postgres: configurable table/index limits (#1200)

config/go.d/postgres.conf

@@ -62,6 +62,19 @@
 #    Syntax:
 #     dsn: postgres://postgres:[email protected]:5432/postgres
 #
+#  - max_db_tables
+#    Maximum number of tables in the database.
+#    Table metrics will not be collected for databases that have more tables than max_db_tables.
+#    Default is 50. 0 means no limit.
+#    Syntax:
+#     max_db_tables: 50
+#
+#  - max_db_indexes
+#    Maximum number of indexes in the database.
+#    Index metrics will not be collected for databases that have more indexes than max_db_indexes. 0 means no limit.
+#    Default is 250. 0 means no limit.
+#    Syntax:
+#     max_db_indexes: 250
 #
 # [ JOB defaults ]:
 #  No parameters

modules/postgres/do_query_misc.go

@@ -119,10 +119,9 @@ func (p *Postgres) doQueryQueryableDatabases() error {
 			continue
 		}
 
-		// charts: 20 x table, 4 x index.
-		// https://discord.com/channels/847502280503590932/1022693928874549368
-		if tables > 50 || indexes > 250 {
-			p.Warningf("database '%s' has too many user tables(%d)/indexes(%d), skipping it", dbname, tables, indexes)
+		if (p.MaxDBTables != 0 && tables > p.MaxDBTables) || (p.MaxDBIndexes != 0 && indexes > p.MaxDBIndexes) {
+			p.Warningf("database '%s' has too many user tables(%d/%d)/indexes(%d/%d), skipping it",
+				dbname, tables, p.MaxDBTables, indexes, p.MaxDBIndexes)
 			conn.connErrors = connErrMax
 			_ = db.Close()
 			stdlib.UnregisterConnConfig(connStr)

modules/postgres/postgres.go

@@ -29,6 +29,10 @@ func New() *Postgres {
 			DSN:                "postgres://postgres:[email protected]:5432/postgres",
 			XactTimeHistogram:  []float64{.1, .5, 1, 2.5, 5, 10},
 			QueryTimeHistogram: []float64{.1, .5, 1, 2.5, 5, 10},
+			// charts: 20 x table, 4 x index.
+			// https://discord.com/channels/847502280503590932/1022693928874549368
+			MaxDBTables:  50,
+			MaxDBIndexes: 250,
 		},
 		charts:  baseCharts.Copy(),
 		dbConns: make(map[string]*dbConn),
@@ -52,6 +56,8 @@ type Config struct {
 	DBSelector         string       `yaml:"collect_databases_matching"`
 	XactTimeHistogram  []float64    `yaml:"transaction_time_histogram"`
 	QueryTimeHistogram []float64    `yaml:"query_time_histogram"`
+	MaxDBTables        int64        `yaml:"max_db_tables"`
+	MaxDBIndexes       int64        `yaml:"max_db_indexes"`
 }
 
 type (