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Previously system.paxos TTL was set as max(3h, gc_grace_seconds). Introduce new per-table option named `paxos_grace_seconds` to set the amount of seconds which are used to TTL data in paxos tables when using LWT queries against the base table. Default value is equal to `DEFAULT_GC_GRACE_SECONDS`, which is 10 days. This change allows to easily test various issues related to paxos TTL. Fixes #6284 Tests: unit (dev, debug) Co-authored-by: Alejo Sanchez <alejo.sanchez@scylladb.com> Signed-off-by: Alejo Sanchez <alejo.sanchez@scylladb.com> Signed-off-by: Pavel Solodovnikov <pa.solodovnikov@scylladb.com> Message-Id: <20200816223935.919081-1-pa.solodovnikov@scylladb.com>
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Scylla CQL extensions
Scylla extends the CQL language to provide a few extra features. This document lists those extensions.
BYPASS CACHE clause
The BYPASS CACHE clause on SELECT statements informs the database that the data
being read is unlikely to be read again in the near future, and also
was unlikely to have been read in the near past; therefore no attempt
should be made to read it from the cache or to populate the cache with
the data. This is mostly useful for range scans; these typically
process large amounts of data with no temporal locality and do not
benefit from the cache.
The clause is placed immediately after the optional ALLOW FILTERING
clause:
SELECT ... FROM ...
WHERE ...
ALLOW FILTERING -- optional
BYPASS CACHE
"Paxos grace seconds" per-table option
The paxos_grace_seconds option is used to set the amount of seconds which
are used to TTL data in paxos tables when using LWT queries against the base
table.
This value is intentionally decoupled from gc_grace_seconds since,
in general, the base table could use completely different strategy to garbage
collect entries, e.g. can set gc_grace_seconds to 0 if it doesn't use
deletions and hence doesn't need to repair.
However, paxos tables still rely on repair to achieve consistency, and
the user is required to execute repair within paxos_grace_seconds.
Default value is equal to DEFAULT_GC_GRACE_SECONDS, which is 10 days.
The option can be specified at CREATE TABLE or ALTER TABLE queries in the same
way as other options by using WITH clause:
CREATE TABLE tbl ...
WITH paxos_grace_seconds=1234