Enable use of 'unset' values in prepared statements by default

[penberg]

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We have support for the use of 'unset' values to reduce the number of prepared statements as of commit b432a08dad2816273184cab54c5ccbef4e7e14dd. However, user needs to explicitly enable that with the -u command line option, which they will easily forget to do.

We should make this enabled by default just like we do for prepared statements and batching since commit b382110eb962d2ff7d3b32d2c0fa626c08a18f25. @haaawk did want us to check the performance impact of 'unset' before we do that, though.

[haaawk]

It would probably be good as the default option should be the one that performs better. I won't insist though :)

[penberg]

@haaawk No, I think it's a reasonable requirement before defaulting to the new option.

[haaawk]

@penberg @elcallio I would wait with enabling this by default. I was testing sstable loader with data generated by cassandra stress. Default schema is:

CREATE KEYSPACE keyspace1 WITH replication = {'class': 'SimpleStrategy', 'replication_factor': '1'} AND durable_writes = true;

CREATE TABLE keyspace1.counter1 ( key blob, column1 text, "C0" counter static, "C1" counter static, "C2" counter static, "C3" counter static, "C4" counter static, value counter, PRIMARY KEY (key, column1) ) WITH COMPACT STORAGE AND CLUSTERING ORDER BY (column1 ASC) AND bloom_filter_fp_chance = 0.01 AND caching = {'keys': 'ALL', 'rows_per_partition': 'NONE'} AND comment = '' AND compaction = {'class': 'org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy', 'max_threshold': '32', 'min_threshold': '4'} AND compression = {'enabled': 'false'} AND crc_check_chance = 1.0 AND dclocal_read_repair_chance = 0.1 AND default_time_to_live = 0 AND gc_grace_seconds = 864000 AND max_index_interval = 2048 AND memtable_flush_period_in_ms = 0 AND min_index_interval = 128 AND read_repair_chance = 0.0 AND speculative_retry = '99PERCENTILE';

CREATE TABLE keyspace1.standard1 ( key blob PRIMARY KEY, "C0" blob, "C1" blob, "C2" blob, "C3" blob, "C4" blob ) WITH COMPACT STORAGE AND bloom_filter_fp_chance = 0.01 AND caching = {'keys': 'ALL', 'rows_per_partition': 'NONE'} AND comment = '' AND compaction = {'class': 'org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy', 'max_threshold': '32', 'min_threshold': '4'} AND compression = {'enabled': 'false'} AND crc_check_chance = 1.0 AND dclocal_read_repair_chance = 0.1 AND default_time_to_live = 0 AND gc_grace_seconds = 864000 AND max_index_interval = 2048 AND memtable_flush_period_in_ms = 0 AND min_index_interval = 128 AND read_repair_chance = 0.0 AND speculative_retry = '99PERCENTILE';

and running sstable loader like this: ./bin/sstableloader -u -d 127.0.0.1 /home/haaawk/.ccm/loader-1/node1/data0/keyspace1/standard1-c17511f0bb2111e8ac3f47eff2803657/

generates lots of errors:

com.datastax.driver.core.exceptions.InvalidQueryException: Unknown identifier column1