1REINDEX(7)                       SQL Commands                       REINDEX(7)
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NAME

6       REINDEX - rebuild indexes
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SYNOPSIS

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

14       REINDEX  rebuilds  an index using the data stored in the index's table,
15       replacing the old copy of the index. There  are  several  scenarios  in
16       which to use REINDEX:
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18       · An  index  has  become  corrupted, and no longer contains valid data.
19         Although in theory this should never happen, in practice indexes  can
20         become  corrupted  due to software bugs or hardware failures. REINDEX
21         provides a recovery method.
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23       · An index has become ``bloated'', that it is contains  many  empty  or
24         nearly-empty  pages. This can occur with B-tree indexes in PostgreSQL
25         under certain uncommon access patterns. REINDEX  provides  a  way  to
26         reduce the space consumption of the index by writing a new version of
27         the index without the dead pages. See in the documentation  for  more
28         information.
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30       · You  have  altered  a  storage  parameter (such as fillfactor) for an
31         index, and wish to ensure that the change has taken full effect.
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33       · An index build  with  the  CONCURRENTLY  option  failed,  leaving  an
34         ``invalid''  index. Such indexes are useless but it can be convenient
35         to use REINDEX to rebuild them. Note that REINDEX will not perform  a
36         concurrent build. To build the index without interfering with produc‐
37         tion you should drop the index and reissue the CREATE  INDEX  CONCUR‐
38         RENTLY command.
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PARAMETERS

41       INDEX  Recreate the specified index.
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43       TABLE  Recreate  all indexes of the specified table. If the table has a
44              secondary ``TOAST'' table, that is reindexed as well.
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46       DATABASE
47              Recreate all indexes within the current  database.   Indexes  on
48              shared  system  catalogs  are skipped except in stand-alone mode
49              (see below). This form of REINDEX cannot be  executed  inside  a
50              transaction block.
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52       SYSTEM Recreate all indexes on system catalogs within the current data‐
53              base.  Indexes on user tables are not processed.  Also,  indexes
54              on shared system catalogs are skipped except in stand-alone mode
55              (see below).  This form of REINDEX cannot be executed  inside  a
56              transaction block.
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58       name   The  name  of the specific index, table, or database to be rein‐
59              dexed.  Index  and  table   names   can   be   schema-qualified.
60              Presently,  REINDEX DATABASE and REINDEX SYSTEM can only reindex
61              the current database, so their parameter must match the  current
62              database's name.
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64       FORCE  This is an obsolete option; it is ignored if specified.
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NOTES

67       If  you  suspect corruption of an index on a user table, you can simply
68       rebuild that index, or all indexes on the table, using REINDEX INDEX or
69       REINDEX TABLE.
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71       Things  are more difficult if you need to recover from corruption of an
72       index on a system table. In this case it's important for the system  to
73       not have used any of the suspect indexes itself.  (Indeed, in this sort
74       of scenario you might find that server processes are  crashing  immedi‐
75       ately  at  start-up,  due  to  reliance  on  the corrupted indexes.) To
76       recover safely, the server must be started with the  -P  option,  which
77       prevents it from using indexes for system catalog lookups.
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79       One  way  to do this is to shut down the server and start a single-user
80       PostgreSQL server with the -P option  included  on  its  command  line.
81       Then, REINDEX DATABASE, REINDEX SYSTEM, REINDEX TABLE, or REINDEX INDEX
82       can be issued, depending on how much you want  to  reconstruct.  If  in
83       doubt,  use  REINDEX  SYSTEM  to  select  reconstruction  of all system
84       indexes in the database. Then quit the single-user server  session  and
85       restart  the  regular  server.   See the postgres(1) reference page for
86       more information about how to  interact  with  the  single-user  server
87       interface.
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89       Alternatively, a regular server session can be started with -P included
90       in its command line options.  The method for doing this  varies  across
91       clients,  but  in  all  libpq-based  clients, it is possible to set the
92       PGOPTIONS environment variable to -P before starting the  client.  Note
93       that  while  this method does not require locking out other clients, it
94       might still be wise to prevent other users from connecting to the  dam‐
95       aged database until repairs have been completed.
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97       If  corruption  is suspected in the indexes of any of the shared system
98       catalogs (which are pg_authid, pg_auth_members, pg_database,  pg_pltem‐
99       plate, pg_shdepend, pg_shdescription, and pg_tablespace), then a stand‐
100       alone server must be used to repair it. REINDEX will not process shared
101       catalogs in multiuser mode.
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103       For  all  indexes  except the shared system catalogs, REINDEX is crash-
104       safe  and  transaction-safe.  REINDEX  is  not  crash-safe  for  shared
105       indexes,  which is why this case is disallowed during normal operation.
106       If a failure occurs while reindexing one of these  catalogs  in  stand‐
107       alone mode, it will not be possible to restart the regular server until
108       the problem is rectified. (The typical symptom of a  partially  rebuilt
109       shared index is ``index is not a btree'' errors.)
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111       REINDEX  is  similar  to  a  drop and recreate of the index in that the
112       index contents are rebuilt from scratch. However, the locking consider‐
113       ations  are rather different. REINDEX locks out writes but not reads of
114       the index's parent table. It also takes an exclusive lock on  the  spe‐
115       cific index being processed, which will block reads that attempt to use
116       that index. In contrast, DROP INDEX momentarily takes exclusive lock on
117       the parent table, blocking both writes and reads. The subsequent CREATE
118       INDEX locks out writes but not reads; since the index is not there,  no
119       read will attempt to use it, meaning that there will be no blocking but
120       reads might be forced into expensive sequential scans.
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122       Reindexing a single index or table requires being  the  owner  of  that
123       index  or  table. Reindexing a database requires being the owner of the
124       database (note that the owner can therefore rebuild indexes  of  tables
125       owned  by  other  users). Of course, superusers can always reindex any‐
126       thing.
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128       Prior  to  PostgreSQL  8.1,  REINDEX  DATABASE  processed  only  system
129       indexes,  not  all  indexes as one would expect from the name. This has
130       been changed to reduce the surprise factor. The old behavior is  avail‐
131       able as REINDEX SYSTEM.
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133       Prior  to  PostgreSQL  7.4, REINDEX TABLE did not automatically process
134       TOAST tables, and so those had to be reindexed  by  separate  commands.
135       This is still possible, but redundant.
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EXAMPLES

138       Rebuild a single index:
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140       REINDEX INDEX my_index;
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143       Rebuild all the indexes on the table my_table:
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145       REINDEX TABLE my_table;
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148       Rebuild all indexes in a particular database, without trusting the sys‐
149       tem indexes to be valid already:
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151       $ export PGOPTIONS="-P"
152       $ psql broken_db
153       broken_db=> REINDEX DATABASE broken_db;
154       broken_db=> \q
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COMPATIBILITY

158       There is no REINDEX command in the SQL standard.
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162SQL - Language Statements         2011-09-22                        REINDEX(7)
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