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Information schema improvements

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Peter Eisentraut
2003-05-25 09:36:09 +00:00
parent 310049a19b
commit 297c1658ed
2 changed files with 374 additions and 128 deletions
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doc/src/sgml/information_schema.sgml
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@ -1,4 +1,4 @@
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/information_schema.sgml,v 1.1 2003/05/18 20:55:56 petere Exp $ -->
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/information_schema.sgml,v 1.2 2003/05/25 09:36:09 petere Exp $ -->
<chapter id="information-schema">
<title>The Information Schema</title>
@ -148,7 +148,8 @@
<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.
owned by the current user. (The owner of the table or domain is
the owner of the constraint.)
</para>
<table>
@ -266,7 +267,9 @@
<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.
(<literal>oid</>, etc.) are not included. Only those columns are
shown that the current user has access to (by way of being the
owner or having some privilege).
</para>
<table>
@ -335,16 +338,24 @@
<row>
<entry><literal>data_type</literal></entry>
<entry><type>character_data</type></entry>
<entry>Data type of the column</entry>
<entry>
Data type of the column, if it is a built-in type, else
<literal>USER-DEFINED</literal> (in that case, the type is
identified in <literal>udt_name</literal> and associated
columns). If the column is based on a domain, this column
refers to the type underlying the domain (and the domain is
identified in <literal>domain_name</literal> and associated
columns).
</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.
If <literal>data_type</literal> identifies 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>
@ -352,9 +363,10 @@
<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.
If <literal>data_type</literal> identifies 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>
@ -362,11 +374,11 @@
<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
If <literal>data_type</literal> identifies 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>
@ -376,8 +388,8 @@
<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
If <literal>data_type</literal> identifies 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.
@ -388,11 +400,12 @@
<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
If <literal>data_type</literal> identifies 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>
@ -402,9 +415,9 @@
<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.
If <literal>data_type</literal> identifies a date, time, or
interval type, the declared precision; null for all other data
types or if no precision was declared.
</entry>
</row>
@ -485,9 +498,9 @@
<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.
Name of the database that the column data type (the underlying
type of the domain, if applicable) is defined in (always the
current database)
</entry>
</row>
@ -495,15 +508,18 @@
<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.
Name of the schema that the column data type (the underlying
type of the domain, if applicable) is defined in
</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>
<entry>
Name of the column data type (the underlying type of the
domain, if applicable)
</entry>
</row>
<row>
@ -533,7 +549,11 @@
<row>
<entry><literal>dtd_identifier</literal></entry>
<entry><type>sql_identifier</type></entry>
<entry>Applies to a feature not available in PostgreSQL</entry>
<entry>
A unique identifier of the data type of the column (The
specific format of the identifier is not defined and not
guaranteed to remain the same in future versions.)
</entry>
</row>
<row>
@ -544,6 +564,109 @@
</tbody>
</tgroup>
</table>
<para>
Since data types can be defined in a variety of ways in SQL, and
PostgreSQL contains additional ways to define data types, their
representation in the information schema can be somewhat difficult.
The column <literal>data_type</literal> is supposed to identify the
underlying built-in type of the column. In PostgreSQL, this means
that the type is defined in the system catalog schema
<literal>pg_catalog</literal>. This column may be useful if the
application can handle the well-known built-in types specially (for
example, format the numeric types differently or use the data in
the precision columns). The columns <literal>udt_name</literal>,
<literal>udt_schema</literal>, and <literal>udt_catalog</literal>
always identify the underlying data type of the column, even if the
column is based on a domain. (Since PostgreSQL treats built-in
types like user-defined types, built-in types appear here as well.
This is an extension of the SQL standard.) These columns should be
used if an application wants to process data differently according
to the type, because in that case it wouldn't matter if the column
is really based on a domain. If the column is based on a domain,
the identity of the domain is stored in the columns
<literal>domain_name</literal>, <literal>domain_schema</literal>,
and <literal>domain_catalog</literal>. If you want to pair up
columns with their associated data types and treat domains as
separate types, you could write <literal>coalesce(domain_name,
udt_name)</literal>, etc. Finally, if you want to check whether
two columns have the same type, use
<literal>dtd_identifier</literal>.
</para>
</sect1>
<sect1 id="infoschema-constraint-table-usage">
<title><literal>constraint_table_usage</literal></title>
<para>
The view <literal>constraint_table_usage</literal> identifies all
tables in the current database that are used by some constraint and
are owned by the current user. (This is different from the view
<literal>table_constraints</literal>, which identifies all table
constraints along with the table they are defined on.) For a
foreign key constraint, this view identifies the table that the
foreign key references. Unique and primary key constraints simply
identify the table they belong to. Check constraints and not-null
constraints are not included in this view.
</para>
<table>
<title><literal>constraint_table_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>table_catalog</literal></entry>
<entry><type>sql_identifier</type></entry>
<entry>
Name of the database that contains the table that is used by
some constraint (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 that is used by some
constraint
</entry>
</row>
<row>
<entry><literal>table_name</literal</entry>
<entry><type>sql_identifier</type></entry>
<entry>Name of the table that is used by some constraint</entry>
</row>
<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>
</tbody>
</tgroup>
</table>
</sect1>
<sect1 id="infoschema-domain-constraints">
@ -551,7 +674,7 @@
<para>
The view <literal>domain_constraints</literal> contains all
constraints belonging to domains.
constraints belonging to domains owned by the current user.
</para>
<table>
@ -883,26 +1006,36 @@
<row>
<entry><literal>unique_constraint_catalog</literal></entry>
<entry><literal>sql_identifier</literal></entry>
<entry>Not yet implemented</entry>
<entry>
Name of the database that contains the unique or primary key
constraint that the foreign key constraint references (always
the current database)
</entry>
</row>
<row>
<entry><literal>unique_constraint_schema</literal></entry>
<entry><literal>sql_identifier</literal></entry>
<entry>Not yet implemented</entry>
<entry>
Name of the schema that contains the unique or primary key
constraint that the foreign key constraint references
</entry>
</row>
<row>
<entry><literal>unique_constraint_name</literal></entry>
<entry><literal>sql_identifier</literal></entry>
<entry>Not yet implemented</entry>
<entry>
Name of the unique or primary key constraint that the foreign
key constraint references
</entry>
</row>
<row>
<entry><literal>match_option</literal></entry>
<entry><literal>character_data</literal></entry>
<entry>
Match option of the referential constraint:
Match option of the foreign key constraint:
<literal>FULL</literal>, <literal>PARTIAL</literal>, or
<literal>NONE</literal>.
</entry>
@ -912,7 +1045,7 @@
<entry><literal>update_rule</literal></entry>
<entry><literal>character_data</literal></entry>
<entry>
Update rule of the referential constraint:
Update rule of the foreign key constraint:
<literal>CASCADE</literal>, <literal>SET NULL</literal>,
<literal>SET DEFAULT</literal>, <literal>RESTRICT</literal>,or
<literal>NO ACTION</literal>.
@ -923,7 +1056,7 @@
<entry><literal>delete_rule</literal></entry>
<entry><literal>character_data</literal></entry>
<entry>
Delete rule of the referential constraint:
Delete rule of the foreign key constraint:
<literal>CASCADE</literal>, <literal>SET NULL</literal>,
<literal>SET DEFAULT</literal>, <literal>RESTRICT</literal>,or
<literal>NO ACTION</literal>.
@ -939,7 +1072,7 @@
<para>
The view <literal>schemata</literal> contains all schemas in the
current database.
current database that are owned by the current user.
</para>
<table>
@ -1420,7 +1553,7 @@
<para>
The view <literal>table_constraints</literal> contains all
constraints belonging to tables.
constraints belonging to tables owned by the current user.
</para>
<table>
@ -1583,7 +1716,9 @@
<para>
The view <literal>tables</literal> contains all tables and views
defined in the current database.
defined in the current database. Only those tables and views are
shown that the current user has access to (by way of being the
owner or having some privilege).
</para>
<table>
@ -1667,7 +1802,8 @@
<para>
The view <literal>views</literal> contains all views defined in the
current database.
current database. Only those views are shown that the current user
has access to (by way of being the owner or having some privilege).
</para>
<table>