Tomas Vondra wrote:
> On 10/10/2017 05:03 AM, David Rowley wrote:
> > Basically, $subject is causing us not to properly find matching
> > extended stats in this case.
> >
> > The attached patch fixes it.
> >
> > The following test cases is an example of the misbehaviour. Note
> > rows=1 vs rows=98 in the Gather node.
>
> Thanks for noticing this. The patch seems fine to me.
I propose this slightly larger change.
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
diff --git a/src/backend/statistics/dependencies.c
b/src/backend/statistics/dependencies.c
index 2e7c0ad6ba..0a51639d9d 100644
--- a/src/backend/statistics/dependencies.c
+++ b/src/backend/statistics/dependencies.c
@@ -736,12 +736,9 @@ pg_dependencies_send(PG_FUNCTION_ARGS)
* dependency_is_compatible_clause
* Determines if the clause is compatible with functional
dependencies
*
- * Only OpExprs with two arguments using an equality operator are supported.
- * When returning True attnum is set to the attribute number of the Var within
- * the supported clause.
- *
- * Currently we only support Var = Const, or Const = Var. It may be possible
- * to expand on this later.
+ * Returns true, and sets *attnum to the attribute number of the Var in the
+ * clause, if the clause is compatible with functional dependencies on the
+ * given relation. Otherwise, return false.
*/
static bool
dependency_is_compatible_clause(Node *clause, Index relid, AttrNumber *attnum)
@@ -762,39 +759,47 @@ dependency_is_compatible_clause(Node *clause, Index
relid, AttrNumber *attnum)
if (is_opclause(rinfo->clause))
{
OpExpr *expr = (OpExpr *) rinfo->clause;
+ Node *left;
+ Node *right;
Var *var;
- bool varonleft = true;
- bool ok;
- /* Only expressions with two arguments are considered
compatible. */
+ /* Only expressions with two arguments are considered
compatible ... */
if (list_length(expr->args) != 2)
return false;
- /* see if it actually has the right */
- ok = (NumRelids((Node *) expr) == 1) &&
- (is_pseudo_constant_clause(lsecond(expr->args)) ||
- (varonleft = false,
- is_pseudo_constant_clause(linitial(expr->args))));
-
- /* unsupported structure (two variables or so) */
- if (!ok)
+ /* ... and only if they operate on a single relation */
+ if (NumRelids((Node *) expr) != 1)
return false;
/*
- * If it's not "=" operator, just ignore the clause, as it's not
- * compatible with functional dependencies.
- *
- * This uses the function for estimating selectivity, not the
operator
- * directly (a bit awkward, but well ...).
+ * See which one is the pseudo-constant one, if any. If neither
is, the
+ * clause is not compatible.
*/
- if (get_oprrest(expr->opno) != F_EQSEL)
+ left = (Node *) linitial(expr->args);
+ right = (Node *) lsecond(expr->args);
+
+ if (IsA(left, Var) || IsA(left, RelabelType))
+ {
+ if (!is_pseudo_constant_clause(right))
+ return false;
+ var = (Var *) left;
+ }
+ else if (IsA(right, Var) || IsA(right, RelabelType))
+ {
+ if (!is_pseudo_constant_clause(left))
+ return false;
+ var = (Var *) right;
+ }
+ else
return false;
- var = (varonleft) ? linitial(expr->args) : lsecond(expr->args);
-
- /* We only support plain Vars for now */
- if (!IsA(var, Var))
- return false;
+ /*
+ * We may ignore any RelabelType node above the operand.
(There won't
+ * be more than one, since eval_const_expressions() has been
applied
+ * already.)
+ */
+ if (IsA(var, RelabelType))
+ var = (Var *) ((RelabelType *) var)->arg;
/* Ensure var is from the correct relation */
if (var->varno != relid)
@@ -808,6 +813,16 @@ dependency_is_compatible_clause(Node *clause, Index relid,
AttrNumber *attnum)
if (!AttrNumberIsForUserDefinedAttr(var->varattno))
return false;
+ /*
+ * If it's not "=" operator, just ignore the clause, as it's not
+ * compatible with functional dependencies.
+ *
+ * This uses the function for estimating selectivity, not the
operator
+ * directly (a bit awkward, but well ...).
+ */
+ if (get_oprrest(expr->opno) != F_EQSEL)
+ return false;
+
*attnum = var->varattno;
return true;
}
--
2.11.0
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