Common time-series rollups are of the form SELECT date_trunc(const,
time) as t, aggregates... GROUP BY t ORDER BY t DESC LIMIT const2.
Previously, Postgres would not optimize such queries because it
could not match date_trunc(const, time) to any indexes on time, since
it has no way to know that a sort on time is always a valid sort on
date_trunc(const, time).
This commit implements this optimization for date_trunc but it could
apply to a wider range of functions, to be implemented later.
Previously, each test set their own (although mostly the same)
configuration for log output and error verbosity. This is now set
globally in the test runner so that tests only need to set these
configuration parameters if they need to override the defaults. The
log verbosity is also reduced so that errors aren't generated with the
line number of the source file that output the error. Line numbers in
the output can break tests when upgrading to a new PostgreSQL version
that outputs a different line number.
These tests show that non-aggregated queries that have an ORDER BY time
DESC LIMIT x structure perform well. Postgres processes such queries by
using a time DESC index and then performs a MergeAppend. Some further
optimization to avoid touching unnecessary tables due to constraints
can be added but they are not a priority. Much worse is that these
optimizations do not work when grouping by time (either through
integer division or using date_trunc).
In order to use the non-aggregated query optimizations we had
to create an index with time as the leading field and no
WHERE clause on the index.
Since create_hypertable() allows you to optionally specify a
partitioning column, it makes sense to default to one partition when
no column is specified and asking for the number of partitions when a
column is specified and the number of partitions is not (instead of
defaulting to one).
This patch also changes the order and type of partitioning-related
input arguments to create_hypertable() so that the number of
partitions can easily be specified alongside the partitioning column
and without type casting.
- Directory structure now matches common practices
- Regression tests now run with pg_regress via the PGXS infrastructure.
- Unit tests do not integrate well with pg_regress and have to be run
separately.
- Docker functionality is separate from main Makefile. Run with
`make -f docker.mk` to build and `make -f docker.mk run` to run
the database in a container.
