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47 lines
2.8 KiB
Markdown
47 lines
2.8 KiB
Markdown
System Models
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=============
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[Clickhouse docs](https://clickhouse.yandex/docs/en/system_tables/).
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System models are read only models for implementing part of the system's functionality, and for providing access to information about how the system is working.
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Currently the following system models are supported:
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| Class | DB Table | Comments
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| ------------ | -------------- | ---------------------------------------------------
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| SystemPart | system.parts | Gives methods to work with partitions. See below.
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Partitions and Parts
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--------------------
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[ClickHouse docs](https://clickhouse.yandex/docs/en/query_language/queries/#manipulations-with-partitions-and-parts).
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A partition in a table is data for a single calendar month. Table "system.parts" contains information about each part.
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| Method | Parameters | Comments
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| --------------------- | ------------------------- | -----------------------------------------------------------------------------------------------
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| get(static) | database, conditions="" | Gets database partitions, filtered by conditions
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| get_active(static) | database, conditions="" | Gets only active (not detached or dropped) partitions, filtered by conditions
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| detach | settings=None | Detaches the partition. Settings is a dict of params to pass to http request
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| drop | settings=None | Drops the partition. Settings is a dict of params to pass to http request
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| attach | settings=None | Attaches already detached partition. Settings is a dict of params to pass to http request
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| freeze | settings=None | Freezes (makes backup) of the partition. Settings is a dict of params to pass to http request
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| fetch | settings=None | Fetches partition. Settings is a dict of params to pass to http request
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Usage example:
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from infi.clickhouse_orm.database import Database
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from infi.clickhouse_orm.system_models import SystemPart
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db = Database('my_test_db', db_url='http://192.168.1.1:8050', username='scott', password='tiger')
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partitions = SystemPart.get_active(db, conditions='') # Getting all active partitions of the database
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if len(partitions) > 0:
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partitions = sorted(partitions, key=lambda obj: obj.name) # Partition name is YYYYMM, so we can sort so
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partitions[0].freeze() # Make a backup in /opt/clickhouse/shadow directory
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partitions[0].drop() # Dropped partition
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`Note`: system.parts stores information for all databases. To be correct, SystemPart model was designed to receive only parts belonging to the given database instance.
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---
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[<< Schema Migrations](schema_migrations.md) | [Table of Contents](toc.md) | [Contributing >>](contributing.md) |