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Replace ad-hoc insertions into pg_opclass and friends with CREATE

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OPERATOR CLASS commands.  Further tweaking of documentation for same.
This commit is contained in:
Tom Lane
2002-07-30 17:34:37 +00:00
parent ea2d97414c
commit 65b6868b13
10 changed files with 208 additions and 1102 deletions
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8
doc/src/sgml/extend.sgml
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@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/extend.sgml,v 1.15 2002/01/07 02:29:11 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/extend.sgml,v 1.16 2002/07/30 17:34:37 tgl Exp $
-->
<chapter id="extend">
@ -255,11 +255,7 @@ $Header: /cvsroot/pgsql/doc/src/sgml/extend.sgml,v 1.15 2002/01/07 02:29:11 pete
There are many columns and relationships that
have obvious meanings, but there are many
(particularly those that have to do with access
methods) that do not. The relationships between
<classname>pg_am</>, <classname>pg_amop</>, <classname>pg_amproc</>, <classname>pg_operator</>, and
<classname>pg_opclass</> are particularly hard to understand
and will be described in depth (in <xref linkend="xindex">)
after we have discussed basic extensions.
methods) that do not.
</para>
</listitem>
</itemizedlist>

20
doc/src/sgml/indices.sgml
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@ -1,4 +1,4 @@
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/indices.sgml,v 1.34 2002/06/21 19:06:44 momjian Exp $ -->
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/indices.sgml,v 1.35 2002/07/30 17:34:37 tgl Exp $ -->
<chapter id="indexes">
<title id="indexes-title">Indexes</title>
@ -407,8 +407,18 @@ CREATE INDEX <replaceable>name</replaceable> ON <replaceable>table</replaceable>
</para>
<para>
The following query shows all defined operator classes:
<programlisting>
The following query shows all defined operator classes:
<programlisting>
SELECT am.amname AS acc_method,
opc.opcname AS ops_name
FROM pg_am am, pg_opclass opc
WHERE opc.opcamid = am.oid
ORDER BY acc_method, ops_name;
</programlisting>
It can be extended to show all the operators included in each class:
<programlisting>
SELECT am.amname AS acc_method,
opc.opcname AS ops_name,
opr.oprname AS ops_comp
@ -416,8 +426,8 @@ SELECT am.amname AS acc_method,
WHERE opc.opcamid = am.oid AND
amop.amopclaid = opc.oid AND
amop.amopopr = opr.oid
ORDER BY acc_method, ops_name, ops_comp
</programlisting>
ORDER BY acc_method, ops_name, ops_comp;
</programlisting>
</para>
</sect1>

13
doc/src/sgml/ref/create_index.sgml
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@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_index.sgml,v 1.34 2002/06/21 19:06:44 momjian Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_index.sgml,v 1.35 2002/07/30 17:34:37 tgl Exp $
PostgreSQL documentation
-->
@ -382,13 +382,10 @@ ERROR: Cannot create index: 'index_name' already exists.
<programlisting>
SELECT am.amname AS acc_method,
opc.opcname AS ops_name,
opr.oprname AS ops_comp
FROM pg_am am, pg_opclass opc, pg_amop amop, pg_operator opr
WHERE opc.opcamid = am.oid AND
amop.amopclaid = opc.oid AND
amop.amopopr = opr.oid
ORDER BY acc_method, ops_name, ops_comp;
opc.opcname AS ops_name
FROM pg_am am, pg_opclass opc
WHERE opc.opcamid = am.oid
ORDER BY acc_method, ops_name;
</programlisting>
</para>
</refsect2>

42
doc/src/sgml/xindex.sgml
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@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/xindex.sgml,v 1.27 2002/07/30 05:24:56 tgl Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/xindex.sgml,v 1.28 2002/07/30 17:34:37 tgl Exp $
PostgreSQL documentation
-->
@ -97,7 +97,7 @@ PostgreSQL documentation
Because
<productname>PostgreSQL</productname> allows the user to define operators,
<productname>PostgreSQL</productname> cannot look at the name of an operator
(e.g., <literal>&gt;</> or <literal>&lt;</>) and tell what kind of
(e.g., <literal>&lt;</> or <literal>&gt;=</>) and tell what kind of
comparison it is. Instead, the index access method defines a set of
<quote>strategies</>, which can be thought of as generalized operators.
Each operator class shows which actual operator corresponds to each
@ -279,18 +279,16 @@ PostgreSQL documentation
<tgroup cols="2">
<thead>
<row>
<entry>Operation</entry>
<entry>Function</entry>
<entry>Support Number</entry>
</row>
</thead>
<tbody>
<row>
<entry>
Compare two keys and return -1, 0,
or +1, depending on whether the first key is less than, equal to,
or greater than the second. (Actually, this routine can
return any negative int32 value (&lt; 0), zero, or any non-zero positive
int32 value (&gt; 0).)
Compare two keys and return an integer less than zero, zero, or
greater than zero, indicating whether the first key is less than, equal to,
or greater than the second.
</entry>
<entry>1</entry>
</row>
@ -309,13 +307,13 @@ PostgreSQL documentation
<tgroup cols="2">
<thead>
<row>
<entry>Operation</entry>
<entry>Function</entry>
<entry>Support Number</entry>
</row>
</thead>
<tbody>
<row>
<entry>compute the hash value for a key</entry>
<entry>Compute the hash value for a key</entry>
<entry>1</entry>
</row>
</tbody>
@ -333,7 +331,7 @@ PostgreSQL documentation
<tgroup cols="2">
<thead>
<row>
<entry>Operation</entry>
<entry>Function</entry>
<entry>Support Number</entry>
</row>
</thead>
@ -365,7 +363,7 @@ PostgreSQL documentation
<tgroup cols="2">
<thead>
<row>
<entry>Operation</entry>
<entry>Function</entry>
<entry>Support Number</entry>
</row>
</thead>
@ -442,8 +440,8 @@ PostgreSQL documentation
return (amag==bmag);
}
</programlisting>
(Note that we will only show the equality operator for the rest of
the examples. The other four operators are very similar. Refer to
(Note that we will only show the equality operator in this text.
The other four operators are very similar. Refer to
<filename>complex.c</filename> or
<filename>complex.source</filename> for the details.)
</para>
@ -555,11 +553,11 @@ CREATE FUNCTION complex_abs_cmp(complex, complex)
<programlisting>
CREATE OPERATOR CLASS complex_abs_ops
DEFAULT FOR TYPE complex USING btree AS
OPERATOR 1 < ,
OPERATOR 2 <= ,
OPERATOR 1 &lt; ,
OPERATOR 2 &lt;= ,
OPERATOR 3 = ,
OPERATOR 4 >= ,
OPERATOR 5 > ,
OPERATOR 4 &gt;= ,
OPERATOR 5 &gt; ,
FUNCTION 1 complex_abs_cmp(complex, complex);
</programlisting>
</para>
@ -572,7 +570,7 @@ CREATE OPERATOR CLASS complex_abs_ops
<para>
We could have written the operator entries more verbosely, as in
<programlisting>
OPERATOR 1 < (complex, complex) ,
OPERATOR 1 &lt; (complex, complex) ,
</programlisting>
but there is no need to do so when the operators take the same datatype
we are defining the operator class for.
@ -599,7 +597,7 @@ CREATE OPERATOR CLASS complex_abs_ops
that the index access method can retrieve exactly the set of rows
that satisfy a WHERE condition using the operator. For example,
<programlisting>
SELECT * FROM table WHERE integer_column < 4;
SELECT * FROM table WHERE integer_column &lt; 4;
</programlisting>
can be satisfied exactly by a B-tree index on the integer column.
But there are cases where an index is useful as an inexact guide to
@ -610,8 +608,8 @@ SELECT * FROM table WHERE integer_column < 4;
box overlaps the bounding box of the target object, and then do the
exact overlap test only on the objects found by the index. If this
scenario applies, the index is said to be <quote>lossy</> for the
operator, and we mark the <literal>OPERATOR</> clause in the
<command>CREATE OPERATOR CLASS</> command with <literal>RECHECK</>.
operator, and we add <literal>RECHECK</> to the <literal>OPERATOR</> clause
in the <command>CREATE OPERATOR CLASS</> command.
<literal>RECHECK</> is valid if the index is guaranteed to return
all the required tuples, plus perhaps some additional tuples, which
can be eliminated by performing the original operator comparison.