contrib/bloom documentation improvement

This commit documents rounding of "length" parameter and absence of support
for unique indexes and NULLs searching.  Backpatch to 9.6 where contrib/bloom
was introduced.

Discussion: https://postgr.es/m/CAF4Au4wPQQ7EHVSnzcLjsbY3oLSzVk6UemZLD1Sbmwysy3R61g%40mail.gmail.com
Author: Oleg Bartunov with minor editorialization by me
Backpatch-through: 9.6
This commit is contained in:
Alexander Korotkov 2018-10-15 00:40:17 +03:00
parent b403ea43e4
commit 98afb83905

View File

@ -51,8 +51,8 @@
<term><literal>length</literal></term>
<listitem>
<para>
Length of each signature (index entry) in bits. The default
is <literal>80</literal> bits and maximum is <literal>4096</literal>.
Length of each signature (index entry) in bits, it is rounded up to the nearest
multiple of 16. The default is <literal>80</literal> bits and maximum is <literal>4096</literal>.
</para>
</listitem>
</varlistentry>
@ -242,6 +242,20 @@ DEFAULT FOR TYPE text USING bloom AS
operations in the future.
</para>
</listitem>
<listitem>
<para>
<literal>bloom</literal> access method doesn't support
<literal>UNIQUE</literal> indexes.
</para>
</listitem>
<listitem>
<para>
<literal>bloom</literal> access method doesn't support searching for
<literal>NULL</literal> values.
</para>
</listitem>
</itemizedlist>
</para>
</sect2>