vmctl: fixed import duplicate data when query result contains multiple series (#7330)

### Describe Your Changes

Fix https://github.com/VictoriaMetrics/VictoriaMetrics/issues/7301

When querying with condition like `WHERE a=1` (looking for series A),
InfluxDB can return data with the tag `a=1` (series A) and data with the
tag `a=1,b=1` (series B).

However, series B is will be queried later and it's data should not be
combined into series A's data.

This PR filter those series that are not identical to the original query
condition.

For table `example`:
```
// time                           host    region  value
// ----                           ----    ------  -----
// 2024-10-25T02:12:13.469720983Z serverA us_west 0.64
// 2024-10-25T02:12:21.832755213Z serverA us_west 0.75
// 2024-10-25T02:12:32.351876479Z serverA         0.88
// 2024-10-25T02:12:37.766320484Z serverA         0.95
```

The query for series A (`example_value{host="serverA"}`) and result will
be:
```SQL
SELECT * FROM example WHERE host = "serverA"
```
```json
{
	"results": [{
		"statement_id": 0,
		"series": [{
			"name": "cpu",
			"columns": ["time", "host", "region", "value"],
			"values": [
				["2024-10-25T02:12:13.469720983Z", "serverA", "us_west", 0.64],
				["2024-10-25T02:12:21.832755213Z", "serverA", "us_west", 0.75],
				["2024-10-25T02:12:32.351876479Z", "serverA", null, 0.88],
				["2024-10-25T02:12:37.766320484Z", "serverA", null, 0.95]
			]
		}]
	}]
}
```

We need to abandon `values[0]` and `values[1]` because the value of
**unwanted** column `region` is not null.

As for series B (`example_value{host="serverA", region="us_west"}`), no
change needed since the query filter out unwanted rows already.

### Note
This is a draft PR for verifying the fix.

### Checklist

The following checks are **mandatory**:

- [x] My change adheres [VictoriaMetrics contributing
guidelines](https://docs.victoriametrics.com/contributing/).

---------

Signed-off-by: hagen1778 <roman@victoriametrics.com>
Co-authored-by: hagen1778 <roman@victoriametrics.com>
(cherry picked from commit f16a58f14c)

app/vmctl/influx/influx.go

@@ -51,30 +51,31 @@ type Series struct {
 	Measurement string
 	Field       string
 	LabelPairs  []LabelPair
+
+	// EmptyTags contains tags in measurement whose value must be empty.
+	EmptyTags []string
 }
 
 var valueEscaper = strings.NewReplacer(`\`, `\\`, `'`, `\'`)
 
 func (s Series) fetchQuery(timeFilter string) string {
-	f := &strings.Builder{}
-	fmt.Fprintf(f, "select %q from %q", s.Field, s.Measurement)
-	if len(s.LabelPairs) > 0 || len(timeFilter) > 0 {
-		f.WriteString(" where")
+	conditions := make([]string, 0, len(s.LabelPairs)+len(s.EmptyTags))
+	for _, pair := range s.LabelPairs {
+		conditions = append(conditions, fmt.Sprintf("%q::tag='%s'", pair.Name, valueEscaper.Replace(pair.Value)))
 	}
-	for i, pair := range s.LabelPairs {
-		pairV := valueEscaper.Replace(pair.Value)
-		fmt.Fprintf(f, " %q::tag='%s'", pair.Name, pairV)
-		if i != len(s.LabelPairs)-1 {
-			f.WriteString(" and")
-		}
+	for _, label := range s.EmptyTags {
+		conditions = append(conditions, fmt.Sprintf("%q::tag=''", label))
 	}
 	if len(timeFilter) > 0 {
-		if len(s.LabelPairs) > 0 {
-			f.WriteString(" and")
-		}
-		fmt.Fprintf(f, " %s", timeFilter)
+		conditions = append(conditions, timeFilter)
 	}
-	return f.String()
+
+	q := fmt.Sprintf("select %q from %q", s.Field, s.Measurement)
+	if len(conditions) > 0 {
+		q += fmt.Sprintf(" where %s", strings.Join(conditions, " and "))
+	}
+
+	return q
 }
 
 // LabelPair is the key-value record
@@ -118,7 +119,7 @@ func NewClient(cfg Config) (*Client, error) {
 }
 
 // Database returns database name
-func (c Client) Database() string {
+func (c *Client) Database() string {
 	return c.database
 }
 
@@ -140,7 +141,7 @@ func timeFilter(start, end string) string {
 }
 
 // Explore checks the existing data schema in influx
-// by checking available fields and series,
+// by checking available (non-empty) tags, fields and measurements
 // which unique combination represents all possible
 // time series existing in database.
 // The explore required to reduce the load on influx
@@ -150,6 +151,8 @@ func timeFilter(start, end string) string {
 // May contain non-existing time series.
 func (c *Client) Explore() ([]*Series, error) {
 	log.Printf("Exploring scheme for database %q", c.database)
+
+	// {"measurement1": ["value1", "value2"]}
 	mFields, err := c.fieldsByMeasurement()
 	if err != nil {
 		return nil, fmt.Errorf("failed to get field keys: %s", err)
@@ -159,6 +162,12 @@ func (c *Client) Explore() ([]*Series, error) {
 		return nil, fmt.Errorf("found no numeric fields for import in database %q", c.database)
 	}
 
+	// {"measurement1": {"tag1", "tag2"}}
+	measurementTags, err := c.getMeasurementTags()
+	if err != nil {
+		return nil, fmt.Errorf("failed to get tags of measurements: %s", err)
+	}
+
 	series, err := c.getSeries()
 	if err != nil {
 		return nil, fmt.Errorf("failed to get series: %s", err)
@@ -171,11 +180,17 @@ func (c *Client) Explore() ([]*Series, error) {
 			log.Printf("skip measurement %q since it has no fields", s.Measurement)
 			continue
 		}
+		tags, ok := measurementTags[s.Measurement]
+		if !ok {
+			return nil, fmt.Errorf("failed to find tags of measurement %s", s.Measurement)
+		}
+		emptyTags := getEmptyTags(tags, s.LabelPairs)
 		for _, field := range fields {
 			is := &Series{
 				Measurement: s.Measurement,
 				Field:       field,
 				LabelPairs:  s.LabelPairs,
+				EmptyTags:   emptyTags,
 			}
 			iSeries = append(iSeries, is)
 		}
@@ -183,6 +198,22 @@ func (c *Client) Explore() ([]*Series, error) {
 	return iSeries, nil
 }
 
+// getEmptyTags returns tags of a measurement that are missing in a specific series.
+// Tags represent all tags of a measurement. LabelPairs represent tags of a specific series.
+func getEmptyTags(tags map[string]struct{}, LabelPairs []LabelPair) []string {
+	labelMap := make(map[string]struct{})
+	for _, pair := range LabelPairs {
+		labelMap[pair.Name] = struct{}{}
+	}
+	result := make([]string, 0, len(labelMap)-len(LabelPairs))
+	for tag := range tags {
+		if _, ok := labelMap[tag]; !ok {
+			result = append(result, tag)
+		}
+	}
+	return result
+}
+
 // ChunkedResponse is a wrapper over influx.ChunkedResponse.
 // Used for better memory usage control while iterating
 // over huge time series.
@@ -357,6 +388,57 @@ func (c *Client) getSeries() ([]*Series, error) {
 	return result, nil
 }
 
+// getMeasurementTags get the tags for each measurement.
+// tags are placed in a map without values (similar to a set) for quick lookups:
+// {"measurement1": {"tag1", "tag2"}, "measurement2": {"tag3", "tag4"}}
+func (c *Client) getMeasurementTags() (map[string]map[string]struct{}, error) {
+	com := "show tag keys"
+	q := influx.Query{
+		Command:         com,
+		Database:        c.database,
+		RetentionPolicy: c.retention,
+		Chunked:         true,
+		ChunkSize:       c.chunkSize,
+	}
+
+	log.Printf("fetching tag keys: %s", stringify(q))
+	cr, err := c.QueryAsChunk(q)
+	if err != nil {
+		return nil, fmt.Errorf("error while executing query %q: %s", q.Command, err)
+	}
+
+	const tagKey = "tagKey"
+	var tagsCount int
+	result := make(map[string]map[string]struct{})
+	for {
+		resp, err := cr.NextResponse()
+		if err != nil {
+			if err == io.EOF {
+				break
+			}
+			return nil, err
+		}
+		if resp.Error() != nil {
+			return nil, fmt.Errorf("response error for query %q: %s", q.Command, resp.Error())
+		}
+		qValues, err := parseResult(resp.Results[0])
+		if err != nil {
+			return nil, err
+		}
+		for _, qv := range qValues {
+			if result[qv.name] == nil {
+				result[qv.name] = make(map[string]struct{}, len(qv.values[tagKey]))
+			}
+			for _, tk := range qv.values[tagKey] {
+				result[qv.name][tk.(string)] = struct{}{}
+				tagsCount++
+			}
+		}
+	}
+	log.Printf("found %d tag(s) for %d measurements", tagsCount, len(result))
+	return result, nil
+}
+
 func (c *Client) do(q influx.Query) ([]queryValues, error) {
 	res, err := c.Query(q)
 	if err != nil {

app/vmctl/influx/influx_test.go

@@ -73,6 +73,12 @@ func TestFetchQuery(t *testing.T) {
 		Measurement: "cpu",
 		Field:       "value",
 	}, "", `select "value" from "cpu"`)
+
+	f(&Series{
+		Measurement: "cpu",
+		Field:       "value1",
+		EmptyTags:   []string{"e1", "e2", "e3"},
+	}, "", `select "value1" from "cpu" where "e1"::tag='' and "e2"::tag='' and "e3"::tag=''`)
 }
 
 func TestTimeFilter(t *testing.T) {

docs/changelog/CHANGELOG.md

@@ -18,6 +18,8 @@ See also [LTS releases](https://docs.victoriametrics.com/lts-releases/).
 
 ## tip
 
+* BUGFIX: [vmctl](https://docs.victoriametrics.com/vmctl/): drop rows that do not belong to the current series during import. The dropped rows should belong to another series whose tags are a superset of the current series. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/7301) and [this pull request](https://github.com/VictoriaMetrics/VictoriaMetrics/pull/7330). Thanks to @dpedu for reporting and cooperating with the test.
+
 ## [v1.106.0](https://github.com/VictoriaMetrics/VictoriaMetrics/releases/tag/v1.106.0)
 
 Released at 2024-11-04