I have a 3 node cluster of Cassandra version 2.0.9. My keyspace replication
factor is 3 and I'm querying with consistency level ALL.
Problem: When I do an insert to overwrite an old row, the old data still
appears in all select queries! This does not apply to all cases, just a
subset of the rows in this table. Some are a day old, some are 3 hours old.
It happens both using commandline cqlsh and via the datastax java cql
driver (in that case with CL=2)
Of course this is a huge concern since the insert is accepted but has no
effect, meaning that the write is effectively lost!
Here is how it happens:
First I do a select to see the original data:
cqlsh> use mykeyspace
cqlsh:mykeyspace> consistency all;
Consistency level set to ALL.
cqlsh:mykeyspace> select created_timestamp, stored_value from mytable where
key_a = 'the_value' and key_b = '43052960';
It returns the original row, as expected.
Then I do the insert to overwrite it:
cqlsh:mykeyspace> insert into mytable (key_a, key_b, created_timestamp,
created_yyyymmdd, stored_value)
values('the_value','43052960',dateof(now()),'20150312','test6');
And re-run the previous select query, expecting to see the overwritten
values, but it returns the old values for all columns.
If I use a totally different value for the value of key_b, then the problem
does not appear instantly, but it seems that in at least some cases, the
issue appears over time. Not sure.
My table looks like this:
CREATE TABLE mytable (
key_a text,
key_b text,
value_a text,
created_timestamp timestamp,
created_yyyymmdd text,
stored_value text,
PRIMARY KEY ((key_a), key_b)
) WITH
bloom_filter_fp_chance=0.010000 AND
caching='KEYS_ONLY' AND
comment='' AND
dclocal_read_repair_chance=0.000000 AND
gc_grace_seconds=864000 AND
index_interval=128 AND
read_repair_chance=0.100000 AND
replicate_on_write='true' AND
populate_io_cache_on_flush='false' AND
default_time_to_live=0 AND
speculative_retry='99.0PERCENTILE' AND
memtable_flush_period_in_ms=0 AND
compaction={'class': 'SizeTieredCompactionStrategy'} AND
compression={'sstable_compression': 'LZ4Compressor'};
CREATE INDEX mytable_idx_yyyymmdd ON mytable (created_yyyymmdd);
--
regards,
Gudmundur Johannsson
