Use Decimal.String() for hashkey in hashjoin lookups

Author: angelamayxie

enginetest/join_op_tests.go

@@ -2046,6 +2046,26 @@ WHERE
 			},
 		},
 	},
+	{
+		name: "join with % condition",
+		setup: [][]string{
+			{
+				"create table t1(c0 int)",
+				"create table t2(c0 int)",
+				"insert into t1 values (1),(2)",
+				"insert into t2 values (3),(4)",
+			},
+		},
+		tests: []JoinOpTests{
+			{
+				Query: `select * from t1 join t2 on (t1.c0 % 2) = (t2.c0 % 2)`,
+				Expected: []sql.Row{
+					{1, 3},
+					{2, 4},
+				},
+			},
+		},
+	},
 }
 
 var rangeJoinOpTests = []JoinOpTests{

sql/plan/hash_lookup.go

@@ -16,6 +16,7 @@ package plan
 
 import (
 	"fmt"
+	"github.com/shopspring/decimal"
 	"sync"
 
 	"github.com/dolthub/go-mysql-server/sql"
@@ -137,6 +138,10 @@ func (n *HashLookup) GetHashKey(ctx *sql.Context, e sql.Expression, row sql.Row)
 	if k, ok := key.([]byte); ok {
 		key = string(k)
 	}
+	// decimals are not hashable
+	if d, ok := key.(decimal.Decimal); ok {
+		key = d.String()
+	}
 	return key, nil
 }