database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-06-14 18:42:34 +03:00
Code Activity

Disallow direct change of NO INHERIT of not-null constraints

Browse Source 
We support changing NO INHERIT constraint to INHERIT for constraints in
child relations when adding a constraint to some ancestor relation, and
also during pg_upgrade's schema restore; but other than those special
cases, command ALTER TABLE ADD CONSTRAINT should not be allowed to
change an existing constraint from NO INHERIT to INHERIT, as that would
require to process child relations so that they also acquire an
appropriate constraint, which we may not be in a position to do.  (It'd
also be surprising behavior.)

It is conceivable that we want to allow ALTER TABLE SET NOT NULL to make
such a change; but in that case some more code is needed to implement it
correctly, so for now I've made that throw the same error message.

Also, during the prep phase of ALTER TABLE ADD CONSTRAINT, acquire locks
on all descendant tables; otherwise we might operate on child tables on
which no locks are held, particularly in the mode where a primary key
causes not-null constraints to be created on children.

Reported-by: Alexander Lakhin <exclusion@gmail.com>
Discussion: https://postgr.es/m/7d923a66-55f0-3395-cd40-81c142b5448b@gmail.com
This commit is contained in:
Alvaro Herrera
2024-05-02 17:26:30 +02:00
parent 42510c031b
commit d45597f72f
7 changed files with 92 additions and 14 deletions
Download Patch File Download Diff File Expand all files Collapse all files

17
src/backend/commands/tablecmds.c
View File

@ -4980,10 +4980,12 @@ ATPrepCmd(List **wqueue, Relation rel, AlterTableCmd *cmd,
break;
case AT_AddConstraint: /* ADD CONSTRAINT */
ATSimplePermissions(cmd->subtype, rel, ATT_TABLE | ATT_FOREIGN_TABLE);
/* Recursion occurs during execution phase */
/* No command-specific prep needed except saving recurse flag */
if (recurse)
{
/* recurses at exec time; lock descendants and set flag */
(void) find_all_inheritors(RelationGetRelid(rel), lockmode, NULL);
cmd->recurse = true;
}
pass = AT_PASS_ADD_CONSTR;
break;
case AT_AddIndexConstraint: /* ADD CONSTRAINT USING INDEX */
@ -7892,6 +7894,17 @@ ATExecSetNotNull(List **wqueue, Relation rel, char *conName, char *colName,
copytup = heap_copytuple(tuple);
conForm = (Form_pg_constraint) GETSTRUCT(copytup);
/*
* Don't let a NO INHERIT constraint be changed into inherit.
*/
if (conForm->connoinherit && recurse)
ereport(ERROR,
errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot change NO INHERIT status of NOT NULL constraint \"%s\" in relation \"%s\"",
NameStr(conForm->conname),
RelationGetRelationName(rel)));
/*
* If we find an appropriate constraint, we're almost done, but just
* need to change some properties on it: if we're recursing, increment