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* Add support NULL to GiST.

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* some refactoring and simplify code int gistutil.c and gist.c
* now in some cases it can be called used-defined
  picksplit method for non-first column in index, but here
	is a place to do more.
* small fix of docs related to support NULL.
This commit is contained in:
Teodor Sigaev
2006-05-24 11:01:39 +00:00
parent 86722057fd
commit d2158b0281
8 changed files with 375 additions and 430 deletions
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5
doc/src/sgml/indexam.sgml
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@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/indexam.sgml,v 2.11 2006/05/10 23:18:38 tgl Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/indexam.sgml,v 2.12 2006/05/24 11:01:39 teodor Exp $ -->
<chapter id="indexam">
<title>Index Access Method Interface Definition</title>
@ -126,8 +126,7 @@
used to scan for rows with <literal>a = 4</literal>, which is wrong if the
index omits rows where <literal>b</> is null.
It is, however, OK to omit rows where the first indexed column is null.
(GiST currently does so.) Thus,
<structfield>amindexnulls</structfield> should be set true only if the
Thus, <structfield>amindexnulls</structfield> should be set true only if the
index access method indexes all rows, including arbitrary combinations of
null values.
</para>

16
doc/src/sgml/indices.sgml
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@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/indices.sgml,v 1.56 2006/01/18 21:29:45 momjian Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/indices.sgml,v 1.57 2006/05/24 11:01:39 teodor Exp $ -->
<chapter id="indexes">
<title id="indexes-title">Indexes</title>
@ -290,13 +290,13 @@ CREATE INDEX test2_mm_idx ON test2 (major, minor);
</para>
<para>
A multicolumn GiST index can only be used when there is a query condition
on its leading column. Conditions on additional columns restrict the
entries returned by the index, but the condition on the first column is the
most important one for determining how much of the index needs to be
scanned. A GiST index will be relatively ineffective if its first column
has only a few distinct values, even if there are many distinct values in
additional columns.
A multicolumn GiST index can be used with query conditions that
involve any subset of the index's columns. Conditions on additional
columns restrict the entries returned by the index, but the condition on
the first column is the most important one for determining how much of
the index needs to be scanned. A GiST index will be relatively
ineffective if its first column has only a few distinct values, even if
there are many distinct values in additional columns.
</para>
<para>