Add perf_schema quantile columns to collector

This change appends the 3 quantile columns exposed in the
events_statements_summary_by_digest table to the
perf_schema_events_statements collector so that they are available
as metrics

Signed-off-by: Matt Nolf <matt.nolf@grafana.com>

.my.cnf

@@ -0,0 +1,9 @@
+[client]
+host=localhost
+port=3306
+socket=/var/run/mysqld/mysqld.sock
+user=foo
+password=bar
+[client.server1]
+user = bar
+password = bar123

collector/perf_schema_events_statements.go

@@ -42,7 +42,10 @@ const perfEventsStatementsQuery = `
 	    SUM_CREATED_TMP_TABLES,
 	    SUM_SORT_MERGE_PASSES,
 	    SUM_SORT_ROWS,
-	    SUM_NO_INDEX_USED
+	    SUM_NO_INDEX_USED,
+	    QUANTILE_95,
+	    QUANTILE_99,
+	    QUANTILE_999
 	  FROM (
 	    SELECT *
 	    FROM performance_schema.events_statements_summary_by_digest
@@ -67,7 +70,10 @@ const perfEventsStatementsQuery = `
 	    Q.SUM_CREATED_TMP_TABLES,
 	    Q.SUM_SORT_MERGE_PASSES,
 	    Q.SUM_SORT_ROWS,
-	    Q.SUM_NO_INDEX_USED
+	    Q.SUM_NO_INDEX_USED,
+	    Q.QUANTILE_95,
+	    Q.QUANTILE_99,
+	    Q.QUANTILE_999
 	  ORDER BY SUM_TIMER_WAIT DESC
 	  LIMIT %d
 	`
@@ -160,6 +166,21 @@ var (
 		"The total number of statements that used full table scans by digest.",
 		[]string{"schema", "digest", "digest_text"}, nil,
 	)
+	performanceSchemaEventsStatementsQuantile95 = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, performanceSchema, "events_statements_quantile_95"),
+		"The 95th percentile of the statement latency, in picoseconds.",
+		[]string{"schema", "digest", "digest_text"}, nil,
+	)
+	performanceSchemaEventsStatementsQuantile99 = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, performanceSchema, "events_statements_quantile_99"),
+		"The 99th percentile of the statement latency, in picoseconds.",
+		[]string{"schema", "digest", "digest_text"}, nil,
+	)
+	performanceSchemaEventsStatementsQuantile999 = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, performanceSchema, "events_statements_quantile_999"),
+		"The 99.9th percentile of the statement latency, in picoseconds.",
+		[]string{"schema", "digest", "digest_text"}, nil,
+	)
 )
 
 // ScrapePerfEventsStatements collects from `performance_schema.events_statements_summary_by_digest`.
@@ -204,10 +225,11 @@ func (ScrapePerfEventsStatements) Scrape(ctx context.Context, instance *instance
 		tmpTables, tmpDiskTables             uint64
 		sortMergePasses, sortRows            uint64
 		noIndexUsed                          uint64
+		quantile95, quantile99, quantile999  uint64
 	)
 	for perfSchemaEventsStatementsRows.Next() {
 		if err := perfSchemaEventsStatementsRows.Scan(
-			&schemaName, &digest, &digestText, &count, &queryTime, &lockTime, &cpuTime, &errors, &warnings, &rowsAffected, &rowsSent, &rowsExamined, &tmpDiskTables, &tmpTables, &sortMergePasses, &sortRows, &noIndexUsed,
+			&schemaName, &digest, &digestText, &count, &queryTime, &lockTime, &cpuTime, &errors, &warnings, &rowsAffected, &rowsSent, &rowsExamined, &tmpDiskTables, &tmpTables, &sortMergePasses, &sortRows, &noIndexUsed, &quantile95, &quantile99, &quantile999,
 		); err != nil {
 			return err
 		}
@@ -267,6 +289,18 @@ func (ScrapePerfEventsStatements) Scrape(ctx context.Context, instance *instance
 			performanceSchemaEventsStatementsNoIndexUsedDesc, prometheus.CounterValue, float64(noIndexUsed),
 			schemaName, digest, digestText,
 		)
+		ch <- prometheus.MustNewConstMetric(
+			performanceSchemaEventsStatementsQuantile95, prometheus.CounterValue, float64(quantile95),
+			schemaName, digest, digestText,
+		)
+		ch <- prometheus.MustNewConstMetric(
+			performanceSchemaEventsStatementsQuantile99, prometheus.CounterValue, float64(quantile99),
+			schemaName, digest, digestText,
+		)
+		ch <- prometheus.MustNewConstMetric(
+			performanceSchemaEventsStatementsQuantile999, prometheus.CounterValue, float64(quantile999),
+			schemaName, digest, digestText,
+		)
 	}
 	return nil
 }