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diff --git a/doc/src/sgml/html/indexes-types.html b/doc/src/sgml/html/indexes-types.html new file mode 100644 index 0000000..e043b7b --- /dev/null +++ b/doc/src/sgml/html/indexes-types.html @@ -0,0 +1,162 @@ +<?xml version="1.0" encoding="UTF-8" standalone="no"?> +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>11.2. Index Types</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="indexes-intro.html" title="11.1. Introduction" /><link rel="next" href="indexes-multicolumn.html" title="11.3. Multicolumn Indexes" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">11.2. Index Types</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="indexes-intro.html" title="11.1. Introduction">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="indexes.html" title="Chapter 11. Indexes">Up</a></td><th width="60%" align="center">Chapter 11. Indexes</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 15.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="indexes-multicolumn.html" title="11.3. Multicolumn Indexes">Next</a></td></tr></table><hr /></div><div class="sect1" id="INDEXES-TYPES"><div class="titlepage"><div><div><h2 class="title" style="clear: both">11.2. Index Types</h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="sect2"><a href="indexes-types.html#INDEXES-TYPES-BTREE">11.2.1. B-Tree</a></span></dt><dt><span class="sect2"><a href="indexes-types.html#INDEXES-TYPES-HASH">11.2.2. Hash</a></span></dt><dt><span class="sect2"><a href="indexes-types.html#INDEXES-TYPE-GIST">11.2.3. GiST</a></span></dt><dt><span class="sect2"><a href="indexes-types.html#INDEXES-TYPE-SPGIST">11.2.4. SP-GiST</a></span></dt><dt><span class="sect2"><a href="indexes-types.html#INDEXES-TYPES-GIN">11.2.5. GIN</a></span></dt><dt><span class="sect2"><a href="indexes-types.html#INDEXES-TYPES-BRIN">11.2.6. BRIN</a></span></dt></dl></div><p> + <span class="productname">PostgreSQL</span> provides several index types: + B-tree, Hash, GiST, SP-GiST, GIN, BRIN, and the extension <a class="link" href="bloom.html" title="F.7. bloom">bloom</a>. + Each index type uses a different + algorithm that is best suited to different types of queries. + By default, the <a class="link" href="sql-createindex.html" title="CREATE INDEX"><code class="command">CREATE + INDEX</code></a> command creates + B-tree indexes, which fit the most common situations. + The other index types are selected by writing the keyword + <code class="literal">USING</code> followed by the index type name. + For example, to create a Hash index: +</p><pre class="programlisting"> +CREATE INDEX <em class="replaceable"><code>name</code></em> ON <em class="replaceable"><code>table</code></em> USING HASH (<em class="replaceable"><code>column</code></em>); +</pre><p> + </p><div class="sect2" id="INDEXES-TYPES-BTREE"><div class="titlepage"><div><div><h3 class="title">11.2.1. B-Tree</h3></div></div></div><a id="id-1.5.10.5.3.2" class="indexterm"></a><a id="id-1.5.10.5.3.3" class="indexterm"></a><p> + B-trees can handle equality and range queries on data that can be sorted + into some ordering. + In particular, the <span class="productname">PostgreSQL</span> query planner + will consider using a B-tree index whenever an indexed column is + involved in a comparison using one of these operators: + +</p><pre class="synopsis"> +< <= = >= > +</pre><p> + + Constructs equivalent to combinations of these operators, such as + <code class="literal">BETWEEN</code> and <code class="literal">IN</code>, can also be implemented with + a B-tree index search. Also, an <code class="literal">IS NULL</code> or <code class="literal">IS NOT + NULL</code> condition on an index column can be used with a B-tree index. + </p><p> + The optimizer can also use a B-tree index for queries involving the + pattern matching operators <code class="literal">LIKE</code> and <code class="literal">~</code> + <span class="emphasis"><em>if</em></span> the pattern is a constant and is anchored to + the beginning of the string — for example, <code class="literal">col LIKE + 'foo%'</code> or <code class="literal">col ~ '^foo'</code>, but not + <code class="literal">col LIKE '%bar'</code>. However, if your database does not + use the C locale you will need to create the index with a special + operator class to support indexing of pattern-matching queries; see + <a class="xref" href="indexes-opclass.html" title="11.10. Operator Classes and Operator Families">Section 11.10</a> below. It is also possible to use + B-tree indexes for <code class="literal">ILIKE</code> and + <code class="literal">~*</code>, but only if the pattern starts with + non-alphabetic characters, i.e., characters that are not affected by + upper/lower case conversion. + </p><p> + B-tree indexes can also be used to retrieve data in sorted order. + This is not always faster than a simple scan and sort, but it is + often helpful. + </p></div><div class="sect2" id="INDEXES-TYPES-HASH"><div class="titlepage"><div><div><h3 class="title">11.2.2. Hash</h3></div></div></div><a id="id-1.5.10.5.4.2" class="indexterm"></a><a id="id-1.5.10.5.4.3" class="indexterm"></a><p> + Hash indexes store a 32-bit hash code derived from the + value of the indexed column. Hence, + such indexes can only handle simple equality comparisons. + The query planner will consider using a hash index whenever an + indexed column is involved in a comparison using the + equal operator: + +</p><pre class="synopsis"> += +</pre><p> + </p></div><div class="sect2" id="INDEXES-TYPE-GIST"><div class="titlepage"><div><div><h3 class="title">11.2.3. GiST</h3></div></div></div><a id="id-1.5.10.5.5.2" class="indexterm"></a><a id="id-1.5.10.5.5.3" class="indexterm"></a><p> + GiST indexes are not a single kind of index, but rather an infrastructure + within which many different indexing strategies can be implemented. + Accordingly, the particular operators with which a GiST index can be + used vary depending on the indexing strategy (the <em class="firstterm">operator + class</em>). As an example, the standard distribution of + <span class="productname">PostgreSQL</span> includes GiST operator classes + for several two-dimensional geometric data types, which support indexed + queries using these operators: + +</p><pre class="synopsis"> +<< &< &> >> <<| &<| |&> |>> @> <@ ~= && +</pre><p> + + (See <a class="xref" href="functions-geometry.html" title="9.11. Geometric Functions and Operators">Section 9.11</a> for the meaning of + these operators.) + The GiST operator classes included in the standard distribution are + documented in <a class="xref" href="gist-builtin-opclasses.html#GIST-BUILTIN-OPCLASSES-TABLE" title="Table 68.1. Built-in GiST Operator Classes">Table 68.1</a>. + Many other GiST operator + classes are available in the <code class="literal">contrib</code> collection or as separate + projects. For more information see <a class="xref" href="gist.html" title="Chapter 68. GiST Indexes">Chapter 68</a>. + </p><p> + GiST indexes are also capable of optimizing <span class="quote">“<span class="quote">nearest-neighbor</span>”</span> + searches, such as +</p><pre class="programlisting"> +SELECT * FROM places ORDER BY location <-> point '(101,456)' LIMIT 10; + +</pre><p> + which finds the ten places closest to a given target point. The ability + to do this is again dependent on the particular operator class being used. + In <a class="xref" href="gist-builtin-opclasses.html#GIST-BUILTIN-OPCLASSES-TABLE" title="Table 68.1. Built-in GiST Operator Classes">Table 68.1</a>, operators that can be + used in this way are listed in the column <span class="quote">“<span class="quote">Ordering Operators</span>”</span>. + </p></div><div class="sect2" id="INDEXES-TYPE-SPGIST"><div class="titlepage"><div><div><h3 class="title">11.2.4. SP-GiST</h3></div></div></div><a id="id-1.5.10.5.6.2" class="indexterm"></a><a id="id-1.5.10.5.6.3" class="indexterm"></a><p> + SP-GiST indexes, like GiST indexes, offer an infrastructure that supports + various kinds of searches. SP-GiST permits implementation of a wide range + of different non-balanced disk-based data structures, such as quadtrees, + k-d trees, and radix trees (tries). As an example, the standard distribution of + <span class="productname">PostgreSQL</span> includes SP-GiST operator classes + for two-dimensional points, which support indexed + queries using these operators: + +</p><pre class="synopsis"> +<< >> ~= <@ <<| |>> +</pre><p> + + (See <a class="xref" href="functions-geometry.html" title="9.11. Geometric Functions and Operators">Section 9.11</a> for the meaning of + these operators.) + The SP-GiST operator classes included in the standard distribution are + documented in <a class="xref" href="spgist-builtin-opclasses.html#SPGIST-BUILTIN-OPCLASSES-TABLE" title="Table 69.1. Built-in SP-GiST Operator Classes">Table 69.1</a>. + For more information see <a class="xref" href="spgist.html" title="Chapter 69. SP-GiST Indexes">Chapter 69</a>. + </p><p> + Like GiST, SP-GiST supports <span class="quote">“<span class="quote">nearest-neighbor</span>”</span> searches. + For SP-GiST operator classes that support distance ordering, the + corresponding operator is listed in the <span class="quote">“<span class="quote">Ordering Operators</span>”</span> + column in <a class="xref" href="spgist-builtin-opclasses.html#SPGIST-BUILTIN-OPCLASSES-TABLE" title="Table 69.1. Built-in SP-GiST Operator Classes">Table 69.1</a>. + </p></div><div class="sect2" id="INDEXES-TYPES-GIN"><div class="titlepage"><div><div><h3 class="title">11.2.5. GIN</h3></div></div></div><a id="id-1.5.10.5.7.2" class="indexterm"></a><a id="id-1.5.10.5.7.3" class="indexterm"></a><p> + GIN indexes are <span class="quote">“<span class="quote">inverted indexes</span>”</span> which are appropriate for + data values that contain multiple component values, such as arrays. An + inverted index contains a separate entry for each component value, and + can efficiently handle queries that test for the presence of specific + component values. + </p><p> + Like GiST and SP-GiST, GIN can support + many different user-defined indexing strategies, and the particular + operators with which a GIN index can be used vary depending on the + indexing strategy. + As an example, the standard distribution of + <span class="productname">PostgreSQL</span> includes a GIN operator class + for arrays, which supports indexed queries using these operators: + +</p><pre class="synopsis"> +<@ @> = && +</pre><p> + + (See <a class="xref" href="functions-array.html" title="9.19. Array Functions and Operators">Section 9.19</a> for the meaning of + these operators.) + The GIN operator classes included in the standard distribution are + documented in <a class="xref" href="gin-builtin-opclasses.html#GIN-BUILTIN-OPCLASSES-TABLE" title="Table 70.1. Built-in GIN Operator Classes">Table 70.1</a>. + Many other GIN operator + classes are available in the <code class="literal">contrib</code> collection or as separate + projects. For more information see <a class="xref" href="gin.html" title="Chapter 70. GIN Indexes">Chapter 70</a>. + </p></div><div class="sect2" id="INDEXES-TYPES-BRIN"><div class="titlepage"><div><div><h3 class="title">11.2.6. BRIN</h3></div></div></div><a id="id-1.5.10.5.8.2" class="indexterm"></a><a id="id-1.5.10.5.8.3" class="indexterm"></a><p> + BRIN indexes (a shorthand for Block Range INdexes) store summaries about + the values stored in consecutive physical block ranges of a table. + Thus, they are most effective for columns whose values are well-correlated + with the physical order of the table rows. + Like GiST, SP-GiST and GIN, + BRIN can support many different indexing strategies, + and the particular operators with which a BRIN index can be used + vary depending on the indexing strategy. + For data types that have a linear sort order, the indexed data + corresponds to the minimum and maximum values of the + values in the column for each block range. This supports indexed queries + using these operators: + +</p><pre class="synopsis"> +< <= = >= > +</pre><p> + + The BRIN operator classes included in the standard distribution are + documented in <a class="xref" href="brin-builtin-opclasses.html#BRIN-BUILTIN-OPCLASSES-TABLE" title="Table 71.1. Built-in BRIN Operator Classes">Table 71.1</a>. + For more information see <a class="xref" href="brin.html" title="Chapter 71. BRIN Indexes">Chapter 71</a>. + </p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="indexes-intro.html" title="11.1. Introduction">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="indexes.html" title="Chapter 11. Indexes">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="indexes-multicolumn.html" title="11.3. Multicolumn Indexes">Next</a></td></tr><tr><td width="40%" align="left" valign="top">11.1. 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