On 24.02.2024 14:28, jian he wrote:
Hi.
I wrote the first draft patch of the documentation.
it's under the section: Planner Method Configuration (runtime-config-query.html)
but this feature's main meat is in src/backend/parser/parse_expr.c
so it may be slightly inconsistent, as mentioned by others.
You can further furnish it.
Thank you for your work. I found a few spelling mistakes - I fixed this
and added some information about generating a partial index plan. I
attached it.
--
Regards,
Alena Rybakina
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
From e3a0e01c43a70099f6870a468d0cc3a8bdcb2775 Mon Sep 17 00:00:00 2001
From: Alena Rybakina <a.rybak...@postgrespro.ru>
Date: Mon, 26 Feb 2024 06:37:36 +0300
Subject: [PATCH] doc1
---
doc/src/sgml/config.sgml | 74 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 74 insertions(+)
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 36a2a5ce431..47f82ca2dc9 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -5294,6 +5294,80 @@ ANY <replaceable
class="parameter">num_sync</replaceable> ( <replaceable class="
</listitem>
</varlistentry>
+ <varlistentry id="guc-enable-or-transformation"
xreflabel="enable_or_transformation">
+ <term><varname>enable_or_transformation</varname> (<type>boolean</type>)
+ <indexterm>
+ <primary><varname>enable_or_transformation</varname> configuration
parameter</primary>
+ </indexterm>
+ </term>
+ <listitem>
+ <para>
+ Enables or disables in query planner's ability to transform multiple
expressions in (<xref linkend="sql-expressions"/>)
+ <xref linkend="sql-where"/> to a ANY expression (<xref
linkend="functions-comparisons-any-some"/>).
+ This transformations only apply under the following condition:
+ <itemizedlist>
+ <listitem>
+ <para>
+ Each expression should be formed as:
<replaceable>expression</replaceable> <replaceable>operator</replaceable>
(<replaceable>expression</replaceable>).
+ The right-hand side of the operator should be just a plain
constant.
+ The left-hand side of these expressions should remain unchanged.
+ </para>
+ </listitem>
+ </itemizedlist>
+ <itemizedlist>
+ <listitem>
+ <para>
+ At the stage of index formation, a check is made on the
restructuring of the plan using partial indexes or the formation of expressions
combined by the "OR" <replaceable>operator</replaceable>.
+ </para>
+ </listitem>
+ </itemizedlist>
+ <itemizedlist>
+ <listitem>
+ <para>
+ Each expression form should return Boolean (true/false)
result.
+ </para>
+ </listitem>
+ </itemizedlist>
+ <itemizedlist>
+ <listitem>
+ <para>
+ These expressions are logically linked in a OR condition.
+ </para>
+ </listitem>
+ </itemizedlist>
+ The default is <literal>on</literal>.
+ </para>
+ <para>
+ For example, the following query without setting
<varname>enable_or_transformation</varname> is usually applied to the three
filtering conditions separately,
+ but if we set <varname>enable_or_transformation</varname>, we
combine the three expressions into only one expression: <literal>unique1 = ANY
('{1,2,3}'::integer[]) </literal>.
+ <programlisting>
+ EXPLAIN SELECT * FROM tenk1 WHERE unique1 = 1 or unique1 = 2 or
unique1 = 3;
+
+ QUERY PLAN
+ -------------------------------------------------------------
+ Seq Scan on tenk1 (cost=0.00..482.50 rows=3 width=244)
+ Filter: (unique1 = ANY ('{1,2,3}'::integer[]))
+ </programlisting>
+ </para>
+ <para>
+ Another example is the following query with a given
<varname>enable_or_transformation</varname> value, but we have generated a plan
with partial indexes.
+ <programlisting>
+ EXPLAIN SELECT unique2, stringu1 FROM onek2 WHERE unique1 = 1 OR
unique1 = PI()::integer;
+ QUERY PLAN
+ --------------------------------------------------
+ Bitmap Heap Scan on onek2
+ Recheck Cond: ((unique1 = 3) OR (unique1 = 1))
+ -> BitmapOr
+ -> Bitmap Index Scan on onek2_u1_prtl
+ Index Cond: (unique1 = 3)
+ -> Bitmap Index Scan on onek2_u1_prtl
+ Index Cond: (unique1 = 1)
+ (7 rows)
+ </programlisting>
+ </para>
+ </listitem>
+ </varlistentry>
+
<varlistentry id="guc-enable-parallel-append"
xreflabel="enable_parallel_append">
<term><varname>enable_parallel_append</varname> (<type>boolean</type>)
<indexterm>
--
2.34.1
