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BUG#670417: Diverging results in maria-5.3-mwl128-dsmrr-cpk with join buffer, attempt 4

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- Disable identical key handling optimization when
  IndexConditionPushdown is used
This commit is contained in:
Sergey Petrunya
2010-11-08 20:37:01 +03:00
parent 197c99427d
commit 0fb342ba56
4 changed files with 138 additions and 1 deletions
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39
sql/multi_range_read.cc
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@ -472,6 +472,42 @@ int Mrr_ordered_index_reader::init(handler *h_arg, RANGE_SEQ_IF *seq_funcs,
mrr_funcs= *seq_funcs;
know_key_tuple_params= FALSE;
buf_manager= buf_manager_arg;
/*
Short: don't do identical key handling when we have a pushed index
condition.
Long: In order to check pushed index condition, we need to have both
index tuple table->record[0] and range_id.
Key_value_records_iterator has special handling for case when we have
multiple (key_value, range_id) pairs with the same key_value. In that
case it will make an index lookup only for the first such element,
for subsequent elements it will only return the new range_id.
The problem here is that h->table->record[0] is shared with the part that
does full record retrieval with rnd_pos() calls, and if we have the
following scenario:
1. We scan ranges {(key_value, range_id1), (key_value, range_id2)}
2. Iterator makes a lookup with key_value, produces the (index_tuple,
range_id1) pair. Index tuple is read into table->record[0], which
allows us to check index condition.
3. At this point, we figure that key buffer is full, so we sort it,
and return control to Mrr_ordered_rndpos_reader.
3.1 Mrr_ordered_rndpos_reader gets rowids and makes rnd_pos() calls, which
puts some arbitrary data into table->record[0] in the process.
3.2 We ask the iterator for the next (rowid, range_id) pair. The iterator
puts in range_id2, and that shuld be sufficient (this is identical key
handling at work)
However, index tuple in table->record[0] has been destroyed and we
can't check index conditon for (index_tuple, range_id2) now.
TODO: It is possible to support identical key handling and index condition
pushdown, working together (one possible solution is to save/restore the
contents of table->record[0]). We will probably implement that.
*/
disallow_identical_key_handling= test(mrr_funcs.skip_index_tuple);
return 0;
}
@ -1123,7 +1159,8 @@ int Key_value_records_iterator::init(Mrr_ordered_index_reader *owner_arg)
uchar *save_cur_index_tuple= cur_index_tuple;
while (!identical_key_it.read())
{
if (Mrr_ordered_index_reader::key_tuple_cmp(owner, key_in_buf,
if (owner->disallow_identical_key_handling ||
Mrr_ordered_index_reader::key_tuple_cmp(owner, key_in_buf,
cur_index_tuple))
break;
last_identical_key_ptr= cur_index_tuple;