Bug#38005 Partitions: error with insert select.

MyISAM blocks index usage for bulk insert into zero-records tables.
See ha_myisam::start_bulk_insert() lines from
...
    if (file->state->records == 0 ...
...

That causes problems for partition engine when some partitions have records some not
as the engine uses same access method for all partitions.

Now partition engine doesn't call index_first/index_last
for empty tables.

per-file comments:
  mysql-test/r/partition.result
        Bug#38005 Partitions: error with insert select.
        test result

  mysql-test/t/partition.test
        Bug#38005 Partitions: error with insert select.
        test case

  sql/ha_partition.cc
        Bug#38005 Partitions: error with insert select.
        ha_engine::index_first and
        ha_engine::index_last not called for empty tables.

mysql-test/r/partition.result

@@ -1637,4 +1637,74 @@ select count(*) from t1, t2 where t1.createdDate = t2.createdDate;
 count(*)
 1
 drop table t1, t2;
+create table t1 (s1 int) partition by hash(s1) partitions 2;
+create index i on t1 (s1);
+insert into t1 values (1);
+insert into t1 select s1 from t1;
+insert into t1 select s1 from t1;
+insert into t1 select s1 from t1 order by s1 desc;
+select * from t1;
+s1
+1
+1
+1
+1
+1
+1
+1
+1
+drop table t1;
+create table t1 (s1 int) partition by range(s1) 
+(partition pa1 values less than (10),
+partition pa2 values less than MAXVALUE);
+create index i on t1 (s1);
+insert into t1 values (1);
+insert into t1 select s1 from t1;
+insert into t1 select s1 from t1;
+insert into t1 select s1 from t1 order by s1 desc;
+select * from t1;
+s1
+1
+1
+1
+1
+1
+1
+1
+1
+drop table t1;
+create table t1 (s1 int) partition by range(s1) 
+(partition pa1 values less than (10),
+partition pa2 values less than MAXVALUE);
+create index i on t1 (s1);
+insert into t1 values (20);
+insert into t1 select s1 from t1;
+insert into t1 select s1 from t1;
+insert into t1 select s1 from t1 order by s1 desc;
+select * from t1;
+s1
+20
+20
+20
+20
+20
+20
+20
+20
+drop table t1;
+create table t1 (s1 int) partition by range(s1) 
+(partition pa1 values less than (10),
+partition pa2 values less than MAXVALUE);
+create index i on t1 (s1);
+insert into t1 values (1), (2), (3), (4), (5), (6), (7), (8);
+insert into t1 select s1 from t1;
+insert into t1 select s1 from t1;
+insert into t1 select s1 from t1;
+insert into t1 select s1 from t1;
+insert into t1 select s1 from t1 order by s1 desc;
+insert into t1 select s1 from t1 where s1=3;
+select count(*) from t1;
+count(*)
+288
+drop table t1;
 End of 5.1 tests

mysql-test/t/partition.test

@@ -1791,4 +1791,53 @@ select count(*) from t1, t2 where t1.createdDate = t2.createdDate;
 
 drop table t1, t2;
 
+#
+# Bug #38005 Partitions: error with insert select
+#
+
+create table t1 (s1 int) partition by hash(s1) partitions 2;
+create index i on t1 (s1);
+insert into t1 values (1);
+insert into t1 select s1 from t1;
+insert into t1 select s1 from t1;
+insert into t1 select s1 from t1 order by s1 desc;
+select * from t1;
+drop table t1;
+
+create table t1 (s1 int) partition by range(s1) 
+        (partition pa1 values less than (10),
+         partition pa2 values less than MAXVALUE);
+create index i on t1 (s1);
+insert into t1 values (1);
+insert into t1 select s1 from t1;
+insert into t1 select s1 from t1;
+insert into t1 select s1 from t1 order by s1 desc;
+select * from t1;
+drop table t1;
+
+create table t1 (s1 int) partition by range(s1) 
+        (partition pa1 values less than (10),
+         partition pa2 values less than MAXVALUE);
+create index i on t1 (s1);
+insert into t1 values (20);
+insert into t1 select s1 from t1;
+insert into t1 select s1 from t1;
+insert into t1 select s1 from t1 order by s1 desc;
+select * from t1;
+drop table t1;
+
+create table t1 (s1 int) partition by range(s1) 
+        (partition pa1 values less than (10),
+         partition pa2 values less than MAXVALUE);
+create index i on t1 (s1);
+insert into t1 values (1), (2), (3), (4), (5), (6), (7), (8);
+insert into t1 select s1 from t1;
+insert into t1 select s1 from t1;
+insert into t1 select s1 from t1;
+insert into t1 select s1 from t1;
+insert into t1 select s1 from t1 order by s1 desc;
+insert into t1 select s1 from t1 where s1=3;
+select count(*) from t1;
+drop table t1;
+
 --echo End of 5.1 tests

sql/ha_partition.cc

@@ -4290,6 +4290,17 @@ int ha_partition::handle_unordered_scan_next_partition(uchar * buf)
       break;
     case partition_index_first:
       DBUG_PRINT("info", ("index_first on partition %d", i));
+      /* MyISAM engine can fail if we call index_first() when indexes disabled */
+      /* that happens if the table is empty. */
+      /* Here we use file->stats.records instead of file->records() because */
+      /* file->records() is supposed to return an EXACT count, and it can be   */
+      /* possibly slow. We don't need an exact number, an approximate one- from*/
+      /* the last ::info() call - is sufficient. */
+      if (file->stats.records == 0)
+      {
+        error= HA_ERR_END_OF_FILE;
+        break;
+      }
       error= file->index_first(buf);
       break;
     case partition_index_first_unordered:
@@ -4377,10 +4388,32 @@ int ha_partition::handle_ordered_index_scan(uchar *buf, bool reverse_order)
                                   m_start_key.flag);
       break;
     case partition_index_first:
+      /* MyISAM engine can fail if we call index_first() when indexes disabled */
+      /* that happens if the table is empty. */
+      /* Here we use file->stats.records instead of file->records() because */
+      /* file->records() is supposed to return an EXACT count, and it can be   */
+      /* possibly slow. We don't need an exact number, an approximate one- from*/
+      /* the last ::info() call - is sufficient. */
+      if (file->stats.records == 0)
+      {
+        error= HA_ERR_END_OF_FILE;
+        break;
+      }
       error= file->index_first(rec_buf_ptr);
       reverse_order= FALSE;
       break;
     case partition_index_last:
+      /* MyISAM engine can fail if we call index_last() when indexes disabled */
+      /* that happens if the table is empty. */
+      /* Here we use file->stats.records instead of file->records() because */
+      /* file->records() is supposed to return an EXACT count, and it can be   */
+      /* possibly slow. We don't need an exact number, an approximate one- from*/
+      /* the last ::info() call - is sufficient. */
+      if (file->stats.records == 0)
+      {
+        error= HA_ERR_END_OF_FILE;
+        break;
+      }
       error= file->index_last(rec_buf_ptr);
       reverse_order= TRUE;
       break;