Merge pull request #6146 from planetscale/at-equals-null

Use 'SelectNone' for all equality against null
vitessio · May 4, 2020 · 648e8c2 · 648e8c2
2 parents ab29699 + 00a8109
commit 648e8c2
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Showing 2 changed files with 23 additions and 3 deletions.
diff --git a/go/vt/vtgate/planbuilder/route_option.go b/go/vt/vtgate/planbuilder/route_option.go
@@ -269,6 +269,11 @@ func (ro *routeOption) computePlan(pb *primitiveBuilder, filter sqlparser.Expr)
 func (ro *routeOption) computeEqualPlan(pb *primitiveBuilder, comparison *sqlparser.ComparisonExpr) (opcode engine.RouteOpcode, vindex vindexes.SingleColumn, condition sqlparser.Expr) {
 	left := comparison.Left
 	right := comparison.Right
+
+	if sqlparser.IsNull(right) {
+		return engine.SelectNone, nil, nil
+	}
+
 	vindex = ro.FindVindex(pb, left)
 	if vindex == nil {
 		left, right = right, left
@@ -277,9 +282,6 @@ func (ro *routeOption) computeEqualPlan(pb *primitiveBuilder, comparison *sqlpar
 			return engine.SelectScatter, nil, nil
 		}
 	}
-	if sqlparser.IsNull(right) {
-		return engine.SelectNone, nil, nil
-	}
 	if !ro.exprIsValue(right) {
 		return engine.SelectScatter, nil, nil
 	}

diff --git a/go/vt/vtgate/planbuilder/testdata/filter_cases.txt b/go/vt/vtgate/planbuilder/testdata/filter_cases.txt
@@ -16,6 +16,24 @@
   }
 }
 
+# Query that always return empty
+"select id from user where someColumn = null"
+{
+  "QueryType": "SELECT",
+  "Original": "select id from user where someColumn = null",
+  "Instructions": {
+    "OperatorType": "Route",
+    "Variant": "SelectNone",
+    "Keyspace": {
+      "Name": "user",
+      "Sharded": true
+    },
+    "FieldQuery": "select id from user where 1 != 1",
+    "Query": "select id from user where someColumn = null",
+    "Table": "user"
+  }
+}
+
 # Single table unique vindex route
 "select id from user where user.id = 5"
 {