util: pre-alloc memory for decoding rows (pingcap#22508)

Signed-off-by: Shuaipeng Yu <[email protected]>
johanliu · Jan 25, 2021 · 905e9af · 905e9af
1 parent f3688eb
commit 905e9af
Showing 1 changed file with 2 additions and 2 deletions.
diff --git a/util/rowDecoder/decoder.go b/util/rowDecoder/decoder.go
@@ -120,8 +120,8 @@ func (rd *RowDecoder) DecodeAndEvalRowWithMap(ctx sessionctx.Context, handle kv.
 		}
 		rd.mutRow.SetValue(colInfo.Offset, val.GetValue())
 	}
-	keys := make([]int, 0)
-	ids := make(map[int]int)
+	keys := make([]int, 0, len(rd.colMap))
+	ids := make(map[int]int, len(rd.colMap))
 	for k, col := range rd.colMap {
 		keys = append(keys, col.Col.Offset)
 		ids[col.Col.Offset] = int(k)