diff options
Diffstat (limited to 'doc/src/sgml/html/sql-reindex.html')
| -rw-r--r-- | doc/src/sgml/html/sql-reindex.html | 322 |
1 files changed, 322 insertions, 0 deletions
diff --git a/doc/src/sgml/html/sql-reindex.html b/doc/src/sgml/html/sql-reindex.html new file mode 100644 index 0000000..4cdadcd --- /dev/null +++ b/doc/src/sgml/html/sql-reindex.html @@ -0,0 +1,322 @@ +<?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>REINDEX</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-refreshmaterializedview.html" title="REFRESH MATERIALIZED VIEW" /><link rel="next" href="sql-release-savepoint.html" title="RELEASE SAVEPOINT" /></head><body id="docContent" class="container-fluid col-10"><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">REINDEX</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="sql-refreshmaterializedview.html" title="REFRESH MATERIALIZED VIEW">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 14.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="sql-release-savepoint.html" title="RELEASE SAVEPOINT">Next</a></td></tr></table><hr></hr></div><div class="refentry" id="SQL-REINDEX"><div class="titlepage"></div><a id="id-1.9.3.162.1" class="indexterm"></a><div class="refnamediv"><h2><span class="refentrytitle">REINDEX</span></h2><p>REINDEX — rebuild indexes</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><pre class="synopsis"> +REINDEX [ ( <em class="replaceable"><code>option</code></em> [, ...] ) ] { INDEX | TABLE | SCHEMA | DATABASE | SYSTEM } [ CONCURRENTLY ] <em class="replaceable"><code>name</code></em> + +<span class="phrase">where <em class="replaceable"><code>option</code></em> can be one of:</span> + + CONCURRENTLY [ <em class="replaceable"><code>boolean</code></em> ] + TABLESPACE <em class="replaceable"><code>new_tablespace</code></em> + VERBOSE [ <em class="replaceable"><code>boolean</code></em> ] +</pre></div><div class="refsect1" id="id-1.9.3.162.5"><h2>Description</h2><p> + <code class="command">REINDEX</code> rebuilds an index using the data + stored in the index's table, replacing the old copy of the index. There are + several scenarios in which to use <code class="command">REINDEX</code>: + + </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p> + An index has become corrupted, and no longer contains valid + data. Although in theory this should never happen, in + practice indexes can become corrupted due to software bugs or + hardware failures. <code class="command">REINDEX</code> provides a + recovery method. + </p></li><li class="listitem"><p> + An index has become <span class="quote">“<span class="quote">bloated</span>”</span>, that is it contains many + empty or nearly-empty pages. This can occur with B-tree indexes in + <span class="productname">PostgreSQL</span> under certain uncommon access + patterns. <code class="command">REINDEX</code> provides a way to reduce + the space consumption of the index by writing a new version of + the index without the dead pages. See <a class="xref" href="routine-reindex.html" title="25.2. Routine Reindexing">Section 25.2</a> for more information. + </p></li><li class="listitem"><p> + You have altered a storage parameter (such as fillfactor) + for an index, and wish to ensure that the change has taken full effect. + </p></li><li class="listitem"><p> + If an index build fails with the <code class="literal">CONCURRENTLY</code> option, + this index is left as <span class="quote">“<span class="quote">invalid</span>”</span>. Such indexes are useless + but it can be convenient to use <code class="command">REINDEX</code> to rebuild + them. Note that only <code class="command">REINDEX INDEX</code> is able + to perform a concurrent build on an invalid index. + </p></li></ul></div></div><div class="refsect1" id="id-1.9.3.162.6"><h2>Parameters</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">INDEX</code></span></dt><dd><p> + Recreate the specified index. This form of <code class="command">REINDEX</code> + cannot be executed inside a transaction block when used with a + partitioned index. + </p></dd><dt><span class="term"><code class="literal">TABLE</code></span></dt><dd><p> + Recreate all indexes of the specified table. If the table has a + secondary <span class="quote">“<span class="quote">TOAST</span>”</span> table, that is reindexed as well. + This form of <code class="command">REINDEX</code> cannot be executed inside a + transaction block when used with a partitioned table. + </p></dd><dt><span class="term"><code class="literal">SCHEMA</code></span></dt><dd><p> + Recreate all indexes of the specified schema. If a table of this + schema has a secondary <span class="quote">“<span class="quote">TOAST</span>”</span> table, that is reindexed as + well. Indexes on shared system catalogs are also processed. + This form of <code class="command">REINDEX</code> cannot be executed inside a + transaction block. + </p></dd><dt><span class="term"><code class="literal">DATABASE</code></span></dt><dd><p> + Recreate all indexes within the current database. + Indexes on shared system catalogs are also processed. + This form of <code class="command">REINDEX</code> cannot be executed inside a + transaction block. + </p></dd><dt><span class="term"><code class="literal">SYSTEM</code></span></dt><dd><p> + Recreate all indexes on system catalogs within the current database. + Indexes on shared system catalogs are included. + Indexes on user tables are not processed. + This form of <code class="command">REINDEX</code> cannot be executed inside a + transaction block. + </p></dd><dt><span class="term"><em class="replaceable"><code>name</code></em></span></dt><dd><p> + The name of the specific index, table, or database to be + reindexed. Index and table names can be schema-qualified. + Presently, <code class="command">REINDEX DATABASE</code> and <code class="command">REINDEX SYSTEM</code> + can only reindex the current database, so their parameter must match + the current database's name. + </p></dd><dt><span class="term"><code class="literal">CONCURRENTLY</code></span></dt><dd><p> + When this option is used, <span class="productname">PostgreSQL</span> will rebuild the + index without taking any locks that prevent concurrent inserts, + updates, or deletes on the table; whereas a standard index rebuild + locks out writes (but not reads) on the table until it's done. + There are several caveats to be aware of when using this option + — see <a class="xref" href="sql-reindex.html#SQL-REINDEX-CONCURRENTLY" title="Rebuilding Indexes Concurrently">Rebuilding Indexes Concurrently</a> below. + </p><p> + For temporary tables, <code class="command">REINDEX</code> is always + non-concurrent, as no other session can access them, and + non-concurrent reindex is cheaper. + </p></dd><dt><span class="term"><code class="literal">TABLESPACE</code></span></dt><dd><p> + Specifies that indexes will be rebuilt on a new tablespace. + </p></dd><dt><span class="term"><code class="literal">VERBOSE</code></span></dt><dd><p> + Prints a progress report as each index is reindexed. + </p></dd><dt><span class="term"><em class="replaceable"><code>boolean</code></em></span></dt><dd><p> + Specifies whether the selected option should be turned on or off. + You can write <code class="literal">TRUE</code>, <code class="literal">ON</code>, or + <code class="literal">1</code> to enable the option, and <code class="literal">FALSE</code>, + <code class="literal">OFF</code>, or <code class="literal">0</code> to disable it. The + <em class="replaceable"><code>boolean</code></em> value can also + be omitted, in which case <code class="literal">TRUE</code> is assumed. + </p></dd><dt><span class="term"><em class="replaceable"><code>new_tablespace</code></em></span></dt><dd><p> + The tablespace where indexes will be rebuilt. + </p></dd></dl></div></div><div class="refsect1" id="id-1.9.3.162.7"><h2>Notes</h2><p> + If you suspect corruption of an index on a user table, you can + simply rebuild that index, or all indexes on the table, using + <code class="command">REINDEX INDEX</code> or <code class="command">REINDEX TABLE</code>. + </p><p> + Things are more difficult if you need to recover from corruption of + an index on a system table. In this case it's important for the + system to not have used any of the suspect indexes itself. + (Indeed, in this sort of scenario you might find that server + processes are crashing immediately at start-up, due to reliance on + the corrupted indexes.) To recover safely, the server must be started + with the <code class="option">-P</code> option, which prevents it from using + indexes for system catalog lookups. + </p><p> + One way to do this is to shut down the server and start a single-user + <span class="productname">PostgreSQL</span> server + with the <code class="option">-P</code> option included on its command line. + Then, <code class="command">REINDEX DATABASE</code>, <code class="command">REINDEX SYSTEM</code>, + <code class="command">REINDEX TABLE</code>, or <code class="command">REINDEX INDEX</code> can be + issued, depending on how much you want to reconstruct. If in + doubt, use <code class="command">REINDEX SYSTEM</code> to select + reconstruction of all system indexes in the database. Then quit + the single-user server session and restart the regular server. + See the <a class="xref" href="app-postgres.html" title="postgres"><span class="refentrytitle"><span class="application">postgres</span></span></a> reference page for more + information about how to interact with the single-user server + interface. + </p><p> + Alternatively, a regular server session can be started with + <code class="option">-P</code> included in its command line options. + The method for doing this varies across clients, but in all + <span class="application">libpq</span>-based clients, it is possible to set + the <code class="envar">PGOPTIONS</code> environment variable to <code class="literal">-P</code> + before starting the client. Note that while this method does not + require locking out other clients, it might still be wise to prevent + other users from connecting to the damaged database until repairs + have been completed. + </p><p> + <code class="command">REINDEX</code> is similar to a drop and recreate of the index + in that the index contents are rebuilt from scratch. However, the locking + considerations are rather different. <code class="command">REINDEX</code> locks out writes + but not reads of the index's parent table. It also takes an + <code class="literal">ACCESS EXCLUSIVE</code> lock on the specific index being processed, + which will block reads that attempt to use that index. In contrast, + <code class="command">DROP INDEX</code> momentarily takes an + <code class="literal">ACCESS EXCLUSIVE</code> lock on the parent table, blocking both + writes and reads. The subsequent <code class="command">CREATE INDEX</code> locks out + writes but not reads; since the index is not there, no read will attempt to + use it, meaning that there will be no blocking but reads might be forced + into expensive sequential scans. + </p><p> + Reindexing a single index or table requires being the owner of that + index or table. Reindexing a schema or database requires being the + owner of that schema or database. Note specifically that it's thus + possible for non-superusers to rebuild indexes of tables owned by + other users. However, as a special exception, when + <code class="command">REINDEX DATABASE</code>, <code class="command">REINDEX SCHEMA</code> + or <code class="command">REINDEX SYSTEM</code> is issued by a non-superuser, + indexes on shared catalogs will be skipped unless the user owns the + catalog (which typically won't be the case). Of course, superusers + can always reindex anything. + </p><p> + Reindexing partitioned indexes or partitioned tables is supported + with <code class="command">REINDEX INDEX</code> or <code class="command">REINDEX TABLE</code>, + respectively. Each partition of the specified partitioned relation is + reindexed in a separate transaction. Those commands cannot be used inside + a transaction block when working on a partitioned table or index. + </p><p> + When using the <code class="literal">TABLESPACE</code> clause with + <code class="command">REINDEX</code> on a partitioned index or table, only the + tablespace references of the leaf partitions are updated. As partitioned + indexes are not updated, it is recommended to separately use + <code class="command">ALTER TABLE ONLY</code> on them so as any new partitions + attached inherit the new tablespace. On failure, it may not have moved + all the indexes to the new tablespace. Re-running the command will rebuild + all the leaf partitions and move previously-unprocessed indexes to the new + tablespace. + </p><p> + If <code class="literal">SCHEMA</code>, <code class="literal">DATABASE</code> or + <code class="literal">SYSTEM</code> is used with <code class="literal">TABLESPACE</code>, + system relations are skipped and a single <code class="literal">WARNING</code> + will be generated. Indexes on TOAST tables are rebuilt, but not moved + to the new tablespace. + </p><div class="refsect2" id="SQL-REINDEX-CONCURRENTLY"><h3>Rebuilding Indexes Concurrently</h3><a id="id-1.9.3.162.7.11.2" class="indexterm"></a><p> + Rebuilding an index can interfere with regular operation of a database. + Normally <span class="productname">PostgreSQL</span> locks the table whose index is rebuilt + against writes and performs the entire index build with a single scan of the + table. Other transactions can still read the table, but if they try to + insert, update, or delete rows in the table they will block until the + index rebuild is finished. This could have a severe effect if the system is + a live production database. Very large tables can take many hours to be + indexed, and even for smaller tables, an index rebuild can lock out writers + for periods that are unacceptably long for a production system. + </p><p> + <span class="productname">PostgreSQL</span> supports rebuilding indexes with minimum locking + of writes. This method is invoked by specifying the + <code class="literal">CONCURRENTLY</code> option of <code class="command">REINDEX</code>. When this option + is used, <span class="productname">PostgreSQL</span> must perform two scans of the table + for each index that needs to be rebuilt and wait for termination of + all existing transactions that could potentially use the index. + This method requires more total work than a standard index + rebuild and takes significantly longer to complete as it needs to wait + for unfinished transactions that might modify the index. However, since + it allows normal operations to continue while the index is being rebuilt, this + method is useful for rebuilding indexes in a production environment. Of + course, the extra CPU, memory and I/O load imposed by the index rebuild + may slow down other operations. + </p><p> + The following steps occur in a concurrent reindex. Each step is run in a + separate transaction. If there are multiple indexes to be rebuilt, then + each step loops through all the indexes before moving to the next step. + + </p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p> + A new transient index definition is added to the catalog + <code class="literal">pg_index</code>. This definition will be used to replace + the old index. A <code class="literal">SHARE UPDATE EXCLUSIVE</code> lock at + session level is taken on the indexes being reindexed as well as their + associated tables to prevent any schema modification while processing. + </p></li><li class="listitem"><p> + A first pass to build the index is done for each new index. Once the + index is built, its flag <code class="literal">pg_index.indisready</code> is + switched to <span class="quote">“<span class="quote">true</span>”</span> to make it ready for inserts, making it + visible to other sessions once the transaction that performed the build + is finished. This step is done in a separate transaction for each + index. + </p></li><li class="listitem"><p> + Then a second pass is performed to add tuples that were added while the + first pass was running. This step is also done in a separate + transaction for each index. + </p></li><li class="listitem"><p> + All the constraints that refer to the index are changed to refer to the + new index definition, and the names of the indexes are changed. At + this point, <code class="literal">pg_index.indisvalid</code> is switched to + <span class="quote">“<span class="quote">true</span>”</span> for the new index and to <span class="quote">“<span class="quote">false</span>”</span> for + the old, and a cache invalidation is done causing all sessions that + referenced the old index to be invalidated. + </p></li><li class="listitem"><p> + The old indexes have <code class="literal">pg_index.indisready</code> switched to + <span class="quote">“<span class="quote">false</span>”</span> to prevent any new tuple insertions, after waiting + for running queries that might reference the old index to complete. + </p></li><li class="listitem"><p> + The old indexes are dropped. The <code class="literal">SHARE UPDATE + EXCLUSIVE</code> session locks for the indexes and the table are + released. + </p></li></ol></div><p> + </p><p> + If a problem arises while rebuilding the indexes, such as a + uniqueness violation in a unique index, the <code class="command">REINDEX</code> + command will fail but leave behind an <span class="quote">“<span class="quote">invalid</span>”</span> new index in addition to + the pre-existing one. This index will be ignored for querying purposes + because it might be incomplete; however it will still consume update + overhead. The <span class="application">psql</span> <code class="command">\d</code> command will report + such an index as <code class="literal">INVALID</code>: + +</p><pre class="programlisting"> +postgres=# \d tab + Table "public.tab" + Column | Type | Modifiers +--------+---------+----------- + col | integer | +Indexes: + "idx" btree (col) + "idx_ccnew" btree (col) INVALID +</pre><p> + + If the index marked <code class="literal">INVALID</code> is suffixed + <code class="literal">ccnew</code>, then it corresponds to the transient + index created during the concurrent operation, and the recommended + recovery method is to drop it using <code class="literal">DROP INDEX</code>, + then attempt <code class="command">REINDEX CONCURRENTLY</code> again. + If the invalid index is instead suffixed <code class="literal">ccold</code>, + it corresponds to the original index which could not be dropped; + the recommended recovery method is to just drop said index, since the + rebuild proper has been successful. + </p><p> + Regular index builds permit other regular index builds on the same table + to occur simultaneously, but only one concurrent index build can occur on a + table at a time. In both cases, no other types of schema modification on + the table are allowed meanwhile. Another difference is that a regular + <code class="command">REINDEX TABLE</code> or <code class="command">REINDEX INDEX</code> + command can be performed within a transaction block, but <code class="command">REINDEX + CONCURRENTLY</code> cannot. + </p><p> + Like any long-running transaction, <code class="command">REINDEX</code> on a table + can affect which tuples can be removed by concurrent + <code class="command">VACUUM</code> on any other table. + </p><p> + <code class="command">REINDEX SYSTEM</code> does not support + <code class="command">CONCURRENTLY</code> since system catalogs cannot be reindexed + concurrently. + </p><p> + Furthermore, indexes for exclusion constraints cannot be reindexed + concurrently. If such an index is named directly in this command, an + error is raised. If a table or database with exclusion constraint indexes + is reindexed concurrently, those indexes will be skipped. (It is possible + to reindex such indexes without the <code class="command">CONCURRENTLY</code> option.) + </p><p> + Each backend running <code class="command">REINDEX</code> will report its progress + in the <code class="structname">pg_stat_progress_create_index</code> view. See + <a class="xref" href="progress-reporting.html#CREATE-INDEX-PROGRESS-REPORTING" title="28.4.2. CREATE INDEX Progress Reporting">Section 28.4.2</a> for details. + </p></div></div><div class="refsect1" id="id-1.9.3.162.8"><h2>Examples</h2><p> + Rebuild a single index: + +</p><pre class="programlisting"> +REINDEX INDEX my_index; +</pre><p> + </p><p> + Rebuild all the indexes on the table <code class="literal">my_table</code>: + +</p><pre class="programlisting"> +REINDEX TABLE my_table; +</pre><p> + </p><p> + Rebuild all indexes in a particular database, without trusting the + system indexes to be valid already: + +</p><pre class="programlisting"> +$ <strong class="userinput"><code>export PGOPTIONS="-P"</code></strong> +$ <strong class="userinput"><code>psql broken_db</code></strong> +... +broken_db=> REINDEX DATABASE broken_db; +broken_db=> \q +</pre><p> + Rebuild indexes for a table, without blocking read and write operations + on involved relations while reindexing is in progress: + +</p><pre class="programlisting"> +REINDEX TABLE CONCURRENTLY my_broken_table; +</pre></div><div class="refsect1" id="id-1.9.3.162.9"><h2>Compatibility</h2><p> + There is no <code class="command">REINDEX</code> command in the SQL standard. + </p></div><div class="refsect1" id="id-1.9.3.162.10"><h2>See Also</h2><span class="simplelist"><a class="xref" href="sql-createindex.html" title="CREATE INDEX"><span class="refentrytitle">CREATE INDEX</span></a>, <a class="xref" href="sql-dropindex.html" title="DROP INDEX"><span class="refentrytitle">DROP INDEX</span></a>, <a class="xref" href="app-reindexdb.html" title="reindexdb"><span class="refentrytitle"><span class="application">reindexdb</span></span></a>, <a class="xref" href="progress-reporting.html#CREATE-INDEX-PROGRESS-REPORTING" title="28.4.2. CREATE INDEX Progress Reporting">Section 28.4.2</a></span></div></div><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navfooter"><hr></hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="sql-refreshmaterializedview.html" title="REFRESH MATERIALIZED VIEW">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-release-savepoint.html" title="RELEASE SAVEPOINT">Next</a></td></tr><tr><td width="40%" align="left" valign="top">REFRESH MATERIALIZED VIEW </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 14.5 Documentation">Home</a></td><td width="40%" align="right" valign="top"> RELEASE SAVEPOINT</td></tr></table></div></body></html>
\ No newline at end of file |