ALTER_TYPE(7)

✨ ALTER TYPE — bestie edition 💅

okay so this is the PostgreSQL 18.6 Documentation page for ALTER TYPE, and it's literally about changing the definition of an existing type. it's giving ✨makeover episode✨ but for your database schema. no cap.

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🌸 NAME 🌸

ALTER_TYPE — change the definition of a type 🦋

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💖 SYNOPSIS 💖

ALTER TYPE name OWNER TO { new_owner | CURRENT_ROLE | CURRENT_USER | SESSION_USER }
ALTER TYPE name RENAME TO new_name
ALTER TYPE name SET SCHEMA new_schema
ALTER TYPE name RENAME ATTRIBUTE attribute_name TO new_attribute_name [ CASCADE | RESTRICT ]
ALTER TYPE name action [, ... ]
ALTER TYPE name ADD VALUE [ IF NOT EXISTS ] new_enum_value [ { BEFORE | AFTER } neighbor_enum_value ]
ALTER TYPE name RENAME VALUE existing_enum_value TO new_enum_value
ALTER TYPE name SET ( property = value [, ... ] )

where action is one of:

    ADD ATTRIBUTE attribute_name data_type [ COLLATE collation ] [ CASCADE | RESTRICT ]
    DROP ATTRIBUTE [ IF EXISTS ] attribute_name [ CASCADE | RESTRICT ]
    ALTER ATTRIBUTE attribute_name [ SET DATA ] TYPE data_type [ COLLATE collation ] [ CASCADE | RESTRICT ]

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👑 DESCRIPTION 👑

ALTER TYPE changes the definition of an existing type. there are several subforms and honestly each one is a little main character:

🎀 OWNER

this form changes the owner of the type. passing the aux, basically.

🎀 RENAME

this form changes the name of the type. glow-up via new government name ✨

🎀 SET SCHEMA

this form moves the type into another schema. it's moving out, it's getting its own apartment 🏠

🎀 RENAME ATTRIBUTE

this form is only usable with composite types. it changes the name of an individual attribute of the type.

🎀 ADD ATTRIBUTE

this form adds a new attribute to a composite type, using the same syntax as CREATE TYPE.

🎀 DROP ATTRIBUTE [ IF EXISTS ]

this form drops an attribute from a composite type. if IF EXISTS is specified and the attribute does not exist, no error is thrown. in this case a notice is issued instead. (so it's like, "bestie i looked, she's not here, but no drama 💅")

🎀 ALTER ATTRIBUTE ... SET DATA TYPE

this form changes the type of an attribute of a composite type.

🎀 ADD VALUE [ IF NOT EXISTS ] [ BEFORE | AFTER ]

this form adds a new value to an enum type. the new value's place in the enum's ordering can be specified as being BEFORE or AFTER one of the existing values. otherwise, the new item is added at the end of the list of values.

if IF NOT EXISTS is specified, it is not an error if the type already contains the new value: a notice is issued but no other action is taken. otherwise, an error will occur if the new value is already present.

🎀 RENAME VALUE

this form renames a value of an enum type. the value's place in the enum's ordering is not affected. an error will occur if the specified value is not present or the new name is already present.

🎀 SET ( property = value [, ... ] )

this form is only applicable to base types. it allows adjustment of a subset of the base-type properties that can be set in CREATE TYPE. specifically, these properties can be changed:

• RECEIVE can be set to the name of a binary input function, or NONE to remove the type's binary input function. using this option requires superuser privilege.
• SEND can be set to the name of a binary output function, or NONE to remove the type's binary output function. using this option requires superuser privilege.
• TYPMOD_IN can be set to the name of a type modifier input function, or NONE to remove the type's type modifier input function. using this option requires superuser privilege.
• TYPMOD_OUT can be set to the name of a type modifier output function, or NONE to remove the type's type modifier output function. using this option requires superuser privilege.
• ANALYZE can be set to the name of a type-specific statistics collection function, or NONE to remove the type's statistics collection function. using this option requires superuser privilege.
• SUBSCRIPT can be set to the name of a type-specific subscripting handler function, or NONE to remove the type's subscripting handler function. using this option requires superuser privilege.
• STORAGE can be set to plain, extended, external, or main (see Section 66.2 for more information about what these mean). however, changing from plain to another setting requires superuser privilege (because it requires that the type's C functions all be TOAST-ready), and changing to plain from another setting is not allowed at all (since the type may already have TOASTed values present in the database). note that changing this option doesn't by itself change any stored data, it just sets the default TOAST strategy to be used for table columns created in the future. see ALTER TABLE (ALTER_TABLE(7)) to change the TOAST strategy for existing table columns.

see CREATE TYPE (CREATE_TYPE(7)) for more details about these type properties. note that where appropriate, a change in these properties for a base type will be propagated automatically to domains based on that type. it's giving generational wealth 💸

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the ADD ATTRIBUTE, DROP ATTRIBUTE, and ALTER ATTRIBUTE actions can be combined into a list of multiple alterations to apply in parallel. for example, it is possible to add several attributes and/or alter the type of several attributes in a single command. efficiency queen 👑

you must own the type to use ALTER TYPE. to change the schema of a type, you must also have CREATE privilege on the new schema. to alter the owner, you must be able to SET ROLE to the new owning role, and that role must have CREATE privilege on the type's schema. (these restrictions enforce that altering the owner doesn't do anything you couldn't do by dropping and recreating the type. however, a superuser can alter ownership of any type anyway.) to add an attribute or alter an attribute type, you must also have USAGE privilege on the attribute's data type.

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🦋 PARAMETERS 🦋

• name — the name (possibly schema-qualified) of an existing type to alter.
• new_name — the new name for the type.
• new_owner — the user name of the new owner of the type.
• new_schema — the new schema for the type.
• attribute_name — the name of the attribute to add, alter, or drop.
• new_attribute_name — the new name of the attribute to be renamed.
• data_type — the data type of the attribute to add, or the new type of the attribute to alter.
• new_enum_value — the new value to be added to an enum type's list of values, or the new name to be given to an existing value. like all enum literals, it needs to be quoted.
• neighbor_enum_value — the existing enum value that the new value should be added immediately before or after in the enum type's sort ordering. like all enum literals, it needs to be quoted.
• existing_enum_value — the existing enum value that should be renamed. like all enum literals, it needs to be quoted.
• property — the name of a base-type property to be modified; see above for possible values.
• CASCADE — automatically propagate the operation to typed tables of the type being altered, and their descendants.
• RESTRICT — refuse the operation if the type being altered is the type of a typed table. this is the default.

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💜 NOTES 💜

if ALTER TYPE ... ADD VALUE (the form that adds a new value to an enum type) is executed inside a transaction block, the new value cannot be used until after the transaction has been committed. like girl, she's not available yet, she's still getting ready 🚪✨

comparisons involving an added enum value will sometimes be slower than comparisons involving only original members of the enum type. this will usually only occur if BEFORE or AFTER is used to set the new value's sort position somewhere other than at the end of the list. however, sometimes it will happen even though the new value is added at the end (this occurs if the OID counter "wrapped around" since the original creation of the enum type). the slowdown is usually insignificant; but if it matters, optimal performance can be regained by dropping and recreating the enum type, or by dumping and restoring the database. sometimes the only fix is a hard reset bestie 😭

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🌈 EXAMPLES 🌈

to rename a data type:

ALTER TYPE electronic_mail RENAME TO email;

to change the owner of the type email to joe:

ALTER TYPE email OWNER TO joe;

to change the schema of the type email to customers:

ALTER TYPE email SET SCHEMA customers;

to add a new attribute to a composite type:

ALTER TYPE compfoo ADD ATTRIBUTE f3 int;

to add a new value to an enum type in a particular sort position:

ALTER TYPE colors ADD VALUE 'orange' AFTER 'red';

to rename an enum value:

ALTER TYPE colors RENAME VALUE 'purple' TO 'mauve';

to create binary I/O functions for an existing base type:

CREATE FUNCTION mytypesend(mytype) RETURNS bytea ...;
CREATE FUNCTION mytyperecv(internal, oid, integer) RETURNS mytype ...;
ALTER TYPE mytype SET (
    SEND = mytypesend,
    RECEIVE = mytyperecv
);

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🍓 COMPATIBILITY 🍓

the variants to add and drop attributes are part of the SQL standard; the other variants are PostgreSQL extensions. iykyk 💅

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🧚 SEE ALSO 🧚

• CREATE TYPE (CREATE_TYPE(7))
• DROP TYPE (DROP_TYPE(7))

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that's the whole page bestie, you ate that 🫶 this was PostgreSQL 18.6, documented 2026, and it's iconic fr fr. go alter something (responsibly, and with the right privileges) 💖✨🎀🦋🌸💅