Export query itself together with queryId in stat_statement metrics (prometheus-community#940)

* Export query itself together with queryId in stat_statement metrics * The feature must be enabled via flag. * Limit length of selected query. The query is not added to every metrics, but instead of new metric stat_statement_query_id is introduced that contains mapping between queryId and query. Fixes: prometheus-community#813 --------- Signed-off-by: Jakub Štiller <stiller@2n.cz> Signed-off-by: Jakub Štiller <jakstiller@atlas.cz>

Author: Delorien84

README.md

@@ -150,6 +150,12 @@ This will build the docker image as `prometheuscommunity/postgres_exporter:${bra
 * `[no-]collector.stat_statements`
  Enable the `stat_statements` collector (default: disabled).
 
+* `[no-]collector.stat_statements.include_query`
+ Enable selecting statement query together with queryId. (default: disabled)
+
+* `--collector.stat_statements.query_length`
+ Maximum length of the statement text. Default is 120.
+
 * `[no-]collector.stat_user_tables`
  Enable the `stat_user_tables` collector (default: enabled).
 

collector/collector.go

@@ -37,8 +37,9 @@ const (
 // Namespace for all metrics.
 namespace = "pg"
 
-defaultEnabled = true
-defaultDisabled = false
+collectorFlagPrefix = "collector."
+defaultEnabled = true
+defaultDisabled = false
 )
 
 var (
@@ -74,7 +75,7 @@ func registerCollector(name string, isDefaultEnabled bool, createFunc func(colle
 }
 
 // Create flag for this collector
-flagName := fmt.Sprintf("collector.%s", name)
+flagName := collectorFlagPrefix + name
 flagHelp := fmt.Sprintf("Enable the %s collector (default: %s).", name, helpDefaultState)
 defaultValue := fmt.Sprintf("%v", isDefaultEnabled)
 

collector/pg_stat_statements.go

@@ -16,27 +16,51 @@ package collector
 import (
 "context"
 "database/sql"
+"fmt"
 "log/slog"
 
+"github.com/alecthomas/kingpin/v2"
 "github.com/blang/semver/v4"
 "github.com/prometheus/client_golang/prometheus"
 )
 
 const statStatementsSubsystem = "stat_statements"
 
+var (
+includeQueryFlag *bool = nil
+statementLengthFlag *uint = nil
+)
+
 func init() {
 // WARNING:
 // Disabled by default because this set of metrics can be quite expensive on a busy server
 // Every unique query will cause a new timeseries to be created
 registerCollector(statStatementsSubsystem, defaultDisabled, NewPGStatStatementsCollector)
+
+includeQueryFlag = kingpin.Flag(
+fmt.Sprint(collectorFlagPrefix, statStatementsSubsystem, ".include_query"),
+"Enable selecting statement query together with queryId. (default: disabled)").
+Default(fmt.Sprintf("%v", defaultDisabled)).
+Bool()
+statementLengthFlag = kingpin.Flag(
+fmt.Sprint(collectorFlagPrefix, statStatementsSubsystem, ".query_length"),
+"Maximum length of the statement text.").
+Default("120").
+Uint()
 }
 
 type PGStatStatementsCollector struct {
-log *slog.Logger
+log *slog.Logger
+includeQueryStatement bool
+statementLength uint
 }
 
 func NewPGStatStatementsCollector(config collectorConfig) (Collector, error) {
-return &PGStatStatementsCollector{log: config.logger}, nil
+return &PGStatStatementsCollector{
+log: config.logger,
+includeQueryStatement: *includeQueryFlag,
+statementLength: *statementLengthFlag,
+}, nil
 }
 
 var (
@@ -71,10 +95,22 @@ var (
 prometheus.Labels{},
 )
 
+statStatementsQuery = prometheus.NewDesc(
+prometheus.BuildFQName(namespace, statStatementsSubsystem, "query_id"),
+"SQL Query to queryid mapping",
+[]string{"queryid", "query"},
+prometheus.Labels{},
+)
+)
+
+const (
+pgStatStatementQuerySelect = `LEFT(pg_stat_statements.query, %d) as query,`
+
 pgStatStatementsQuery = `SELECT
 pg_get_userbyid(userid) as user,
 pg_database.datname,
 pg_stat_statements.queryid,
+%s
 pg_stat_statements.calls as calls_total,
 pg_stat_statements.total_time / 1000.0 as seconds_total,
 pg_stat_statements.rows as rows_total,
@@ -96,6 +132,7 @@ var (
 pg_get_userbyid(userid) as user,
 pg_database.datname,
 pg_stat_statements.queryid,
+%s
 pg_stat_statements.calls as calls_total,
 pg_stat_statements.total_exec_time / 1000.0 as seconds_total,
 pg_stat_statements.rows as rows_total,
@@ -117,6 +154,7 @@ var (
 pg_get_userbyid(userid) as user,
 pg_database.datname,
 pg_stat_statements.queryid,
+%s
 pg_stat_statements.calls as calls_total,
 pg_stat_statements.total_exec_time / 1000.0 as seconds_total,
 pg_stat_statements.rows as rows_total,
@@ -135,30 +173,42 @@ var (
 LIMIT 100;`
 )
 
-func (PGStatStatementsCollector) Update(ctx context.Context, instance *instance, ch chan<- prometheus.Metric) error {
-var query string
+func (c PGStatStatementsCollector) Update(ctx context.Context, instance *instance, ch chan<- prometheus.Metric) error {
+var queryTemplate string
 switch {
 case instance.version.GE(semver.MustParse("17.0.0")):
-query = pgStatStatementsQuery_PG17
+queryTemplate = pgStatStatementsQuery_PG17
 case instance.version.GE(semver.MustParse("13.0.0")):
-query = pgStatStatementsNewQuery
+queryTemplate = pgStatStatementsNewQuery
 default:
-query = pgStatStatementsQuery
+queryTemplate = pgStatStatementsQuery
 }
+var querySelect = ""
+if c.includeQueryStatement {
+querySelect = fmt.Sprintf(pgStatStatementQuerySelect, c.statementLength)
+}
+query := fmt.Sprintf(queryTemplate, querySelect)
 
 db := instance.getDB()
 rows, err := db.QueryContext(ctx, query)
 
+var presentQueryIds = make(map[string]struct{})
+
 if err != nil {
 return err
 }
 defer rows.Close()
 for rows.Next() {
-var user, datname, queryid sql.NullString
+var user, datname, queryid, statement sql.NullString
 var callsTotal, rowsTotal sql.NullInt64
 var secondsTotal, blockReadSecondsTotal, blockWriteSecondsTotal sql.NullFloat64
-
-if err := rows.Scan(&user, &datname, &queryid, &callsTotal, &secondsTotal, &rowsTotal, &blockReadSecondsTotal, &blockWriteSecondsTotal); err != nil {
+var columns []any
+if c.includeQueryStatement {
+columns = []any{&user, &datname, &queryid, &statement, &callsTotal, &secondsTotal, &rowsTotal, &blockReadSecondsTotal, &blockWriteSecondsTotal}
+} else {
+columns = []any{&user, &datname, &queryid, &callsTotal, &secondsTotal, &rowsTotal, &blockReadSecondsTotal, &blockWriteSecondsTotal}
+}
+if err := rows.Scan(columns...); err != nil {
 return err
 }
 
@@ -229,6 +279,25 @@ func (PGStatStatementsCollector) Update(ctx context.Context, instance *instance,
 blockWriteSecondsTotalMetric,
 userLabel, datnameLabel, queryidLabel,
 )
+
+if c.includeQueryStatement {
+_, ok := presentQueryIds[queryidLabel]
+if !ok {
+presentQueryIds[queryidLabel] = struct{}{}
+
+queryLabel := "unknown"
+if statement.Valid {
+queryLabel = statement.String
+}
+
+ch <- prometheus.MustNewConstMetric(
+statStatementsQuery,
+prometheus.CounterValue,
+1,
+queryidLabel, queryLabel,
+)
+}
+}
 }
 if err := rows.Err(); err != nil {
 return err