Timestamp-versioned row deletion was exposed to a collisional problem: if
current timestamp wasn't changed, then a sequence of row delete+insert could
get a duplication error. A row delete would find another conflicting history row
and return an error.
This is true both for REPLACE and DELETE statements, however in REPLACE, the
"optimized" path is usually taken, especially in the tests. There, delete+insert
is substituted for a single versioned row update. In the end, both paths end up
as ha_update_row + ha_write_row.
The solution is to handle a history collision somehow.
From the design perspective, the user shouldn't experience history rows loss,
unless there's a technical limitation.
To the contrary, trxid-based changes should never generate history for the same
transaction, see MDEV-15427.
If two operations on the same row happened too quickly, so that they happen at
the same timestamp, the history row shouldn't be lost. We can still write a
history row, though it'll have row_start == row_end.
We cannot store more than one such historical row, as this will violate the
unique constraint on row_end. So we will have to phisically delete the row if
the history row is already available.
In this commit:
1. Improve TABLE::delete_row to handle the history collision: if an update
results with a duplicate error, delete a row for real.
2. use TABLE::delete_row in a non-optimistic path of REPLACE, where the
system-versioned case now belongs entirely.
We had a protection against it, by allowing versioned delete if:
trx->id != table->vers_start_id()
For replace this check fails: replace calls ha_delete_row(record[2]), but
table->vers_start_id() returns the value from record[0], which is irrelevant.
The same problem hits Field::is_max, which may have checked the wrong record.
Fix:
* Refactor Field::is_max to optionally accept a pointer as an argument.
* Refactor vers_start_id and vers_end_id to always accept a pointer to the
record. there is a difference with is_max is that is_max accepts the pointer to
the
field data, rather than to the record.
Method val_int() would be too effortful to refactor to accept the argument, so
instead the value in record is fetched directly, like it is done in
Field_longlong.
system versioned table
For versioned table REPLACE first tries to insert a row, if it gets
duplicate key error and optimization is possible it does UPDATE +
INSERT history. If optimization is not possible it goes normal branch
for UPDATE to history and repeats the cycle of INSERT.
The failure was in normal branch when we tried UPDATE to history but
such history already exists from previous cycles. There is no such
failures in optimized branch because vers_insert_history_row() already
ignores duplicates.
The fix ignores duplicate errors for UPDATE to history and does DELETE
instead.
Problem: Assertion `transactional_table || !changed ||
thd->transaction.stmt.modified_non_trans_table' failed due REPLACE into a
versioned table.
It is not specific to system versioning/pertitioning/heap, but this
combination makes it much easier to reproduce.
The thing is to make first ha_update_row call succeed to make
info->deleted != 0. And then make REPLACE fail by any reason.
In this scenario we overflow versioned partition, so next ha_update_row
succeeds, but corresponding ha_write_row fails to insert history record.
Fix: modified_non_trans_table is set in one missed place
Preparation for MDEV-16210:
replace.test:
key_type combinations: PK and UNIQUE.
foreign.test:
Preparation for key_type combinations.
Other fixes:
* Merged versioning.update2 into versioning.update;
* Removed test2 database and done individual drop instead.
row_insert_for_mysql(): InnoDB sets values for row_start and row_end.
And this function used to return those values to server in
ha_innobase::write_row(). This buggy behavior was removed. Also,
a piece of code in this function was reformatted.
upd_node_t::make_versioned_helper(): Assert that the preallocated size
of the update vector is not exceeded.
Tests started to fail after a merge of MDEV-15107 (from bb-10.2-ext to 10.3),
because MDEV-15107 additionally fixed this problem:
MDEV-15112 Inconsistent evaluation of spvariable=0 in strict mode
Modifying tests not to reply on the pre-MDEV-15112 behavior.
