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Allow specifying column list for foreign key ON DELETE SET actions

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Extend the foreign key ON DELETE actions SET NULL and SET DEFAULT by
allowing the specification of a column list, like

    CREATE TABLE posts (
        ...
        FOREIGN KEY (tenant_id, author_id) REFERENCES users ON DELETE SET NULL (author_id)
    );

If a column list is specified, only those columns are set to
null/default, instead of all the columns in the foreign-key
constraint.

This is useful for multitenant or sharded schemas, where the tenant or
shard ID is included in the primary key of all tables but shouldn't be
set to null.

Author: Paul Martinez <paulmtz@google.com>
Discussion: https://www.postgresql.org/message-id/flat/CACqFVBZQyMYJV=njbSMxf+rbDHpx=W=B7AEaMKn8dWn9OZJY7w@mail.gmail.com
This commit is contained in:
Peter Eisentraut
2021-12-08 11:09:44 +01:00
parent e464cb7af3
commit d6f96ed94e
22 changed files with 557 additions and 72 deletions
Download Patch File Download Diff File Expand all files Collapse all files

53
src/backend/catalog/pg_constraint.c
View File

@@ -68,6 +68,8 @@ CreateConstraintEntry(const char *constraintName,
int foreignNKeys,
char foreignUpdateType,
char foreignDeleteType,
const int16 *fkDeleteSetCols,
int numFkDeleteSetCols,
char foreignMatchType,
const Oid *exclOp,
Node *conExpr,
@@ -88,6 +90,7 @@ CreateConstraintEntry(const char *constraintName,
ArrayType *conppeqopArray;
ArrayType *conffeqopArray;
ArrayType *conexclopArray;
ArrayType *confdelsetcolsArray;
NameData cname;
int i;
ObjectAddress conobject;
@@ -136,6 +139,16 @@ CreateConstraintEntry(const char *constraintName,
fkdatums[i] = ObjectIdGetDatum(ffEqOp[i]);
conffeqopArray = construct_array(fkdatums, foreignNKeys,
OIDOID, sizeof(Oid), true, TYPALIGN_INT);
if (numFkDeleteSetCols > 0)
{
for (i = 0; i < numFkDeleteSetCols; i++)
fkdatums[i] = Int16GetDatum(fkDeleteSetCols[i]);
confdelsetcolsArray = construct_array(fkdatums, numFkDeleteSetCols,
INT2OID, 2, true, TYPALIGN_SHORT);
}
else
confdelsetcolsArray = NULL;
}
else
{
@@ -143,6 +156,7 @@ CreateConstraintEntry(const char *constraintName,
conpfeqopArray = NULL;
conppeqopArray = NULL;
conffeqopArray = NULL;
confdelsetcolsArray = NULL;
}
if (exclOp != NULL)
@@ -211,6 +225,11 @@ CreateConstraintEntry(const char *constraintName,
else
nulls[Anum_pg_constraint_conffeqop - 1] = true;
if (confdelsetcolsArray)
values[Anum_pg_constraint_confdelsetcols - 1] = PointerGetDatum(confdelsetcolsArray);
else
nulls[Anum_pg_constraint_confdelsetcols - 1] = true;
if (conexclopArray)
values[Anum_pg_constraint_conexclop - 1] = PointerGetDatum(conexclopArray);
else
@@ -1157,13 +1176,15 @@ get_primary_key_attnos(Oid relid, bool deferrableOk, Oid *constraintOid)
/*
* Extract data from the pg_constraint tuple of a foreign-key constraint.
*
* All arguments save the first are output arguments; the last three of them
* can be passed as NULL if caller doesn't need them.
* All arguments save the first are output arguments. All output arguments
* other than numfks, conkey and confkey can be passed as NULL if caller
* doesn't need them.
*/
void
DeconstructFkConstraintRow(HeapTuple tuple, int *numfks,
AttrNumber *conkey, AttrNumber *confkey,
Oid *pf_eq_oprs, Oid *pp_eq_oprs, Oid *ff_eq_oprs)
Oid *pf_eq_oprs, Oid *pp_eq_oprs, Oid *ff_eq_oprs,
int *num_fk_del_set_cols, AttrNumber *fk_del_set_cols)
{
Oid constrId;
Datum adatum;
@@ -1260,6 +1281,32 @@ DeconstructFkConstraintRow(HeapTuple tuple, int *numfks,
pfree(arr); /* free de-toasted copy, if any */
}
if (fk_del_set_cols)
{
adatum = SysCacheGetAttr(CONSTROID, tuple,
Anum_pg_constraint_confdelsetcols, &isNull);
if (isNull)
{
*num_fk_del_set_cols = 0;
}
else
{
int num_delete_cols;
arr = DatumGetArrayTypeP(adatum); /* ensure not toasted */
if (ARR_NDIM(arr) != 1 ||
ARR_HASNULL(arr) ||
ARR_ELEMTYPE(arr) != INT2OID)
elog(ERROR, "confdelsetcols is not a 1-D smallint array");
num_delete_cols = ARR_DIMS(arr)[0];
memcpy(fk_del_set_cols, ARR_DATA_PTR(arr), num_delete_cols * sizeof(int16));
if ((Pointer) arr != DatumGetPointer(adatum))
pfree(arr); /* free de-toasted copy, if any */
*num_fk_del_set_cols = num_delete_cols;
}
}
*numfks = numkeys;
}