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1<?xml version="1.0" encoding="UTF-8" standalone="no"?>2<!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>CREATE INDEX</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="sql-creategroup.html" title="CREATE GROUP" /><link rel="next" href="sql-createlanguage.html" title="CREATE LANGUAGE" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">CREATE INDEX</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="sql-creategroup.html" title="CREATE GROUP">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="sql-commands.html" title="SQL Commands">Up</a></td><th width="60%" align="center">SQL Commands</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 16.3 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="sql-createlanguage.html" title="CREATE LANGUAGE">Next</a></td></tr></table><hr /></div><div class="refentry" id="SQL-CREATEINDEX"><div class="titlepage"></div><a id="id-1.9.3.69.1" class="indexterm"></a><div class="refnamediv"><h2><span class="refentrytitle">CREATE INDEX</span></h2><p>CREATE INDEX — define a new index</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><pre class="synopsis">3CREATE [ UNIQUE ] INDEX [ CONCURRENTLY ] [ [ IF NOT EXISTS ] <em class="replaceable"><code>name</code></em> ] ON [ ONLY ] <em class="replaceable"><code>table_name</code></em> [ USING <em class="replaceable"><code>method</code></em> ]4    ( { <em class="replaceable"><code>column_name</code></em> | ( <em class="replaceable"><code>expression</code></em> ) } [ COLLATE <em class="replaceable"><code>collation</code></em> ] [ <em class="replaceable"><code>opclass</code></em> [ ( <em class="replaceable"><code>opclass_parameter</code></em> = <em class="replaceable"><code>value</code></em> [, ... ] ) ] ] [ ASC | DESC ] [ NULLS { FIRST | LAST } ] [, ...] )5    [ INCLUDE ( <em class="replaceable"><code>column_name</code></em> [, ...] ) ]6    [ NULLS [ NOT ] DISTINCT ]7    [ WITH ( <em class="replaceable"><code>storage_parameter</code></em> [= <em class="replaceable"><code>value</code></em>] [, ... ] ) ]8    [ TABLESPACE <em class="replaceable"><code>tablespace_name</code></em> ]9    [ WHERE <em class="replaceable"><code>predicate</code></em> ]10</pre></div><div class="refsect1" id="id-1.9.3.69.5"><h2>Description</h2><p>11   <code class="command">CREATE INDEX</code> constructs an index on the specified column(s)12   of the specified relation, which can be a table or a materialized view.13   Indexes are primarily used to enhance database performance (though14   inappropriate use can result in slower performance).15  </p><p>16   The key field(s) for the index are specified as column names,17   or alternatively as expressions written in parentheses.18   Multiple fields can be specified if the index method supports19   multicolumn indexes.20  </p><p>21   An index field can be an expression computed from the values of22   one or more columns of the table row.  This feature can be used23   to obtain fast access to data based on some transformation of24   the basic data. For example, an index computed on25   <code class="literal">upper(col)</code> would allow the clause26   <code class="literal">WHERE upper(col) = 'JIM'</code> to use an index.27  </p><p>28   <span class="productname">PostgreSQL</span> provides the index methods29   B-tree, hash, GiST, SP-GiST, GIN, and BRIN.  Users can also define their own30   index methods, but that is fairly complicated.31  </p><p>32    When the <code class="literal">WHERE</code> clause is present, a33    <em class="firstterm">partial index</em> is created.34    A partial index is an index that contains entries for only a portion of35    a table, usually a portion that is more useful for indexing than the36    rest of the table. For example, if you have a table that contains both37    billed and unbilled orders where the unbilled orders take up a small38    fraction of the total table and yet that is an often used section, you39    can improve performance by creating an index on just that portion.40    Another possible application is to use <code class="literal">WHERE</code> with41    <code class="literal">UNIQUE</code> to enforce uniqueness over a subset of a42    table.  See <a class="xref" href="indexes-partial.html" title="11.8. Partial Indexes">Section 11.8</a> for more discussion.43  </p><p>44    The expression used in the <code class="literal">WHERE</code> clause can refer45    only to columns of the underlying table, but it can use all columns,46    not just the ones being indexed.  Presently, subqueries and47    aggregate expressions are also forbidden in <code class="literal">WHERE</code>.48    The same restrictions apply to index fields that are expressions.49  </p><p>50   All functions and operators used in an index definition must be51   <span class="quote">“<span class="quote">immutable</span>”</span>, that is, their results must depend only on52   their arguments and never on any outside influence (such as53   the contents of another table or the current time).  This restriction54   ensures that the behavior of the index is well-defined.  To use a55   user-defined function in an index expression or <code class="literal">WHERE</code>56   clause, remember to mark the function immutable when you create it.57  </p></div><div class="refsect1" id="id-1.9.3.69.6"><h2>Parameters</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">UNIQUE</code></span></dt><dd><p>58        Causes the system to check for59        duplicate values in the table when the index is created (if data60        already exist) and each time data is added. Attempts to61        insert or update data which would result in duplicate entries62        will generate an error.63       </p><p>64        Additional restrictions apply when unique indexes are applied to65        partitioned tables; see <a class="xref" href="sql-createtable.html" title="CREATE TABLE"><span class="refentrytitle">CREATE TABLE</span></a>.66       </p></dd><dt><span class="term"><code class="literal">CONCURRENTLY</code></span></dt><dd><p>67        When this option is used, <span class="productname">PostgreSQL</span> will build the68        index without taking any locks that prevent concurrent inserts,69        updates, or deletes on the table; whereas a standard index build70        locks out writes (but not reads) on the table until it's done.71        There are several caveats to be aware of when using this option72        — see <a class="xref" href="sql-createindex.html#SQL-CREATEINDEX-CONCURRENTLY" title="Building Indexes Concurrently">Building Indexes Concurrently</a> below.73       </p><p>74        For temporary tables, <code class="command">CREATE INDEX</code> is always75        non-concurrent, as no other session can access them, and76        non-concurrent index creation is cheaper.77       </p></dd><dt><span class="term"><code class="literal">IF NOT EXISTS</code></span></dt><dd><p>78        Do not throw an error if a relation with the same name already exists.79        A notice is issued in this case. Note that there is no guarantee that80        the existing index is anything like the one that would have been created.81        Index name is required when <code class="literal">IF NOT EXISTS</code> is specified.82       </p></dd><dt><span class="term"><code class="literal">INCLUDE</code></span></dt><dd><p>83        The optional <code class="literal">INCLUDE</code> clause specifies a84        list of columns which will be included in the index85        as <em class="firstterm">non-key</em> columns.  A non-key column cannot86        be used in an index scan search qualification, and it is disregarded87        for purposes of any uniqueness or exclusion constraint enforced by88        the index.  However, an index-only scan can return the contents of89        non-key columns without having to visit the index's table, since90        they are available directly from the index entry.  Thus, addition of91        non-key columns allows index-only scans to be used for queries that92        otherwise could not use them.93       </p><p>94        It's wise to be conservative about adding non-key columns to an95        index, especially wide columns.  If an index tuple exceeds the96        maximum size allowed for the index type, data insertion will fail.97        In any case, non-key columns duplicate data from the index's table98        and bloat the size of the index, thus potentially slowing searches.99        Furthermore, B-tree deduplication is never used with indexes100        that have a non-key column.101       </p><p>102        Columns listed in the <code class="literal">INCLUDE</code> clause don't need103        appropriate operator classes; the clause can include104        columns whose data types don't have operator classes defined for105        a given access method.106       </p><p>107        Expressions are not supported as included columns since they cannot be108        used in index-only scans.109       </p><p>110        Currently, the B-tree, GiST and SP-GiST index access methods support111        this feature.  In these indexes, the values of columns listed112        in the <code class="literal">INCLUDE</code> clause are included in leaf tuples113        which correspond to heap tuples, but are not included in upper-level114        index entries used for tree navigation.115       </p></dd><dt><span class="term"><em class="replaceable"><code>name</code></em></span></dt><dd><p>116        The name of the index to be created.  No schema name can be included117        here; the index is always created in the same schema as its parent118        table.  The name of the index must be distinct from the name of any119        other relation (table, sequence, index, view, materialized view, or120        foreign table) in that schema.121        If the name is omitted, <span class="productname">PostgreSQL</span> chooses a122        suitable name based on the parent table's name and the indexed column123        name(s).124       </p></dd><dt><span class="term"><code class="literal">ONLY</code></span></dt><dd><p>125        Indicates not to recurse creating indexes on partitions, if the126        table is partitioned.  The default is to recurse.127       </p></dd><dt><span class="term"><em class="replaceable"><code>table_name</code></em></span></dt><dd><p>128        The name (possibly schema-qualified) of the table to be indexed.129       </p></dd><dt><span class="term"><em class="replaceable"><code>method</code></em></span></dt><dd><p>130        The name of the index method to be used.  Choices are131        <code class="literal">btree</code>, <code class="literal">hash</code>,132        <code class="literal">gist</code>, <code class="literal">spgist</code>, <code class="literal">gin</code>,133        <code class="literal">brin</code>, or user-installed access methods like134        <a class="link" href="bloom.html" title="F.7. bloom — bloom filter index access method">bloom</a>.135        The default method is <code class="literal">btree</code>.136       </p></dd><dt><span class="term"><em class="replaceable"><code>column_name</code></em></span></dt><dd><p>137        The name of a column of the table.138       </p></dd><dt><span class="term"><em class="replaceable"><code>expression</code></em></span></dt><dd><p>139        An expression based on one or more columns of the table.  The140        expression usually must be written with surrounding parentheses,141        as shown in the syntax.  However, the parentheses can be omitted142        if the expression has the form of a function call.143       </p></dd><dt><span class="term"><em class="replaceable"><code>collation</code></em></span></dt><dd><p>144        The name of the collation to use for the index.  By default,145        the index uses the collation declared for the column to be146        indexed or the result collation of the expression to be147        indexed.  Indexes with non-default collations can be useful for148        queries that involve expressions using non-default collations.149       </p></dd><dt><span class="term"><em class="replaceable"><code>opclass</code></em></span></dt><dd><p>150        The name of an operator class. See below for details.151       </p></dd><dt><span class="term"><em class="replaceable"><code>opclass_parameter</code></em></span></dt><dd><p>152        The name of an operator class parameter. See below for details.153       </p></dd><dt><span class="term"><code class="literal">ASC</code></span></dt><dd><p>154        Specifies ascending sort order (which is the default).155       </p></dd><dt><span class="term"><code class="literal">DESC</code></span></dt><dd><p>156        Specifies descending sort order.157       </p></dd><dt><span class="term"><code class="literal">NULLS FIRST</code></span></dt><dd><p>158        Specifies that nulls sort before non-nulls.  This is the default159        when <code class="literal">DESC</code> is specified.160       </p></dd><dt><span class="term"><code class="literal">NULLS LAST</code></span></dt><dd><p>161        Specifies that nulls sort after non-nulls.  This is the default162        when <code class="literal">DESC</code> is not specified.163       </p></dd><dt><span class="term"><code class="literal">NULLS DISTINCT</code><br /></span><span class="term"><code class="literal">NULLS NOT DISTINCT</code></span></dt><dd><p>164        Specifies whether for a unique index, null values should be considered165        distinct (not equal).  The default is that they are distinct, so that166        a unique index could contain multiple null values in a column.167       </p></dd><dt><span class="term"><em class="replaceable"><code>storage_parameter</code></em></span></dt><dd><p>168        The name of an index-method-specific storage parameter.  See169        <a class="xref" href="sql-createindex.html#SQL-CREATEINDEX-STORAGE-PARAMETERS" title="Index Storage Parameters">Index Storage Parameters</a> below170        for details.171       </p></dd><dt><span class="term"><em class="replaceable"><code>tablespace_name</code></em></span></dt><dd><p>172        The tablespace in which to create the index.  If not specified,173        <a class="xref" href="runtime-config-client.html#GUC-DEFAULT-TABLESPACE">default_tablespace</a> is consulted, or174        <a class="xref" href="runtime-config-client.html#GUC-TEMP-TABLESPACES">temp_tablespaces</a> for indexes on temporary175        tables.176       </p></dd><dt><span class="term"><em class="replaceable"><code>predicate</code></em></span></dt><dd><p>177        The constraint expression for a partial index.178       </p></dd></dl></div><div class="refsect2" id="SQL-CREATEINDEX-STORAGE-PARAMETERS"><h3>Index Storage Parameters</h3><p>179    The optional <code class="literal">WITH</code> clause specifies <em class="firstterm">storage180    parameters</em> for the index.  Each index method has its own set of allowed181    storage parameters.  The B-tree, hash, GiST and SP-GiST index methods all182    accept this parameter:183   </p><div class="variablelist"><dl class="variablelist"><dt id="INDEX-RELOPTION-FILLFACTOR"><span class="term"><code class="literal">fillfactor</code> (<code class="type">integer</code>)184     <a id="id-1.9.3.69.6.3.3.1.1.3" class="indexterm"></a>185    </span> <a href="#INDEX-RELOPTION-FILLFACTOR" class="id_link">#</a></dt><dd><p>186      The fillfactor for an index is a percentage that determines how full187      the index method will try to pack index pages.  For B-trees, leaf pages188      are filled to this percentage during initial index builds, and also189      when extending the index at the right (adding new largest key values).190      If pages191      subsequently become completely full, they will be split, leading to192      fragmentation of the on-disk index structure.  B-trees use a default193      fillfactor of 90, but any integer value from 10 to 100 can be selected.194     </p><p>195      B-tree indexes on tables where many inserts and/or updates are196      anticipated can benefit from lower fillfactor settings at197      <code class="command">CREATE INDEX</code> time (following bulk loading into the198      table).  Values in the range of 50 - 90 can usefully <span class="quote">“<span class="quote">smooth199       out</span>”</span> the <span class="emphasis"><em>rate</em></span> of page splits during the200      early life of the B-tree index (lowering fillfactor like this may even201      lower the absolute number of page splits, though this effect is highly202      workload dependent).  The B-tree bottom-up index deletion technique203      described in <a class="xref" href="btree-implementation.html#BTREE-DELETION" title="67.4.2. Bottom-up Index Deletion">Section 67.4.2</a> is dependent on having204      some <span class="quote">“<span class="quote">extra</span>”</span> space on pages to store <span class="quote">“<span class="quote">extra</span>”</span>205      tuple versions, and so can be affected by fillfactor (though the effect206      is usually not significant).207     </p><p>208      In other specific cases it might be useful to increase fillfactor to209      100 at <code class="command">CREATE INDEX</code> time as a way of maximizing210      space utilization.  You should only consider this when you are211      completely sure that the table is static (i.e. that it will never be212      affected by either inserts or updates).  A fillfactor setting of 100213      otherwise risks <span class="emphasis"><em>harming</em></span> performance: even a few214      updates or inserts will cause a sudden flood of page splits.215     </p><p>216      The other index methods use fillfactor in different but roughly217      analogous ways; the default fillfactor varies between methods.218     </p></dd></dl></div><p>219    B-tree indexes additionally accept this parameter:220   </p><div class="variablelist"><dl class="variablelist"><dt id="INDEX-RELOPTION-DEDUPLICATE-ITEMS"><span class="term"><code class="literal">deduplicate_items</code> (<code class="type">boolean</code>)221     <a id="id-1.9.3.69.6.3.5.1.1.3" class="indexterm"></a>222    </span> <a href="#INDEX-RELOPTION-DEDUPLICATE-ITEMS" class="id_link">#</a></dt><dd><p>223      Controls usage of the B-tree deduplication technique described224      in <a class="xref" href="btree-implementation.html#BTREE-DEDUPLICATION" title="67.4.3. Deduplication">Section 67.4.3</a>.  Set to225      <code class="literal">ON</code> or <code class="literal">OFF</code> to enable or226      disable the optimization.  (Alternative spellings of227      <code class="literal">ON</code> and <code class="literal">OFF</code> are allowed as228      described in <a class="xref" href="config-setting.html" title="20.1. Setting Parameters">Section 20.1</a>.) The default is229      <code class="literal">ON</code>.230    </p><div class="note"><h3 class="title">Note</h3><p>231      Turning <code class="literal">deduplicate_items</code> off via232      <code class="command">ALTER INDEX</code> prevents future insertions from233      triggering deduplication, but does not in itself make existing234      posting list tuples use the standard tuple representation.235     </p></div></dd></dl></div><p>236    GiST indexes additionally accept this parameter:237   </p><div class="variablelist"><dl class="variablelist"><dt id="INDEX-RELOPTION-BUFFERING"><span class="term"><code class="literal">buffering</code> (<code class="type">enum</code>)238     <a id="id-1.9.3.69.6.3.7.1.1.3" class="indexterm"></a>239    </span> <a href="#INDEX-RELOPTION-BUFFERING" class="id_link">#</a></dt><dd><p>240     Determines whether the buffered build technique described in241     <a class="xref" href="gist-implementation.html#GIST-BUFFERING-BUILD" title="68.4.1. GiST Index Build Methods">Section 68.4.1</a> is used to build the index. With242     <code class="literal">OFF</code> buffering is disabled, with <code class="literal">ON</code>243     it is enabled, and with <code class="literal">AUTO</code> it is initially disabled,244     but is turned on on-the-fly once the index size reaches245     <a class="xref" href="runtime-config-query.html#GUC-EFFECTIVE-CACHE-SIZE">effective_cache_size</a>.  The default246     is <code class="literal">AUTO</code>.247     Note that if sorted build is possible, it will be used instead of248     buffered build unless <code class="literal">buffering=ON</code> is specified.249    </p></dd></dl></div><p>250    GIN indexes accept different parameters:251   </p><div class="variablelist"><dl class="variablelist"><dt id="INDEX-RELOPTION-FASTUPDATE"><span class="term"><code class="literal">fastupdate</code> (<code class="type">boolean</code>)252     <a id="id-1.9.3.69.6.3.9.1.1.3" class="indexterm"></a>253    </span> <a href="#INDEX-RELOPTION-FASTUPDATE" class="id_link">#</a></dt><dd><p>254     This setting controls usage of the fast update technique described in255     <a class="xref" href="gin-implementation.html#GIN-FAST-UPDATE" title="70.4.1. GIN Fast Update Technique">Section 70.4.1</a>.  It is a Boolean parameter:256     <code class="literal">ON</code> enables fast update, <code class="literal">OFF</code> disables it.257     The default is <code class="literal">ON</code>.258    </p><div class="note"><h3 class="title">Note</h3><p>259      Turning <code class="literal">fastupdate</code> off via <code class="command">ALTER INDEX</code> prevents260      future insertions from going into the list of pending index entries,261      but does not in itself flush previous entries.  You might want to262      <code class="command">VACUUM</code> the table or call <code class="function">gin_clean_pending_list</code>263      function afterward to ensure the pending list is emptied.264     </p></div></dd></dl></div><div class="variablelist"><dl class="variablelist"><dt id="INDEX-RELOPTION-GIN-PENDING-LIST-LIMIT"><span class="term"><code class="literal">gin_pending_list_limit</code> (<code class="type">integer</code>)265     <a id="id-1.9.3.69.6.3.10.1.1.3" class="indexterm"></a>266    </span> <a href="#INDEX-RELOPTION-GIN-PENDING-LIST-LIMIT" class="id_link">#</a></dt><dd><p>267     Custom <a class="xref" href="runtime-config-client.html#GUC-GIN-PENDING-LIST-LIMIT">gin_pending_list_limit</a> parameter.268     This value is specified in kilobytes.269    </p></dd></dl></div><p>270    <acronym class="acronym">BRIN</acronym> indexes accept different parameters:271   </p><div class="variablelist"><dl class="variablelist"><dt id="INDEX-RELOPTION-PAGES-PER-RANGE"><span class="term"><code class="literal">pages_per_range</code> (<code class="type">integer</code>)272     <a id="id-1.9.3.69.6.3.12.1.1.3" class="indexterm"></a>273    </span> <a href="#INDEX-RELOPTION-PAGES-PER-RANGE" class="id_link">#</a></dt><dd><p>274     Defines the number of table blocks that make up one block range for275     each entry of a <acronym class="acronym">BRIN</acronym> index (see <a class="xref" href="brin-intro.html" title="71.1. Introduction">Section 71.1</a>276     for more details).  The default is <code class="literal">128</code>.277    </p></dd><dt id="INDEX-RELOPTION-AUTOSUMMARIZE"><span class="term"><code class="literal">autosummarize</code> (<code class="type">boolean</code>)278     <a id="id-1.9.3.69.6.3.12.2.1.3" class="indexterm"></a>279    </span> <a href="#INDEX-RELOPTION-AUTOSUMMARIZE" class="id_link">#</a></dt><dd><p>280     Defines whether a summarization run is queued for the previous page281     range whenever an insertion is detected on the next one.282     See <a class="xref" href="brin-intro.html#BRIN-OPERATION" title="71.1.1. Index Maintenance">Section 71.1.1</a> for more details.283     The default is <code class="literal">off</code>.284    </p></dd></dl></div></div><div class="refsect2" id="SQL-CREATEINDEX-CONCURRENTLY"><h3>Building Indexes Concurrently</h3><a id="id-1.9.3.69.6.4.2" class="indexterm"></a><p>285    Creating an index can interfere with regular operation of a database.286    Normally <span class="productname">PostgreSQL</span> locks the table to be indexed against287    writes and performs the entire index build with a single scan of the288    table. Other transactions can still read the table, but if they try to289    insert, update, or delete rows in the table they will block until the290    index build is finished. This could have a severe effect if the system is291    a live production database.  Very large tables can take many hours to be292    indexed, and even for smaller tables, an index build can lock out writers293    for periods that are unacceptably long for a production system.294   </p><p>295    <span class="productname">PostgreSQL</span> supports building indexes without locking296    out writes.  This method is invoked by specifying the297    <code class="literal">CONCURRENTLY</code> option of <code class="command">CREATE INDEX</code>.298    When this option is used,299    <span class="productname">PostgreSQL</span> must perform two scans of the table, and in300    addition it must wait for all existing transactions that could potentially301    modify or use the index to terminate.  Thus302    this method requires more total work than a standard index build and takes303    significantly longer to complete.  However, since it allows normal304    operations to continue while the index is built, this method is useful for305    adding new indexes in a production environment.  Of course, the extra CPU306    and I/O load imposed by the index creation might slow other operations.307   </p><p>308    In a concurrent index build, the index is actually entered as an309    <span class="quote">“<span class="quote">invalid</span>”</span> index into310    the system catalogs in one transaction, then two table scans occur in311    two more transactions.  Before each table scan, the index build must312    wait for existing transactions that have modified the table to terminate.313    After the second scan, the index build must wait for any transactions314    that have a snapshot (see <a class="xref" href="mvcc.html" title="Chapter 13. Concurrency Control">Chapter 13</a>) predating the second315    scan to terminate, including transactions used by any phase of concurrent316    index builds on other tables, if the indexes involved are partial or have317    columns that are not simple column references.318    Then finally the index can be marked <span class="quote">“<span class="quote">valid</span>”</span> and ready for use,319    and the <code class="command">CREATE INDEX</code> command terminates.320    Even then, however, the index may not be immediately usable for queries:321    in the worst case, it cannot be used as long as transactions exist that322    predate the start of the index build.323   </p><p>324    If a problem arises while scanning the table, such as a deadlock or a325    uniqueness violation in a unique index, the <code class="command">CREATE INDEX</code>326    command will fail but leave behind an <span class="quote">“<span class="quote">invalid</span>”</span> index. This index327    will be ignored for querying purposes because it might be incomplete;328    however it will still consume update overhead. The <span class="application">psql</span>329    <code class="command">\d</code> command will report such an index as <code class="literal">INVALID</code>:330 331</p><pre class="programlisting">332postgres=# \d tab333       Table "public.tab"334 Column |  Type   | Collation | Nullable | Default335--------+---------+-----------+----------+---------336 col    | integer |           |          |337Indexes:338    "idx" btree (col) INVALID339</pre><p>340 341    The recommended recovery342    method in such cases is to drop the index and try again to perform343    <code class="command">CREATE INDEX CONCURRENTLY</code>.  (Another possibility is344    to rebuild the index with <code class="command">REINDEX INDEX CONCURRENTLY</code>).345   </p><p>346    Another caveat when building a unique index concurrently is that the347    uniqueness constraint is already being enforced against other transactions348    when the second table scan begins.  This means that constraint violations349    could be reported in other queries prior to the index becoming available350    for use, or even in cases where the index build eventually fails.  Also,351    if a failure does occur in the second scan, the <span class="quote">“<span class="quote">invalid</span>”</span> index352    continues to enforce its uniqueness constraint afterwards.353   </p><p>354    Concurrent builds of expression indexes and partial indexes are supported.355    Errors occurring in the evaluation of these expressions could cause356    behavior similar to that described above for unique constraint violations.357   </p><p>358    Regular index builds permit other regular index builds on the359    same table to occur simultaneously, but only one concurrent index build360    can occur on a table at a time.  In either case, schema modification of the361    table is not allowed while the index is being built.  Another difference is362    that a regular <code class="command">CREATE INDEX</code> command can be performed363    within a transaction block, but <code class="command">CREATE INDEX CONCURRENTLY</code>364    cannot.365   </p><p>366    Concurrent builds for indexes on partitioned tables are currently not367    supported.  However, you may concurrently build the index on each368    partition individually and then finally create the partitioned index369    non-concurrently in order to reduce the time where writes to the370    partitioned table will be locked out.  In this case, building the371    partitioned index is a metadata only operation.372   </p></div></div><div class="refsect1" id="id-1.9.3.69.7"><h2>Notes</h2><p>373   See <a class="xref" href="indexes.html" title="Chapter 11. Indexes">Chapter 11</a> for information about when indexes can374   be used, when they are not used, and in which particular situations375   they can be useful.376  </p><p>377   Currently, only the B-tree, GiST, GIN, and BRIN index methods support378   multiple-key-column indexes.  Whether there can be multiple key379   columns is independent of whether <code class="literal">INCLUDE</code> columns380   can be added to the index.  Indexes can have up to 32 columns,381   including <code class="literal">INCLUDE</code> columns.382   (This limit can be altered when building383   <span class="productname">PostgreSQL</span>.)  Only B-tree currently384   supports unique indexes.385  </p><p>386   An <em class="firstterm">operator class</em> with optional parameters387   can be specified for each column of an index.388   The operator class identifies the operators to be389   used by the index for that column. For example, a B-tree index on390   four-byte integers would use the <code class="literal">int4_ops</code> class;391   this operator class includes comparison functions for four-byte392   integers. In practice the default operator class for the column's data393   type is usually sufficient. The main point of having operator classes394   is that for some data types, there could be more than one meaningful395   ordering. For example, we might want to sort a complex-number data396   type either by absolute value or by real part. We could do this by397   defining two operator classes for the data type and then selecting398   the proper class when creating an index.  More information about399   operator classes is in <a class="xref" href="indexes-opclass.html" title="11.10. Operator Classes and Operator Families">Section 11.10</a> and in <a class="xref" href="xindex.html" title="38.16. Interfacing Extensions to Indexes">Section 38.16</a>.400  </p><p>401   When <code class="literal">CREATE INDEX</code> is invoked on a partitioned402   table, the default behavior is to recurse to all partitions to ensure403   they all have matching indexes.404   Each partition is first checked to determine whether an equivalent405   index already exists, and if so, that index will become attached as a406   partition index to the index being created, which will become its407   parent index.408   If no matching index exists, a new index will be created and409   automatically attached; the name of the new index in each partition410   will be determined as if no index name had been specified in the411   command.412   If the <code class="literal">ONLY</code> option is specified, no recursion413   is done, and the index is marked invalid.414   (<code class="command">ALTER INDEX ... ATTACH PARTITION</code> marks the index415   valid, once all partitions acquire matching indexes.)  Note, however,416   that any partition that is created in the future using417   <code class="command">CREATE TABLE ... PARTITION OF</code> will automatically418   have a matching index, regardless of whether <code class="literal">ONLY</code> is419   specified.420  </p><p>421   For index methods that support ordered scans (currently, only B-tree),422   the optional clauses <code class="literal">ASC</code>, <code class="literal">DESC</code>, <code class="literal">NULLS423   FIRST</code>, and/or <code class="literal">NULLS LAST</code> can be specified to modify424   the sort ordering of the index.  Since an ordered index can be425   scanned either forward or backward, it is not normally useful to create a426   single-column <code class="literal">DESC</code> index — that sort ordering is already427   available with a regular index.  The value of these options is that428   multicolumn indexes can be created that match the sort ordering requested429   by a mixed-ordering query, such as <code class="literal">SELECT ... ORDER BY x ASC, y430   DESC</code>.  The <code class="literal">NULLS</code> options are useful if you need to support431   <span class="quote">“<span class="quote">nulls sort low</span>”</span> behavior, rather than the default <span class="quote">“<span class="quote">nulls432   sort high</span>”</span>, in queries that depend on indexes to avoid sorting steps.433  </p><p>434   The system regularly collects statistics on all of a table's435   columns.  Newly-created non-expression indexes can immediately436   use these statistics to determine an index's usefulness.437   For new expression indexes, it is necessary to run <a class="link" href="sql-analyze.html" title="ANALYZE"><code class="command">ANALYZE</code></a> or wait for438   the <a class="link" href="routine-vacuuming.html#AUTOVACUUM" title="25.1.6. The Autovacuum Daemon">autovacuum daemon</a> to analyze439   the table to generate statistics for these indexes.440  </p><p>441   For most index methods, the speed of creating an index is442   dependent on the setting of <a class="xref" href="runtime-config-resource.html#GUC-MAINTENANCE-WORK-MEM">maintenance_work_mem</a>.443   Larger values will reduce the time needed for index creation, so long444   as you don't make it larger than the amount of memory really available,445   which would drive the machine into swapping.446  </p><p>447   <span class="productname">PostgreSQL</span> can build indexes while448   leveraging multiple CPUs in order to process the table rows faster.449   This feature is known as <em class="firstterm">parallel index450   build</em>.  For index methods that support building indexes451   in parallel (currently, only B-tree),452   <code class="varname">maintenance_work_mem</code> specifies the maximum453   amount of memory that can be used by each index build operation as454   a whole, regardless of how many worker processes were started.455   Generally, a cost model automatically determines how many worker456   processes should be requested, if any.457  </p><p>458   Parallel index builds may benefit from increasing459   <code class="varname">maintenance_work_mem</code> where an equivalent serial460   index build will see little or no benefit.  Note that461   <code class="varname">maintenance_work_mem</code> may influence the number of462   worker processes requested, since parallel workers must have at463   least a <code class="literal">32MB</code> share of the total464   <code class="varname">maintenance_work_mem</code> budget.  There must also be465   a remaining <code class="literal">32MB</code> share for the leader process.466   Increasing <a class="xref" href="runtime-config-resource.html#GUC-MAX-PARALLEL-MAINTENANCE-WORKERS">max_parallel_maintenance_workers</a>467   may allow more workers to be used, which will reduce the time468   needed for index creation, so long as the index build is not469   already I/O bound.  Of course, there should also be sufficient470   CPU capacity that would otherwise lie idle.471  </p><p>472   Setting a value for <code class="literal">parallel_workers</code> via <a class="link" href="sql-altertable.html" title="ALTER TABLE"><code class="command">ALTER TABLE</code></a> directly controls how many parallel473   worker processes will be requested by a <code class="command">CREATE474   INDEX</code> against the table.  This bypasses the cost model475   completely, and prevents <code class="varname">maintenance_work_mem</code>476   from affecting how many parallel workers are requested.  Setting477   <code class="literal">parallel_workers</code> to 0 via <code class="command">ALTER478   TABLE</code> will disable parallel index builds on the table in479   all cases.480  </p><div class="tip"><h3 class="title">Tip</h3><p>481    You might want to reset <code class="literal">parallel_workers</code> after482    setting it as part of tuning an index build.  This avoids483    inadvertent changes to query plans, since484    <code class="literal">parallel_workers</code> affects485    <span class="emphasis"><em>all</em></span> parallel table scans.486   </p></div><p>487   While <code class="command">CREATE INDEX</code> with the488   <code class="literal">CONCURRENTLY</code> option supports parallel builds489   without special restrictions, only the first table scan is actually490   performed in parallel.491  </p><p>492   Use <a class="link" href="sql-dropindex.html" title="DROP INDEX"><code class="command">DROP INDEX</code></a>493   to remove an index.494  </p><p>495   Like any long-running transaction, <code class="command">CREATE INDEX</code> on a496   table can affect which tuples can be removed by concurrent497   <code class="command">VACUUM</code> on any other table.498  </p><p>499   Prior releases of <span class="productname">PostgreSQL</span> also had an500   R-tree index method.  This method has been removed because501   it had no significant advantages over the GiST method.502   If <code class="literal">USING rtree</code> is specified, <code class="command">CREATE INDEX</code>503   will interpret it as <code class="literal">USING gist</code>, to simplify conversion504   of old databases to GiST.505  </p><p>506    Each backend running <code class="command">CREATE INDEX</code> will report its507    progress in the <code class="structname">pg_stat_progress_create_index</code>508    view. See <a class="xref" href="progress-reporting.html#CREATE-INDEX-PROGRESS-REPORTING" title="28.4.4. CREATE INDEX Progress Reporting">Section 28.4.4</a> for details.509  </p></div><div class="refsect1" id="id-1.9.3.69.8"><h2>Examples</h2><p>510   To create a unique B-tree index on the column <code class="literal">title</code> in511   the table <code class="literal">films</code>:512</p><pre class="programlisting">513CREATE UNIQUE INDEX title_idx ON films (title);514</pre><p>515  </p><p>516   To create a unique B-tree index on the column <code class="literal">title</code>517   with included columns <code class="literal">director</code>518   and <code class="literal">rating</code> in the table <code class="literal">films</code>:519</p><pre class="programlisting">520CREATE UNIQUE INDEX title_idx ON films (title) INCLUDE (director, rating);521</pre><p>522  </p><p>523   To create a B-Tree index with deduplication disabled:524</p><pre class="programlisting">525CREATE INDEX title_idx ON films (title) WITH (deduplicate_items = off);526</pre><p>527  </p><p>528   To create an index on the expression <code class="literal">lower(title)</code>,529   allowing efficient case-insensitive searches:530</p><pre class="programlisting">531CREATE INDEX ON films ((lower(title)));532</pre><p>533   (In this example we have chosen to omit the index name, so the system534   will choose a name, typically <code class="literal">films_lower_idx</code>.)535  </p><p>536   To create an index with non-default collation:537</p><pre class="programlisting">538CREATE INDEX title_idx_german ON films (title COLLATE "de_DE");539</pre><p>540  </p><p>541   To create an index with non-default sort ordering of nulls:542</p><pre class="programlisting">543CREATE INDEX title_idx_nulls_low ON films (title NULLS FIRST);544</pre><p>545  </p><p>546   To create an index with non-default fill factor:547</p><pre class="programlisting">548CREATE UNIQUE INDEX title_idx ON films (title) WITH (fillfactor = 70);549</pre><p>550  </p><p>551   To create a <acronym class="acronym">GIN</acronym> index with fast updates disabled:552</p><pre class="programlisting">553CREATE INDEX gin_idx ON documents_table USING GIN (locations) WITH (fastupdate = off);554</pre><p>555  </p><p>556   To create an index on the column <code class="literal">code</code> in the table557   <code class="literal">films</code> and have the index reside in the tablespace558   <code class="literal">indexspace</code>:559</p><pre class="programlisting">560CREATE INDEX code_idx ON films (code) TABLESPACE indexspace;561</pre><p>562  </p><p>563   To create a GiST index on a point attribute so that we564   can efficiently use box operators on the result of the565   conversion function:566</p><pre class="programlisting">567CREATE INDEX pointloc568    ON points USING gist (box(location,location));569SELECT * FROM points570    WHERE box(location,location) &amp;&amp; '(0,0),(1,1)'::box;571</pre><p>572  </p><p>573   To create an index without locking out writes to the table:574</p><pre class="programlisting">575CREATE INDEX CONCURRENTLY sales_quantity_index ON sales_table (quantity);576</pre></div><div class="refsect1" id="id-1.9.3.69.9"><h2>Compatibility</h2><p>577   <code class="command">CREATE INDEX</code> is a578   <span class="productname">PostgreSQL</span> language extension.  There579   are no provisions for indexes in the SQL standard.580  </p></div><div class="refsect1" id="id-1.9.3.69.10"><h2>See Also</h2><span class="simplelist"><a class="xref" href="sql-alterindex.html" title="ALTER INDEX"><span class="refentrytitle">ALTER INDEX</span></a>, <a class="xref" href="sql-dropindex.html" title="DROP INDEX"><span class="refentrytitle">DROP INDEX</span></a>, <a class="xref" href="sql-reindex.html" title="REINDEX"><span class="refentrytitle">REINDEX</span></a>, <a class="xref" href="progress-reporting.html#CREATE-INDEX-PROGRESS-REPORTING" title="28.4.4. CREATE INDEX Progress Reporting">Section 28.4.4</a></span></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="sql-creategroup.html" title="CREATE GROUP">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="sql-commands.html" title="SQL Commands">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="sql-createlanguage.html" title="CREATE LANGUAGE">Next</a></td></tr><tr><td width="40%" align="left" valign="top">CREATE GROUP </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 16.3 Documentation">Home</a></td><td width="40%" align="right" valign="top"> CREATE LANGUAGE</td></tr></table></div></body></html>
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