The Ultimate Guide to High Availability with MariaDB

Cassandra storage engine issues

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This page lists difficulties and peculiarities of Cassandra Storage Engine. I'm not putting them into bug tracker because it is not clear whether these properties should be considered bugs.

No way to get E(#rows in column family)

There seems to be no way to get even a rough estimate of how many different keys are present in a column family. I'm using an arbitrary value of 1000 now, which causes

  • EXPLAIN will always show rows=1000 for full table scans. In the future, this may cause poor query plans.
  • DELETE FROM table always prints "1000 rows affected", with no regards how many records were actually there in the table. 
MariaDB [j1]> delete from t1;
Query OK, 1000 rows affected (0.14 sec)

We could use the new engine-independent-table-statistics feature to get some data statistics.

SHOW CREATE TABLE requires connection to Cassandra to work

Currently, one can create or open a ha_cassandra table only when connection Cassandra works.

This may be inconvenient: if Cassandra backend is down, there is no way to find out where the ha_cassandra table is pointing to.

It seems, we could change ha_cassandra not to establish connection as soon as the table is opened.

NULL values

TODO

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