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Add temporal PRIMARY KEY and UNIQUE constraints

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Add WITHOUT OVERLAPS clause to PRIMARY KEY and UNIQUE constraints.
These are backed by GiST indexes instead of B-tree indexes, since they
are essentially exclusion constraints with = for the scalar parts of
the key and && for the temporal part.

Author: Paul A. Jungwirth <pj@illuminatedcomputing.com>
Reviewed-by: Peter Eisentraut <peter@eisentraut.org>
Reviewed-by: jian he <jian.universality@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/CA+renyUApHgSZF9-nd-a0+OPGharLQLO=mDHcY4_qQ0+noCUVg@mail.gmail.com
This commit is contained in:
Peter Eisentraut
2024-01-24 15:43:41 +01:00
parent 74a7306310
commit 46a0cd4cef
34 changed files with 1135 additions and 52 deletions
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45
doc/src/sgml/ref/create_table.sgml
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@@ -78,8 +78,8 @@ CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } | UNLOGGED ] TABLE [ IF NOT EXI
[ CONSTRAINT <replaceable class="parameter">constraint_name</replaceable> ]
{ CHECK ( <replaceable class="parameter">expression</replaceable> ) [ NO INHERIT ] |
NOT NULL <replaceable class="parameter">column_name</replaceable> [ NO INHERIT ] |
UNIQUE [ NULLS [ NOT ] DISTINCT ] ( <replaceable class="parameter">column_name</replaceable> [, ... ] ) <replaceable class="parameter">index_parameters</replaceable> |
PRIMARY KEY ( <replaceable class="parameter">column_name</replaceable> [, ... ] ) <replaceable class="parameter">index_parameters</replaceable> |
UNIQUE [ NULLS [ NOT ] DISTINCT ] ( <replaceable class="parameter">column_name</replaceable> [, ... ] [, <replaceable class="parameter">column_name</replaceable> WITHOUT OVERLAPS ] ) <replaceable class="parameter">index_parameters</replaceable> |
PRIMARY KEY ( <replaceable class="parameter">column_name</replaceable> [, ... ] [, <replaceable class="parameter">column_name</replaceable> WITHOUT OVERLAPS ] ) <replaceable class="parameter">index_parameters</replaceable> |
EXCLUDE [ USING <replaceable class="parameter">index_method</replaceable> ] ( <replaceable class="parameter">exclude_element</replaceable> WITH <replaceable class="parameter">operator</replaceable> [, ... ] ) <replaceable class="parameter">index_parameters</replaceable> [ WHERE ( <replaceable class="parameter">predicate</replaceable> ) ] |
FOREIGN KEY ( <replaceable class="parameter">column_name</replaceable> [, ... ] ) REFERENCES <replaceable class="parameter">reftable</replaceable> [ ( <replaceable class="parameter">refcolumn</replaceable> [, ... ] ) ]
[ MATCH FULL | MATCH PARTIAL | MATCH SIMPLE ] [ ON DELETE <replaceable
@@ -965,7 +965,7 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
<varlistentry id="sql-createtable-parms-unique">
<term><literal>UNIQUE [ NULLS [ NOT ] DISTINCT ]</literal> (column constraint)</term>
<term><literal>UNIQUE [ NULLS [ NOT ] DISTINCT ] ( <replaceable class="parameter">column_name</replaceable> [, ... ] )</literal>
<term><literal>UNIQUE [ NULLS [ NOT ] DISTINCT ] ( <replaceable class="parameter">column_name</replaceable> [, ... ] [, <replaceable class="parameter">column_name</replaceable> WITHOUT OVERLAPS ] )</literal>
<optional> <literal>INCLUDE ( <replaceable class="parameter">column_name</replaceable> [, ...])</literal> </optional> (table constraint)</term>
<listitem>
@@ -979,6 +979,30 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
of these columns.
</para>
<para>
If the <literal>WITHOUT OVERLAPS</literal> option is specified for the
last column, then that column is checked for overlaps instead of
equality. In that case, the other columns of the constraint will allow
duplicates so long as the duplicates don't overlap in the
<literal>WITHOUT OVERLAPS</literal> column. (This is sometimes called a
temporal key, if the column is a range of dates or timestamps, but
PostgreSQL allows ranges over any base type.) In effect, such a
constraint is enforced with an <literal>EXCLUDE</literal> constraint
rather than a <literal>UNIQUE</literal> constraint. So for example
<literal>UNIQUE (id, valid_at WITHOUT OVERLAPS)</literal> behaves like
<literal>EXCLUDE USING GIST (id WITH =, valid_at WITH
&amp;&amp;)</literal>. The <literal>WITHOUT OVERLAPS</literal> column
must have a range or multirange type. (Technically, any type is allowed
whose default GiST opclass includes an overlaps operator. See the
<literal>stratnum</literal> support function under <xref
linkend="gist-extensibility"/> for details.) The non-<literal>WITHOUT
OVERLAPS</literal> columns of the constraint can be any type that can be
compared for equality in a GiST index. By default, only range types are
supported, but you can use other types by adding the <xref
linkend="btree-gist"/> extension (which is the expected way to use this
feature).
</para>
<para>
For the purpose of a unique constraint, null values are not
considered equal, unless <literal>NULLS NOT DISTINCT</literal> is
@@ -1000,8 +1024,10 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
</para>
<para>
Adding a unique constraint will automatically create a unique btree
index on the column or group of columns used in the constraint.
Adding a unique constraint will automatically create a unique B-tree
index on the column or group of columns used in the constraint. But if
the constraint includes a <literal>WITHOUT OVERLAPS</literal> clause, it
will use a GiST index.
</para>
<para>
@@ -1019,7 +1045,7 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
<varlistentry id="sql-createtable-parms-primary-key">
<term><literal>PRIMARY KEY</literal> (column constraint)</term>
<term><literal>PRIMARY KEY ( <replaceable class="parameter">column_name</replaceable> [, ... ] )</literal>
<term><literal>PRIMARY KEY ( <replaceable class="parameter">column_name</replaceable> [, ... ] [, <replaceable class="parameter">column_name</replaceable> WITHOUT OVERLAPS ] )</literal>
<optional> <literal>INCLUDE ( <replaceable class="parameter">column_name</replaceable> [, ...])</literal> </optional> (table constraint)</term>
<listitem>
<para>
@@ -1052,9 +1078,10 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
</para>
<para>
Adding a <literal>PRIMARY KEY</literal> constraint will automatically
create a unique btree index on the column or group of columns used in the
constraint.
As with a <literal>UNIQUE</literal> constraint, adding a
<literal>PRIMARY KEY</literal> constraint will automatically create a
unique B-tree index, or GiST if <literal>WITHOUT OVERLAPS</literal> was
specified, on the column or group of columns used in the constraint.
</para>
<para>