BUG#46961 - archive engine loses rows during self joining select!

SELECT with join (not only self-join) from archive table may
return incomplete result set, when result set size exceeds
join buffer size.

The problem was that archive row counter was initialzed too
early, when ha_archive::info() method was called. Later,
when optimizer exceeds join buffer, it attempts to reuse
handler without calling ha_archive::info() again (which is
correct).

Fixed by moving row counter initialization from
ha_archive::info() to ha_archive::rnd_init().

mysql-test/r/archive.result:
  A test case for BUG#46961.
mysql-test/t/archive.test:
  A test case for BUG#46961.
storage/archive/ha_archive.cc:
  Since a cursor may get reused without a call to ::info(),
  move assignment of scan_rows to a proper place, that is
  ::rnd_init().

mysql-test/r/archive.result

@@ -12695,3 +12695,14 @@ a	b
 1	NULL
 2	NULL
 DROP TABLE t1;
+SET @save_join_buffer_size= @@join_buffer_size;
+SET @@join_buffer_size= 8228;
+CREATE TABLE t1(a CHAR(255)) ENGINE=archive;
+INSERT INTO t1 VALUES('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'),
+('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'),
+('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa');
+SELECT COUNT(t1.a) FROM t1, t1 a, t1 b, t1 c, t1 d, t1 e;
+COUNT(t1.a)
+729
+DROP TABLE t1;
+SET @@join_buffer_size= @save_join_buffer_size;

mysql-test/t/archive.test

@@ -1599,3 +1599,16 @@ INSERT INTO t1 VALUES (NULL, NULL),(NULL, NULL);
 FLUSH TABLE t1;
 SELECT * FROM t1 ORDER BY a;
 DROP TABLE t1;
+
+#
+# BUG#46961 - archive engine loses rows during self joining select!
+#
+SET @save_join_buffer_size= @@join_buffer_size;
+SET @@join_buffer_size= 8228;
+CREATE TABLE t1(a CHAR(255)) ENGINE=archive;
+INSERT INTO t1 VALUES('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'),
+                     ('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'),
+                     ('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa');
+SELECT COUNT(t1.a) FROM t1, t1 a, t1 b, t1 c, t1 d, t1 e;
+DROP TABLE t1;
+SET @@join_buffer_size= @save_join_buffer_size;

storage/archive/ha_archive.cc

@@ -993,6 +993,7 @@ int ha_archive::rnd_init(bool scan)
   /* We rewind the file so that we can read from the beginning if scan */
   if (scan)
   {
+    scan_rows= stats.records;
     DBUG_PRINT("info", ("archive will retrieve %llu rows", 
                         (unsigned long long) scan_rows));
 
@@ -1461,7 +1462,6 @@ int ha_archive::info(uint flag)
   stats.records= share->rows_recorded;
   pthread_mutex_unlock(&share->mutex);
 
-  scan_rows= stats.records;
   stats.deleted= 0;
 
   DBUG_PRINT("ha_archive", ("Stats rows is %d\n", (int)stats.records));