Add hint to run "pgbench -i", if test tables don't exist.

Fabien Coelho, reviewed by Julien Rouhaud

src/bin/pgbench/pgbench.c

@@ -55,6 +55,8 @@
 
 #include "pgbench.h"
 
+#define ERRCODE_UNDEFINED_TABLE  "42P01"
+
 /*
  * Multi-platform pthread implementations
  */
@@ -3252,7 +3254,14 @@ main(int argc, char **argv)
 		res = PQexec(con, "select count(*) from pgbench_branches");
 		if (PQresultStatus(res) != PGRES_TUPLES_OK)
 		{
+			char	   *sqlState = PQresultErrorField(res, PG_DIAG_SQLSTATE);
+
 			fprintf(stderr, "%s", PQerrorMessage(con));
+			if (sqlState && strcmp(sqlState, ERRCODE_UNDEFINED_TABLE) == 0)
+			{
+				fprintf(stderr, "Perhaps you need to do initialization (\"pgbench -i\") in database \"%s\"\n", PQdb(con));
+			}
+
 			exit(1);
 		}
 		scale = atoi(PQgetvalue(res, 0, 0));