Merge pull request cockroachdb#63826 from rytaft/backport20.2-63574

release-20.2: sql: fix index out of range error in inverted filterer

pkg/sql/opt/invertedexpr/expression.go

@@ -617,11 +617,16 @@ func opSpanExpressionAndDefault(
 
 // Intersects two SpanExpressions.
 func intersectSpanExpressions(left, right *SpanExpression) *SpanExpression {
-	// Since we simply union into SpansToRead, we can end up with
-	// FactoredUnionSpans as a subset of SpanToRead *and* both children pruned.
-	// TODO(sumeer): tighten the SpansToRead for this case.
 	expr := &SpanExpression{
-		Tight:              left.Tight && right.Tight,
+		Tight: left.Tight && right.Tight,
+
+		// We calculate SpansToRead as the union of the left and right sides as a
+		// first approximation, but this may result in too many spans if either of
+		// the children are pruned below. SpansToRead will be recomputed in
+		// tryPruneChildren if needed. (It is important that SpansToRead be exactly
+		// what would be computed if a caller traversed the tree and explicitly
+		// unioned all the FactoredUnionSpans, and no looser, since the execution
+		// code path relies on this property.)
 		SpansToRead:        unionSpans(left.SpansToRead, right.SpansToRead),
 		FactoredUnionSpans: intersectSpans(left.FactoredUnionSpans, right.FactoredUnionSpans),
 		Operator:           SetIntersection,
@@ -675,6 +680,19 @@ func tryPruneChildren(expr *SpanExpression, op SetOperator) {
 		expr.Operator = child.Operator
 		expr.Left = child.Left
 		expr.Right = child.Right
+
+		// If child.FactoredUnionSpans is non-empty, we need to recalculate
+		// SpansToRead since it may have contained some spans that were removed by
+		// discarding child.FactoredUnionSpans.
+		if child.FactoredUnionSpans != nil {
+			expr.SpansToRead = expr.FactoredUnionSpans
+			if expr.Left != nil {
+				expr.SpansToRead = unionSpans(expr.SpansToRead, expr.Left.(*SpanExpression).SpansToRead)
+			}
+			if expr.Right != nil {
+				expr.SpansToRead = unionSpans(expr.SpansToRead, expr.Right.(*SpanExpression).SpansToRead)
+			}
+		}
 	}
 	promoteLeft := expr.Left != nil && expr.Right == nil
 	promoteRight := expr.Left == nil && expr.Right != nil

pkg/sql/opt/invertedexpr/testdata/expression

@@ -242,7 +242,7 @@ and result=_ left=b right=ac
 ----
 span expression
  ├── tight: true
- ├── to read: ["a", "c")
+ ├── to read: ["b", "b"]
  └── union spans: ["b", "b"]
 
 new-span-leaf name=bj tight=true span=b,j
@@ -265,7 +265,7 @@ and result=_ left=b right=bj
 ----
 span expression
  ├── tight: true
- ├── to read: ["b", "j")
+ ├── to read: ["b", "b"]
  └── union spans: ["b", "b"]
 
 # [b, j) or [a, c) = [a, j)

pkg/sql/opt/xform/testdata/rules/select

@@ -2009,7 +2009,8 @@ project
       │              ├── inverted constraint: /7/1
       │              │    └── spans
       │              │         ├── ["B\xfdL\x00\x00\x00\x00\x00\x00\x00", "B\xfdL\x00\x00\x00\x00\x00\x00\x00"]
-      │              │         └── ["B\xfdN\x00\x00\x00\x00\x00\x00\x01", "B\xfdP\x00\x00\x00\x00\x00\x00\x01")
+      │              │         ├── ["B\xfdO\x00\x00\x00\x00\x00\x00\x00", "B\xfdO\x00\x00\x00\x00\x00\x00\x00"]
+      │              │         └── ["B\xfdP\x00\x00\x00\x00\x00\x00\x00", "B\xfdP\x00\x00\x00\x00\x00\x00\x00"]
       │              ├── key: (1)
       │              └── fd: (1)-->(7)
       └── filters