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MDEV-39644 Wrong result with ICP in reverse ordered partition scans

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Ordered partition scans keep one row per partition in queue buffers.
However, pushed index conditions use Field objects bound to
table->record[0]. Reading directly into a queue buffer can therefore
evaluate the condition against a different row and skip matching rows.

Route ha_index_last() and ha_index_prev() through read_with_icp(), as
already done for forward ordered reads. With ICP, read into
table->record[0] and copy the row to the queue buffer only on success.
Preserve the queue buffer when a read returns EOF or another error.

Full forward index scans do not use ICP. Assert this invariant before
calling ha_index_first() directly. Add a minimal MyISAM regression with
matching and rejected rows in two partitions.

Bug report: https://jira.mariadb.org/browse/MDEV-39644
This commit is contained in:
DerZc
2026-09-28 14:18:20 +08:00
committed by Sergei Petrunia
parent 9a1123dc45
commit 5a3a6b5582
3 changed files with 38 additions and 3 deletions
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10
mysql-test/main/partition_order.result
View File

@@ -796,3 +796,13 @@ a b
2 2
3 3
drop table t1;
# MDEV-39644 Evaluate ICP on the current row in reverse partition scans
CREATE TABLE t1 (c1 INT,c2 INT,c3 INT,KEY k(c2,c3))
ENGINE=MyISAM PARTITION BY HASH(c1) PARTITIONS 2;
INSERT INTO t1 VALUES (1,4,1),(2,3,1),(3,2,0),(4,1,1);
SELECT * FROM t1 WHERE c2>=1 AND c3=1 ORDER BY c2 DESC;
c1 c2 c3
1 4 1
2 3 1
4 1 1
DROP TABLE t1;

6
mysql-test/main/partition_order.test
View File

@@ -846,3 +846,9 @@ insert into t1 values (1,1),(2,2),(3,3),(4,4),(5,5),(6,6);
explain select * from t1 order by a limit 3;
select * from t1 order by a limit 3;
drop table t1;
--echo # MDEV-39644 Evaluate ICP on the current row in reverse partition scans
CREATE TABLE t1 (c1 INT,c2 INT,c3 INT,KEY k(c2,c3))
ENGINE=MyISAM PARTITION BY HASH(c1) PARTITIONS 2;
INSERT INTO t1 VALUES (1,4,1),(2,3,1),(3,2,0),(4,1,1);
SELECT * FROM t1 WHERE c2>=1 AND c3=1 ORDER BY c2 DESC;
DROP TABLE t1;

25
sql/ha_partition.cc
View File

@@ -104,7 +104,8 @@ static int read_with_icp(TABLE* table,
return func(record_buf);
int error= func(table->record[0]);
memcpy(record_buf, table->record[0], record_buf_len);
if (likely(!error))
memcpy(record_buf, table->record[0], record_buf_len);
return error;
}
@@ -8208,11 +8209,22 @@ int ha_partition::handle_ordered_index_scan(uchar *buf, bool reverse_order)
/* Caller has specified reverse_order */
break;
case partition_index_first:
/*
We don't call read_with_icp() here as full index scans are not done
with ICP.
*/
DBUG_ASSERT(!pushed_idx_cond);
error= file->ha_index_first(rec_buf_ptr);
reverse_order= FALSE;
break;
case partition_index_last:
error= file->ha_index_last(rec_buf_ptr);
error= read_with_icp(table,
pushed_idx_cond != nullptr,
rec_buf_ptr,
m_rec_length,
[file] (uchar* read_buf) {
return file->ha_index_last(read_buf);
});
reverse_order= TRUE;
break;
case partition_read_range:
@@ -8738,7 +8750,14 @@ int ha_partition::handle_ordered_prev(uchar *buf)
uchar *rec_buf= queue_top(&m_queue) + ORDERED_REC_OFFSET;
handler *file= m_file[part_id];
if (unlikely((error= file->ha_index_prev(rec_buf))))
error= read_with_icp(table,
pushed_idx_cond != nullptr,
rec_buf,
m_rec_length,
[file] (uchar* read_buf) {
return file->ha_index_prev(read_buf);
});
if (unlikely(error))
{
if (error == HA_ERR_END_OF_FILE && m_queue.elements)
{