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From: Tomas Vondra <[email protected]>
Subject: [PATCH 01/11] Apply functional dependencies to ScalarArrayOpExpr
Date: Wed, 4 Mar 2020 15:55:46 +0100

Until now functional dependencies handled only plain equality clauses.
We can apply them to IN some cases of ANY, which can be translated to
an equality.
---
 src/backend/statistics/dependencies.c | 28 +++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/src/backend/statistics/dependencies.c b/src/backend/statistics/dependencies.c
index e2f6c5bb97..36941b8535 100644
--- a/src/backend/statistics/dependencies.c
+++ b/src/backend/statistics/dependencies.c
@@ -801,6 +801,34 @@ dependency_is_compatible_clause(Node *clause, Index relid, AttrNumber *attnum)
 
 		/* OK to proceed with checking "var" */
 	}
+	else if (IsA(rinfo->clause, ScalarArrayOpExpr))
+	{
+		/* If it's an opclause, check for Var IN Const. */
+		ScalarArrayOpExpr	   *expr = (ScalarArrayOpExpr *) rinfo->clause;
+
+		/* Only expressions with two arguments are candidates. */
+		if (list_length(expr->args) != 2)
+			return false;
+
+		/* Make sure non-selected argument is a pseudoconstant. */
+		if (is_pseudo_constant_clause(lsecond(expr->args)))
+			var = linitial(expr->args);
+		else if (is_pseudo_constant_clause(linitial(expr->args)))
+			var = lsecond(expr->args);
+		else
+			return false;
+
+		/*
+		 * If it's not an "=" operator, just ignore the clause, as it's not
+		 * compatible with functional dependencies. The operator is identified
+		 * simply by looking at which function it uses to estimate selectivity.
+		 * That's a bit strange, but it's what other similar places do.
+		 */
+		if (get_oprrest(expr->opno) != F_EQSEL)
+			return false;
+
+		/* OK to proceed with checking "var" */
+	}
 	else if (is_notclause(rinfo->clause))
 	{
 		/*
-- 
2.21.1


--slpdzd2ak5mtvkke
Content-Type: text/plain; charset=us-ascii
Content-Disposition: attachment;
	filename="0002-Simplify-parsing-of-ScalarArrayOpExpr.patch"

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