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Add support for not-null constraints on virtual generated columns

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This was left out of the original patch for virtual generated columns
(commit 83ea6c5402).

This just involves a bit of extra work in the executor to expand the
generation expressions and run a "IS NOT NULL" test against them.

There is also a bit of work to make sure that not-null constraints are
checked during a table rewrite.

Author: jian he <jian.universality@gmail.com>
Reviewed-by: Xuneng Zhou <xunengzhou@gmail.com>
Reviewed-by: Navneet Kumar <thanit3111@gmail.com>
Reviewed-by: Álvaro Herrera <alvherre@alvh.no-ip.org>
Discussion: https://postgr.es/m/CACJufxHArQysbDkWFmvK+D1TPHQWWTxWN15cMuUaTYX3xhQXgg@mail.gmail.com
This commit is contained in:
Peter Eisentraut
2025-03-28 13:53:37 +01:00
parent 747ddd38cb
commit cdc168ad4b
9 changed files with 363 additions and 122 deletions
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71
src/backend/commands/tablecmds.c
View File

@ -6101,6 +6101,7 @@ ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap)
TupleDesc newTupDesc;
bool needscan = false;
List *notnull_attrs;
List *notnull_virtual_attrs;
int i;
ListCell *l;
EState *estate;
@ -6185,22 +6186,32 @@ ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap)
ex->exprstate = ExecInitExpr((Expr *) ex->expr, NULL);
}
notnull_attrs = NIL;
notnull_attrs = notnull_virtual_attrs = NIL;
if (newrel || tab->verify_new_notnull)
{
/*
* If we are rebuilding the tuples OR if we added any new but not
* verified not-null constraints, check all not-null constraints. This
* is a bit of overkill but it minimizes risk of bugs.
*
* notnull_attrs does *not* collect attribute numbers for not-null
* constraints over virtual generated columns; instead, they are
* collected in notnull_virtual_attrs.
*/
for (i = 0; i < newTupDesc->natts; i++)
{
Form_pg_attribute attr = TupleDescAttr(newTupDesc, i);
if (attr->attnotnull && !attr->attisdropped)
notnull_attrs = lappend_int(notnull_attrs, attr->attnum);
{
if (attr->attgenerated != ATTRIBUTE_GENERATED_VIRTUAL)
notnull_attrs = lappend_int(notnull_attrs, attr->attnum);
else
notnull_virtual_attrs = lappend_int(notnull_virtual_attrs,
attr->attnum);
}
}
if (notnull_attrs)
if (notnull_attrs || notnull_virtual_attrs)
needscan = true;
}
@ -6214,6 +6225,29 @@ ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap)
List *dropped_attrs = NIL;
ListCell *lc;
Snapshot snapshot;
ResultRelInfo *rInfo = NULL;
/*
* When adding or changing a virtual generated column with a not-null
* constraint, we need to evaluate whether the generation expression
* is null. For that, we borrow ExecRelGenVirtualNotNull(). Here, we
* prepare a dummy ResultRelInfo.
*/
if (notnull_virtual_attrs != NIL)
{
MemoryContext oldcontext;
Assert(newTupDesc->constr->has_generated_virtual);
Assert(newTupDesc->constr->has_not_null);
oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);
rInfo = makeNode(ResultRelInfo);
InitResultRelInfo(rInfo,
oldrel,
0, /* dummy rangetable index */
NULL,
estate->es_instrument);
MemoryContextSwitchTo(oldcontext);
}
if (newrel)
ereport(DEBUG1,
@ -6394,6 +6428,26 @@ ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap)
}
}
if (notnull_virtual_attrs != NIL)
{
AttrNumber attnum;
attnum = ExecRelGenVirtualNotNull(rInfo, insertslot,
estate,
notnull_virtual_attrs);
if (attnum != InvalidAttrNumber)
{
Form_pg_attribute attr = TupleDescAttr(newTupDesc, attnum - 1);
ereport(ERROR,
errcode(ERRCODE_NOT_NULL_VIOLATION),
errmsg("column \"%s\" of relation \"%s\" contains null values",
NameStr(attr->attname),
RelationGetRelationName(oldrel)),
errtablecol(oldrel, attnum));
}
}
foreach(l, tab->constraints)
{
NewConstraint *con = lfirst(l);
@ -7843,14 +7897,6 @@ ATExecSetNotNull(List **wqueue, Relation rel, char *conName, char *colName,
errmsg("cannot alter system column \"%s\"",
colName)));
/* TODO: see transformColumnDefinition() */
if (TupleDescAttr(RelationGetDescr(rel), attnum - 1)->attgenerated == ATTRIBUTE_GENERATED_VIRTUAL)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("not-null constraints are not supported on virtual generated columns"),
errdetail("Column \"%s\" of relation \"%s\" is a virtual generated column.",
colName, RelationGetRelationName(rel))));
/* See if there's already a constraint */
tuple = findNotNullConstraintAttnum(RelationGetRelid(rel), attnum);
if (HeapTupleIsValid(tuple))
@ -8519,6 +8565,9 @@ ATExecSetExpression(AlteredTableInfo *tab, Relation rel, const char *colName,
errdetail("Column \"%s\" of relation \"%s\" is a virtual generated column.",
colName, RelationGetRelationName(rel))));
if (attgenerated == ATTRIBUTE_GENERATED_VIRTUAL && attTup->attnotnull)
tab->verify_new_notnull = true;
/*
* We need to prevent this because a change of expression could affect a
* row filter and inject expressions that are not permitted in a row