Hi!
>>>>> "Timothy" == Timothy P Clark <Timothy> writes:
Timothy> The storage engine that I am developing handles error reporting for
Timothy> duplicate key values differently than MySQL expects. Specifically, when a
Timothy> row causes duplicate value conflicts with multiple keys, only the last key
Timothy> that caused the dup error is known. However, MySQL expects the keys to be
Timothy> reported in ascending order.
Timothy> For example, for the following sequence:
Timothy> CREATE TABLE t1 (a INT, UNIQUE (a), b INT NOT NULL, UNIQUE (b), c INT NOT
Timothy> NULL, INDEX(c));
Timothy> REPLACE INTO t1 VALUES (1,1,1),(2,2,2),(2,1,3);
Timothy> MySQL expects the conflict with 'a' to be reported before the conflict with
Timothy> 'b'. Our storage engine always reports 'b' before 'a'.
Timothy> This causes a problem in sql_insert.cc::write_record() when a REPLACE
Timothy> command is executed, because the loop that retries the replace after a
Timothy> duplicate key error depends on the ascending key order. As a result, the
Timothy> REPLACE command above will fail for our storage engine and return "ERROR
Timothy> 1062 (23000): Duplicate entry '1' for key 'b'".
Timothy> I have a possible workaround, which is to always set handler::errkey to 0
Timothy> when (thd_sql_command() == SQLCOM_REPLACE*). This seems to work for the
Timothy> limited set of operations that I have tried and a quick inspection of
Timothy> write_row leads me to believe that this should be OK. Can anyone convince
Timothy> me that this is a bad idea?
This is probably ok, but a better way would to introduce a new table
flag HA_DUPLICATE_KEY_NOT_IN_ORDER and change the test in
write_record() from:
static int last_uniq_key(TABLE *table,uint keynr)
{
while (++keynr < table->s->keys)
if (table->key_info[keynr].flags & HA_NOSAME)
return 0;
return 1;
}
to
static int last_uniq_key(TABLE *table,uint keynr)
{
if (table->file->ha_table_flags() & HA_DUPLICATE_KEY_NOT_IN_ORDER)
return 0;
while (++keynr < table->s->keys)
if (table->key_info[keynr].flags & HA_NOSAME)
return 0;
return 1;
}
Regards,
Monty
