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Fix English in bloom module documentation

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Author: Erik Rijkers
This commit is contained in:
Teodor Sigaev 2016-04-01 18:47:44 +03:00
parent 9ee014fc89
commit a361c22ebf
1 changed files with 38 additions and 34 deletions
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doc/src/sgml/bloom.sgml
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@ -8,32 +8,32 @@
</indexterm>
<para>
<literal>bloom</> is a contrib which implements index access method. It comes
as example of custom access methods and generic WAL records usage. But it
is also useful itself.
<literal>bloom</> is a module which implements an index access method. It comes
as an example of custom access methods and generic WAL records usage. But it
is also useful in itself.
</para>
<sect2>
<title>Introduction</title>
<para>
Implementation of
The implementation of a
<ulink url="http://en.wikipedia.org/wiki/Bloom_filter">Bloom filter</ulink>
allows fast exclusion of non-candidate tuples.
Since signature is a lossy representation of all indexed attributes,
search results should be rechecked using heap information.
User can specify signature length (in uint16, default is 5) and the number of
bits, which can be setted, per attribute (1 < colN < 2048).
allows fast exclusion of non-candidate tuples via signatures.
Since a signature is a lossy representation of all indexed attributes,
search results must be rechecked using heap information.
The user can specify signature length (in uint16, default is 5) and the
number of bits, which can be set per attribute (1 < colN < 2048).
</para>
<para>
This index is useful if table has many attributes and queries can include
their arbitary combinations. Traditional <literal>btree</> index is faster
than bloom index, but it'd require too many indexes to support all possible
queries, while one need only one bloom index. Bloom index supports only
equality comparison. Since it's a signature file, not a tree, it always
should be readed fully, but sequentially, so index search performance is
constant and doesn't depend on a query.
This index is useful if a table has many attributes and queries include
arbitrary combinations of them. A traditional <literal>btree</> index is
faster than a bloom index, but it can require many indexes to support all
possible queries where one needs only a single bloom index. A Bloom index
supports only equality comparison. Since it's a signature file, and not a
tree, it always must be read fully, but sequentially, so that index search
performance is constant and doesn't depend on a query.
</para>
</sect2>
@ -41,7 +41,8 @@
<title>Parameters</title>
<para>
<literal>bloom</> indexes accept following parameters in <literal>WITH</>
<literal>bloom</> indexes accept the following parameters in the
<literal>WITH</>
clause.
</para>
@ -71,7 +72,7 @@
<title>Examples</title>
<para>
Example of index definition is given below.
An example of an index definition is given below.
</para>
<programlisting>
@ -80,12 +81,12 @@ CREATE INDEX bloomidx ON tbloom(i1,i2,i3)
</programlisting>
<para>
Here, we create bloom index with signature length 80 bits and attributes
i1, i2 mapped to 2 bits, attribute i3 - to 4 bits.
Here, we created a bloom index with a signature length of 80 bits,
and attributes i1 and i2 mapped to 2 bits, and attribute i3 to 4 bits.
</para>
<para>
Example of index definition and usage is given below.
Here is a fuller example of index definition and usage:
</para>
<programlisting>
@ -142,7 +143,7 @@ SELECT pg_relation_size('btree_idx');
</programlisting>
<para>
Btree index will be not used for this query.
A btree index will be not used for this query.
</para>
<programlisting>
@ -162,10 +163,10 @@ SELECT pg_relation_size('btree_idx');
<title>Opclass interface</title>
<para>
Bloom opclass interface is simple. It requires 1 supporting function:
hash function for indexing datatype. And it provides 1 search operator:
equality operator. The example below shows <literal>opclass</> definition
for <literal>text</> datatype.
The Bloom opclass interface is simple. It requires 1 supporting function:
a hash function for the indexing datatype. It provides 1 search operator:
the equality operator. The example below shows <literal>opclass</>
definition for <literal>text</> datatype.
</para>
<programlisting>
@ -183,16 +184,16 @@ DEFAULT FOR TYPE text USING bloom AS
<itemizedlist>
<listitem>
<para>
For now, only opclasses for <literal>int4</>, <literal>text</> comes
with contrib. However, users may define more of them.
For now, only opclasses for <literal>int4</>, <literal>text</> come
with the module. However, users may define more of them.
</para>
</listitem>
<listitem>
<para>
Only <literal>=</literal> operator is supported for search now. But it's
possible to add support of arrays with contains and intersection
operations in future.
Only the <literal>=</literal> operator is supported for search at the
moment. But it's possible to add support for arrays with contains and
intersection operations in the future.
</para>
</listitem>
</itemizedlist>
@ -203,15 +204,18 @@ DEFAULT FOR TYPE text USING bloom AS
<title>Authors</title>
<para>
Teodor Sigaev <email>teodor@postgrespro.ru</email>, Postgres Professional, Moscow, Russia
Teodor Sigaev <email>teodor@postgrespro.ru</email>,
Postgres Professional, Moscow, Russia
</para>
<para>
Alexander Korotkov <email>a.korotkov@postgrespro.ru</email>, Postgres Professional, Moscow, Russia
Alexander Korotkov <email>a.korotkov@postgrespro.ru</email>,
Postgres Professional, Moscow, Russia
</para>
<para>
Oleg Bartunov <email>obartunov@postgrespro.ru</email>, Postgres Professional, Moscow, Russia
Oleg Bartunov <email>obartunov@postgrespro.ru</email>,
Postgres Professional, Moscow, Russia
</para>
</sect2>