opt: fix incorrect results from zigzag join with different index directions

pkg/sql/logictest/testdata/logic_test/zigzag_join

@@ -340,3 +340,21 @@ CREATE TABLE t71271(a INT, b INT, c INT, d INT, INDEX (c), INDEX (d))
 
 statement ok
 SELECT d FROM t71271 WHERE c = 3 AND d = 4
+
+# Regression test for #97090. We should not plan a zigzag join when the
+# direction of the equality columns doesn't match.
+statement ok
+CREATE TABLE t97090 (
+  c INT NOT NULL,
+  l INT NOT NULL,
+  r INT NOT NULL,
+  INDEX (l ASC, c DESC),
+  INDEX (r ASC, c ASC)
+);
+INSERT INTO t97090 VALUES (1, 1, -1), (2, 1, -2)
+
+# This query should return one row.
+query III
+SELECT * FROM t97090 WHERE l = 1 AND r = -1
+----
+1  1  -1

pkg/sql/opt/exec/execbuilder/testdata/zigzag_join

@@ -74,3 +74,17 @@ vectorized: true
   right table: t71271@t71271_d_idx
   right columns: (d, rowid)
   right fixed values: 1 column
+
+# Regression test for #97090. We should not plan a zigzag join when the
+# direction of the equality columns doesn't match.
+statement ok
+CREATE TABLE t97090 (
+  c INT NOT NULL,
+  l INT NOT NULL,
+  r INT NOT NULL,
+  INDEX (l ASC, c DESC),
+  INDEX (r ASC, c ASC)
+)
+
+statement error could not produce a query plan conforming to the FORCE_ZIGZAG hint
+EXPLAIN SELECT * FROM t97090@{FORCE_ZIGZAG} WHERE l = 1 AND r = -1

pkg/sql/opt/xform/select_funcs.go

@@ -1345,6 +1345,12 @@ func eqColsForZigzag(
 	}
 
 	for i < leftCnt && j < rightCnt {
+		// The zigzag joiner cannot handle equality columns that are not in the
+		// same direction. See #97090.
+		if leftIndex.Column(i).Descending != rightIndex.Column(j).Descending {
+			break
+		}
+
 		leftColID := tabID.IndexColumnID(leftIndex, i)
 		rightColID := tabID.IndexColumnID(rightIndex, j)
 		i++

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

@@ -6223,6 +6223,35 @@ inner-join (zigzag pqr@q pqr@s)
       ├── r:3 = 1 [outer=(3), constraints=(/3: [/1 - /1]; tight), fd=()-->(3)]
       └── s:4 = 'foo' [outer=(4), constraints=(/4: [/'foo' - /'foo']; tight), fd=()-->(4)]
 
+# Regression test for #97090. We should not plan a zigzag join when the
+# direction of the equality columns doesn't match.
+exec-ddl
+CREATE TABLE t97090 (
+  c INT NOT NULL,
+  l INT NOT NULL,
+  r INT NOT NULL,
+  INDEX (l ASC, c DESC),
+  INDEX (r ASC, c ASC)
+)
+----
+
+opt expect-not=GenerateZigzagJoins
+SELECT * FROM t97090 WHERE l = 1 AND r = -1
+----
+select
+ ├── columns: c:1!null l:2!null r:3!null
+ ├── fd: ()-->(2,3)
+ ├── index-join t97090
+ │    ├── columns: c:1!null l:2!null r:3!null
+ │    ├── fd: ()-->(2)
+ │    └── scan t97090@t97090_l_c_idx
+ │         ├── columns: c:1!null l:2!null rowid:4!null
+ │         ├── constraint: /2/-1/4: [/1 - /1]
+ │         ├── key: (4)
+ │         └── fd: ()-->(2), (4)-->(1)
+ └── filters
+      └── r:3 = -1 [outer=(3), constraints=(/3: [/-1 - /-1]; tight), fd=()-->(3)]
+
 # Zigzag join should not be produced when there is a NO_ZIGZAG_JOIN hint.
 opt expect-not=GenerateZigzagJoins
 SELECT q,r FROM pqr@{NO_ZIGZAG_JOIN} WHERE q = 1 AND r = 2