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* Update of english version of descriprion of the table function `file`. * New syntax for ReplacingMergeTree. Some improvements in text. * Significantly change article about SummingMergeTree. Article is restructured, text is changed in many places of the document. New syntax for table creation is described. * Descriptions of AggregateFunction and AggregatingMergeTree are updated. Russian version. * New syntax for new syntax of CREATE TABLE * Added english docs on Aggregating, Replacing and SummingMergeTree. * CollapsingMergeTree docs. English version. * 1. Update of CollapsingMergeTree. 2. Minor changes in markup * Update aggregatefunction.md * Update aggregatefunction.md * Update aggregatefunction.md * Update aggregatingmergetree.md * GraphiteMergeTree docs update. New syntax for creation of Replicated* tables. Minor changes in *MergeTree tables creation syntax. * Markup fix * Markup and language fixes * Clarification in the CollapsingMergeTree article * DOCAPI-4821. Sync between ru and en versions of docs. * Fixed the ambiguity in geo functions description. * Example of JOIN in ru docs * Deleted misinforming example. * Fixed links to IN operators. * Updated the description of ALTER MODIFY. * [RU] Updated ALTER MODIFY description. * Fixed anchors. * DOCAPI-3818: The Family of Log engines. StripeLog. Tocs sync. * DOCAPI-3818: Edits after review by Ivan Blinkov.
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TinyLog
Engine belongs to the family of log engines. See the common properties of log engines and their differences in the Log Engine Family article.
The simplest table engine, which stores data on a disk. Each column is stored in a separate compressed file. When writing, data is appended to the end of files.
Concurrent data access is not restricted in any way:
- If you are simultaneously reading from a table and writing to it in a different query, the read operation will complete with an error.
- If you are writing to a table in multiple queries simultaneously, the data will be broken.
The typical way to use this table is write-once: first just write the data one time, then read it as many times as needed. Queries are executed in a single stream. In other words, this engine is intended for relatively small tables (recommended up to 1,000,000 rows). It makes sense to use this table engine if you have many small tables, since it is simpler than the Log engine (fewer files need to be opened). The situation when you have a large number of small tables guarantees poor productivity, but may already be used when working with another DBMS, and you may find it easier to switch to using TinyLog types of tables. Indexes are not supported.
In Yandex.Metrica, TinyLog tables are used for intermediary data that is processed in small batches.