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branches/zip: Apply some fixes suggested by Heikki.

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btr_cur_pessimistic_update(): Note why the externally stored columns
of a record on a latched page cannot have been purged.

trx_undo_get_undo_rec(): Clarify that the stack of versions is locked
all the way down to the purge view.

trx_undo_prev_version_build(): Set *old_vers = NULL also when the record
could have been purged already.  Add some clarifying comments.
This commit is contained in:
marko 2008-02-04 12:47:00 +00:00
parent efc7639dac
commit c9087d7d90
2 changed files with 35 additions and 5 deletions
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7
btr/btr0cur.c
View file

@ -2138,8 +2138,11 @@ btr_cur_pessimistic_update(
rec_offs_make_valid(rec, index, offsets);
/* The page containing the clustered index record
corresponding to new_entry is latched in mtr.
Thus the following call is safe. */
corresponding to new_entry is latched in mtr. If the
clustered index record is delete-marked, then its externally
stored fields cannot have been purged yet, because then the
purge would also have removed the clustered index record
itself. Thus the following call is safe. */
row_upd_index_replace_new_col_vals_index_pos(new_entry, index, update,
FALSE, *heap, *heap);
if (!(flags & BTR_KEEP_SYS_FLAG)) {

33
trx/trx0rec.c
View file

@ -1363,7 +1363,7 @@ trx_undo_get_undo_rec(
Build a previous version of a clustered index record. This function checks
that the caller has a latch on the index page of the clustered index record
and an s-latch on the purge_view. This guarantees that the stack of versions
is locked. */
is locked all the way down to the purge_view. */
ulint
trx_undo_prev_version_build(
@ -1384,7 +1384,9 @@ trx_undo_prev_version_build(
needed is allocated */
rec_t** old_vers)/* out, own: previous version, or NULL if
rec is the first inserted version, or if
history data has been deleted */
history data has been deleted (an error),
or if the purge COULD have removed the version
though it has not yet done so */
{
trx_undo_rec_t* undo_rec;
dtuple_t* entry;
@ -1440,7 +1442,9 @@ trx_undo_prev_version_build(
err = trx_undo_get_undo_rec(roll_ptr, rec_trx_id, &undo_rec, heap);
if (err != DB_SUCCESS) {
if (UNIV_UNLIKELY(err != DB_SUCCESS)) {
/* The undo record may already have been purged.
This should never happen in InnoDB. */
return(err);
}
@ -1450,6 +1454,29 @@ trx_undo_prev_version_build(
ptr = trx_undo_update_rec_get_sys_cols(ptr, &trx_id, &roll_ptr,
&info_bits);
/* (a) If a clustered index record version is such that the
trx id stamp in it is bigger than purge_sys->view, then the
BLOBs in that version are known to exist (the purge has not
progressed that far);
(b) if the version is the first version such that trx id in it
is less than purge_sys->view, and it is not delete-marked,
then the BLOBs in that version are known to exist (the purge
cannot have purged the BLOBs referenced by that version
yet). */
if ((info_bits & REC_INFO_DELETED_FLAG)
&& !trx_purge_update_undo_must_exist(trx_id)) {
/* The purge may have already freed the externally
stored fields associated with this update undo log
record. Do not try to fetch them, as our read view
would see this row version as delete-marked anyway. */
return(DB_SUCCESS);
}
ptr = trx_undo_rec_skip_row_ref(ptr, index);
ptr = trx_undo_update_rec_get_update(ptr, index, type, trx_id,