From 00af0401d945267d83e280541657057b45da4eaf Mon Sep 17 00:00:00 2001
From: Radu Berinde <radu@cockroachlabs.com>
Date: Mon, 11 Oct 2021 06:38:02 -0700
Subject: [PATCH] opt: fix implicit lateral for SRFs when using JOIN syntax

When SRFs are used as a table, they imply that the join is lateral.
This works for the multiple table syntax, but not for the JOIN syntax.
This commit addresses this omission.

Fixes #70342.

Release note (bug fix): Fixes an incorrect "no data source matches
prefix" error for queries that use a set-returning function on the
right-hand side of a `JOIN` (unless `LATERAL` is explicitly
specified).
---
 pkg/sql/opt/optbuilder/join.go       | 12 ++---
 pkg/sql/opt/optbuilder/select.go     |  1 +
 pkg/sql/opt/optbuilder/testdata/srfs | 75 +++++++++++++++++++++++++++-
 3 files changed, 79 insertions(+), 9 deletions(-)

diff --git a/pkg/sql/opt/optbuilder/join.go b/pkg/sql/opt/optbuilder/join.go
index 9b48fc5ecaa2..1c68ff1380a4 100644
--- a/pkg/sql/opt/optbuilder/join.go
+++ b/pkg/sql/opt/optbuilder/join.go
@@ -35,14 +35,12 @@ func (b *Builder) buildJoin(
 ) (outScope *scope) {
 	leftScope := b.buildDataSource(join.Left, nil /* indexFlags */, locking, inScope)
 
-	isLateral := false
 	inScopeRight := inScope
-	// If this is a lateral join, use leftScope as inScope for the right side.
-	// The right side scope of a LATERAL join includes the columns produced by
-	// the left side.
-	if t, ok := join.Right.(*tree.AliasedTableExpr); ok && t.Lateral {
-		telemetry.Inc(sqltelemetry.LateralJoinUseCounter)
-		isLateral = true
+	isLateral := b.exprIsLateral(join.Right)
+	if isLateral {
+		// If this is a lateral join, use leftScope as inScope for the right side.
+		// The right side scope of a LATERAL join includes the columns produced by
+		// the left side.
 		inScopeRight = leftScope
 		inScopeRight.context = exprKindLateralJoin
 	}
diff --git a/pkg/sql/opt/optbuilder/select.go b/pkg/sql/opt/optbuilder/select.go
index e9f5e047650f..c7c2524edce5 100644
--- a/pkg/sql/opt/optbuilder/select.go
+++ b/pkg/sql/opt/optbuilder/select.go
@@ -1205,6 +1205,7 @@ func (b *Builder) exprIsLateral(t tree.TableExpr) bool {
 	}
 	// Expressions which explicitly use the LATERAL keyword are lateral.
 	if ate.Lateral {
+		telemetry.Inc(sqltelemetry.LateralJoinUseCounter)
 		return true
 	}
 	// SRFs are always lateral.
diff --git a/pkg/sql/opt/optbuilder/testdata/srfs b/pkg/sql/opt/optbuilder/testdata/srfs
index b71779e180b8..88fb3b3be849 100644
--- a/pkg/sql/opt/optbuilder/testdata/srfs
+++ b/pkg/sql/opt/optbuilder/testdata/srfs
@@ -672,9 +672,9 @@ SELECT a.*, b.*, c.* FROM upper('abc') a
 JOIN ROWS FROM (upper('def'), generate_series(1, 3)) b ON true
 JOIN generate_series(1, 4) c ON true
 ----
-inner-join (cross)
+inner-join-apply
  ├── columns: a:1 upper:2 generate_series:3 c:4
- ├── inner-join (cross)
+ ├── inner-join-apply
  │    ├── columns: upper:1 upper:2 generate_series:3
  │    ├── project-set
  │    │    ├── columns: upper:1
@@ -894,3 +894,74 @@ project-set
                           │         ├── columns: tab31755.a:1 rowid:2!null crdb_internal_mvcc_timestamp:3 tableoid:4
                           │         └── limit hint: 1.00
                           └── 1
+
+# Regression test for #70342.
+exec-ddl
+CREATE TABLE t70342 (i INT PRIMARY KEY);
+----
+
+# Verify that an SRF is implicitly lateral.
+build
+WITH data AS (SELECT row_to_json(t70342) AS row FROM t70342)
+SELECT count(*)
+FROM data, json_each_text(data.row);
+----
+with &1 (data)
+ ├── columns: count:8!null
+ ├── project
+ │    ├── columns: row:4
+ │    ├── scan t70342
+ │    │    └── columns: i:1!null crdb_internal_mvcc_timestamp:2 tableoid:3
+ │    └── projections
+ │         └── row_to_json(((i:1,) AS i)) [as=row:4]
+ └── scalar-group-by
+      ├── columns: count_rows:8!null
+      ├── project
+      │    └── inner-join-apply
+      │         ├── columns: row:5 key:6 value:7
+      │         ├── with-scan &1 (data)
+      │         │    ├── columns: row:5
+      │         │    └── mapping:
+      │         │         └──  row:4 => row:5
+      │         ├── project-set
+      │         │    ├── columns: key:6 value:7
+      │         │    ├── values
+      │         │    │    └── ()
+      │         │    └── zip
+      │         │         └── json_each_text(row:5)
+      │         └── filters (true)
+      └── aggregations
+           └── count-rows [as=count_rows:8]
+
+# Verify that an SRF is implicitly lateral when using the JOIN syntax.
+build
+WITH data AS (SELECT row_to_json(t70342) AS row FROM t70342)
+SELECT count(*)
+FROM data CROSS JOIN json_each_text(data.row);
+----
+with &1 (data)
+ ├── columns: count:8!null
+ ├── project
+ │    ├── columns: row:4
+ │    ├── scan t70342
+ │    │    └── columns: i:1!null crdb_internal_mvcc_timestamp:2 tableoid:3
+ │    └── projections
+ │         └── row_to_json(((i:1,) AS i)) [as=row:4]
+ └── scalar-group-by
+      ├── columns: count_rows:8!null
+      ├── project
+      │    └── inner-join-apply
+      │         ├── columns: row:5 key:6 value:7
+      │         ├── with-scan &1 (data)
+      │         │    ├── columns: row:5
+      │         │    └── mapping:
+      │         │         └──  row:4 => row:5
+      │         ├── project-set
+      │         │    ├── columns: key:6 value:7
+      │         │    ├── values
+      │         │    │    └── ()
+      │         │    └── zip
+      │         │         └── json_each_text(row:5)
+      │         └── filters (true)
+      └── aggregations
+           └── count-rows [as=count_rows:8]