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Documentation corrections for opclass parameters

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Discussion: https://postgr.es/m/20200331024419.GB14618%40telsasoft.com
Author: Justin Pryzby
This commit is contained in:
Alexander Korotkov
2020-04-01 14:42:17 +03:00
parent 8d84dd0012
commit 3f1802e1fd
5 changed files with 42 additions and 41 deletions
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12
doc/src/sgml/hstore.sgml
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@ -468,13 +468,13 @@ CREATE INDEX hidx ON testhstore USING GIN (h);
</programlisting>
<para>
<literal>gist_hstore_ops</literal> GiST opclass approximates set of
key/value pairs as a bitmap signature. Optional integer parameter
<literal>siglen</literal> of <literal>gist_hstore_ops</literal> determines
signature length in bytes. Default signature length is 16 bytes.
<literal>gist_hstore_ops</literal> GiST opclass approximates a set of
key/value pairs as a bitmap signature. Its optional integer parameter
<literal>siglen</literal> determines the
signature length in bytes. The default length is 16 bytes.
Valid values of signature length are between 1 and 2024 bytes. Longer
signatures leads to more precise search (scan less fraction of index, scan
less heap pages), but larger index.
signatures lead to a more precise search (scanning a smaller fraction of the index and
fewer heap pages), at the cost of a larger index.
</para>
<para>

27
doc/src/sgml/intarray.sgml
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@ -265,7 +265,7 @@
</para>
<para>
Two parametrized GiST index operator classes are provided:
Two parameterized GiST index operator classes are provided:
<literal>gist__int_ops</literal> (used by default) is suitable for
small- to medium-size data sets, while
<literal>gist__intbig_ops</literal> uses a larger signature and is more
@ -276,22 +276,23 @@
</para>
<para>
<literal>gist__int_ops</literal> approximates integer set as an array of
integer ranges. Optional integer parameter <literal>numranges</literal> of
<literal>gist__int_ops</literal> determines maximum number of ranges in
one index key. Default value of <literal>numranges</literal> is 100.
<literal>gist__int_ops</literal> approximates an integer set as an array of
integer ranges. Its optional integer parameter <literal>numranges</literal>
determines the maximum number of ranges in
one index key. The default value of <literal>numranges</literal> is 100.
Valid values are between 1 and 253. Using larger arrays as GiST index
keys leads to more precise search (scan less fraction of index, scan less
heap pages), but larger index.
keys leads to a more precise search (scaning a smaller fraction of the index and
fewer heap pages), at the cost of a larger index.
</para>
<para>
<literal>gist__intbig_ops</literal> approximates integer set as a bitmap
signature. Optional integer parameter <literal>siglen</literal> of
<literal>gist__intbig_ops</literal> determines signature length in bytes.
Default signature length is 16 bytes. Valid values of signature length
are between 1 and 2024 bytes. Longer signatures leads to more precise
search (scan less fraction of index, scan less heap pages), but larger index.
<literal>gist__intbig_ops</literal> approximates an integer set as a bitmap
signature. Its optional integer parameter <literal>siglen</literal>
determines the signature length in bytes.
The default signature length is 16 bytes. Valid values of signature length
are between 1 and 2024 bytes. Longer signatures lead to a more precise
search (scanning a smaller fraction of the index and fewer heap pages), at
the cost of a larger index.
</para>
<para>

20
doc/src/sgml/ltree.sgml
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@ -516,16 +516,16 @@ Europe &amp; Russia*@ &amp; !Transportation
<literal>@</literal>, <literal>~</literal>, <literal>?</literal>
</para>
<para>
<literal>gist_ltree_ops</literal> GiST opclass approximates set of
path labels as a bitmap signature. Optional integer parameter
<literal>siglen</literal> of <literal>gist_ltree_ops</literal> determines
signature length in bytes. Default signature length is 8 bytes.
<literal>gist_ltree_ops</literal> GiST opclass approximates a set of
path labels as a bitmap signature. Its optional integer parameter
<literal>siglen</literal> determines the
signature length in bytes. The default signature length is 8 bytes.
Valid values of signature length are between 1 and 2024 bytes. Longer
signatures leads to more precise search (scan less fraction of index, scan
less heap pages), but larger index.
signatures lead to a more precise search (scanning a smaller fraction of the index and
fewer heap pages), at the cost of a larger index.
</para>
<para>
Example of creating such an index with a default signature length of 8 bytes:
Example of creating such an index with the default signature length of 8 bytes:
</para>
<programlisting>
CREATE INDEX path_gist_idx ON test USING GIST (path);
@ -545,13 +545,13 @@ CREATE INDEX path_gist_idx ON test USING GIST (path gist_ltree_ops(siglen=100));
<literal>@</literal>, <literal>~</literal>, <literal>?</literal>
</para>
<para>
<literal>gist__ltree_ops</literal> GiST opclass works similar to
<literal>gist__ltree_ops</literal> GiST opclass works similarly to
<literal>gist_ltree_ops</literal> and also takes signature length as
a parameter. Default value of <literal>siglen</literal> in
a parameter. The default value of <literal>siglen</literal> in
<literal>gist__ltree_ops</literal> is 28 bytes.
</para>
<para>
Example of creating such an index with a default signature length of 28 bytes:
Example of creating such an index with the default signature length of 28 bytes:
</para>
<programlisting>
CREATE INDEX path_gist_idx ON test USING GIST (array_path);

12
doc/src/sgml/pgtrgm.sgml
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@ -391,13 +391,13 @@ CREATE INDEX trgm_idx ON test_trgm USING GIN (t gin_trgm_ops);
</para>
<para>
<literal>gist_trgm_ops</literal> GiST opclass approximates set of
trigrams as a bitmap signature. Optional integer parameter
<literal>siglen</literal> of <literal>gist_trgm_ops</literal> determines
signature length in bytes. Default signature length is 12 bytes.
<literal>gist_trgm_ops</literal> GiST opclass approximates a set of
trigrams as a bitmap signature. Its optional integer parameter
<literal>siglen</literal> determines the
signature length in bytes. The default length is 12 bytes.
Valid values of signature length are between 1 and 2024 bytes. Longer
signatures leads to more precise search (scan less fraction of index, scan
less heap pages), but larger index.
signatures lead to a more precise search (scanning a smaller fraction of the index and
fewer heap pages), at the cost of a larger index.
</para>
<para>

12
doc/src/sgml/textsearch.sgml
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@ -3670,17 +3670,17 @@ SELECT plainto_tsquery('supernovae stars');
to check the actual table row to eliminate such false matches.
(<productname>PostgreSQL</productname> does this automatically when needed.)
GiST indexes are lossy because each document is represented in the
index by a fixed-length signature. Signature length in bytes is determined
index by a fixed-length signature. The signature length in bytes is determined
by the value of the optional integer parameter <literal>siglen</literal>.
Default signature length (when <literal>siglen</literal> is not specied) is
124 bytes, maximal length is 2024 bytes. The signature is generated by hashing
The default signature length (when <literal>siglen</literal> is not specified) is
124 bytes, the maximum signature length is 2024 bytes. The signature is generated by hashing
each word into a single bit in an n-bit string, with all these bits OR-ed
together to produce an n-bit document signature. When two words hash to
the same bit position there will be a false match. If all words in
the query have matches (real or false) then the table row must be
retrieved to see if the match is correct. Longer signatures leads to more
precise search (scan less fraction of index, scan less heap pages), but
larger index.
retrieved to see if the match is correct. Longer signatures lead to a more
precise search (scanning a smaller fraction of the index and fewer heap
pages), at the cost of a larger index.
</para>
<para>