May 2017
Beginner
416 pages
10h 37m
English
Content preview from Mastering PostgreSQL 9.6
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Adding support for parallel queries
What you have just seen is a simple aggregate, which has no support for parallel queries and all that. To solve those challenges the next couple of examples are all about improvements and speedups.
When creating an aggregate you can optionally define the following things:
[ , PARALLEL = { SAFE | RESTRICTED | UNSAFE } ]
By default, an aggregate does not support parallel queries. For performance reasons it does make sense, however, to explicitly state, what the aggregate is capable of:
- UNSAFE: In this mode no parallel queries are allowed
- RESTRICTED: In this mode the aggregate can be executed in parallel mode, but the execution is restricted to parallel group leader
- SAFE: It provides full support for parallel ...
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