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 happen, in practice indexes can become corrupted due to software
           bugs or hardware failures.  REINDEX provides a recovery method.

       •   An index has become “bloated”, that is it 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 Section 23.2, “Routine
           Reindexing”, in the documentation 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 CREATE 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 reindexed as well.

       DATABASE
           Recreate all indexes within the current database. Indexes on shared system catalogs
           are also processed. This form of REINDEX cannot be executed inside a transaction
           block.

       SYSTEM
           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
           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 corrupted 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 PGOPTIONS environment variable to -P 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.

       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 an 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 reindexed 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.