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Complete merge of all old man page information.

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ecpg reference page still needs formatting.
This commit is contained in:
Thomas G. Lockhart
1999-07-22 15:09:15 +00:00
parent 2aa64f79f5
commit a27512e634
81 changed files with 2292 additions and 772 deletions
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56
doc/src/sgml/ref/explain.sgml
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@@ -1,6 +1,11 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/explain.sgml,v 1.8 1999/07/22 15:09:12 thomas Exp $
Postgres documentation
-->
<refentry id="SQL-EXPLAIN">
<refmeta>
<refentrytitle>
<refentrytitle id="SQL-EXPLAIN-TITLE">
EXPLAIN
</refentrytitle>
<refmiscinfo>SQL - Language Statements</refmiscinfo>
@@ -16,7 +21,7 @@
<refsynopsisdiv>
<refsynopsisdivinfo>
<date>1998-09-01</date>
<date>1999-07-20</date>
</refsynopsisdivinfo>
<synopsis>
EXPLAIN [ VERBOSE ] <replaceable class="PARAMETER">query</replaceable>
@@ -95,6 +100,7 @@ EXPLAIN
<title>
Description
</title>
<para>
This command outputs details about the supplied query.
The default output is the computed query cost.
@@ -127,16 +133,54 @@ EXPLAIN
<title>
Usage
</title>
<para>
To show a query plan for a simple query:
To show a query plan for a simple query on a table with a single
<type>int4</type> column and 128 rows:
<programlisting>
EXPLAIN select * from foo;
EXPLAIN SELECT * FROM foo;
<computeroutput>
NOTICE: QUERY PLAN:
Seq Scan on foo (cost=0.00 rows=0 width=4)
Seq Scan on foo (cost=5.22 rows=128 width=4)
EXPLAIN
</computeroutput>
</programlisting>
</para>
<para>
For the same table with an index to support an
<firstterm>equijoin</firstterm> condition on the query,
<command>EXPLAIN</command> will show a different plan:
<programlisting>
EXPLAIN SELECT * FROM foo WHERE i = 4;
<computeroutput>
NOTICE: QUERY PLAN:
Index Scan using fi on foo (cost=2.05 rows=1 width=4)
EXPLAIN
</computeroutput>
</programlisting>
</para>
<para>
And finally, for the same table with an index to support an
<firstterm>equijoin</firstterm> condition on the query,
<command>EXPLAIN</command> will show the following for a query
using an aggregate function:
<programlisting>
EXPLAIN SELECT sum(i) FROM foo WHERE i = 4;
<computeroutput>
NOTICE: QUERY PLAN:
Aggregate (cost=2.05 rows=1 width=4)
-> Index Scan using fi on foo (cost=2.05 rows=1 width=4)
</computeroutput>
</programlisting>
</para>
</refsect1>
@@ -145,8 +189,6 @@ EXPLAIN
<title>
Compatibility
</title>
<para>
</para>
<refsect2 id="R2-SQL-EXPLAIN-4">
<refsect2info>