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REINDEX(7)                       SQL Commands                       REINDEX(7)



NAME
       REINDEX - rebuild indexes


SYNOPSIS
       REINDEX { INDEX | TABLE | DATABASE | SYSTEM } name [ FORCE ]


DESCRIPTION
       REINDEX  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 REINDEX:

       ? An index has become corrupted, and no longer contains valid data. Although in theory this should  never  hap-
         pen,  in  practice indexes can become corrupted due to software bugs or hardware failures. REINDEX provides a
         recovery method.

       ? An index has become ''bloated'', that it is contains many empty or nearly-empty pages. This can occur with B-
         tree indexes in PostgreSQL under certain uncommon access patterns. REINDEX provides a way to reduce the space
         consumption of the index by writing a new version of the index without the dead pages. See in the  documenta-
         tion for more information.

       ? You  have  altered  a storage parameter (such as fillfactor) for an index, and wish to ensure that the change
         has taken full effect.

       ? An index build with the CONCURRENTLY option failed, leaving an ''invalid'' index. Such  indexes  are  useless
         but  it  can  be  convenient  to use REINDEX to rebuild them. Note that REINDEX will not perform a concurrent
         build. To build the index without interfering with production you should drop the index and reissue the  CRE-
         ATE INDEX CONCURRENTLY command.


PARAMETERS
       INDEX  Recreate the specified index.

       TABLE  Recreate all indexes of the specified table. If the table has a secondary ''TOAST'' table, that is rein-
              dexed as well.

       DATABASE
              Recreate all indexes within the current database.  Indexes on shared system catalogs are skipped  except
              in stand-alone mode (see below). This form of REINDEX cannot be executed inside a transaction block.

       SYSTEM Recreate  all  indexes  on  system catalogs within the current database.  Indexes on user tables are not
              processed. Also, indexes on shared system catalogs are skipped except in stand-alone mode  (see  below).
              This form of REINDEX cannot be executed inside a transaction block.

       name   The name of the specific index, table, or database to be reindexed. Index and table names can be schema-
              qualified.  Presently, REINDEX DATABASE and REINDEX SYSTEM can only reindex  the  current  database,  so
              their parameter must match the current database's name.

       FORCE  This is an obsolete option; it is ignored if specified.

NOTES
       If you suspect corruption of an index on a user table, you can simply rebuild that index, or all indexes on the
       table, using REINDEX INDEX or REINDEX TABLE.

       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 cor-
       rupted indexes.) To recover safely, the server must be started with the -P option, which prevents it from using
       indexes for system catalog lookups.

       One way to do this is to shut down the server and start a single-user PostgreSQL  server  with  the  -P  option
       included  on  its command line.  Then, REINDEX DATABASE, REINDEX SYSTEM, REINDEX TABLE, or REINDEX INDEX can be
       issued, depending on how much you want to reconstruct. If in doubt, use REINDEX SYSTEM to select reconstruction
       of all system indexes in the database. Then quit the single-user server session and restart the regular server.
       See the postgres(1) reference page for more information about how  to  interact  with  the  single-user  server
       interface.

       Alternatively,  a  regular  server  session  can  be started with -P included in its command line options.  The
       method for doing this varies across clients, but in all libpq-based clients, it is possible to  set  the  PGOP-
       TIONS environment variable to -P before starting the client. Note that while this method does not require lock-
       ing out other clients, it might still be wise to prevent other users from connecting to  the  damaged  database
       until repairs have been completed.

       If  corruption  is  suspected  in  the  indexes  of  any  of  the  shared system catalogs (which are pg_authid,
       pg_auth_members, pg_database, pg_pltemplate, pg_shdepend, pg_shdescription, and pg_tablespace),  then  a  stan-
       dalone server must be used to repair it. REINDEX will not process shared catalogs in multiuser mode.

       For  all  indexes except the shared system catalogs, REINDEX is crash-safe and transaction-safe. REINDEX is not
       crash-safe for shared indexes, which is why this case is disallowed  during  normal  operation.  If  a  failure
       occurs  while reindexing one of these catalogs in standalone mode, it will not be possible to restart the regu-
       lar server until the problem is rectified. (The typical symptom of a partially rebuilt shared index is  ''index
       is not a btree'' errors.)

       REINDEX  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. REINDEX locks out writes but not reads of the index's
       parent  table.  It  also  takes an exclusive lock on the specific index being processed, which will block reads
       that attempt to use that index. In contrast, DROP INDEX momentarily takes exclusive lock on the  parent  table,
       blocking  both writes and reads. The subsequent CREATE INDEX 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.

       Reindexing  a  single  index  or  table  requires being the owner of that index or table. Reindexing a database
       requires being the owner of the database (note that the owner can therefore rebuild indexes of tables owned  by
       other users). Of course, superusers can always reindex anything.

       Prior  to  PostgreSQL  8.1, REINDEX DATABASE processed only system indexes, not all indexes as one would expect
       from the name. This has been changed to reduce the surprise factor. The old behavior is  available  as  REINDEX
       SYSTEM.

       Prior to PostgreSQL 7.4, REINDEX TABLE did not automatically process TOAST tables, and so those had to be rein-
       dexed by separate commands. This is still possible, but redundant.

EXAMPLES
       Rebuild a single index:

       REINDEX INDEX my_index;


       Rebuild all the indexes on the table my_table:

       REINDEX TABLE my_table;


       Rebuild all indexes in a particular database, without trusting the system indexes to be valid already:

       $ export PGOPTIONS="-P"
       $ psql broken_db
       broken_db=> REINDEX DATABASE broken_db;
       broken_db=> \q


COMPATIBILITY
       There is no REINDEX command in the SQL standard.



SQL - Language Statements         2014-02-17                        REINDEX(7)