This commit introduces 4 compression algorithms
as well as 3 ADTs to support them. The compression
algorithms are time-series optimized. The following
algorithms are implemented:
- DeltaDelta compresses integer and timestamp values
- Gorilla compresses floats
- Dictionary compression handles any data type
and is optimized for low-cardinality datasets.
- Array stores any data type in an array-like
structure and does not actually compress it (though
TOAST-based compression can be applied on top).
These compression algorithms are are fully described in
tsl/src/compression/README.md.
The Abstract Data Types that are implemented are
- Vector - A dynamic vector that can store any type.
- BitArray - A dynamic vector to store bits.
- SimpleHash - A hash table implementation from PG12.
More information can be found in
src/adts/README.md
We find ourselves needing to store intervals (specifically time_bucket widths) in
upcoming PRs, so this commit adds that functionality, along with tests that we
perform the conversion in a sensible, round-tripa-able, manner.
This commit fixes a longstanding bug in plan_hashagg where negative time values
would prevent us from using a hashagg. The old logic for to_internal had a flag
that caused the function to return -1 instead of throwing an error, if it could
not perform the conversion. This logic was incorrect, as -1 is a valid time val
The new logic throws the error uncoditionally, and forces the user to CATCH it
if they wish to handle that case. Switching plan_hashagg to using the new logic
fixed the bug.
The commit adds a single SQL file, c_unit_tests.sql, to be the driver for all such
pure-C unit tests. Since the tests run quickly, and there is very little work to
be done at the SQL level, it does not seem like each group of such tests requires
their own SQL file.
This commit also upates the test/sql/.gitignore, as some generated files were
missing.
