WITH CHECK OPTION support for auto-updatable VIEWs

For simple views which are automatically updatable, this patch allows
the user to specify what level of checking should be done on records
being inserted or updated.  For 'LOCAL CHECK', new tuples are validated
against the conditionals of the view they are being inserted into, while
for 'CASCADED CHECK' the new tuples are validated against the
conditionals for all views involved (from the top down).

This option is part of the SQL specification.

Dean Rasheed, reviewed by Pavel Stehule

1 files changed, 43 insertions, 0 deletions

diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index 4d7345da577..038f064931e 100644
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -1624,6 +1624,49 @@ ExecConstraints(ResultRelInfo *resultRelInfo,
 }
 
 /*
+ * ExecWithCheckOptions -- check that tuple satisfies any WITH CHECK OPTIONs
+ */
+void
+ExecWithCheckOptions(ResultRelInfo *resultRelInfo,
+					 TupleTableSlot *slot, EState *estate)
+{
+	ExprContext *econtext;
+	ListCell   *l1, *l2;
+
+	/*
+	 * We will use the EState's per-tuple context for evaluating constraint
+	 * expressions (creating it if it's not already there).
+	 */
+	econtext = GetPerTupleExprContext(estate);
+
+	/* Arrange for econtext's scan tuple to be the tuple under test */
+	econtext->ecxt_scantuple = slot;
+
+	/* Check each of the constraints */
+	forboth(l1, resultRelInfo->ri_WithCheckOptions,
+			l2, resultRelInfo->ri_WithCheckOptionExprs)
+	{
+		WithCheckOption *wco = (WithCheckOption *) lfirst(l1);
+		ExprState	   *wcoExpr = (ExprState *) lfirst(l2);
+
+		/*
+		 * WITH CHECK OPTION checks are intended to ensure that the new tuple
+		 * is visible in the view.  If the view's qual evaluates to NULL, then
+		 * the new tuple won't be included in the view.  Therefore we need to
+		 * tell ExecQual to return FALSE for NULL (the opposite of what we do
+		 * above for CHECK constraints).
+		 */
+		if (!ExecQual((List *) wcoExpr, econtext, false))
+			ereport(ERROR,
+					(errcode(ERRCODE_WITH_CHECK_OPTION_VIOLATION),
+					 errmsg("new row violates WITH CHECK OPTION for view \"%s\"",
+							wco->viewname),
+					 errdetail("Failing row contains %s.",
+							   ExecBuildSlotValueDescription(slot, 64))));
+	}
+}
+
+/*
  * ExecBuildSlotValueDescription -- construct a string representing a tuple
  *
  * This is intentionally very similar to BuildIndexValueDescription, but