From aca5683508d22815c4814955d877fe28c901312b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andr=C3=A9s=20Taylor?= <andres@planetscale.com>
Date: Tue, 29 Oct 2024 10:34:04 +0100
Subject: [PATCH] bugfix: make sure to split predicates before planning them
 (#17099)

Signed-off-by: Andres Taylor <andres@planetscale.com>
---
 .../planbuilder/operators/apply_join.go       | 22 ++++++++++-------
 .../planbuilder/testdata/from_cases.json      | 24 ++++++++++++++++++-
 2 files changed, 37 insertions(+), 9 deletions(-)

diff --git a/go/vt/vtgate/planbuilder/operators/apply_join.go b/go/vt/vtgate/planbuilder/operators/apply_join.go
index 279357d98ed..630f90285a2 100644
--- a/go/vt/vtgate/planbuilder/operators/apply_join.go
+++ b/go/vt/vtgate/planbuilder/operators/apply_join.go
@@ -153,15 +153,21 @@ func (aj *ApplyJoin) AddJoinPredicate(ctx *plancontext.PlanningContext, expr sql
 	if expr == nil {
 		return nil
 	}
-	col, err := BreakExpressionInLHSandRHS(ctx, expr, TableID(aj.LHS))
-	if err != nil {
-		return err
-	}
-	aj.JoinPredicates = append(aj.JoinPredicates, col)
-	rhs, err := aj.RHS.AddPredicate(ctx, col.RHSExpr)
-	if err != nil {
-		return err
+	rhs := aj.RHS
+	predicates := sqlparser.SplitAndExpression(nil, expr)
+	for _, pred := range predicates {
+		col, err := BreakExpressionInLHSandRHS(ctx, pred, TableID(aj.LHS))
+		if err != nil {
+			return err
+		}
+		aj.JoinPredicates = append(aj.JoinPredicates, col)
+		ctx.AddJoinPredicates(pred, col.RHSExpr)
+		rhs, err = rhs.AddPredicate(ctx, col.RHSExpr)
+		if err != nil {
+			return err
+		}
 	}
+
 	aj.RHS = rhs
 
 	return nil
diff --git a/go/vt/vtgate/planbuilder/testdata/from_cases.json b/go/vt/vtgate/planbuilder/testdata/from_cases.json
index eb5feecf7f6..8cdf4630655 100644
--- a/go/vt/vtgate/planbuilder/testdata/from_cases.json
+++ b/go/vt/vtgate/planbuilder/testdata/from_cases.json
@@ -511,7 +511,7 @@
           "Sharded": true
         },
         "FieldQuery": "select 42 from `user` as u, user_extra as ue, music as m where 1 != 1",
-        "Query": "select 42 from `user` as u, user_extra as ue, music as m where u.id = ue.user_id and u.id = :m_user_id and (u.foo or :m_foo or ue.foo) and m.user_id = u.id and (u.foo or m.foo or ue.foo)",
+        "Query": "select 42 from `user` as u, user_extra as ue, music as m where u.id = ue.user_id and m.user_id = u.id and (u.foo or m.foo or ue.foo)",
         "Table": "`user`, music, user_extra"
       },
       "TablesUsed": [
@@ -4193,5 +4193,27 @@
         "zlookup_unique.t1"
       ]
     }
+  },
+  {
+    "comment": "lots of joins that can be merged should not confuse the planner",
+    "query": "SELECT `music`.id FROM `music` INNER JOIN music `music2` ON `music2`.`id` = `music`.`id` INNER JOIN music `music3` ON `music3`.`id` = `music2`.`id` INNER JOIN music `music4` ON `music4`.`id` = `music3`.`id` WHERE music.user_index = music4.user_index",
+    "plan": {
+      "QueryType": "SELECT",
+      "Original": "SELECT `music`.id FROM `music` INNER JOIN music `music2` ON `music2`.`id` = `music`.`id` INNER JOIN music `music3` ON `music3`.`id` = `music2`.`id` INNER JOIN music `music4` ON `music4`.`id` = `music3`.`id` WHERE music.user_index = music4.user_index",
+      "Instructions": {
+        "OperatorType": "Route",
+        "Variant": "Scatter",
+        "Keyspace": {
+          "Name": "user",
+          "Sharded": true
+        },
+        "FieldQuery": "select music.id from music, music as music2, music as music3, music as music4 where 1 != 1",
+        "Query": "select music.id from music, music as music2, music as music3, music as music4 where music2.id = music.id and music4.id = music3.id and music3.id = music2.id and music.user_index = music4.user_index",
+        "Table": "music"
+      },
+      "TablesUsed": [
+        "user.music"
+      ]
+    }
   }
 ]