sql: improved diff tool for any namespace

Previously, diff tool worked only for pg_catalog
This was inadequate because it can be used for information_schema as well
To address this, this patch takes the namespace as parameter to compare a
different database

Release note: None

Fixes cockroachdb#58037

pkg/cmd/generate-pg-catalog/main.go

@@ -34,8 +34,9 @@ import (
 const getServerVersion = `SELECT current_setting('server_version');`
 
 var (
-	postgresAddr = flag.String("addr", "localhost:5432", "Postgres server address")
-	postgresUser = flag.String("user", "postgres", "Postgres user")
+	postgresAddr    = flag.String("addr", "localhost:5432", "Postgres server address")
+	postgresUser    = flag.String("user", "postgres", "Postgres user")
+	postgresCatalog = flag.String("catalog", "pg_catalog", "Catalog or namespace, default: pg_catalog")
 )
 
 func main() {
@@ -62,7 +63,7 @@ func main() {
 }
 
 func describePgCatalog(conn *pgx.Conn) *pgx.Rows {
-	rows, err := conn.Query(sql.GetPGCatalogSQL)
+	rows, err := conn.Query(sql.GetPGCatalogSQL, *postgresCatalog)
 	if err != nil {
 		panic(err)
 	}

pkg/sql/pg_catalog_diff.go

@@ -31,7 +31,7 @@ const GetPGCatalogSQL = `
 	JOIN pg_attribute a ON a.attrelid = c.oid
 	JOIN pg_type t ON t.oid = a.atttypid
 	JOIN pg_namespace n ON n.oid = c.relnamespace
-	WHERE n.nspname = 'pg_catalog'
+	WHERE n.nspname = $1
 	AND a.attnum > 0
 	ORDER BY 1, 2;
 `

pkg/sql/pg_catalog_test.go

@@ -46,13 +46,16 @@ import (
 
 // Test data files
 const (
-	pgCatalogDump = "pg_catalog_tables.json"              // PostgreSQL pg_catalog schema
-	expectedDiffs = "pg_catalog_test_expected_diffs.json" // Contains expected difference between postgres and cockroach
-	testdata      = "testdata"                            // testdata directory
+	pgCatalogDump = "%s_tables.json"              // PostgreSQL pg_catalog schema
+	expectedDiffs = "%s_test_expected_diffs.json" // Contains expected difference between postgres and cockroach
+	testdata      = "testdata"                    // testdata directory
 )
 
 // When running test with -rewrite-diffs test will pass and re-create pg_catalog_test-diffs.json
-var rewriteFlag = flag.Bool("rewrite-diffs", false, "This will re-create the expected diffs file")
+var (
+	rewriteFlag     = flag.Bool("rewrite-diffs", false, "This will re-create the expected diffs file")
+	postgresCatalog = flag.String("catalog", "pg_catalog", "Catalog or namespace, default: pg_catalog")
+)
 
 // summary will keep accountability for any unexpected difference and report it in the log
 type summary struct {
@@ -79,7 +82,7 @@ func (sum *summary) report(t *testing.T) {
 // loadTestData retrieves the pg_catalog from the dumpfile generated from Postgres
 func loadTestData(t testing.TB) PGCatalogTables {
 	var pgCatalogFile PGCatalogFile
-	testdataFile := filepath.Join(testdata, pgCatalogDump)
+	testdataFile := filepath.Join(testdata, fmt.Sprintf(pgCatalogDump, *postgresCatalog))
 	f, err := os.Open(testdataFile)
 	if err != nil {
 		t.Fatal(err)
@@ -105,7 +108,7 @@ func loadCockroachPgCatalog(t testing.TB) PGCatalogTables {
 	s, db, _ := serverutils.StartServer(t, base.TestServerArgs{})
 	defer s.Stopper().Stop(ctx)
 	sqlRunner := sqlutils.MakeSQLRunner(db)
-	rows := sqlRunner.Query(t, GetPGCatalogSQL)
+	rows := sqlRunner.Query(t, GetPGCatalogSQL, *postgresCatalog)
 	defer rows.Close()
 
 	for rows.Next() {
@@ -128,7 +131,7 @@ func loadExpectedDiffs(t *testing.T) (diffs PGCatalogTables) {
 		return
 	}
 
-	diffFile := filepath.Join(testdata, expectedDiffs)
+	diffFile := filepath.Join(testdata, fmt.Sprintf(expectedDiffs, *postgresCatalog))
 	if _, err := os.Stat(diffFile); err != nil {
 		if oserror.IsNotExist(err) {
 			// File does not exists it means diffs are not expected
@@ -217,5 +220,5 @@ func TestPGCatalog(t *testing.T) {
 	}
 
 	sum.report(t)
-	rewriteDiffs(t, diffs, filepath.Join(testdata, expectedDiffs))
+	rewriteDiffs(t, diffs, filepath.Join(testdata, fmt.Sprintf(expectedDiffs, *postgresCatalog)))
 }