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Allow GIN's extractQuery method to signal that nothing can satisfy the query.

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In this case extractQuery should returns -1 as nentries. This changes
prototype of extractQuery method to use int32* instead of uint32* for
nentries argument.
Based on that gincostestimate may see two corner cases: nothing will be found
or seqscan should be used.

Per proposal at http://archives.postgresql.org/pgsql-hackers/2007-01/msg01581.php

PS tsearch_core patch should be sightly modified to support changes, but I'm
waiting a verdict about reviewing of tsearch_core patch.
This commit is contained in:
Teodor Sigaev
2007-01-31 15:09:45 +00:00
parent 147a3ce149
commit d4c6da1527
11 changed files with 199 additions and 29 deletions
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12
doc/src/sgml/gin.sgml
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@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/gin.sgml,v 2.7 2006/12/01 23:46:46 tgl Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/gin.sgml,v 2.8 2007/01/31 15:09:45 teodor Exp $ -->
<chapter id="GIN">
<title>GIN Indexes</title>
@ -77,7 +77,7 @@
</varlistentry>
<varlistentry>
<term>Datum* extractValue(Datum inputValue, uint32 *nkeys)</term>
<term>Datum* extractValue(Datum inputValue, int32 *nkeys)</term>
<listitem>
<para>
Returns an array of keys given a value to be indexed. The
@ -87,7 +87,7 @@
</varlistentry>
<varlistentry>
<term>Datum* extractQuery(Datum query, uint32 *nkeys,
<term>Datum* extractQuery(Datum query, int32 *nkeys,
StrategyNumber n)</term>
<listitem>
<para>
@ -100,6 +100,12 @@
to consult <literal>n</> to determine the data type of
<literal>query</> and the key values that need to be extracted.
The number of returned keys must be stored into <literal>*nkeys</>.
If number of keys is equal to zero then <function>extractQuery</>
should store 0 or -1 into <literal>*nkeys</>. 0 means that any
row matches the <literal>query</> and sequence scan should be
produced. -1 means nothing can satisfy <literal>query</>.
Choice of value should be based on semantics meaning of operation with
given strategy number.
</para>
</listitem>
</varlistentry>