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Operators live in namespaces. CREATE/DROP/COMMENT ON OPERATOR take

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qualified operator names directly, for example CREATE OPERATOR myschema.+
( ... ).  To qualify an operator name in an expression you need to write
OPERATOR(myschema.+) (thanks to Peter for suggesting an escape hatch).
I also took advantage of having to reformat pg_operator to fix something
that'd been bugging me for a while: mergejoinable operators should have
explicit links to the associated cross-data-type comparison operators,
rather than hardwiring an assumption that they are named < and >.
This commit is contained in:
Tom Lane
2002-04-16 23:08:12 +00:00
parent 4da51bfd6d
commit 6cef5d2549
39 changed files with 1953 additions and 1803 deletions
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55
doc/src/sgml/catalogs.sgml
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@ -1,6 +1,6 @@
<!--
Documentation of the system catalogs, directed toward PostgreSQL developers
$Header: /cvsroot/pgsql/doc/src/sgml/catalogs.sgml,v 2.41 2002/04/11 19:59:54 tgl Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/catalogs.sgml,v 2.42 2002/04/16 23:08:09 tgl Exp $
-->
<chapter id="catalogs">
@ -1482,6 +1482,15 @@
<entry>Name of the operator</entry>
</row>
<row>
<entry>oprnamespace</entry>
<entry><type>oid</type></entry>
<entry>pg_namespace.oid</entry>
<entry>
The OID of the namespace that contains this operator
</entry>
</row>
<row>
<entry>oprowner</entry>
<entry><type>int4</type></entry>
@ -1493,7 +1502,8 @@
<entry>oprprec</entry>
<entry><type>int2</type></entry>
<entry></entry>
<entry>unused</entry>
<entry>precedence (currently unused, as precedences are hard-wired
in the grammar)</entry>
</row>
<row>
@ -1510,7 +1520,8 @@
<entry>oprisleft</entry>
<entry><type>bool</type></entry>
<entry></entry>
<entry>unused</entry>
<entry>left-associativity (currently unused, as this is hard-wired
in the grammar)</entry>
</row>
<row>
@ -1561,7 +1572,7 @@
<entry>pg_operator.oid</entry>
<entry>
If this operator supports merge joins, the operator that sorts
the type of the left-hand operand
the type of the left-hand operand (<literal>L&lt;L</>)
</entry>
</row>
@ -1571,28 +1582,48 @@
<entry>pg_operator.oid</entry>
<entry>
If this operator supports merge joins, the operator that sorts
the type of the right-hand operand
the type of the right-hand operand (<literal>R&lt;R</>)
</entry>
</row>
<row>
<entry>oprltcmpop</entry>
<entry><type>oid</type></entry>
<entry>pg_operator.oid</entry>
<entry>
If this operator supports merge joins, the less-than operator that
compares the left and right operand types (<literal>L&lt;R</>)
</entry>
</row>
<row>
<entry>oprgtcmpop</entry>
<entry><type>oid</type></entry>
<entry>pg_operator.oid</entry>
<entry>
If this operator supports merge joins, the greater-than operator that
compares the left and right operand types (<literal>L&gt;R</>)
</entry>
</row>
<row>
<entry>oprcode</entry>
<entry><type>regproc</type></entry>
<entry></entry>
<entry>pg_proc.oid</entry>
<entry>Function that implements this operator</entry>
</row>
<row>
<entry>oprrest</entry>
<entry><type>regproc</type></entry>
<entry></entry>
<entry>pg_proc.oid</entry>
<entry>Restriction selectivity estimation function for this operator</entry>
</row>
<row>
<entry>oprjoin</entry>
<entry><type>regproc</type></entry>
<entry></entry>
<entry>pg_proc.oid</entry>
<entry>Join selectivity estimation function for this operator</entry>
</row>
</tbody>
@ -2498,28 +2529,28 @@
<row>
<entry>typinput</entry>
<entry><type>regproc</type></entry>
<entry></entry>
<entry>pg_proc.oid</entry>
<entry>Input function</entry>
</row>
<row>
<entry>typoutput</entry>
<entry><type>regproc</type></entry>
<entry></entry>
<entry>pg_proc.oid</entry>
<entry>Output function</entry>
</row>
<row>
<entry>typreceive</entry>
<entry><type>regproc</type></entry>
<entry></entry>
<entry>pg_proc.oid</entry>
<entry>unused</entry>
</row>
<row>
<entry>typsend</entry>
<entry><type>regproc</type></entry>
<entry></entry>
<entry>pg_proc.oid</entry>
<entry>unused</entry>
</row>

97
doc/src/sgml/ref/create_operator.sgml
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@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_operator.sgml,v 1.25 2002/03/22 19:20:39 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_operator.sgml,v 1.26 2002/04/16 23:08:10 tgl Exp $
PostgreSQL documentation
-->
@ -28,7 +28,9 @@ CREATE OPERATOR <replaceable>name</replaceable> ( PROCEDURE = <replaceable class
] [, RIGHTARG = <replaceable class="parameter">righttype</replaceable> ]
[, COMMUTATOR = <replaceable class="parameter">com_op</replaceable> ] [, NEGATOR = <replaceable class="parameter">neg_op</replaceable> ]
[, RESTRICT = <replaceable class="parameter">res_proc</replaceable> ] [, JOIN = <replaceable class="parameter">join_proc</replaceable> ]
[, HASHES ] [, SORT1 = <replaceable class="parameter">left_sort_op</replaceable> ] [, SORT2 = <replaceable class="parameter">right_sort_op</replaceable> ] )
[, HASHES ] [, MERGES ]
[, SORT1 = <replaceable class="parameter">left_sort_op</replaceable> ] [, SORT2 = <replaceable class="parameter">right_sort_op</replaceable> ]
[, LTCMP = <replaceable class="parameter">less_than_op</replaceable> ] [, GTCMP = <replaceable class="parameter">greater_than_op</replaceable> ] )
</synopsis>
<refsect2 id="R2-SQL-CREATEOPERATOR-1">
@ -115,11 +117,19 @@ CREATE OPERATOR <replaceable>name</replaceable> ( PROCEDURE = <replaceable class
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>MERGES</term>
<listitem>
<para>
Indicates this operator can support a merge join.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">left_sort_op</replaceable></term>
<listitem>
<para>
If this operator can support a merge join, the
If this operator can support a merge join, the less-than
operator that sorts the left-hand data type of this operator.
</para>
</listitem>
@ -128,11 +138,29 @@ CREATE OPERATOR <replaceable>name</replaceable> ( PROCEDURE = <replaceable class
<term><replaceable class="parameter">right_sort_op</replaceable></term>
<listitem>
<para>
If this operator can support a merge join, the
If this operator can support a merge join, the less-than
operator that sorts the right-hand data type of this operator.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">less_than_op</replaceable></term>
<listitem>
<para>
If this operator can support a merge join, the less-than
operator that compares the input data types of this operator.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">greater_than_op</replaceable></term>
<listitem>
<para>
If this operator can support a merge join, the greater-than
operator that compares the input data types of this operator.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
@ -295,30 +323,39 @@ MYBOXES.description !== box '((0,0), (1,1))'
it also works to just have both operators refer to each other.)
</para>
<para>
The HASHES, SORT1, and SORT2 options are present to support the
query optimizer in performing joins.
<productname>PostgreSQL</productname> can always
evaluate a join (i.e., processing a clause with two tuple
variables separated by an operator that returns a <type>boolean</type>)
by iterative substitution [WONG76].
In addition, <productname>PostgreSQL</productname>
can use a hash-join algorithm along
the lines of [SHAP86]; however, it must know whether this
strategy is applicable. The current hash-join algorithm
is only correct for operators that represent equality tests;
furthermore, equality of the data type must mean bitwise equality
of the representation of the type. (For example, a data type that
contains unused bits that don't matter for equality tests could
not be hash-joined.)
The HASHES flag indicates to the query optimizer that a hash join
may safely be used with this operator.</para>
The HASHES, MERGES, SORT1, SORT2, LTCMP, and GTCMP options are present to
support the query optimizer in performing joins.
<productname>PostgreSQL</productname> can always evaluate a join (i.e.,
processing a clause with two tuple variables separated by an operator that
returns a <type>boolean</type>) by iterative substitution [WONG76]. In
addition, <productname>PostgreSQL</productname> can use a hash-join
algorithm along the lines of [SHAP86]; however, it must know whether this
strategy is applicable. The current hash-join algorithm is only correct
for operators that represent equality tests; furthermore, equality of the
data type must mean bitwise equality of the representation of the type.
(For example, a data type that contains unused bits that don't matter for
equality tests could not be hash-joined.) The HASHES flag indicates to the
query optimizer that a hash join may safely be used with this
operator.
</para>
<para>
Similarly, the two sort operators indicate to the query
optimizer whether merge-sort is a usable join strategy and
which operators should be used to sort the two operand
classes. Sort operators should only be provided for an equality
operator, and they should refer to less-than operators for the
left and right side data types respectively.
Similarly, the MERGES flag indicates whether merge-sort is a usable join
strategy for this operator. A merge join requires that the two input
datatypes have consistent orderings, and that the mergejoin operator
behave like equality with respect to that ordering. For example, it is
possible to merge-join equality between an integer and a float variable by
sorting both inputs in ordinary
numeric order. Execution of a merge join requires that the system be
able to identify four operators related to the mergejoin equality operator:
less-than comparison for the left input datatype,
less-than comparison for the right input datatype,
less-than comparison between the two datatypes, and
greater-than comparison between the two datatypes. It is possible to
specify these by name, as the SORT1, SORT2, LTCMP, and GTCMP options
respectively. The system will fill in the default names <literal>&lt;</>,
<literal>&lt;</>, <literal>&lt;</>, <literal>&gt;</> respectively if
any of these are omitted when MERGES is specified. Also, MERGES will
be assumed to be implied if any of these four operator options appear.
</para>
<para>
If other join strategies are found to be practical,
@ -408,8 +445,10 @@ CREATE OPERATOR === (
RESTRICT = area_restriction_procedure,
JOIN = area_join_procedure,
HASHES,
SORT1 = <<<,
SORT2 = <<<
SORT1 = &lt;&lt;&lt;,
SORT2 = &lt;&lt;&lt;
-- Since sort operators were given, MERGES is implied.
-- LTCMP and GTCMP are assumed to be &lt; and &gt; respectively
);
</programlisting>
</refsect1>