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MDEV-13724 ALTER TABLE…ALGORITHM=INPLACE is modifying the source table

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row_merge_read_clustered_index(): The row->fields[] could point
to a record in the clustered index page of the source table, or
to an old version of the record that was constructed in row_heap.

If the row->fields[] points to the clustered index page, then
we were modifying buffer pool data without holding appropriate
block->lock and without appropriate redo logging. The intention
was to modify a copy of the data, not the source file page,
because concurrent readers would still very much need the original
values of the DB_TRX_ID,DB_ROLL_PTR for their multi-versioning.

Either way, it is simplest to not write anything at all, and to
make row->fields[] point to the constant reset_trx_id.
This commit is contained in:
Marko Mäkelä 2017-09-06 18:16:43 +03:00
parent fe47aee3bd
commit 8c0d873b76
3 changed files with 14 additions and 13 deletions
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3
storage/innobase/include/row0merge.h
View File

@ -62,6 +62,9 @@ Created 13/06/2005 Jan Lindstrom
// Forward declaration // Forward declaration
struct ib_sequence_t; struct ib_sequence_t;
/** The DB_TRX_ID,DB_ROLL_PTR values for "no history is available" */
extern const byte reset_trx_id[DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN];
/** @brief Block size for I/O operations in merge sort. /** @brief Block size for I/O operations in merge sort.
The minimum is UNIV_PAGE_SIZE, or page_get_free_space_of_empty() The minimum is UNIV_PAGE_SIZE, or page_get_free_space_of_empty()

6
storage/innobase/row/row0log.cc
View File

@ -45,12 +45,6 @@ ulint onlineddl_rowlog_rows;
ulint onlineddl_rowlog_pct_used; ulint onlineddl_rowlog_pct_used;
ulint onlineddl_pct_progress; ulint onlineddl_pct_progress;
/** The DB_TRX_ID,DB_ROLL_PTR values for "no history is available" */
static const byte reset_trx_id[DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN] = {
0, 0, 0, 0, 0, 0,
0x80, 0, 0, 0, 0, 0, 0
};
/** Table row modification operations during online table rebuild. /** Table row modification operations during online table rebuild.
Delete-marked records are not copied to the rebuilt table. */ Delete-marked records are not copied to the rebuilt table. */
enum row_tab_op { enum row_tab_op {

18
storage/innobase/row/row0merge.cc
View File

@ -62,6 +62,12 @@ float my_log2f(float n)
# define posix_fadvise(fd, offset, len, advice) /* nothing */ # define posix_fadvise(fd, offset, len, advice) /* nothing */
#endif /* _WIN32 */ #endif /* _WIN32 */
/** The DB_TRX_ID,DB_ROLL_PTR values for "no history is available" */
const byte reset_trx_id[DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN] = {
0, 0, 0, 0, 0, 0,
0x80, 0, 0, 0, 0, 0, 0
};
/* Whether to disable file system cache */ /* Whether to disable file system cache */
char srv_disable_sort_file_cache; char srv_disable_sort_file_cache;
@ -2302,13 +2308,11 @@ end_of_index:
for which history is not going to be for which history is not going to be
available after the rebuild operation. available after the rebuild operation.
This essentially mimics row_purge_reset_trx_id(). */ This essentially mimics row_purge_reset_trx_id(). */
byte* ptr = static_cast<byte*>( row->fields[new_trx_id_col].data
row->fields[new_trx_id_col].data); = const_cast<byte*>(reset_trx_id);
row->fields[new_trx_id_col + 1].data
memset(ptr, 0, DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN); = const_cast<byte*>(reset_trx_id
ptr[DATA_TRX_ID_LEN] = 1U + DATA_TRX_ID_LEN);
<< (ROLL_PTR_INSERT_FLAG_POS - CHAR_BIT
* (DATA_ROLL_PTR_LEN - 1));
} }
if (add_autoinc != ULINT_UNDEFINED) { if (add_autoinc != ULINT_UNDEFINED) {