Improve style of pg_upgrade task callback functions.

I wanted to avoid adjusting this code too much when converting
these tasks to use the new parallelization framework (see commit
40e2e5e), which is why this is being done as a follow-up commit.
These stylistic adjustments result in fewer lines of code and fewer
levels of indentation in some places.

While at it, add names to the UpgradeTaskSlotState enum and the
UpgradeTaskSlot struct.  I'm not aware of any established project
policy in this area, but let's at least be consistent within the
same file.

Reviewed-by: Daniel Gustafsson
Discussion: https://postgr.es/m/ZunW7XHLd2uTts4f%40nathan

Author: nathan-bossart

src/bin/pg_upgrade/check.c

@@ -320,7 +320,7 @@ static DataTypesUsageChecks data_types_usage_checks[] =
 struct data_type_check_state
 {
 	DataTypesUsageChecks *check;	/* the check for this step */
-	bool	   *result;			/* true if check failed for any database */
+	bool		result;			/* true if check failed for any database */
 	PQExpBuffer *report;		/* buffer for report on failed checks */
 };
 
@@ -390,69 +390,54 @@ process_data_type_check(DbInfo *dbinfo, PGresult *res, void *arg)
 {
 	struct data_type_check_state *state = (struct data_type_check_state *) arg;
 	int			ntups = PQntuples(res);
+	char		output_path[MAXPGPATH];
+	int			i_nspname = PQfnumber(res, "nspname");
+	int			i_relname = PQfnumber(res, "relname");
+	int			i_attname = PQfnumber(res, "attname");
+	FILE	   *script = NULL;
 
 	AssertVariableIsOfType(&process_data_type_check, UpgradeTaskProcessCB);
 
-	if (ntups)
-	{
-		char		output_path[MAXPGPATH];
-		int			i_nspname;
-		int			i_relname;
-		int			i_attname;
-		FILE	   *script = NULL;
-		bool		db_used = false;
+	if (ntups == 0)
+		return;
 
-		snprintf(output_path, sizeof(output_path), "%s/%s",
-				 log_opts.basedir,
-				 state->check->report_filename);
+	snprintf(output_path, sizeof(output_path), "%s/%s",
+			 log_opts.basedir,
+			 state->check->report_filename);
 
-		/*
-		 * Make sure we have a buffer to save reports to now that we found a
-		 * first failing check.
-		 */
-		if (*state->report == NULL)
-			*state->report = createPQExpBuffer();
+	/*
+	 * Make sure we have a buffer to save reports to now that we found a first
+	 * failing check.
+	 */
+	if (*state->report == NULL)
+		*state->report = createPQExpBuffer();
 
-		/*
-		 * If this is the first time we see an error for the check in question
-		 * then print a status message of the failure.
-		 */
-		if (!(*state->result))
-		{
-			pg_log(PG_REPORT, "failed check: %s", _(state->check->status));
-			appendPQExpBuffer(*state->report, "\n%s\n%s    %s\n",
-							  _(state->check->report_text),
-							  _("A list of the problem columns is in the file:"),
-							  output_path);
-		}
-		*state->result = true;
+	/*
+	 * If this is the first time we see an error for the check in question
+	 * then print a status message of the failure.
+	 */
+	if (!state->result)
+	{
+		pg_log(PG_REPORT, "failed check: %s", _(state->check->status));
+		appendPQExpBuffer(*state->report, "\n%s\n%s    %s\n",
+						  _(state->check->report_text),
+						  _("A list of the problem columns is in the file:"),
+						  output_path);
+	}
+	state->result = true;
 
-		i_nspname = PQfnumber(res, "nspname");
-		i_relname = PQfnumber(res, "relname");
-		i_attname = PQfnumber(res, "attname");
+	if ((script = fopen_priv(output_path, "a")) == NULL)
+		pg_fatal("could not open file \"%s\": %m", output_path);
 
-		for (int rowno = 0; rowno < ntups; rowno++)
-		{
-			if (script == NULL && (script = fopen_priv(output_path, "a")) == NULL)
-				pg_fatal("could not open file \"%s\": %m", output_path);
+	fprintf(script, "In database: %s\n", dbinfo->db_name);
 
-			if (!db_used)
-			{
-				fprintf(script, "In database: %s\n", dbinfo->db_name);
-				db_used = true;
-			}
-			fprintf(script, "  %s.%s.%s\n",
-					PQgetvalue(res, rowno, i_nspname),
-					PQgetvalue(res, rowno, i_relname),
-					PQgetvalue(res, rowno, i_attname));
-		}
+	for (int rowno = 0; rowno < ntups; rowno++)
+		fprintf(script, "  %s.%s.%s\n",
+				PQgetvalue(res, rowno, i_nspname),
+				PQgetvalue(res, rowno, i_relname),
+				PQgetvalue(res, rowno, i_attname));
 
-		if (script)
-		{
-			fclose(script);
-			script = NULL;
-		}
-	}
+	fclose(script);
 }
 
 /*
@@ -477,7 +462,6 @@ process_data_type_check(DbInfo *dbinfo, PGresult *res, void *arg)
 static void
 check_for_data_types_usage(ClusterInfo *cluster)
 {
-	bool	   *results;
 	PQExpBuffer report = NULL;
 	DataTypesUsageChecks *tmp = data_types_usage_checks;
 	int			n_data_types_usage_checks = 0;
@@ -494,8 +478,7 @@ check_for_data_types_usage(ClusterInfo *cluster)
 		tmp++;
 	}
 
-	/* Prepare an array to store the results of checks in */
-	results = pg_malloc0(sizeof(bool) * n_data_types_usage_checks);
+	/* Allocate memory for queries and for task states */
 	queries = pg_malloc0(sizeof(char *) * n_data_types_usage_checks);
 	states = pg_malloc0(sizeof(struct data_type_check_state) * n_data_types_usage_checks);
 
@@ -525,7 +508,6 @@ check_for_data_types_usage(ClusterInfo *cluster)
 		queries[i] = data_type_check_query(i);
 
 		states[i].check = check;
-		states[i].result = &results[i];
 		states[i].report = &report;
 
 		upgrade_task_add_step(task, queries[i], process_data_type_check,
@@ -545,7 +527,6 @@ check_for_data_types_usage(ClusterInfo *cluster)
 		destroyPQExpBuffer(report);
 	}
 
-	pg_free(results);
 	for (int i = 0; i < n_data_types_usage_checks; i++)
 	{
 		if (queries[i])
@@ -1234,7 +1215,6 @@ check_for_prepared_transactions(ClusterInfo *cluster)
 static void
 process_isn_and_int8_passing_mismatch(DbInfo *dbinfo, PGresult *res, void *arg)
 {
-	bool		db_used = false;
 	int			ntups = PQntuples(res);
 	int			i_nspname = PQfnumber(res, "nspname");
 	int			i_proname = PQfnumber(res, "proname");
@@ -1243,20 +1223,19 @@ process_isn_and_int8_passing_mismatch(DbInfo *dbinfo, PGresult *res, void *arg)
 	AssertVariableIsOfType(&process_isn_and_int8_passing_mismatch,
 						   UpgradeTaskProcessCB);
 
+	if (ntups == 0)
+		return;
+
+	if (report->file == NULL &&
+		(report->file = fopen_priv(report->path, "w")) == NULL)
+		pg_fatal("could not open file \"%s\": %m", report->path);
+
+	fprintf(report->file, "In database: %s\n", dbinfo->db_name);
+
 	for (int rowno = 0; rowno < ntups; rowno++)
-	{
-		if (report->file == NULL &&
-			(report->file = fopen_priv(report->path, "w")) == NULL)
-			pg_fatal("could not open file \"%s\": %m", report->path);
-		if (!db_used)
-		{
-			fprintf(report->file, "In database: %s\n", dbinfo->db_name);
-			db_used = true;
-		}
 		fprintf(report->file, "  %s.%s\n",
 				PQgetvalue(res, rowno, i_nspname),
 				PQgetvalue(res, rowno, i_proname));
-	}
 }
 
 /*
@@ -1324,7 +1303,6 @@ process_user_defined_postfix_ops(DbInfo *dbinfo, PGresult *res, void *arg)
 {
 	UpgradeTaskReport *report = (UpgradeTaskReport *) arg;
 	int			ntups = PQntuples(res);
-	bool		db_used = false;
 	int			i_oproid = PQfnumber(res, "oproid");
 	int			i_oprnsp = PQfnumber(res, "oprnsp");
 	int			i_oprname = PQfnumber(res, "oprname");
@@ -1334,26 +1312,22 @@ process_user_defined_postfix_ops(DbInfo *dbinfo, PGresult *res, void *arg)
 	AssertVariableIsOfType(&process_user_defined_postfix_ops,
 						   UpgradeTaskProcessCB);
 
-	if (!ntups)
+	if (ntups == 0)
 		return;
 
+	if (report->file == NULL &&
+		(report->file = fopen_priv(report->path, "w")) == NULL)
+		pg_fatal("could not open file \"%s\": %m", report->path);
+
+	fprintf(report->file, "In database: %s\n", dbinfo->db_name);
+
 	for (int rowno = 0; rowno < ntups; rowno++)
-	{
-		if (report->file == NULL &&
-			(report->file = fopen_priv(report->path, "w")) == NULL)
-			pg_fatal("could not open file \"%s\": %m", report->path);
-		if (!db_used)
-		{
-			fprintf(report->file, "In database: %s\n", dbinfo->db_name);
-			db_used = true;
-		}
 		fprintf(report->file, "  (oid=%s) %s.%s (%s.%s, NONE)\n",
 				PQgetvalue(res, rowno, i_oproid),
 				PQgetvalue(res, rowno, i_oprnsp),
 				PQgetvalue(res, rowno, i_oprname),
 				PQgetvalue(res, rowno, i_typnsp),
 				PQgetvalue(res, rowno, i_typname));
-	}
 }
 
 /*
@@ -1422,29 +1396,26 @@ static void
 process_incompat_polymorphics(DbInfo *dbinfo, PGresult *res, void *arg)
 {
 	UpgradeTaskReport *report = (UpgradeTaskReport *) arg;
-	bool		db_used = false;
 	int			ntups = PQntuples(res);
 	int			i_objkind = PQfnumber(res, "objkind");
 	int			i_objname = PQfnumber(res, "objname");
 
 	AssertVariableIsOfType(&process_incompat_polymorphics,
 						   UpgradeTaskProcessCB);
 
-	for (int rowno = 0; rowno < ntups; rowno++)
-	{
-		if (report->file == NULL &&
-			(report->file = fopen_priv(report->path, "w")) == NULL)
-			pg_fatal("could not open file \"%s\": %m", report->path);
-		if (!db_used)
-		{
-			fprintf(report->file, "In database: %s\n", dbinfo->db_name);
-			db_used = true;
-		}
+	if (ntups == 0)
+		return;
+
+	if (report->file == NULL &&
+		(report->file = fopen_priv(report->path, "w")) == NULL)
+		pg_fatal("could not open file \"%s\": %m", report->path);
 
+	fprintf(report->file, "In database: %s\n", dbinfo->db_name);
+
+	for (int rowno = 0; rowno < ntups; rowno++)
 		fprintf(report->file, "  %s: %s\n",
 				PQgetvalue(res, rowno, i_objkind),
 				PQgetvalue(res, rowno, i_objname));
-	}
 }
 
 /*
@@ -1558,30 +1529,25 @@ static void
 process_with_oids_check(DbInfo *dbinfo, PGresult *res, void *arg)
 {
 	UpgradeTaskReport *report = (UpgradeTaskReport *) arg;
-	bool		db_used = false;
 	int			ntups = PQntuples(res);
 	int			i_nspname = PQfnumber(res, "nspname");
 	int			i_relname = PQfnumber(res, "relname");
 
 	AssertVariableIsOfType(&process_with_oids_check, UpgradeTaskProcessCB);
 
-	if (!ntups)
+	if (ntups == 0)
 		return;
 
+	if (report->file == NULL &&
+		(report->file = fopen_priv(report->path, "w")) == NULL)
+		pg_fatal("could not open file \"%s\": %m", report->path);
+
+	fprintf(report->file, "In database: %s\n", dbinfo->db_name);
+
 	for (int rowno = 0; rowno < ntups; rowno++)
-	{
-		if (report->file == NULL &&
-			(report->file = fopen_priv(report->path, "w")) == NULL)
-			pg_fatal("could not open file \"%s\": %m", report->path);
-		if (!db_used)
-		{
-			fprintf(report->file, "In database: %s\n", dbinfo->db_name);
-			db_used = true;
-		}
 		fprintf(report->file, "  %s.%s\n",
 				PQgetvalue(res, rowno, i_nspname),
 				PQgetvalue(res, rowno, i_relname));
-	}
 }
 
 /*
@@ -1693,7 +1659,6 @@ static void
 process_user_defined_encoding_conversions(DbInfo *dbinfo, PGresult *res, void *arg)
 {
 	UpgradeTaskReport *report = (UpgradeTaskReport *) arg;
-	bool		db_used = false;
 	int			ntups = PQntuples(res);
 	int			i_conoid = PQfnumber(res, "conoid");
 	int			i_conname = PQfnumber(res, "conname");
@@ -1702,24 +1667,20 @@ process_user_defined_encoding_conversions(DbInfo *dbinfo, PGresult *res, void *a
 	AssertVariableIsOfType(&process_user_defined_encoding_conversions,
 						   UpgradeTaskProcessCB);
 
-	if (!ntups)
+	if (ntups == 0)
 		return;
 
+	if (report->file == NULL &&
+		(report->file = fopen_priv(report->path, "w")) == NULL)
+		pg_fatal("could not open file \"%s\": %m", report->path);
+
+	fprintf(report->file, "In database: %s\n", dbinfo->db_name);
+
 	for (int rowno = 0; rowno < ntups; rowno++)
-	{
-		if (report->file == NULL &&
-			(report->file = fopen_priv(report->path, "w")) == NULL)
-			pg_fatal("could not open file \"%s\": %m", report->path);
-		if (!db_used)
-		{
-			fprintf(report->file, "In database: %s\n", dbinfo->db_name);
-			db_used = true;
-		}
 		fprintf(report->file, "  (oid=%s) %s.%s\n",
 				PQgetvalue(res, rowno, i_conoid),
 				PQgetvalue(res, rowno, i_nspname),
 				PQgetvalue(res, rowno, i_conname));
-	}
 }
 
 /*
@@ -1971,27 +1932,28 @@ static void
 process_old_sub_state_check(DbInfo *dbinfo, PGresult *res, void *arg)
 {
 	UpgradeTaskReport *report = (UpgradeTaskReport *) arg;
-	int			ntup = PQntuples(res);
+	int			ntups = PQntuples(res);
 	int			i_srsubstate = PQfnumber(res, "srsubstate");
 	int			i_subname = PQfnumber(res, "subname");
 	int			i_nspname = PQfnumber(res, "nspname");
 	int			i_relname = PQfnumber(res, "relname");
 
 	AssertVariableIsOfType(&process_old_sub_state_check, UpgradeTaskProcessCB);
 
-	for (int i = 0; i < ntup; i++)
-	{
-		if (report->file == NULL &&
-			(report->file = fopen_priv(report->path, "w")) == NULL)
-			pg_fatal("could not open file \"%s\": %m", report->path);
+	if (ntups == 0)
+		return;
 
+	if (report->file == NULL &&
+		(report->file = fopen_priv(report->path, "w")) == NULL)
+		pg_fatal("could not open file \"%s\": %m", report->path);
+
+	for (int i = 0; i < ntups; i++)
 		fprintf(report->file, "The table sync state \"%s\" is not allowed for database:\"%s\" subscription:\"%s\" schema:\"%s\" relation:\"%s\"\n",
 				PQgetvalue(res, i, i_srsubstate),
 				dbinfo->db_name,
 				PQgetvalue(res, i, i_subname),
 				PQgetvalue(res, i, i_nspname),
 				PQgetvalue(res, i, i_relname));
-	}
 }
 
 /*