statistics: change the dnv of default null column to 0 (#4825)

pingcap · Oct 19, 2017 · e035f66 · e035f66
1 parent 16eb0ae
commit e035f66
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Showing 2 changed files with 2 additions and 1 deletion.
diff --git a/statistics/ddl.go b/statistics/ddl.go
@@ -137,7 +137,7 @@ func (h *Handle) insertColStats2KV(tableID int64, colInfo *model.ColumnInfo) err
 		}
 		if value.IsNull() {
 			// If the adding column has default value null, all the existing rows have null value on the newly added column.
-			_, err = exec.Execute(fmt.Sprintf("insert into mysql.stats_histograms (version, table_id, is_index, hist_id, distinct_count, null_count) values (%d, %d, 0, %d, 1, %d)", h.ctx.Txn().StartTS(), tableID, colInfo.ID, count))
+			_, err = exec.Execute(fmt.Sprintf("insert into mysql.stats_histograms (version, table_id, is_index, hist_id, distinct_count, null_count) values (%d, %d, 0, %d, 0, %d)", h.ctx.Txn().StartTS(), tableID, colInfo.ID, count))
 			if err != nil {
 				return errors.Trace(err)
 			}

diff --git a/statistics/ddl_test.go b/statistics/ddl_test.go
@@ -125,6 +125,7 @@ func (s *testStatsCacheSuite) TestDDLHistogram(c *C) {
 	c.Assert(statsTbl.Pseudo, IsFalse)
 	sc := new(variable.StatementContext)
 	c.Assert(statsTbl.ColumnIsInvalid(tableInfo.Columns[2]), IsTrue)
+	c.Check(statsTbl.Columns[tableInfo.Columns[2].ID].NDV, Equals, int64(0))
 
 	testKit.MustExec("alter table t add column c3 int NOT NULL")
 	err = h.HandleDDLEvent(<-h.DDLEventCh())