Fix schema for call to hash.HashOf() in HashLookups (#3038)

Author: jycor

enginetest/queries/join_queries.go

@@ -1161,6 +1161,45 @@ var JoinScriptTests = []ScriptTest{
 			},
 		},
 	},
+	{
+		// After this change: https://github.com/dolthub/go-mysql-server/pull/3038
+		// hash.HashOf takes in a sql.Schema to convert and hash keys, so
+		// we need to pass in the schema of the join key.
+		// This tests a bug introduced in that same PR where we incorrectly pass in the entire schema,
+		// resulting in incorrect conversions.
+		Name: "HashLookup on multiple columns with tables with different schemas",
+		SetUpScript: []string{
+			"create table t1 (i int primary key, k int);",
+			"create table t2 (i int primary key, j varchar(1), k int);",
+			"insert into t1 values (111111, 111111);",
+			"insert into t2 values (111111, 'a', 111111);",
+		},
+		Assertions: []ScriptTestAssertion{
+			{
+				Query: "select /*+ HASH_JOIN(t1, t2) */ * from t1 join t2 on t1.i = t2.i and t1.k = t2.k;",
+				Expected: []sql.Row{
+					{111111, 111111, 111111, "a", 111111},
+				},
+			},
+		},
+	},
+	{
+		Name: "HashLookup on multiple columns with collations",
+		SetUpScript: []string{
+			"create table t1 (i int primary key, j varchar(128) collate utf8mb4_0900_ai_ci);",
+			"create table t2 (i int primary key, j varchar(128) collate utf8mb4_0900_ai_ci);",
+			"insert into t1 values (1, 'ABCDE');",
+			"insert into t2 values (1, 'abcde');",
+		},
+		Assertions: []ScriptTestAssertion{
+			{
+				Query: "select /*+ HASH_JOIN(t1, t2) */ * from t1 join t2 on t1.i = t2.i and t1.j = t2.j;",
+				Expected: []sql.Row{
+					{1, "ABCDE", 1, "abcde"},
+				},
+			},
+		},
+	},
 }
 
 var LateralJoinScriptTests = []ScriptTest{

sql/hash/hash.go

@@ -30,6 +30,17 @@ var digestPool = sync.Pool{
 	},
 }
 
+// ExprsToSchema converts a list of sql.Expression to a sql.Schema.
+// This is used for functions that use HashOf, but don't already have a schema.
+// The generated schema ONLY contains the types of the expressions without any column names or any other info.
+func ExprsToSchema(exprs ...sql.Expression) sql.Schema {
+	var sch sql.Schema
+	for _, expr := range exprs {
+		sch = append(sch, &sql.Column{Type: expr.Type()})
+	}
+	return sch
+}
+
 // HashOf returns a hash of the given value to be used as key in a cache.
 func HashOf(ctx *sql.Context, sch sql.Schema, row sql.Row) (uint64, error) {
 	hash := digestPool.Get().(*xxhash.Digest)

sql/plan/hash_lookup.go

@@ -33,12 +33,14 @@ import (
 // on the projected results. If cached results are not available, it
 // simply delegates to the child.
 func NewHashLookup(n sql.Node, rightEntryKey sql.Expression, leftProbeKey sql.Expression, joinType JoinType) *HashLookup {
+	leftKeySch := hash.ExprsToSchema(leftProbeKey)
 	return &HashLookup{
 		UnaryNode:     UnaryNode{n},
 		RightEntryKey: rightEntryKey,
 		LeftProbeKey:  leftProbeKey,
 		Mutex:         new(sync.Mutex),
 		JoinType:      joinType,
+		leftKeySch:    leftKeySch,
 	}
 }
 
@@ -49,6 +51,7 @@ type HashLookup struct {
 	Mutex         *sync.Mutex
 	Lookup        *map[interface{}][]sql.Row
 	JoinType      JoinType
+	leftKeySch    sql.Schema
 }
 
 var _ sql.Node = (*HashLookup)(nil)
@@ -70,6 +73,7 @@ func (n *HashLookup) WithExpressions(exprs ...sql.Expression) (sql.Node, error)
 	ret := *n
 	ret.RightEntryKey = exprs[0]
 	ret.LeftProbeKey = exprs[1]
+	ret.leftKeySch = hash.ExprsToSchema(ret.LeftProbeKey)
 	return &ret, nil
 }
 
@@ -127,7 +131,7 @@ func (n *HashLookup) GetHashKey(ctx *sql.Context, e sql.Expression, row sql.Row)
 		return nil, err
 	}
 	if s, ok := key.([]interface{}); ok {
-		return hash.HashOf(ctx, n.Schema(), s)
+		return hash.HashOf(ctx, n.leftKeySch, s)
 	}
 	// byte slices are not hashable
 	if k, ok := key.([]byte); ok {