allocate fewer sql.Rows (#3146)

Author: jycor

sql/rowexec/agg.go

@@ -117,6 +117,10 @@ type groupByGroupingIter struct {
 	pos           int
 	child         sql.RowIter
 	dispose       sql.DisposeFunc
+
+	// buffers to reduce slice allocations
+	keyRow sql.Row
+	keySch sql.Schema
 }
 
 func newGroupByGroupingIter(
@@ -128,6 +132,8 @@ func newGroupByGroupingIter(
 		selectedExprs: selectedExprs,
 		groupByExprs:  groupByExprs,
 		child:         child,
+		keyRow:        make(sql.Row, len(groupByExprs)),
+		keySch:        make(sql.Schema, len(groupByExprs)),
 	}
 }
 
@@ -167,7 +173,7 @@ func (i *groupByGroupingIter) compute(ctx *sql.Context) error {
 			return err
 		}
 
-		key, err := groupingKey(ctx, i.groupByExprs, row)
+		key, err := i.groupingKey(ctx, i.groupByExprs, row)
 		if err != nil {
 			return err
 		}
@@ -237,10 +243,8 @@ func (i *groupByGroupingIter) Dispose() {
 	}
 }
 
-func groupingKey(ctx *sql.Context, exprs []sql.Expression, row sql.Row) (uint64, error) {
-	var keyRow = make(sql.Row, len(exprs))
-	var keySch = make(sql.Schema, len(exprs))
-	for i, expr := range exprs {
+func (i *groupByGroupingIter) groupingKey(ctx *sql.Context, exprs []sql.Expression, row sql.Row) (uint64, error) {
+	for idx, expr := range exprs {
 		v, err := expr.Eval(ctx, row)
 		if err != nil {
 			return 0, err
@@ -256,10 +260,10 @@ func groupingKey(ctx *sql.Context, exprs []sql.Expression, row sql.Row) (uint64,
 			v = string(val)
 		}
 
-		keyRow[i] = v
-		keySch[i] = &sql.Column{Type: typ}
+		i.keyRow[idx] = v
+		i.keySch[idx] = &sql.Column{Type: typ}
 	}
-	return hash.HashOf(ctx, keySch, keyRow)
+	return hash.HashOf(ctx, i.keySch, i.keyRow)
 }
 
 func newAggregationBuffer(expr sql.Expression) (sql.AggregationBuffer, error) {

sql/rowexec/ddl_iters.go

@@ -109,7 +109,7 @@ func (l *loadDataIter) Next(ctx *sql.Context) (returnRow sql.Row, returnErr erro
 		}
 	}
 
-	return sql.NewRow(row...), nil
+	return row, nil
 }
 
 func (l *loadDataIter) Close(ctx *sql.Context) error {

sql/rowexec/rel.go

@@ -55,7 +55,7 @@ func (b *BaseBuilder) buildTopN(ctx *sql.Context, n *plan.TopN, row sql.Row) (sq
 func (b *BaseBuilder) buildValueDerivedTable(ctx *sql.Context, n *plan.ValueDerivedTable, row sql.Row) (sql.RowIter, error) {
 	rows := make([]sql.Row, len(n.ExpressionTuples))
 	for i, et := range n.ExpressionTuples {
-		vals := make([]interface{}, len(et))
+		vals := make(sql.Row, len(et))
 		for j, e := range et {
 			var err error
 			p, err := e.Eval(ctx, row)
@@ -72,8 +72,7 @@ func (b *BaseBuilder) buildValueDerivedTable(ctx *sql.Context, n *plan.ValueDeri
 				vals[j] = vals[j].(decimal.Decimal).Round(int32(t.Scale()))
 			}
 		}
-
-		rows[i] = sql.NewRow(vals...)
+		rows[i] = vals
 	}
 
 	return sql.RowsToRowIter(rows...), nil

sql/types/number.go

@@ -601,7 +601,7 @@ func (t NumberTypeImpl_) SQL(ctx *sql.Context, dest []byte, v interface{}) (sqlt
 		case []byte:
 			dest = str
 		case string:
-			dest = []byte(str)
+			dest = append(dest, str...)
 		default:
 			return sqltypes.Value{}, err
 		}
@@ -931,7 +931,7 @@ func (t NumberTypeImpl_) IsSigned() bool {
 	return false
 }
 
-// DisplayWidth() implements NumberType inteface.
+// DisplayWidth implements NumberType interface.
 func (t NumberTypeImpl_) DisplayWidth() int {
 	return t.displayWidth
 }

sql/types/strings.go

@@ -15,7 +15,6 @@
 package types
 
 import (
-	"bytes"
 	"context"
 	"fmt"
 	"reflect"
@@ -480,7 +479,7 @@ func ConvertToBytes(ctx context.Context, v interface{}, t sql.StringType, dest [
 				val = append(dest, b...)
 				start = len(dest)
 			}
-			val = append(val, bytes.Repeat([]byte{0}, int(st.maxCharLength)-len(val))...)
+			val = append(val, make([]byte, int(st.maxCharLength)-len(val))...)
 		}
 	}
 	val = val[start:]
@@ -757,7 +756,7 @@ func (t StringType) SQL(ctx *sql.Context, dest []byte, v interface{}) (sqltypes.
 			valueBytes, err = ConvertToBytes(ctx, v, t, dest)
 		}
 		if t.baseType == sqltypes.Binary {
-			val = append(val, bytes.Repeat([]byte{0}, int(t.maxCharLength)-len(val))...)
+			val = append(val, make([]byte, int(t.maxCharLength)-len(val))...)
 		}
 		// Note: MySQL does not validate charset when returning query results.
 		// It returns whatever data is stored, allowing users to query and clean up
@@ -777,7 +776,6 @@ func (t StringType) SQL(ctx *sql.Context, dest []byte, v interface{}) (sqltypes.
 			snippetStr := strings2.ToValidUTF8(string(snippet), string(utf8.RuneError))
 			return sqltypes.Value{}, sql.ErrCharSetFailedToEncode.New(resultCharset.Name(), utf8.ValidString(snippetStr), snippet)
 		}
-		//val = AppendAndSliceBytes(dest, encodedBytes)
 		val = encodedBytes
 	}
 
@@ -893,10 +891,3 @@ func AppendAndSliceString(buffer []byte, addition string) (slice []byte) {
 	slice = buffer[stop:]
 	return
 }
-
-func AppendAndSliceBytes(buffer, addition []byte) (slice []byte) {
-	stop := len(buffer)
-	buffer = append(buffer, addition...)
-	slice = buffer[stop:]
-	return
-}