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Added update_lag option documentation

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This commit is contained in:
Maksim Kita 2021-06-12 18:42:00 +03:00
parent 8762e40907
commit b16e801fb4
1 changed files with 4 additions and 1 deletions
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5
docs/en/sql-reference/dictionaries/external-dictionaries/external-dicts-dict-lifetime.md
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@ -94,6 +94,8 @@ It is also possible for `Flat`, `Hashed`, `ComplexKeyHashed` dictionaries to onl
- If source is Executable then `update_field` will be added as executable script argument with last update time as argument value.
- If source is ClickHouse, MySQL, PostgreSQL, ODBC there will be additional part of WHERE, where `update_field` is compared as greater or equal with last update time.
If `update_field` option is set. Additional option `update_lag` can be set. Value of `update_lag` option is subtracted from previous update time before request updated data.
Example of settings:
``` xml
@ -102,6 +104,7 @@ Example of settings:
<clickhouse>
...
<update_field>added_time</update_field>
<update_lag>15</update_lag>
</clickhouse>
...
</dictionary>
@ -111,6 +114,6 @@ or
``` sql
...
SOURCE(CLICKHOUSE(... update_field 'added_time'))
SOURCE(CLICKHOUSE(... update_field 'added_time' update_lag 15))
...
```