#27719: Add queryset.alias() to mimic .annotate() for aggregations without
loading
data
-------------------------------------+-------------------------------------
Reporter: Marc Tamlyn | Owner: nobody
Type: New feature | Status: new
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by Christophe Pettus):
Doing a quick example query: In a table with a relatively large text
field, but just 2,400 rows, the difference between returning all rows and
all fields without the ts_vector() call and returning all with it was
12.7ms vs 24,000ms.
Doing a full sequential scan (no index) with both calculating the
to_tsvector() for return ''and'' in query predicate is 27,000ms without
recalculating the to_tsvector for return, 46,700ms with recalculating it.
After having created a functional index on the to_tsvector() call, and
using a relatively common search term, the time to return without
recalculating the to_tsvector was 1.7ms, vs 21,200ms with recalculating
the ts_vector.
So, in any scenario, not having to recalcuate the to_tsvector() is a win.
--
Ticket URL: <https://code.djangoproject.com/ticket/27719#comment:1>
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