Fix psql's \copy command to ensure that it cycles libpq back to the idle state

(in particular, causing the ReadyForQuery message to be eaten) before
returning from do_copy.  The only known consequence of failing to do so is
that get_prompt might show a wrong result for the %x transaction status
escape, as reported by Bernd Helmle; but it's possible there are other issues.

Back-patch as far as 7.4, the oldest version supporting %x.

diff --git a/src/bin/psql/copy.c b/src/bin/psql/copy.c
index a69c63957b571624ae697a217072621d5c3d1510..800fff204a77e7c7a21b66d3b0f403ca2d87fde4 100644 (file)
--- a/src/bin/psql/copy.c
+++ b/src/bin/psql/copy.c
@@ -573,6 +573,18 @@ do_copy(const char *args)
 
        PQclear(result);
 
+       /*
+        * Make sure we have pumped libpq dry of results; else it may still be
+        * in ASYNC_BUSY state, leading to false readings in, eg, get_prompt().
+        */
+       while ((result = PQgetResult(pset.db)) != NULL)
+       {
+               success = false;
+               psql_error("\\copy: unexpected response (%d)\n",
+                                  PQresultStatus(result));
+               PQclear(result);
+       }
+
        if (options->file != NULL)
        {
                if (fclose(copystream) != 0)