Add option to avoid collecting distributed index stats for Citus

In some situations, the problems that DISABLE_CITUS_SCHEMA_STATS is
intended to solve are actually only with indexes, not with other
schema stats. By adding an index-specific setting, we can support more
functionality for affected users.

config/config.go

@@ -133,6 +133,7 @@ type ServerConfig struct {
 
 	AlwaysCollectSystemData bool `ini:"always_collect_system_data"`
 	DisableCitusSchemaStats bool `ini:"disable_citus_schema_stats"`
+	DisableCitusIndexStats  bool `ini:"disable_citus_index_stats"`
 
 	// Configures the location where logfiles are - this can either be a directory,
 	// or a file - needs to readable by the regular pganalyze user

config/read.go

@@ -293,6 +293,9 @@ func getDefaultConfig() *ServerConfig {
 	if disableCitusSchemaStats := os.Getenv("DISABLE_CITUS_SCHEMA_STATS"); disableCitusSchemaStats != "" {
 		config.DisableCitusSchemaStats = parseConfigBool(disableCitusSchemaStats)
 	}
+	if disableCitusIndexStats := os.Getenv("DISABLE_CITUS_INDEX_STATS"); disableCitusIndexStats != "" {
+		config.DisableCitusIndexStats = parseConfigBool(disableCitusIndexStats)
+	}
 	if logPgReadFile := os.Getenv("LOG_PG_READ_FILE"); logPgReadFile != "" {
 		config.LogPgReadFile = parseConfigBool(logPgReadFile)
 	}

input/postgres/relation_stats_aux.go

@@ -106,7 +106,7 @@ GROUP BY
 `
 
 func handleIndexStatsAux(ctx context.Context, db *sql.DB, idxStats state.PostgresIndexStatsMap, postgresVersion state.PostgresVersion, server *state.Server) (state.PostgresIndexStatsMap, error) {
-	if postgresVersion.IsCitus && !server.Config.DisableCitusSchemaStats {
+	if postgresVersion.IsCitus && !server.Config.DisableCitusSchemaStats && !server.Config.DisableCitusIndexStats {
 		stmt, err := db.PrepareContext(ctx, QueryMarkerSQL+citusIndexSizeSQL)
 		if err != nil {
 			return idxStats, fmt.Errorf("IndexStatsExt/Prepare: %s", err)