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Fix ALTER TABLE / INHERIT with generated columns

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When running ALTER TABLE t2 INHERIT t1, we must check that columns in
t2 that correspond to a generated column in t1 are also generated and
have the same generation expression.  Otherwise, this would allow
creating setups that a normal CREATE TABLE sequence would not allow.

Discussion: https://www.postgresql.org/message-id/22de27f6-7096-8d96-4619-7b882932ca25@2ndquadrant.com
This commit is contained in:
Peter Eisentraut
2021-05-04 11:45:37 +02:00
parent ae9492a61b
commit a970edbed3
3 changed files with 95 additions and 0 deletions
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60
src/backend/commands/tablecmds.c
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@ -14381,6 +14381,66 @@ MergeAttributesIntoExisting(Relation child_rel, Relation parent_rel)
errmsg("column \"%s\" in child table must be marked NOT NULL",
attributeName)));
/*
* If parent column is generated, child column must be, too.
*/
if (attribute->attgenerated && !childatt->attgenerated)
ereport(ERROR,
(errcode(ERRCODE_DATATYPE_MISMATCH),
errmsg("column \"%s\" in child table must be a generated column",
attributeName)));
/*
* Check that both generation expressions match.
*
* The test we apply is to see whether they reverse-compile to the
* same source string. This insulates us from issues like whether
* attributes have the same physical column numbers in parent and
* child relations. (See also constraints_equivalent().)
*/
if (attribute->attgenerated && childatt->attgenerated)
{
TupleConstr *child_constr = child_rel->rd_att->constr;
TupleConstr *parent_constr = parent_rel->rd_att->constr;
char *child_expr = NULL;
char *parent_expr = NULL;
Assert(child_constr != NULL);
Assert(parent_constr != NULL);
for (int i = 0; i < child_constr->num_defval; i++)
{
if (child_constr->defval[i].adnum == childatt->attnum)
{
child_expr =
TextDatumGetCString(DirectFunctionCall2(pg_get_expr,
CStringGetTextDatum(child_constr->defval[i].adbin),
ObjectIdGetDatum(child_rel->rd_id)));
break;
}
}
Assert(child_expr != NULL);
for (int i = 0; i < parent_constr->num_defval; i++)
{
if (parent_constr->defval[i].adnum == attribute->attnum)
{
parent_expr =
TextDatumGetCString(DirectFunctionCall2(pg_get_expr,
CStringGetTextDatum(parent_constr->defval[i].adbin),
ObjectIdGetDatum(parent_rel->rd_id)));
break;
}
}
Assert(parent_expr != NULL);
if (strcmp(child_expr, parent_expr) != 0)
ereport(ERROR,
(errcode(ERRCODE_DATATYPE_MISMATCH),
errmsg("column \"%s\" in child table has a conflicting generation expression",
attributeName)));
}
/*
* OK, bump the child column's inheritance count. (If we fail
* later on, this change will just roll back.)