add pg_stat_statements by default to NodeSet

Author: skudasov

book/src/framework/observability/postgresql.md

@@ -9,3 +9,10 @@ We run exporter for the first 5 nodes, that should be enough to debug performanc
 ## Data sources and raw queries
 
 You can use `PostgreSQL X` datasources, first 5 nodes to select things for your [dashboards](http://localhost:3000/explore?panes=%7B%22qrr%22:%7B%22datasource%22:%22P4DD770FAD7295D26%22,%22queries%22:%5B%7B%22refId%22:%22A%22,%22datasource%22:%7B%22type%22:%22postgres%22,%22uid%22:%22P4DD770FAD7295D26%22%7D,%22format%22:%22table%22,%22rawSql%22:%22select%20%2A%20from%20sessions;%22,%22editorMode%22:%22code%22,%22sql%22:%7B%22columns%22:%5B%7B%22type%22:%22function%22,%22parameters%22:%5B%5D%7D%5D,%22groupBy%22:%5B%7B%22type%22:%22groupBy%22,%22property%22:%7B%22type%22:%22string%22%7D%7D%5D,%22limit%22:50%7D,%22rawQuery%22:true%7D%5D,%22range%22:%7B%22from%22:%22now-6h%22,%22to%22:%22now%22%7D%7D%7D&schemaVersion=1&orgId=1) or debug.
+
+## Slow queries debug
+
+Use `pg_stat_statements` extension, it is enabled for all databases in `NodeSet`
+```
+select * from pg_stat_statements;
+```

framework/components/postgres/postgres.go

@@ -55,7 +55,11 @@ func NewPostgreSQL(in *Input) (*Output, error) {
 
 	var sqlCommands []string
 	for i := 0; i <= in.Databases; i++ {
-		sqlCommands = append(sqlCommands, fmt.Sprintf("CREATE DATABASE db_%d;", i))
+		sqlCommands = append(sqlCommands,
+			fmt.Sprintf("CREATE DATABASE db_%d;", i),
+			fmt.Sprintf("\\c db_%d", i),
+			"CREATE EXTENSION pg_stat_statements;",
+		)
 	}
 	if in.JDDatabase {
 		sqlCommands = append(sqlCommands, "CREATE DATABASE jd;")
@@ -89,7 +93,10 @@ func NewPostgreSQL(in *Input) (*Output, error) {
 			"POSTGRES_DB":       Database,
 		},
 		Cmd: []string{
-			"postgres", "-c", fmt.Sprintf("port=%s", Port),
+			"postgres", "-c",
+			fmt.Sprintf("port=%s", Port),
+			"-c", "shared_preload_libraries=pg_stat_statements",
+			"-c", "pg_stat_statements.track=all",
 		},
 		Files: []testcontainers.ContainerFile{
 			{