Postgres will prepend pg_temp to the effective search_path if it
is not present in the search_path. While pg_temp will never be
used to look up functions or operators unless explicitly requested
pg_temp will be used to look up relations. Putting pg_temp in
search_path makes sure objects in pg_temp will be considered last
and pg_temp cannot be used to mask existing objects.
SET LOCAL is only active until end of transaction so we set search_path
again after COMMIT in functions that do transaction control. While we
could use SET at the start of the function we do not want to bleed out
search_path to caller.
This patch locks down search_path in extension install and update
scripts to only contain pg_catalog, this requires that any reference
in those scripts is fully qualified. Additionally we add explicit
create commands to all update scripts for objects added to the
public schema. This change will make update scripts fail if a
function with identical signature already exists when installing
or upgrading instead reusing the existing object.
When executing `recompress_chunk` and a query at the same time, a
deadlock can be generated because the chunk relation and the chunk
index and the compressed and uncompressd chunks are locked in different
orders. In particular, when `recompress_chunk` is executing, it will
first decompress the chunk and as part of that lock the uncompressed
chunk index in AccessExclusive mode and when trying to compress the
chunk again it will try to lock the uncompressed chunk in
AccessExclusive as part of truncating it.
Note that `decompress_chunk` and `compress_chunk` lock the relations in
the same order and the issue arises because the procedures are combined
inth a single transaction.
To avoid the deadlock, this commit rewrites the `recompress_chunk` to
be a procedure and adds a commit between the decompression and
compression. Committing the transaction after the decompress will allow
reads and inserts to proceed by working on the uncompressed chunk, and
the compression part of the procedure will take the necessary locks in
strict order, thereby avoiding a deadlock.
In addition, the isolation test is rewritten so that instead of adding
a waitpoint in the PL/SQL function, we implement the isolation test by
taking a lock on the compressed table after the decompression.
Fixes#3846
Remove copy_chunk_data() function and code needed to support it,
such as the 'transactional' argument.
Rework copy chunk logic using separate stages.
Introduce copy_chunk() API function as an internal wrapper for
the move_chunk().
The building blocks required for implementing end-to-end copy/move
chunk functionality have now been wrapped in a procedure.
A procedure is required because multiple transactions are needed to
carry out the activity across the access node and the involved two data
nodes.
The following steps are encapsulated in this procedure
1) Create an empty chunk table on the destination data node
2) Copy the data from the src data node chunk to this newly created
destination node chunk. This is done via inbuilt PostgreSQL logical
replication functionality
3) Attach this chunk to the hypertable on the dst data node
4) Remove this chunk from the src data node to complete the move if
requested
A new catalog table "chunk_copy_activity" has been added to track
the progress of the above stages. A unique id gets assigned to each
activity and it is updated with the completed stages as things
progress.
After inserts go into a compressed chunk, the chunk is marked as
unordered.This PR adds a new function recompress_chunk that
compresses the data and sets the status back to compressed. Further
optimizations for this function are planned but not part of this PR.
This function can be invoked by calling
SELECT recompress_chunk(<chunk_name>).
recompress_chunk function is automatically invoked by the compression
policy job, when it sees that a chunk is in unordered state.
This commit improves the API of compress_chunk and decompress_chunk:
- have it return the chunk regclass processed (or NULL in the
idempotent case);
- mark it as STRICT
- add if_not_compressed/if_compressed options for idempotency
Add support for compress_chunks function.
This also adds support for compress_orderby and compress_segmentby
parameters in ALTER TABLE. These parameteres are used by the
compress_chunks function.
The parsing code will most likely be changed to use PG raw_parser
function.
Adds a move_chunk function which to a different tablespace. This is
implemented as an extension to the reorder command.
Given that the heap, toast tables, and indexes are being rewritten
during the reorder operation, adding the ability to modify the tablespace
is relatively simple and mostly requires adding parameters to the relevant
functions for the destination tablespace (and index tablespace). The tests
do not focus on further exercising the reorder infrastructure, but instead
ensure that tablespace movement and permissions checks properly occur.
New cluster-like command which writes to a new index than swaps,
much like is done for the data table, and only acquires
exclusive locks for said swap. This trades off disk usage for
lower contention: we hold locks for a much lower period of time,
allowing reads to work concurrently, but we have both the old
and new versions of the table existing at once, approximately
doubling storage usage while reorder is running.
Currently only works on chunks.
