Tag: speedup

Waiting for 9.5 – Use 128-bit math to accelerate some aggregation functions.

On 20th of March, Andres Freund committed patch:

Use 128-bit math to accelerate some aggregation functions.
 
On platforms where we support 128bit integers, use them to implement
faster transition functions for sum(int8), avg(int8),
var_*(int2/int4),stdev_*(int2/int4). Where not supported continue to use
numeric as a transition type.
 
In some synthetic benchmarks this has been shown to provide significant
speedups.
 
Bumps catversion.
 
Discussion: 544BB5F1.50709@proxel.se
Author: Andreas Karlsson
Reviewed-By: Peter Geoghegan, Petr Jelinek, Andres Freund, Oskari Saarenmaa, David Rowley

Continue reading Waiting for 9.5 – Use 128-bit math to accelerate some aggregation functions.

Waiting for 9.5 – Use abbreviated keys for faster sorting of text datums.

On 19th of January, Robert Haas committed patch:

Use abbreviated keys for faster sorting of text datums.
 
This commit extends the SortSupport infrastructure to allow operator
classes the option to provide abbreviated representations of Datums;
in the case of text, we abbreviate by taking the first few characters
of the strxfrm() blob.  If the abbreviated comparison is insufficent
to resolve the comparison, we fall back on the normal comparator.
This can be much faster than the old way of doing sorting if the
first few bytes of the string are usually sufficient to resolve the
comparison.
 
There is the potential for a performance regression if all of the
strings to be sorted are identical for the first 8+ characters and
differ only in later positions; therefore, the SortSupport machinery
now provides an infrastructure to abort the use of abbreviation if
it appears that abbreviation is producing comparatively few distinct
keys.  HyperLogLog, a streaming cardinality estimator, is included in
this commit and used to make that determination for text.
 
Peter Geoghegan, reviewed by me.

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Waiting for 9.5 – vacuumdb: enable parallel mode

On 23rd of January, Alvaro Herrera committed patch:

vacuumdb: enable parallel mode
 
This mode allows vacuumdb to open several server connections to vacuum
or analyze several tables simultaneously.
 
Author: Dilip Kumar.  Some reworking by Álvaro Herrera
Reviewed by: Jeff Janes, Amit Kapila, Magnus Hagander, Andres Freund

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Waiting for 8.4 – UNION / INTERSECT / EXCEPT

During last month or so, Tom Lane commited changes in PostgreSQL, which were foundations for adding hash-based versions of popular features.

I already described first such feature – DISTINCT.

Now, there were 3 more commits which were related to this:

Continue reading Waiting for 8.4 – UNION / INTERSECT / EXCEPT