When refactoring the job code the job_type was removed from our
catalog but a few places got overlooked that still had a variable
holding the job type.

Corrected a function name and replaced a variable with the explicit
commands to use.

The update tests for PG11, PG12, and PG13 are updated to include
release 2.3.0.

Link to Telemetry page explains more than disable it

Co-authored-by: Mike Freedman <mfreed@cs.princeton.edu>

Stop background workers in test after calling timescaledb_post_restore
since this function restarts background workers.

Previously the assignment of data nodes to chunks had a bit
of a thundering-herd problem for multiple hypertables
without space partions: the data node assigned for the
first chunk was always the same across hypertables.
We fix this by adding the hypertable_id to the
index into the datanode array. This de-synchronizes
across hypertables but maintains consistency for any
given hypertable.

We could make this consistent for space partitioned tables
as well but avoid doing so now to prevent partitions
jumping nodes due to this change.

This also effects tablespace selection in the same way.

continuous_agg_update_materialization() doesn't use this argument and
we can't rely on a fixed bucket_width in the future anyway.

Fix heap buffer overflow in remote connection cache.

We explicilty filter paths for compressed chunks that
have spurious join clauses between the compressed chunk and
the original chunk or hypertable. However there are other
cases where a chunk could be a child rel
(i.e. RELOPT_OTHER_MEMBER_REL) such as when the chunk is
referenced as part of a UNION ALL query. We remove all
paths that have spurious join clauses between the compressed
chunk and any implied parent for the chunk.

Fixes timescale#2917

Upstream fixed a bug with miscomputation of relids for
PlaceHolderVar. Those fixes changed the signature of pull_varnos,
make_simple_restrictinfo and make_restrictinfo.
The fixes got backported to the PG12 and PG13 branch but to not
break compatibility with extensions the old functions were left in.
This patch makes our code use the new functions when compiling
against a postgres version that has them.

postgres/postgres@1cce024fd2
postgres/postgres@73fc2e5bab

Error: 'nest_level' may be used uninitialized in this function.

When querying continuous aggregate views with a search_path not
including public the query will fail cause the function reference
in the finalize call is not fully qualified.

This can surface when querying caggs through postgres_fdw which
resets search_path to contain only pg_catalog.

Fixes timescale#1919
Fixes timescale#3326

Harden core APIs by adding the `const` qualifier to pointer parameters
and return values passed by reference. Adding `const` to APIs has
several benefits and potentially reduces bugs.

* Allows core APIs to be called using `const` objects.
* Callers know that objects passed by reference are not modified as a
  side-effect of a function call.
* Returning `const` pointers enforces "read-only" usage of pointers to
  internal objects, forcing users to copy objects when mutating them
  or using explicit APIs for mutations.
* Allows compiler to apply optimizations and helps static analysis.

Note that these changes are so far only applied to core API
functions. Further work can be done to improve other parts of the
code.

pg_init_privs can have multiple entries per relation if the relation
has per column privileges. An objsubid different from 0 means that
the entry is for a column privilege. Since we do not currently
restore column privileges we have to ignore those rows otherwise
the update script will fail when tables with column privileges are
present.

When executing "ALTER EXTENSION timescaledb UPDATE TO ..." it will fail
if parallel workers spawn for the update itself. Disable parallel
execution during the update.

Call pg_terminate_backend on all active sessions on the database to
be used as template database to prevent on error on CREATE DATABASE.

Since we are only interested in entries with classoid pg_class
our queries should reflect that. Without these restrictions
objects that have entries for multiple classoids can cause the
extension update to fail.

Triggers on distributed hypertables can now be renamed due to having
the rename statement forwarded to data nodes. This also applies to
other objects on such tables, like constraints and indexes, since they
share the same DDL "rename" machinery. Tests are added for these
cases.

For convenience, trigger functions on distributed hypertables will now
also be created automatically on the data nodes. In other words, it is
no longer necessary to pre-create the trigger function on all data
nodes.

This change also fixes an issue with statement-level triggers, which
weren't properly propagated to data nodes during `CREATE TRIGGER`.

Fixes timescale#3238

Currently any tests in regresscheck-shared can only include
EXPLAIN output if they only access the precreated hypertables
as hypertables and chunks created in the test itself will
have ids depending on execution order of the shared tests.
This patch filters out those ids so shared tests can include
EXPLAIN output for local hypertables.

Format the CMake files using the `cmake-format`.

The post-update script was handling preserving initprivs for newly
added catalog tables and views. However, newly added catalog sequences
need separate handling otherwise update tests start failing. We also
now grant privileges for all future sequences in the update tests.

In passing, default the PG_VERSION in the update tests to 12 since we
don't work with PG11 anymore.

Change sanitizer test to run on PG12 and make it use the same
infrastructure as the other linux regression tests.

Co-authored-by: Sven Klemm <sven@timescale.com>

Change the postgresql ftp URL from snapshot/ to source/. This way we
do not need to react to every new commit upstream, but only whenever
the postgresql minor version changes.

Co-authored-by: Mats Kindahl <mats.kindahl@gmail.com>

Fix heap buffer overflow when renaming compressed hypertable columns.

Move the timestamp_limits and with_clause_parser test to
regresscheck-shared since those tests don't need a private
database incurring less overhead to run those tests.
Also add missing ORDER BY clauses to some of the queries
in timestamp_limits to make the output more stable.

PG13 removes the msg parameter for convert_tuples_by_name so this
patch provides a compatibility macro that abstracts the version
differences away.

The SkipScan code assumed the first entry in PathKeys would match
the distinct column. This is not always true as postgres will remove
entries from PathKeys it considers constant leading to SkipScan
operating on the wrong column under those circumstances.
This did most likely not cause any wrong results as the other
constraints for SkipScan to apply still had to be satisfied but
resulted in very inefficient query execution for those affected
queries.
This patch refactors the SkipScan code to use the distinctClause
from the Query instead.

Fixes timescale#3330

Remove the chunk name completely from output as the name might have
different length leading to different output as table headers are
adjusted to the length of the field values.

This commit add functions and code to generate a downgrade script from
the current version to the previous version. This requires execution
from a Git repository since it retrieves the prolog and epilog for the
"downgrade" file from the version given by `update_from_version` in the
`version.config` file.

The commit adds several CMake functions that simplifies the composition
of script files, but these are not used to generate the update scripts.
A potential improvement is to use the scripts to also generate the
update scripts.

This commit supports generating a downgrade script from the
current version to the previous version. Other versions are handled
using a variable containing file names of reverse update
scripts and  the source and target version is extracted from the file
names, which is assumed to be of the form
`<source-version>--<target-version>.sql`.

In addition to adding support for generating downgrade scripts, the
commit adds a downgrade test file that tests a release in a similar way
to the update script and adds it as a workflow.

Fix heap buffer overflow in hypertable expansion.

Add the files that had been missing from the docker environment since
the introduction of the downgrade scripts.

Allow pushdown of RelabelType expressions into the scan below the
DecompressChunk node. When using varchar columns as segmentby
columns constraints on those columns would not be pushed down
because postgres would inject RelabelType nodes that where not
accepted as valid expression for pushdown leading to bad performance
because the filter could only be applied after decompression.

Fixes timescale#3351

The output file `compression_qualpushdown-11.out` was not updated.

Output for `compression_qualpushdown-13.out` was not correct.

If `clang-format` is not found `CLANG_FORMAT` will be set to a false
value, which will prevent the `format` target from being defined if
`cmake-format` is not installed.

This commit fixes that by always creating a `format` target since
`clang-format` is always created even if `CLANG_FORMAT` is false.

We do not redefine `CLANG_FORMAT` to a non-false value since it is
expected to contain a path to an executable and if set to a true value
that is not a path it could be used in a way that leads to strange
errors.

This commit export the `GENERATE_DOWNGRADE_SCRIPT` and `PG_VERSION`
variables from `test_downgrade_to_tag.sh` to `docker-build.sh`.

In contrast to `realloc`, the PostgreSQL function `repalloc` does not
accept a NULL pointer and fall back on `palloc`. For that reason it is
necessary to check if the pointer is NULL and either use `palloc` or
`repalloc`.

During an update, it is not possible to run the downgrade scripts until
the release has been tagged, but the update scripts can be run. This
means that we need to split the previous version into two different
fields: one for running the update tests and one for running the
downgrade tests.

This maintenance release contains bugfixes since the 2.3.0 release. We
deem it moderate priority for upgrading. The release introduces the
possibility of generating downgrade scripts, improves the trigger
handling for distributed hypertables, adds some more randomness to
chunk assignment to avoid thundering herd issues in chunk assignment,
and fixes some issues in update handling as well as some other bugs.

**Bugfixes**
* timescale#3279 Add some more randomness to chunk assignment
* timescale#3288 Fix failed update with parallel workers
* timescale#3300 Improve trigger handling on distributed hypertables
* timescale#3304 Remove paths that reference parent relids for compressed chunks
* timescale#3305 Fix pull_varnos miscomputation of relids set
* timescale#3310 Generate downgrade script
* timescale#3314 Fix heap buffer overflow in hypertable expansion
* timescale#3317 Fix heap buffer overflow in remote connection cache.
* timescale#3327 Make aggregate in caggs fully qualified
* timescale#3327 Make aggregates in caggs fully qualified
* timescale#3336 Fix pg_init_privs objsubid handling
* timescale#3345 Fix SkipScan distinct column identification
* timescale#3355 Fix heap buffer overflow when renaming compressed hypertable columns.
* timescale#3367 Improve DecompressChunk qual pushdown
* timescale#3377 Fix bad use of repalloc

**Thanks**
* @db-adrian for reporting an issue when accessing cagg view through postgres_fdw
* @fncaldas and @pgwhalen for reporting an issue accessing caggs when public is not in search_path
* @fvannee, @mglonnro and @ebreijo for reporting an issue with the upgrade script
* @fvannee for reporting a performance regression with SkipScan