importer: generate int data by histogram

cmd/importer/db.go

@@ -54,6 +54,9 @@ func randStringValue(column *column, n int) string {
 }
 
 func randInt64Value(column *column, min int64, max int64) int64 {
+	if column.hist != nil {
+		return column.hist.randInt()
+	}
 	if len(column.set) > 0 {
 		idx := randInt(0, len(column.set)-1)
 		data, err := strconv.ParseInt(column.set[idx], 10, 64)

cmd/importer/main.go

@@ -51,9 +51,25 @@ func main() {
 	defer closeDBs(dbs)
 
 	if len(cfg.StatsCfg.Path) > 0 {
-		table.statsInfo, err = loadStats(table.tblInfo, cfg.StatsCfg.Path)
-		if err != nil {
-			log.Fatal(err)
+		statsInfo, err1 := loadStats(table.tblInfo, cfg.StatsCfg.Path)
+		if err1 != nil {
+			log.Fatal(err1)
+		}
+		for _, idxInfo := range table.tblInfo.Indices {
+			offset := idxInfo.Columns[0].Offset
+			if hist, ok := statsInfo.Indices[idxInfo.ID]; ok && len(hist.Buckets) > 0 {
+				table.columns[offset].hist = &histogram{
+					Histogram: hist.Histogram,
+					index:     hist.Info,
+				}
+			}
+		}
+		for i, colInfo := range table.tblInfo.Columns {
+			if hist, ok := statsInfo.Columns[colInfo.ID]; ok && table.columns[i].hist == nil && len(hist.Buckets) > 0 {
+				table.columns[i].hist = &histogram{
+					Histogram: hist.Histogram,
+				}
+			}
 		}
 	}
 

cmd/importer/parser.go

@@ -24,7 +24,6 @@ import (
 	"github.com/pingcap/tidb/model"
 	"github.com/pingcap/tidb/parser"
 	_ "github.com/pingcap/tidb/plan"
-	stats "github.com/pingcap/tidb/statistics"
 	"github.com/pingcap/tidb/types"
 	"github.com/pingcap/tidb/util/mock"
 	log "github.com/sirupsen/logrus"
@@ -42,6 +41,8 @@ type column struct {
 	set     []string
 
 	table *table
+
+	hist *histogram
 }
 
 func (col *column) String() string {
@@ -128,7 +129,6 @@ type table struct {
 	indices     map[string]*column
 	uniqIndices map[string]*column
 	tblInfo     *model.TableInfo
-	statsInfo   *stats.Table
 }
 
 func (t *table) printColumns() string {

cmd/importer/stats.go

@@ -20,7 +20,10 @@ import (
 	"github.com/juju/errors"
 	"github.com/pingcap/tidb/model"
 	stats "github.com/pingcap/tidb/statistics"
+	"github.com/pingcap/tidb/util/chunk"
+	"github.com/pingcap/tidb/util/codec"
 	"github.com/pingcap/tidb/util/mock"
+	log "github.com/sirupsen/logrus"
 )
 
 func loadStats(tblInfo *model.TableInfo, path string) (*stats.Table, error) {
@@ -36,3 +39,47 @@ func loadStats(tblInfo *model.TableInfo, path string) (*stats.Table, error) {
 	handle := stats.NewHandle(mock.NewContext(), 0)
 	return handle.LoadStatsFromJSON(tblInfo, jsTable)
 }
+
+type histogram struct {
+	stats.Histogram
+
+	index *model.IndexInfo
+}
+
+// When the cnt falls in the middle of bucket, we return the idx of lower bound which is an even number.
+// When the cnt falls in the end of bucket, we return the upper bound which is odd.
+func (h *histogram) getRandomBoundIdx() int {
+	cnt := h.Buckets[len(h.Buckets)-1].Count
+	randCnt := randInt64(0, cnt)
+	for i, bkt := range h.Buckets {
+		if bkt.Count >= randCnt {
+			if bkt.Count-bkt.Repeat > randCnt {
+				return 2 * i
+			}
+			return 2*i + 1
+		}
+	}
+	return 0
+}
+
+func (h *histogram) decodeInt(row *chunk.Row) int64 {
+	if h.index == nil {
+		return row.GetInt64(0)
+	}
+	data := row.GetBytes(0)
+	_, result, err := codec.DecodeInt(data)
+	if err != nil {
+		log.Fatal(err)
+	}
+	return result
+}
+
+func (h *histogram) randInt() int64 {
+	idx := h.getRandomBoundIdx()
+	if idx%2 == 0 {
+		lower := h.Bounds.GetRow(idx).GetInt64(0)
+		upper := h.Bounds.GetRow(idx + 1).GetInt64(0)
+		return randInt64(lower, upper)
+	}
+	return h.Bounds.GetRow(idx).GetInt64(0)
+}