<sect1 id="infoschema-character-sets">

<title><literal>character_sets</literal></title>

<para>

The view <literal>character_sets</literal> identifies the character

sets available in the current database. Since PostgreSQL does not

support multiple character sets within one database, this view only

shows one, which is the database encoding.

</para>

<para>

Take note of how the following terms are used in the SQL standard:

<variablelist>

<varlistentry>

<term>character repertoire</term>

<listitem>

<para>

An abstract collection of characters, for

example <literal>UNICODE</literal>, <literal>UCS</literal>, or

<literal>LATIN1</literal>. Not exposed as an SQL object, but

visible in this view.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>character encoding form</term>

<listitem>

<para>

An encoding of some character repertoire. Most older character

repertoires only use one encoding form, and so there are no

separate names for them (e.g., <literal>LATIN1</literal> is an

encoding form applicable to the <literal>LATIN1</literal>

repertoire). But for example Unicode has the encoding forms

<literal>UTF8</literal>, <literal>UTF16</literal>, etc. (not

all supported by PostgreSQL). Encoding forms are not exposed

as an SQL object, but are visible in this view.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>character set</term>

<listitem>

<para>

A named SQL object that identifies a character repertoire, a

character encoding, and a default collation. A predefined

character set would typically have the same name as an encoding

form, but users could define other names. For example, the

character set <literal>UTF8</literal> would typically identify

the character repertoire <literal>UCS</literal>, encoding

form <literal>UTF8</literal>, and some default collation.

</para>

</listitem>

</varlistentry>

</variablelist>

You can think of an <quote>encoding</quote> in PostgreSQL either as

a character set or a character encoding form. They will have the

same name, and there can only be one in one database.

</para>

<table>

<title><literal>character_sets</literal> Columns</title>

<tgroup cols="3">

<thead>

<row>

<entry>Name</entry>

<entry>Data Type</entry>

<entry>Description</entry>

</row>

</thead>

<tbody>

<row>

<entry><literal>character_set_catalog</literal></entry>

<entry><literal>sql_identifier</literal></entry>

<entry>Character sets are currently not implemented as schema objects, so this column is null.</entry>

</row>

<row>

<entry><literal>character_set_schema</literal></entry>

<entry><literal>sql_identifier</literal></entry>

<entry>Character sets are currently not implemented as schema objects, so this column is null.</entry>

</row>

<row>

<entry><literal>character_set_name</literal></entry>

<entry><literal>sql_identifier</literal></entry>

<entry>Name of the character set, currently implemented as showing the name of the database encoding</entry>

</row>

<row>

<entry><literal>character_repertoire</literal></entry>

<entry><literal>sql_identifier</literal></entry>

<entry>Character repertoire, showing <literal>UCS</literal> if the encoding is <literal>UTF8</literal>, else just the encoding name</entry>

</row>

<row>

<entry><literal>form_of_use</literal></entry>

<entry><literal>sql_identifier</literal></entry>

<entry>Character encoding form, same as the database encoding</entry>

</row>

<row>

<entry><literal>default_collate_catalog</literal></entry>

<entry><literal>sql_identifier</literal></entry>

<entry>Name of the database containing the default collation (always the current database, if any collation is identified)</entry>

</row>

<row>

<entry><literal>default_collate_schema</literal></entry>

<entry><literal>sql_identifier</literal></entry>

<entry>Name of the schema containing the default collation</entry>

</row>

<row>

<entry><literal>default_collate_name</literal></entry>

<entry><literal>sql_identifier</literal></entry>

<entry>

Name of the default collation. The default collation is

identified as the collation that matches

the <literal>COLLATE</literal> and <literal>CTYPE</literal>

settings of the current database. If there is no such

collation, then this column and the associated schema and

catalog columns are null.

</entry>

</row>

</tbody>

</tgroup>

</table>

</sect1>

<sect1 id="infoschema-collations">

<title><literal>collations</literal></title>

<para>

The view <literal>collations</literal> contains the collations

available in the current database.

</para>

<table>

<title><literal>collations</literal> Columns</title>

<tgroup cols="3">

<thead>

<row>

<entry>Name</entry>

<entry>Data Type</entry>

<entry>Description</entry>

</row>

</thead>

<tbody>

<row>

<entry><literal>collation_catalog</literal></entry>

<entry><literal>sql_identifier</literal></entry>

<entry>Name of the database containing the collation (always the current database)</entry>

</row>

<row>

<entry><literal>collation_schema</literal></entry>

<entry><literal>sql_identifier</literal></entry>

<entry>Name of the schema containing the collation</entry>

</row>

<row>

<entry><literal>collation_name</literal></entry>

<entry><literal>sql_identifier</literal></entry>

<entry>Name of the default collation</entry>

</row>

<row>

<entry><literal>pad_attribute</literal></entry>

<entry><literal>character_data</literal></entry>

<entry>

Always <literal>NO PAD</literal> (The alternative <literal>PAD

SPACE</literal> is not supported by PostgreSQL.)

</entry>

</row>

</tbody>

</tgroup>

</table>

</sect1>

<sect1 id="infoschema-collation-character-set-applicability">

<title><literal>collation_character_set_applicability</literal></title>

<para>

The view <literal>collation_character_set_applicability</literal>

identifies which character set the available collations are

applicable to. In PostgreSQL, there is only one character set per

database (see explanation

in <xref linkend="infoschema-character-sets">), so this view does

not provide much useful information.

</para>

<table>

<title><literal>collation_character_set_applicability</literal> Columns</title>

<tgroup cols="3">

<thead>

<row>

<entry>Name</entry>

<entry>Data Type</entry>

<entry>Description</entry>

</row>

</thead>

<tbody>

<row>

<entry><literal>collation_catalog</literal></entry>

<entry><literal>sql_identifier</literal></entry>

<entry>Name of the database containing the collation (always the current database)</entry>

</row>

<row>

<entry><literal>collation_schema</literal></entry>

<entry><literal>sql_identifier</literal></entry>

<entry>Name of the schema containing the collation</entry>

</row>

<row>

<entry><literal>collation_name</literal></entry>

<entry><literal>sql_identifier</literal></entry>

<entry>Name of the default collation</entry>

</row>

<row>

<entry><literal>character_set_catalog</literal></entry>

<entry><literal>sql_identifier</literal></entry>

<entry>Character sets are currently not implemented as schema objects, so this column is null</entry>

</row>

<row>

<entry><literal>character_set_schema</literal></entry>

<entry><literal>sql_identifier</literal></entry>

<entry>Character sets are currently not implemented as schema objects, so this column is null</entry>

</row>

<row>

<entry><literal>character_set_name</literal></entry>

<entry><literal>sql_identifier</literal></entry>

<entry>Name of the character set</entry>

</row>

</tbody>

</tgroup>

</table>

</sect1>

CREATE VIEW character_sets AS

SELECT CAST(null AS sql_identifier) AS character_set_catalog,

CAST(null AS sql_identifier) AS character_set_schema,

CAST(getdatabaseencoding() AS sql_identifier) AS character_set_name,

CAST(CASE WHEN getdatabaseencoding() = 'UTF8' THEN 'UCS' ELSE getdatabaseencoding() END AS sql_identifier) AS character_repertoire,

CAST(getdatabaseencoding() AS sql_identifier) AS form_of_use,

CAST(current_database() AS sql_identifier) AS default_collate_catalog,

CAST(nc.nspname AS sql_identifier) AS default_collate_schema,

CAST(c.collname AS sql_identifier) AS default_collate_name

FROM pg_database d

LEFT JOIN (pg_collation c JOIN pg_namespace nc ON (c.collnamespace = nc.oid))

ON (datcollate = collcollate AND datctype = collctype)

WHERE d.datname = current_database()

ORDER BY char_length(c.collname) DESC, c.collname ASC -- prefer full/canonical name

LIMIT 1;

GRANT SELECT ON character_sets TO PUBLIC;

CREATE VIEW collations AS

SELECT CAST(current_database() AS sql_identifier) AS collation_catalog,

CAST(nc.nspname AS sql_identifier) AS collation_schema,

CAST(c.collname AS sql_identifier) AS collation_name,

CAST('NO PAD' AS character_data) AS pad_attribute

FROM pg_collation c, pg_namespace nc

WHERE c.collnamespace = nc.oid

AND collencoding = (SELECT encoding FROM pg_catalog.pg_database WHERE datname = pg_catalog.current_database());

GRANT SELECT ON collations TO PUBLIC;

CREATE VIEW collation_character_set_applicability AS

SELECT CAST(current_database() AS sql_identifier) AS collation_catalog,

CAST(nc.nspname AS sql_identifier) AS collation_schema,

CAST(c.collname AS sql_identifier) AS collation_name,

CAST(null AS sql_identifier) AS character_set_catalog,

CAST(null AS sql_identifier) AS character_set_schema,

CAST(getdatabaseencoding() AS sql_identifier) AS character_set_name

FROM pg_collation c, pg_namespace nc

WHERE c.collnamespace = nc.oid

AND collencoding = (SELECT encoding FROM pg_catalog.pg_database WHERE datname = pg_catalog.current_database());

GRANT SELECT ON collation_character_set_applicability TO PUBLIC;

#define CATALOG_VERSION_NO 201102091