lib/logstorage: do not count dictionary values which have no matching logs in count_uniq stats function

Create blockResultColumn.forEachDictValue* helper functions for visiting matching
dictionary values. These helper functions should prevent from counting dictionary values
without matching logs in the future.

This is a follow-up for 0c0f013a60
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/7152

docs/VictoriaLogs/CHANGELOG.md

@@ -17,6 +17,8 @@ according to [these docs](https://docs.victoriametrics.com/victorialogs/quicksta
 
 * FEATURE: add interactive command-line tool for querying VictoriaLogs - [`vlogscli`](https://docs.victoriametrics.com/victorialogs/querying/vlogscli/).
 
+* BUGFIX: [`count_uniq` stats function](https://docs.victoriametrics.com/victorialogs/logsql/#count_uniq-stats): do not count field values, which aren't matched by the used filters. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/7152).
+
 ## [v0.32.1](https://github.com/VictoriaMetrics/VictoriaMetrics/releases/tag/v0.32.1-victorialogs)
 
 Released at 2024-09-30

lib/logstorage/block_result.go

@@ -1728,6 +1728,60 @@ func (c *blockResultColumn) getValuesEncoded(br *blockResult) []string {
 	return c.valuesEncoded
 }
 
+// forEachDictValue calls f for every value in the column dictionary.
+func (c *blockResultColumn) forEachDictValue(br *blockResult, f func(v string)) {
+	if c.valueType != valueTypeDict {
+		logger.Panicf("BUG: unexpected column valueType=%d; want %d", c.valueType, valueTypeDict)
+	}
+	if uint64(br.rowsLen) == br.bs.bsw.bh.rowsCount {
+		// Fast path - there is no need in reading encoded values
+		for _, v := range c.dictValues {
+			f(v)
+		}
+		return
+	}
+
+	// Slow path - need to read encoded values in order filter not referenced columns.
+	a := encoding.GetUint64s(len(c.dictValues))
+	hits := a.A
+	clear(hits)
+	valuesEncoded := c.getValuesEncoded(br)
+	for _, v := range valuesEncoded {
+		idx := unmarshalUint8(v)
+		hits[idx]++
+	}
+	for i, v := range c.dictValues {
+		if h := hits[i]; h > 0 {
+			f(v)
+		}
+	}
+	encoding.PutUint64s(a)
+}
+
+// forEachDictValueWithHits calls f for every value in the column dictionary.
+//
+// hits is the number of rows with the given value v in the column.
+func (c *blockResultColumn) forEachDictValueWithHits(br *blockResult, f func(v string, hits uint64)) {
+	if c.valueType != valueTypeDict {
+		logger.Panicf("BUG: unexpected column valueType=%d; want %d", c.valueType, valueTypeDict)
+	}
+
+	a := encoding.GetUint64s(len(c.dictValues))
+	hits := a.A
+	clear(hits)
+	valuesEncoded := c.getValuesEncoded(br)
+	for _, v := range valuesEncoded {
+		idx := unmarshalUint8(v)
+		hits[idx]++
+	}
+	for i, v := range c.dictValues {
+		if h := hits[i]; h > 0 {
+			f(v, h)
+		}
+	}
+	encoding.PutUint64s(a)
+}
+
 func (c *blockResultColumn) getFloatValueAtRow(br *blockResult, rowIdx int) (float64, bool) {
 	if c.isConst {
 		v := c.valuesEncoded[0]

lib/logstorage/pipe_top.go

@@ -164,18 +164,7 @@ func (shard *pipeTopProcessorShard) writeBlock(br *blockResult) {
 			return
 		}
 		if c.valueType == valueTypeDict {
-			a := encoding.GetUint64s(len(c.dictValues))
-			hits := a.A
-			clear(hits)
-			valuesEncoded := c.getValuesEncoded(br)
-			for _, v := range valuesEncoded {
-				idx := unmarshalUint8(v)
-				hits[idx]++
-			}
-			for i, v := range c.dictValues {
-				shard.updateState(v, hits[i])
-			}
-			encoding.PutUint64s(a)
+			c.forEachDictValueWithHits(br, shard.updateState)
 			return
 		}
 
@@ -207,10 +196,6 @@ func (shard *pipeTopProcessorShard) writeBlock(br *blockResult) {
 }
 
 func (shard *pipeTopProcessorShard) updateState(v string, hits uint64) {
-	if hits == 0 {
-		return
-	}
-
 	m := shard.getM()
 	pHits, ok := m[v]
 	if !ok {

lib/logstorage/pipe_uniq.go

@@ -166,18 +166,7 @@ func (shard *pipeUniqProcessorShard) writeBlock(br *blockResult) bool {
 			return true
 		}
 		if c.valueType == valueTypeDict {
-			a := encoding.GetUint64s(len(c.dictValues))
-			hits := a.A
-			clear(hits)
-			valuesEncoded := c.getValuesEncoded(br)
-			for _, v := range valuesEncoded {
-				idx := unmarshalUint8(v)
-				hits[idx]++
-			}
-			for i, v := range c.dictValues {
-				shard.updateState(v, hits[i])
-			}
-			encoding.PutUint64s(a)
+			c.forEachDictValueWithHits(br, shard.updateState)
 			return true
 		}
 
@@ -224,10 +213,6 @@ func (shard *pipeUniqProcessorShard) writeBlock(br *blockResult) bool {
 }
 
 func (shard *pipeUniqProcessorShard) updateState(v string, hits uint64) {
-	if hits == 0 {
-		return
-	}
-
 	m := shard.getM()
 	pHits, ok := m[v]
 	if !ok {

lib/logstorage/stats_count_uniq.go

@@ -42,6 +42,7 @@ type statsCountUniqProcessor struct {
 
 	columnValues [][]string
 	keyBuf       []byte
+	tmpNum       int
 }
 
 func (sup *statsCountUniqProcessor) updateStatsForAllRows(br *blockResult) int {
@@ -133,18 +134,19 @@ func (sup *statsCountUniqProcessor) updateStatsForAllRows(br *blockResult) int {
 			return stateSizeIncrease
 		}
 		if c.valueType == valueTypeDict {
-			// count unique non-zero c.dictValues
-			keyBuf := sup.keyBuf[:0]
-			for _, v := range c.dictValues {
+			// count unique non-zero dict values for the selected logs
+			sup.tmpNum = 0
+			c.forEachDictValue(br, func(v string) {
 				if v == "" {
 					// Do not count empty values
-					continue
+					return
 				}
-				keyBuf = append(keyBuf[:0], 0)
+				keyBuf := append(sup.keyBuf[:0], 0)
 				keyBuf = append(keyBuf, v...)
-				stateSizeIncrease += sup.updateState(keyBuf)
-			}
+				sup.tmpNum += sup.updateState(keyBuf)
 				sup.keyBuf = keyBuf
+			})
+			stateSizeIncrease += sup.tmpNum
 			return stateSizeIncrease
 		}