lib/logstorage: add an ability to return rank from top pipe results

docs/VictoriaLogs/CHANGELOG.md

@@ -19,6 +19,7 @@ according to [these docs](https://docs.victoriametrics.com/victorialogs/quicksta
 * FEATURE: improve performance for queries over large volume of logs with big number of [fields](https://docs.victoriametrics.com/victorialogs/keyconcepts/#data-model) (aka `wide events`).
 * FEATURE: improve performance for [`/select/logsql/field_values` HTTP endpoint](https://docs.victoriametrics.com/victorialogs/querying/#querying-field-values).
 * FEATURE: improve performance for [`field_values` pipe](https://docs.victoriametrics.com/victorialogs/logsql/#field_values-pipe) when it is applied directly to [log filter](https://docs.victoriametrics.com/victorialogs/logsql/#filters).
+* FEATURE: add an ability to return `rank` field from [`top` pipe](https://docs.victoriametrics.com/victorialogs/logsql/#top-pipe). For example, the following query returns `1..5` rank per each returned `ip` with the biggest number of logs over the last 5 minute: `_time:5m | top 5 by (ip) with rank`.
 
 * BUGFIX: [web UI](https://docs.victoriametrics.com/victorialogs/querying/#web-ui): fix various glitches with updating query responses. The issue was introduced in [v0.36.0](https://github.com/VictoriaMetrics/VictoriaMetrics/releases/tag/v0.36.0-victorialogs). See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/7279).
 

docs/VictoriaLogs/LogsQL.md

@@ -2400,6 +2400,18 @@ For example, the following query is equivalent to the previous one:
 _time:5m | fields ip | top
 ```
 
+It is possible to set `rank` field per each returned entry for `top` pipe by adding `with rank`. For example, the following query sets the `rank` field per each returned `ip`:
+
+```logsql
+_time:5m | top 10 by (ip) with rank
+```
+
+The `rank` field can have other name. For example, the following query uses the `position` field name instead of `rank` field name in the output:
+
+```logsql
+_time:5m | top 10 by (ip) with rank as position
+```
+
 See also:
 
 - [`uniq` pipe](#uniq-pipe)

lib/logstorage/pipe_top.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"slices"
 	"sort"
+	"strconv"
 	"strings"
 	"sync"
 	"sync/atomic"
@@ -34,8 +35,11 @@ type pipeTop struct {
 	// limitStr is string representation of the limit.
 	limitStr string
 
-	// if hitsFieldName isn't empty, then the number of hits per each unique value is returned in this field.
+	// the number of hits per each unique value is returned in this field.
 	hitsFieldName string
+
+	// if rankFieldName isn't empty, then the rank per each unique value is returned in this field.
+	rankFieldName string
 }
 
 func (pt *pipeTop) String() string {
@@ -46,6 +50,12 @@ func (pt *pipeTop) String() string {
 	if len(pt.byFields) > 0 {
 		s += " by (" + fieldNamesString(pt.byFields) + ")"
 	}
+	if pt.rankFieldName != "" {
+		s += " with rank"
+		if pt.rankFieldName != "rank" {
+			s += " as " + pt.rankFieldName
+		}
+	}
 	return s
 }
 
@@ -273,8 +283,20 @@ func (ptp *pipeTopProcessor) flush() error {
 		return dst
 	}
 
+	addRankField := func(dst []Field, rank int) []Field {
+		if ptp.pt.rankFieldName == "" {
+			return dst
+		}
+		rankStr := strconv.Itoa(rank + 1)
+		dst = append(dst, Field{
+			Name:  ptp.pt.rankFieldName,
+			Value: rankStr,
+		})
+		return dst
+	}
+
 	if len(byFields) == 0 {
-		for _, e := range entries {
+		for i, e := range entries {
 			if needStop(ptp.stopCh) {
 				return nil
 			}
@@ -300,11 +322,12 @@ func (ptp *pipeTopProcessor) flush() error {
 				})
 			}
 			rowFields = addHitsField(rowFields, e.hits)
+			rowFields = addRankField(rowFields, i)
 			wctx.writeRow(rowFields)
 		}
 	} else if len(byFields) == 1 {
 		fieldName := byFields[0]
-		for _, e := range entries {
+		for i, e := range entries {
 			if needStop(ptp.stopCh) {
 				return nil
 			}
@@ -314,10 +337,11 @@ func (ptp *pipeTopProcessor) flush() error {
 				Value: e.k,
 			})
 			rowFields = addHitsField(rowFields, e.hits)
+			rowFields = addRankField(rowFields, i)
 			wctx.writeRow(rowFields)
 		}
 	} else {
-		for _, e := range entries {
+		for i, e := range entries {
 			if needStop(ptp.stopCh) {
 				return nil
 			}
@@ -339,6 +363,7 @@ func (ptp *pipeTopProcessor) flush() error {
 				fieldIdx++
 			}
 			rowFields = addHitsField(rowFields, e.hits)
+			rowFields = addRankField(rowFields, i)
 			wctx.writeRow(rowFields)
 		}
 	}
@@ -660,5 +685,26 @@ func parsePipeTop(lex *lexer) (*pipeTop, error) {
 		hitsFieldName: hitsFieldName,
 	}
 
+	if !lex.isKeyword("with") {
+		return pt, nil
+	}
+
+	lex.nextToken()
+	if !lex.isKeyword("rank") {
+		return nil, fmt.Errorf("missing 'rank' word after 'with' in [%s]", pt)
+	}
+	lex.nextToken()
+	pt.rankFieldName = "rank"
+	if lex.isKeyword("as") {
+		lex.nextToken()
+		if lex.isKeyword("", "|", ")", "(") {
+			return nil, fmt.Errorf("missing rank name in [%s as]", pt)
+		}
+	}
+	if !lex.isKeyword("", "|", ")") {
+		pt.rankFieldName = lex.token
+		lex.nextToken()
+	}
+
 	return pt, nil
 }

lib/logstorage/pipe_top_test.go

@@ -11,11 +11,15 @@ func TestParsePipeTopSuccess(t *testing.T) {
 	}
 
 	f(`top`)
+	f(`top with rank`)
 	f(`top 5`)
+	f(`top 5 with rank as foo`)
 	f(`top by (x)`)
 	f(`top 5 by (x)`)
 	f(`top by (x, y)`)
 	f(`top 5 by (x, y)`)
+	f(`top by (x) with rank`)
+	f(`top by (x) with rank as foo`)
 }
 
 func TestParsePipeTopFailure(t *testing.T) {
@@ -30,6 +34,8 @@ func TestParsePipeTopFailure(t *testing.T) {
 	f(`top 5foo`)
 	f(`top foo`)
 	f(`top by`)
+	f(`top (x) with`)
+	f(`top (x) with rank as`)
 }
 
 func TestPipeTop(t *testing.T) {
@@ -66,6 +72,36 @@ func TestPipeTop(t *testing.T) {
 		},
 	})
 
+	f("top with rank", [][]Field{
+		{
+			{"a", `2`},
+			{"b", `3`},
+		},
+		{
+			{"a", "2"},
+			{"b", "3"},
+		},
+		{
+			{"a", `2`},
+			{"b", `54`},
+			{"c", "d"},
+		},
+	}, [][]Field{
+		{
+			{"a", "2"},
+			{"b", "3"},
+			{"hits", "2"},
+			{"rank", "1"},
+		},
+		{
+			{"a", `2`},
+			{"b", `54`},
+			{"c", "d"},
+			{"hits", "1"},
+			{"rank", "2"},
+		},
+	})
+
 	f("top 1", [][]Field{
 		{
 			{"a", `2`},
@@ -134,6 +170,33 @@ func TestPipeTop(t *testing.T) {
 		},
 	})
 
+	f("top by (b) with rank as x", [][]Field{
+		{
+			{"a", `2`},
+			{"b", `3`},
+		},
+		{
+			{"a", "2"},
+			{"b", "3"},
+		},
+		{
+			{"a", `2`},
+			{"b", `54`},
+			{"c", "d"},
+		},
+	}, [][]Field{
+		{
+			{"b", "3"},
+			{"hits", "2"},
+			{"x", "1"},
+		},
+		{
+			{"b", "54"},
+			{"hits", "1"},
+			{"x", "2"},
+		},
+	})
+
 	f("top by (hits)", [][]Field{
 		{
 			{"a", `2`},