pg_dump: Further reduce reliance on global variables.

This is another round of refactoring to make things simpler for parallel
pg_dump.  pg_dump.c now issues SQL queries through the relevant Archive
object, rather than relying on the global variable g_conn.  This commit
isn't quite enough to get rid of g_conn entirely, but it makes a big
dent in its utilization and, along the way, manages to be slightly less
code than before.

src/bin/pg_dump/pg_backup_archiver.c

@@ -1453,6 +1453,16 @@ die_horribly(ArchiveHandle *AH, const char *modulename, const char *fmt,...)
 	va_end(ap);
 }
 
+/* As above, but with a complaint about a particular query. */
+void
+die_on_query_failure(ArchiveHandle *AH, const char *modulename,
+					 const char *query)
+{
+	write_msg(modulename, "query failed: %s",
+			  PQerrorMessage(AH->connection));
+	die_horribly(AH, modulename, "query was: %s\n", query);
+}
+
 /* on some error, we may decide to go on... */
 void
 warn_or_die_horribly(ArchiveHandle *AH,

src/bin/pg_dump/pg_backup_archiver.h

@@ -325,6 +325,7 @@ typedef struct _tocEntry
 
 
 extern void die_horribly(ArchiveHandle *AH, const char *modulename, const char *fmt,...) __attribute__((format(PG_PRINTF_ATTRIBUTE, 3, 4), noreturn));
+extern void die_on_query_failure(ArchiveHandle *AH, const char *modulename, const char *query) __attribute__((noreturn));
 extern void warn_or_die_horribly(ArchiveHandle *AH, const char *modulename, const char *fmt,...) __attribute__((format(PG_PRINTF_ATTRIBUTE, 3, 4)));
 
 extern void WriteTOC(ArchiveHandle *AH);

src/bin/pg_dump/pg_backup_db.c

@@ -318,6 +318,30 @@ notice_processor(void *arg, const char *message)
 }
 
 
+void
+ExecuteSqlStatement(Archive *AHX, const char *query)
+{
+	ArchiveHandle	   *AH = (ArchiveHandle *) AHX;
+	PGresult   *res;
+
+	res = PQexec(AH->connection, query);
+	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+		die_on_query_failure(AH, modulename, query);
+	PQclear(res);
+}
+
+PGresult *
+ExecuteSqlQuery(Archive *AHX, const char *query, ExecStatusType status)
+{
+	ArchiveHandle	   *AH = (ArchiveHandle *) AHX;
+	PGresult   *res;
+
+	res = PQexec(AH->connection, query);
+	if (PQresultStatus(res) != status)
+		die_on_query_failure(AH, modulename, query);
+	return res;
+}
+
 /*
  * Convenience function to send a query.
  * Monitors result to detect COPY statements

src/bin/pg_dump/pg_backup_db.h

@@ -12,6 +12,10 @@
 
 extern int	ExecuteSqlCommandBuf(ArchiveHandle *AH, const char *buf, size_t bufLen);
 
+extern void ExecuteSqlStatement(Archive *AHX, const char *query);
+extern PGresult *ExecuteSqlQuery(Archive *AHX, const char *query,
+				ExecStatusType status);
+
 extern void EndDBCopyMode(ArchiveHandle *AH, struct _tocEntry * te);
 
 extern void StartTransaction(ArchiveHandle *AH);