This PR adds the ability to have multiple different versions of the timescaledb
extension be used by different databases in the same PostgreSQL
instance (server).
This is accomplished by splitting this extension into two .so files.
1) timescaledb.so -- stuff under loader/. Really not a lot of code.
This code MUST be backwards compatible in the future.
2) timescaledb-version.so (most of our code). Need
not be backwards compatible.
Timescaledb.so becomes a small stub which is preloaded and whose main
reason for existing is to dynamically load the right
timescaledb-version.so when the time comes.
This change allows either of the above .so to be loaded in
shared_preload_libraries. But timescaledb.so allows for multiple
versions used on different databases in the same instance along
with smoother upgrades. Using timescaledb-version.so allows for
finer-grained control and lock-in and is appropriate in only a few
production environments.
This PR also adds version checking so that a clear failure message
will be displayed if the .so version does not match the SQL extension
version.
To support multi-version functionality we changed the way SQL update
scripts are generated. Previously, the system used a bunch of
intermediate upgrade scripts. So with 3 versions, you would have an
update script of 1--2, 2--3. But, this PR changes things so that we
produce direct "shortcut" update files: 1--3, 2--3.
This is done for 2 reasons:
1) Each of the update files should point to
$libdir/timescaledb-current_version. Since you cannot guarantee that
Previous .so for each intermediate version has been installed.
2) You don't want intermediate version updates installed without the
.so. For example, if you have versions 1,2,3
and you are installing version 3, you want the upgrade files 1--3,
2--3 but not 1--2 because if you have 1--2
then a user could do ALTER EXTENSION timescaledb UPDATE TO 2. But
the .so for version 2 may not be installed.
In order to test this functionality, we add a mock extension version .so
that we can test extension loading inside the regression framework.
TimescaleDB cache invalidation happens as a side effect of doing a
full SQL statement (INSERT/UPDATE/DELETE) on a catalog table (via
table triggers). However, triggers aren't invoked when using
PostgreSQL's internal catalog API for updates, since PostgreSQL's
catalog tables don't have triggers that require full statement
parsing, planning, and execution.
Since we are now using the regular PostgreSQL catalog update API for
some TimescaleDB catalog operations, we need to do cache invalidation
also on such operations.
This change adds cache invalidation when updating catalogs using the
internal (C) API and also makes the cache invalidation more fine
grained. For instance, caches are no longer invalidated on some
INSERTS that do not affect the validity of objects already in the
cache, such as adding a new chunk.
SQL code is now split into setup, functions, and init files to
allow a subset to be run when the extension is updated. During
build, an update script is now also generated.
