ALTER_INDEX(7pg13)

💅 ALTER INDEX 💅

Okay so bestie, welcome to ALTER INDEX — the PostgreSQL 13.23 glow-up manual for your indexes 👑. This is the page where we learn how to change the definition of an existing index, and honestly? It's giving main character energy for your database. Let's get into it ✨.

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🌸 SYNOPSIS 🌸

ALTER INDEX [ IF EXISTS ] name RENAME TO new_name
ALTER INDEX [ IF EXISTS ] name SET TABLESPACE tablespace_name
ALTER INDEX name ATTACH PARTITION index_name
ALTER INDEX name [ NO ] DEPENDS ON EXTENSION extension_name
ALTER INDEX [ IF EXISTS ] name SET ( storage_parameter [= value] [, ... ] )
ALTER INDEX [ IF EXISTS ] name RESET ( storage_parameter [, ... ] )
ALTER INDEX [ IF EXISTS ] name ALTER [ COLUMN ] column_number
    SET STATISTICS integer
ALTER INDEX ALL IN TABLESPACE name [ OWNED BY role_name [, ... ] ]
    SET TABLESPACE new_tablespace [ NOWAIT ]

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🦋 DESCRIPTION 🦋

So ALTER INDEX changes the definition of an existing index — that's the whole vibe. There are several subforms described below, and ngl, the lock level required can differ for each one. An ACCESS EXCLUSIVE lock is held unless explicitly noted. And when you list multiple subcommands? The lock held will be the strictest one required from any subcommand. So plan accordingly, bestie 💀.

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🌈 RENAME

The RENAME form changes the name of the index. If the index is associated with a table constraint (either UNIQUE, PRIMARY KEY, or EXCLUDE), the constraint is renamed as well. There is no effect on the stored data — it's just a rebrand, no cap ✨.

Renaming an index acquires a SHARE UPDATE EXCLUSIVE lock.

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🌈 SET TABLESPACE

This form changes the index's tablespace to the specified tablespace and moves the data file(s) associated with the index to the new tablespace. To change the tablespace of an index, you must own the index and have CREATE privilege on the new tablespace. All indexes in the current database in a tablespace can be moved by using the ALL IN TABLESPACE form, which will lock all indexes to be moved and then move each one. This form also supports OWNED BY, which will only move indexes owned by the roles specified. If the NOWAIT option is specified then the command will fail if it is unable to acquire all of the locks required immediately. Note that system catalogs will not be moved by this command, use ALTER DATABASE or explicit ALTER INDEX invocations instead if desired. See also CREATE TABLESPACE (CREATE_TABLESPACE(7)). Moving your faves to a better neighborhood — iconic 🏡💖.

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🌈 ATTACH PARTITION index_name

Causes the named index (possibly schema-qualified) to become attached to the altered index. The named index must be on a partition of the table containing the index being altered, and have an equivalent definition. An attached index cannot be dropped by itself, and will automatically be dropped if its parent index is dropped. It's giving chosen family 🫶 — you're linked now, for better or worse.

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🌈 DEPENDS ON EXTENSION extension_name / NO DEPENDS ON EXTENSION extension_name

This form marks the index as dependent on the extension, or no longer dependent on that extension if NO is specified. An index that's marked as dependent on an extension is automatically dropped when the extension is dropped. So if the extension goes down, this index goes down with it — ride or die energy, fr fr 😭.

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🌈 SET ( storage_parameter [= value] [, ... ] )

This form changes one or more index-method-specific storage parameters for the index. See CREATE INDEX (CREATE_INDEX(7)) for details on the available parameters. Note that the index contents will not be modified immediately by this command; depending on the parameter you might need to rebuild the index with REINDEX(7) to get the desired effects. So don't expect instant results — sometimes you gotta put in the work 💅.

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🌈 RESET ( storage_parameter [, ... ] )

This form resets one or more index-method-specific storage parameters to their defaults. As with SET, a REINDEX might be needed to update the index entirely. Reset era, we're going back to factory settings 🎀.

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🌈 ALTER [ COLUMN ] column_number SET STATISTICS integer

This form sets the per-column statistics-gathering target for subsequent ANALYZE(7) operations, though can be used only on index columns that are defined as an expression. Since expressions lack a unique name, we refer to them using the ordinal number of the index column. The target can be set in the range 0 to 10000; alternatively, set it to -1 to revert to using the system default statistics target (default_statistics_target). For more information on the use of statistics by the PostgreSQL query planner, refer to Section 14.2. Setting your stats target is like curating your feed — you're telling the planner what to pay attention to 🔥.

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🎀 PARAMETERS 🎀

• IF EXISTS — Do not throw an error if the index does not exist. A notice is issued in this case. So if your index ghosted you, you get a polite little heads-up instead of a full meltdown 🙈.
• column_number — The ordinal number refers to the ordinal (left-to-right) position of the index column. Count 'em from the left, bestie 👈.
• name — The name (possibly schema-qualified) of an existing index to alter. This is the whole point, the star of the show ⭐.
• new_name — The new name for the index. Fresh name, fresh start 💖.
• tablespace_name — The tablespace to which the index will be moved. New home, new vibe 🏠.
• extension_name — The name of the extension that the index is to depend on. Bffr this is the main link 🔗.
• storage_parameter — The name of an index-method-specific storage parameter. The knob you're turning 🎛️.
• value — The new value for an index-method-specific storage parameter. This might be a number or a word depending on the parameter. Could be a 42, could be a 'something' — iykyk 😉.

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💜 NOTES 💜

These operations are also possible using ALTER TABLE (ALTER_TABLE(7)). ALTER INDEX is in fact just an alias for the forms of ALTER TABLE that apply to indexes. So lowkey they're the same person wearing different outfits 💅.

There was formerly an ALTER INDEX OWNER variant, but this is now ignored (with a warning). An index cannot have an owner different from its table's owner. Changing the table's owner automatically changes the index as well. So no separate owner era — the table's owner is the index's owner, periodt 👑.

Changing any part of a system catalog index is not permitted. Hard no, bestie — don't touch the system catalogs 🚫.

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🔥 EXAMPLES 🔥

To rename an existing index:

ALTER INDEX distributors RENAME TO suppliers;

To move an index to a different tablespace:

ALTER INDEX distributors SET TABLESPACE fasttablespace;

To change an index's fill factor (assuming that the index method supports it):

ALTER INDEX distributors SET (fillfactor = 75);
REINDEX INDEX distributors;

Set the statistics-gathering target for an expression index:

CREATE INDEX coord_idx ON measured (x, y, (z + t));
ALTER INDEX coord_idx ALTER COLUMN 3 SET STATISTICS 1000;

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🌈 COMPATIBILITY 🌈

ALTER INDEX is a PostgreSQL extension. So it's not standard SQL — it's our own special sauce 🥫✨.

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🦋 SEE ALSO 🦋

CREATE INDEX (CREATE_INDEX(7)), REINDEX(7)

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Okay that's the whole manual, bestie. Go forth and alter those indexes with confidence. You're literally so good at this 💖.

Written for PostgreSQL 13.23 documentation, dated 2025. Was giving main character energy the whole time, no cap 💅✨.