>
   <title><literal>referential_constraints</literal> Columns</title>

   <tgroup cols="3">
    <thead>
     <row>
      <entry>Name</entry>
      <entry>Data Type</entry>
      <entry>Description</entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry><literal>constraint_catalog</literal></entry>
      <entry><literal>sql_identifier</literal></entry>
      <entry>Name of the database containing the constraint (always the current database)</entry>
     </row>

     <row>
      <entry><literal>constraint_schema</literal></entry>
      <entry><literal>sql_identifier</literal></entry>
      <entry>Name of the schema containing the constraint</entry>
     </row>

     <row>
      <entry><literal>constraint_name</literal></entry>
      <entry><literal>sql_identifier</literal></entry>
      <entry>Name of the constraint</entry>
     </row>

     <row>
      <entry><literal>unique_constraint_catalog</literal></entry>
      <entry><literal>sql_identifier</literal></entry>
      <entry>Not yet implemented</entry>
     </row>

     <row>
      <entry><literal>unique_constraint_schema</literal></entry>
      <entry><literal>sql_identifier</literal></entry>
      <entry>Not yet implemented</entry>
     </row>

     <row>
      <entry><literal>unique_constraint_name</literal></entry>
      <entry><literal>sql_identifier</literal></entry>
      <entry>Not yet implemented</entry>
     </row>

     <row>
      <entry><literal>match_option</literal></entry>
      <entry><literal>character_data</literal></entry>
      <entry>
       Match option of the referential constraint:
       <literal>FULL</literal>, <literal>PARTIAL</literal>, or
       <literal>NONE</literal>.
      </entry>
     </row>

     <row>
      <entry><literal>update_rule</literal></entry>
      <entry><literal>character_data</literal></entry>
      <entry>
       Update rule of the referential constraint:
       <literal>CASCADE</literal>, <literal>SET NULL</literal>,
       <literal>SET DEFAULT</literal>, <literal>RESTRICT</literal>,or
       <literal>NO ACTION</literal>.
      </entry>
     </row>

     <row>
      <entry><literal>delete_rule</literal></entry>
      <entry><literal>character_data</literal></entry>
      <entry>
       Delete rule of the referential constraint:
       <literal>CASCADE</literal>, <literal>SET NULL</literal>,
       <literal>SET DEFAULT</literal>, <literal>RESTRICT</literal>,or
       <literal>NO ACTION</literal>.
      </entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>

 <sect1 id="infoschema-schemata">
  <title><literal>schemata</literal></title>

  <para>
   The view <literal>schemata</literal> contains all schemas in the
   current database.
  </para>

  <table>
   <title><literal>schemata</literal> Columns</title>

   <tgroup cols="3">
    <thead>
     <row>
      <entry>Name</entry>
      <entry>Data Type</entry>
      <entry>Description</entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry><literal>catalog_name</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the database that the schema is contained in (always the current database)</entry>
     </row>

     <row>
      <entry><literal>schema_name</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the schema</entry>
     </row>

     <row>
      <entry><literal>schema_owner</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the owner of the schema</entry>
     </row>

     <row>
      <entry><literal>default_character_set_catalog</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>

     <row>
      <entry><literal>default_character_set_schema</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>

     <row>
      <entry><literal>default_character_set_name</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>

     <row>
      <entry><literal>sql_path</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>

 <sect1 id="infoschema-sql-features">
  <title><literal>sql_features</literal></title>

  <para>
   The table <literal>sql_features</literal> contains information
   about which formal features defined in the SQL standard are
   supported by PostgreSQL.  This is the same information that is
   presented in <xref linkend="features">.  There you can also find
   some additional background information.
  </para>

  <table>
   <title><literal>sql_features</literal> Columns</title>

   <tgroup cols="3">
    <thead>
     <row>
      <entry>Name</entry>
      <entry>Data Type</entry>
      <entry>Description</entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry><literal>feature_id</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>Identifier string of the feature</entry>
     </row>

     <row>
      <entry><literal>feature_name</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>Descriptive name of the feature</entry>
     </row>

     <row>
      <entry><literal>sub_feature_id</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>Identifier string of the subfeature, or a zero-length string if not a subfeature</entry>
     </row>

     <row>
      <entry><literal>sub_feature_name</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>Descriptive name of the subfeature, or a zero-length string if not a subfeature</entry>
     </row>

     <row>
      <entry><literal>is_supported</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>
       <literal>YES</literal> if the feature is fully supported by the
       current version of PostgreSQL, <literal>NO</literal> if not
      </entry>
     </row>

     <row>
      <entry><literal>is_verified_by</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>
       Always null, since the PostgreSQL development group does not
       perform formal testing of feature conformance
      </entry>
     </row>

     <row>
      <entry><literal>comments</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>Possibly a comment about the supported status of the feature</entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>

 <sect1 id="infoschema-sql-implementation-info">
  <title><literal>sql_implementation_info</literal></title>

  <para>
   The table <literal>sql_information_info</literal> contains
   information about various aspects that are left
   implementation-defined by the SQL standard.  This information is
   primarily intended for use in the context of the ODBC interface;
   users of other interfaces will probably find this information to be
   of little use.  For this reason, the individual implementation
   information items are not described here; you will find them in the
   description of the ODBC interface.
  </para>

  <table>
   <title><literal>sql_implementation_info</literal> Columns</title>

   <tgroup cols="3">
    <thead>
     <row>
      <entry>Name</entry>
      <entry>Data Type</entry>
      <entry>Description</entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry><literal>implementation_info_id</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>Identifier string of the implementation information item</entry>
     </row>

     <row>
      <entry><literal>implementation_info_name</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>Descriptive name of the implementation information item</entry>
     </row>

     <row>
      <entry><literal>integer_value</literal></entry>
      <entry><type>cardinal_number</type></entry>
      <entry>
       Value of the implementation information item, or null if the
       value is contained in the column
       <literal>character_value</literal>
      </entry>
     </row>

     <row>
      <entry><literal>character_value</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>
       Value of the implementation information item, or null if the
       value is contained in the column
       <literal>integer_value</literal>
      </entry>
     </row>

     <row>
      <entry><literal>comments</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>Possibly a comment pertaining to the implementation information item</entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>

 <sect1 id="infoschema-sql-languages">
  <title><literal>sql_languages</literal></title>

  <para>
   The table <literal>sql_languages</literal> contains one row for
   each SQL language binding that is supported by PostgreSQL.
   PostgreSQL supports direct SQL and embedded SQL in C; that is all
   you will learn from this table.
  </para>

  <table>
   <title><literal>sql_languages</literal> Columns</title>

   <tgroup cols="3">
    <thead>
     <row>
      <entry>Name</entry>
      <entry>Data Type</entry>
      <entry>Description</entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry><literal>sql_language_source</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>
       The name of the source of the language definition; always
       <literal>ISO 9075</literal>, that is, the SQL standard
      </entry>
     </row>

     <row>
      <entry><literal>sql_language_year</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>
       The year the standard referenced in
       <literal>sql_language_source</literal> was approved; currently
       <literal>1999</>
      </entry>
     </row>

     <row>
      <entry><literal>sql_language_comformance</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>
       The standard conformance level for the language binding.  For
       ISO 9075:1999 this is always <literal>CORE</literal>.
      </entry>
     </row>

     <row>
      <entry><literal>sql_language_integrity</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>Always null (This value is relevant to an earlier version of the SQL standard.)</entry>
     </row>

     <row>
      <entry><literal>sql_language_implementation</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>Always null</entry>
     </row>

     <row>
      <entry><literal>sql_language_binding_style</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>
       The language binding style, either <literal>DIRECT</literal> or
       <literal>EMBEDDED</literal>
      </entry>
     </row>

     <row>
      <entry><literal>sql_language_programming_language</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>
       The programming language, if the binding style is
       <literal>EMBEDDED</literal>, else null.  PostgreSQL only
       supports the language C.
      </entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>

 <sect1 id="infoschema-sql-packages">
  <title><literal>sql_packages</literal></title>

  <para>
   The table <literal>sql_packages</literal> contains information
   about which features packages defined in the SQL standard are
   supported by PostgreSQL.  Refer to <xref linkend="features"> for
   background information on feature packages.
  </para>

  <table>
   <title><literal>sql_packages</literal> Columns</title>

   <tgroup cols="3">
    <thead>
     <row>
      <entry>Name</entry>
      <entry>Data Type</entry>
      <entry>Description</entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry><literal>feature_id</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>Identifier string of the package</entry>
     </row>

     <row>
      <entry><literal>feature_name</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>Descriptive name of the package</entry>
     </row>

     <row>
      <entry><literal>is_supported</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>
       <literal>YES</literal> if the package is fully supported by the
       current version of PostgreSQL, <literal>NO</literal> if not
      </entry>
     </row>

     <row>
      <entry><literal>is_verified_by</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>
       Always null, since the PostgreSQL development group does not
       perform formal testing of feature conformance
      </entry>
     </row>

     <row>
      <entry><literal>comments</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>Possibly a comment about the supported status of the package</entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>

 <sect1 id="infoschema-sql-sizing">
  <title><literal>sql_sizing</literal></title>

  <para>
   The table <literal>sql_sizing</literal> contains information about
   various size limits and maximum values in PostgreSQL.  This
   information is primarily intended for use in the context of the
   ODBC interface; users of other interfaces will probably find this
   information to be of little use.  For this reason, the individual
   sizing items are not described here; you will find them in the
   description of the ODBC interface.
  </para>

  <table>
   <title><literal>sql_sizing</literal> Columns</title>

   <tgroup cols="3">
    <thead>
     <row>
      <entry>Name</entry>
      <entry>Data Type</entry>
      <entry>Description</entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry><literal>sizing_id</literal></entry>
      <entry><type>cardinal_number</type></entry>
      <entry>Identifier of the sizing item</entry>
     </row>

     <row>
      <entry><literal>sizing_name</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>Descriptive name of the sizing item</entry>
     </row>

     <row>
      <entry><literal>supported_value</literal></entry>
      <entry><type>cardinal_number</type></entry>
      <entry>
       Value of the sizing item, or 0 if the size is unlimited or
       cannot be determined, or null if the features for which the
       sizing item is applicable are not supported
      </entry>
     </row>

     <row>
      <entry><literal>comments</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>Possibly a comment pertaining to the sizing item</entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>

 <sect1 id="infoschema-sql-sizing-profiles">
  <title><literal>sql_sizing_profiles</literal></title>

  <para>
   The table <literal>sql_sizing_profiles</literal> contains
   information about the <literal>sql_sizing</literal> values that are
   required by various profiles of the SQL standard.  PostgreSQL does
   not track any SQL profiles, so this table is empty.
  </para>

  <table>
   <title><literal>sql_sizing_profiles</literal> Columns</title>

   <tgroup cols="3">
    <thead>
     <row>
      <entry>Name</entry>
      <entry>Data Type</entry>
      <entry>Description</entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry><literal>sizing_id</literal></entry>
      <entry><type>cardinal_number</type></entry>
      <entry>Identifier of the sizing item</entry>
     </row>

     <row>
      <entry><literal>sizing_name</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>Descriptive name of the sizing item</entry>
     </row>

     <row>
      <entry><literal>profile_id</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>Identifier string of a profile</entry>
     </row>

     <row>
      <entry><literal>required_value</literal></entry>
      <entry><type>cardinal_number</type></entry>
      <entry>
       The value required by the SQL profile for the sizing item, or 0
       if the profile places no limit on the sizing item, or null if
       the profile does not require any of the features for which the
       sizing item is applicable
      </entry>
     </row>

     <row>
      <entry><literal>comments</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>Possibly a comment pertaining to the sizing item within the profile</entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>

 <sect1 id="infoschema-table-constraints">
  <title><literal>table_constraints</literal></title>

  <para>
   The view <literal>table_constraints</literal> contains all
   constraints belonging to tables.
  </para>

  <table>
   <title><literal>table_constraints</literal> Columns</title>

   <tgroup cols="3">
    <thead>
     <row>
      <entry>Name</entry>
      <entry>Data Type</entry>
      <entry>Description</entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry><literal>constraint_catalog</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the database that contains the constraint (always the current database)</entry>
     </row>

     <row>
      <entry><literal>constraint_schema</literal</entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the schema that contains the constraint</entry>
     </row>

     <row>
      <entry><literal>constraint_name</literal</entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the constraint</entry>
     </row>

     <row>
      <entry><literal>table_catalog</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the database that contains the table (always the current database)</entry>
     </row>

     <row>
      <entry><literal>table_schema</literal</entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the schema that contains the table</entry>
     </row>

     <row>
      <entry><literal>table_name</literal</entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the table</entry>
     </row>

     <row>
      <entry><literal>constraint_type</literal</entry>
      <entry><type>character_data</type></entry>
      <entry>
       Type of the constraint: <literal>CHECK</literal>,
       <literal>FOREIGN KEY</literal>, <literal>PRIMARY KEY</literal>,
       or <literal>UNIQUE</literal>
      </entry>
     </row>

     <row>
      <entry><literal>is_deferrable</literal></entry>
      <entry><type>character_data</type></entry>
      <entry><literal>YES</literal> if the constraint is deferrable, <literal>NO</literal> if not</entry>
     </row>

     <row>
      <entry><literal>initially_deferred</literal></entry>
      <entry><type>character_data</type></entry>
      <entry><literal>YES</literal> if the constraint is deferrable and initially deferred, <literal>NO</literal> if not</entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>

 <sect1 id="infoschema-table-privileges">
  <title><literal>table_privileges</literal></title>

  <para>
   The view <literal>table_privileges</literal> identifies all
   privileges granted on tables to the current user or by the current
   user.  There is one row for each combination of table, grantor, and
   grantee.
  </para>

  <table>
   <title><literal>table_privileges</literal> Columns</title>

   <tgroup cols="3">
    <thead>
     <row>
      <entry>Name</entry>
      <entry>Data Type</entry>
      <entry>Description</entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry><literal>grantor</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the user that granted the privileges</entry>
     </row>

     <row>
      <entry><literal>grantee</literal</entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the user that the privilege was granted to</entry>
     </row>

     <row>
      <entry><literal>table_catalog</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the database that contains the table (always the current database)</entry>
     </row>

     <row>
      <entry><literal>table_schema</literal</entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the schema that contains the table</entry>
     </row>

     <row>
      <entry><literal>table_name</literal</entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the table</entry>
     </row>

     <row>
      <entry><literal>privilege_type</literal</entry>
      <entry><type>character_data</type></entry>
      <entry>
       Type of the privilege: <literal>SELECT</literal>,
       <literal>DELETE</literal>, <literal>INSERT</literal>,
       <literal>UPDATE</literal>, <literal>REFERENCES</literal>, or
       <literal>TRIGGER</literal>
      </entry>
     </row>

     <row>
      <entry><literal>is_grantable</literal></entry>
      <entry><type>character_data</type></entry>
      <entry><literal>YES</literal> if the privilege is grantable, <literal>NO</literal> if not</entry>
     </row>

     <row>
      <entry><literal>with_hierarchy</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>

 <sect1 id="infoschema-tables">
  <title><literal>tables</literal></title>

  <para>
   The view <literal>tables</literal> contains all tables and views
   defined in the current database.
  </para>

  <table>
   <title><literal>tables</literal> Columns</title>

   <tgroup cols="3">
    <thead>
     <row>
      <entry>Name</entry>
      <entry>Data Type</entry>
      <entry>Description</entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry><literal>table_catalog</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the database that contains the table (always the current database)</entry>
     </row>

     <row>
      <entry><literal>table_schema</literal</entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the schema that contains the table</entry>
     </row>

     <row>
      <entry><literal>table_name</literal</entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the table</entry>
     </row>

     <row>
      <entry><literal>table_type</literal</entry>
      <entry><type>character_data</type></entry>
      <entry>
       Type of the table: <literal>BASE TABLE</literal> for a
       persistent base table (the normal table type),
       <literal>VIEW</literal> for a view, or <literal>LOCAL
       TEMPORARY</literal> for a temporary table
      </entry>
     </row>

     <row>
      <entry><literal>self_referencing_column_name</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>

     <row>
      <entry><literal>reference_generation</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>

     <row>
      <entry><literal>user_defined_type_catalog</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>

     <row>
      <entry><literal>user_defined_type_schema</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>

     <row>
      <entry><literal>user_defined_type_name</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>

 <sect1 id="infoschema-views">
  <title><literal>views</literal></title>

  <para>
   The view <literal>views</literal> contains all views defined in the
   current database.
  </para>

  <table>
   <title><literal>views</literal> Columns</title>

   <tgroup cols="3">
    <thead>
     <row>
      <entry>Name</entry>
      <entry>Data Type</entry>
      <entry>Description</entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry><literal>table_catalog</literal></entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the database that contains the view (always the current database)</entry>
     </row>

     <row>
      <entry><literal>table_schema</literal</entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the schema that contains the view</entry>
     </row>

     <row>
      <entry><literal>table_name</literal</entry>
      <entry><type>sql_identifier</type></entry>
      <entry>Name of the view</entry>
     </row>

     <row>
      <entry><literal>view definition</literal</entry>
      <entry><type>character_data</type></entry>
      <entry>
       Query expression defining the view (null if the current user is
       not the owner of the view)
      </entry>
     </row>

     <row>
      <entry><literal>check_option</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>Applies to a feature not available in PostgreSQL</entry>
     </row>

     <row>
      <entry><literal>is_updatable</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>Not yet implemented</entry>
     </row>

     <row>
      <entry><literal>is_insertable_into</literal></entry>
      <entry><type>character_data</type></entry>
      <entry>Not yet implemented</entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>

</chapter>
