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Information schema views for collation support

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Add the views character_sets, collations, and
collation_character_set_applicability.
pull/1/head
Peter Eisentraut 15 years ago
parent 183d3cff85
commit 2e2d56fea9
3 changed files with 292 additions and 4 deletions
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  1. 251
      doc/src/sgml/information_schema.sgml
  2. 43
      src/backend/catalog/information_schema.sql
  3. 2
      src/include/catalog/catversion.h

251
doc/src/sgml/information_schema.sgml
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@ -498,6 +498,140 @@
</para>
</sect1>
<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-check-constraint-routine-usage">
<title><literal>check_constraint_routine_usage</literal></title>
@ -615,6 +749,123 @@
</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>
<sect1 id="infoschema-column-domain-usage">
<title><literal>column_domain_usage</literal></title>

43
src/backend/catalog/information_schema.sql
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@ -354,7 +354,23 @@ GRANT SELECT ON attributes TO PUBLIC;
* CHARACTER_SETS view
*/
-- feature not supported
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;
/*
@ -425,14 +441,35 @@ GRANT SELECT ON check_constraints TO PUBLIC;
* COLLATIONS view
*/
-- feature not supported
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;
/*
* 5.16
* COLLATION_CHARACTER_SET_APPLICABILITY view
*/
-- feature not supported
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;
/*

2
src/include/catalog/catversion.h
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@ -53,6 +53,6 @@
*/
/* yyyymmddN */
#define CATALOG_VERSION_NO 201102084
#define CATALOG_VERSION_NO 201102091
#endif

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