goglangel.blogg.se - Deduplicator operator

#DEDUPLICATOR OPERATOR HOW TO#
#DEDUPLICATOR OPERATOR MANUAL#
#DEDUPLICATOR OPERATOR ARCHIVE#

can work with acceptable speed in some special conditions: Īpproach 3.

#DEDUPLICATOR OPERATOR MANUAL#

and may require tricky manual optimization.

selects with FINAL clause ( select * from table_name FINAL) are much slower.

deduplication is eventual - you never know when it will happen, and you will get some duplicates if you don’t use FINAL clause.

can force you to use suboptimal primary key (which will guarantee record uniqueness).

all selects will be significantly slowerĪpproach 2.

Remove them on SELECT level (by things like GROUP BY) Replicated / Distributed tables) - due to eventual consistency.Īpproach 1. ! check if row exists in clickhouse before insert can give non-satisfing results if you use ClickHouse cluster (i.e.

clean and simple schema and selects in ClickHouse.extra coding and ‘moving parts’, storing some ids somewhere.

Make deduplication before ingesting data to ClickHouse

#DEDUPLICATOR OPERATOR ARCHIVE#

In general case - across the whole huge table (which can be terabyte/petabyte size).īut there many usecase when you can archive something like row-level deduplication in ClickHouse:Īpproach 0. The reason in simple: to check if the row already exists you need to do some lookup (key-value) alike (ClickHouse is bad for key-value lookups),

Sometimes you just expect insert idempotency on row level.įor now that problem has no good solution in general case using ClickHouse only.

Sometime they appear due the the fact that message queue system (Kafka/Rabbit/etc) offers at-least-once guarantees.

Sometimes duplicates are appear naturally on collector side.

There is quite common requirement to do deduplication on a record level in ClickHouse. (Block level deduplication exists in Replicated tables, and is not the subject of that article).

Dictionary on the top of the several tables using VIEWĬlickHouse row-level deduplication.

Possible issues with running ClickHouse in k8s.

Backfill/populate MV in a controlled manner.

#DEDUPLICATOR OPERATOR HOW TO#

How to test different compression codecs.

Best schema for storing many metrics registered from the single source.

Recovering from complete metadata loss in ZooKeeper.

JVM sizes and garbage collector settings.X rows of Y total rows in filesystem are suspicious.differential backups using clickhouse-backup.There are N unfinished hosts (0 of them are currently active).Altinity packaging compatibility >21.x and earlier.source parts sizeis greater than the current maximum.Can not connect to my ClickHouse server.AggregateFunction(uniq, UUID) doubled after ClickHouse upgrade.arrayMap, arrayJoin or ARRAY JOIN memory usage.Time-series alignment with interpolation.Simple aggregate functions & combinators.Roaring bitmaps for calculating retention.JSONExtract to parse many attributes at a time.ALTER MODIFY COLUMN is stuck, the column is inaccessible.Using array functions to mimic window-functions alike behavior.Multiple aligned date columns in PARTITION BY expression.Imprecise literal Decimal or Float64 values.DISTINCT & GROUP BY & LIMIT 1 BY what the difference.ReplacingMergeTree does not collapse duplicates.Proper ordering and partitioning the MergeTree tables.CollapsingMergeTree vs ReplacingMergeTree.