From 013c0baaddd9df7e1f940184a8ab8e478214b46c Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Fri, 16 Mar 2018 13:44:34 -0400 Subject: [PATCH] Doc: explicitly point out that enum values can't be dropped. This was not stated in so many words anywhere. Document it to make clear that it's a design limitation and not just an oversight or documentation omission. Discussion: https://postgr.es/m/152089733343.1222.6927268289645380498@wrigleys.postgresql.org --- doc/src/sgml/datatype.sgml | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-) diff --git a/doc/src/sgml/datatype.sgml b/doc/src/sgml/datatype.sgml index 9aa9b28f3e..1736478a42 100644 --- a/doc/src/sgml/datatype.sgml +++ b/doc/src/sgml/datatype.sgml @@ -3059,6 +3059,20 @@ SELECT person.name, holidays.num_weeks FROM person, holidays Implementation Details + + Enum labels are case sensitive, so + 'happy' is not the same as 'HAPPY'. + White space in the labels is significant too. + + + + Although enum types are primarily intended for static sets of values, + there is support for adding new values to an existing enum type, and for + renaming values (see ). Existing values + cannot be removed from an enum type, nor can the sort ordering of such + values be changed, short of dropping and re-creating the enum type. + + An enum value occupies four bytes on disk. The length of an enum value's textual label is limited by the NAMEDATALEN @@ -3066,12 +3080,6 @@ SELECT person.name, holidays.num_weeks FROM person, holidays builds this means at most 63 bytes. - - Enum labels are case sensitive, so - 'happy' is not the same as 'HAPPY'. - White space in the labels is significant too. - - The translations from internal enum values to textual labels are kept in the system catalog