Commit 15c729347 was a couple bricks shy of a load: we need to
ensure that expr->plan gets reset to NULL on any error exit,
if it's not supposed to be saved. Also ensure that the
stmt->target calculation gets redone if needed.
The easy way to exhibit a problem is to set up code that
violates the writable-argument restriction and then execute
it twice. But error exits out of, eg, setup_param_list()
could also break it. Make the existing PG_TRY block cover
all of that code to be sure.
Per report from Pavel Stehule.
Discussion: https://postgr.es/m/CAFj8pRAeXNTO43W2Y0Cn0YOVFPv1WpYyOqQrrzUiN6s=dn7gCg@mail.gmail.com
exec_stmt_call() tried to extract information out of a CALL statement's
argument list without using expand_function_arguments(), apparently in
the hope of saving a few nanoseconds by not processing defaulted
arguments. It got that quite wrong though, leading to crashes with
named arguments, as well as failure to enforce writability of the
argument for a defaulted INOUT parameter. Fix and simplify the logic
by using expand_function_arguments() before examining the list.
Also, move the argument-examination to just after producing the CALL
command's plan, before invoking the called procedure. This ensures
that we'll track possible changes in the procedure's argument list
correctly, and avoids a hazard of the plan cache being flushed while
the procedure executes.
Also fix assorted falsehoods and omissions in associated documentation.
Per bug #15477 from Alexey Stepanov.
Patch by me, with some help from Pavel Stehule. Back-patch to v11.
Discussion: https://postgr.es/m/15477-86075b1d1d319e0a@postgresql.org
Discussion: https://postgr.es/m/CAFj8pRA6UsujpTs9Sdwmk-R6yQykPx46wgjj+YZ7zxm4onrDyw@mail.gmail.com
To avoid the sorts of problems complained of by Jakob Egger, it'd be
best if configure didn't emit any references to the sysroot path at all.
In the case of PL/Tcl, we can do that just by keeping our hands off the
TCL_INCLUDE_SPEC string altogether. In the case of PL/Perl, we need to
substitute -iwithsysroot for -I in the compile commands, which is easily
handled if we change to using a configure output variable that includes
the switch not only the directory name. Since PL/Tcl and PL/Python
already do it like that, this seems like good consistency cleanup anyway.
Hence, this replaces the advice given to Perl-related extensions in commit
5e2217131; instead of writing "-I$(perl_archlibexp)/CORE", they should
just write "$(perl_includespec)". (The old way continues to work, but not
on recent macOS.)
It's still the case that configure needs to be aware of the sysroot
path internally, but that's cleaner than what we had before.
As before, back-patch to all supported versions.
Discussion: https://postgr.es/m/20840.1537850987@sss.pgh.pa.us
A warning on a NetBSD box revealed to me that pg_waldump/compat.c
is using vprintf(), which snprintf.c did not provide coverage for.
This is not good if we want to have uniform *printf behavior, and
it's pretty silly to omit when it's a one-line function.
I also noted that snprintf.c has pg_vsprintf() but for some reason
it was not exposed to the outside world, creating another way in
which code might accidentally invoke the platform *printf family.
Let's just make sure that we replace all eight of the POSIX-standard
printf family.
Also, upgrade plperl.h and plpython.h to make sure that they do
their undefine/redefine rain dance for all eight, not some random
maybe-sufficient subset thereof.
It's inefficient to use a single slot for mapping between tuple
descriptors for multiple tuples, as previously done when using
ConvertPartitionTupleSlot(), as that means the slot's tuple descriptors
change for every tuple.
Previously we also, via ConvertPartitionTupleSlot(), built new tuples
after the mapping even in cases where we, immediately afterwards,
access individual columns again.
Refactor the code so one slot, on demand, is used for each
partition. That avoids having to change the descriptor (and allows to
use the more efficient "fixed" tuple slots). Then use slot->slot
mapping, to avoid unnecessarily forming a tuple.
As the naming between the tuple and slot mapping functions wasn't
consistent, rename them to execute_attr_map_{tuple,slot}. It's likely
that we'll also rename convert_tuples_by_* to denote that these
functions "only" build a map, but that's left for later.
Author: Amit Khandekar and Amit Langote, editorialized by me
Reviewed-By: Amit Langote, Amit Khandekar, Andres Freund
Discussion:
https://postgr.es/m/CAJ3gD9fR0wRNeAE8VqffNTyONS_UfFPRpqxhnD9Q42vZB+Jvpg@mail.gmail.comhttps://postgr.es/m/e4f9d743-cd4b-efb0-7574-da21d86a7f36%40lab.ntt.co.jp
Backpatch: -
We must define the macro "printf" with arguments, else it can mess
up format archetype attributes in builds where PG_PRINTF_ATTRIBUTE
is just "printf". Fortunately, that's easy to do now that we're
requiring C99; we can use __VA_ARGS__.
On the other hand, it's better not to use __VA_ARGS__ for the rest
of the *printf crew, so that one can take the addresses of those
functions without surprises.
I'd proposed doing this some time ago, but forgot to make it happen;
buildfarm failures subsequent to 96bf88d52 reminded me.
Discussion: https://postgr.es/m/22709.1535135640@sss.pgh.pa.us
Discussion: https://postgr.es/m/20180926190934.ea4xvzhkayuw7gkx@alap3.anarazel.de
I started out with the idea that we needed to detect use of %m format specs
in contexts other than elog/ereport calls, because we couldn't rely on that
working in *printf calls. But a better answer is to fix things so that it
does work. Now that we're using snprintf.c all the time, we can implement
%m in that and we've fixed the problem.
This requires also adjusting our various printf-wrapping functions so that
they ensure "errno" is preserved when they call snprintf.c.
Remove elog.c's handmade implementation of %m, and let it rely on
snprintf to support the feature. That should provide some performance
gain, though I've not attempted to measure it.
There are a lot of places where we could now simplify 'printf("%s",
strerror(errno))' into 'printf("%m")', but I'm not in any big hurry
to make that happen.
Patch by me, reviewed by Michael Paquier
Discussion: https://postgr.es/m/2975.1526862605@sss.pgh.pa.us
We've spent an awful lot of effort over the years in coping with
platform-specific vagaries of the *printf family of functions. Let's just
forget all that mess and standardize on always using src/port/snprintf.c.
This gets rid of a lot of configure logic, and it will allow a saner
approach to dealing with %m (though actually changing that is left for
a follow-on patch).
Preliminary performance testing suggests that as it stands, snprintf.c is
faster than the native printf functions for some tasks on some platforms,
and slower for other cases. A pending patch will improve that, though
cases with floating-point conversions will doubtless remain slower unless
we want to put a *lot* of effort into that. Still, we've not observed
that *printf is really a performance bottleneck for most workloads, so
I doubt this matters much.
Patch by me, reviewed by Michael Paquier
Discussion: https://postgr.es/m/2975.1526862605@sss.pgh.pa.us
elog.c has long had a private strerror wrapper that handles assorted
possible failures or deficiencies of the platform's strerror. On Windows,
it also knows how to translate Winsock error codes, which the native
strerror does not. Move all this code into src/port/strerror.c and
define strerror() as a macro that invokes it, so that both our frontend
and backend code will have all of this behavior.
I believe this constitutes an actual bug fix on Windows, since AFAICS
our frontend code did not report Winsock error codes properly before this.
However, the main point is to lay the groundwork for implementing %m
in src/port/snprintf.c: the behavior we want %m to have is this one,
not the native strerror's.
Note that this throws away the prior use of src/port/strerror.c,
which was to implement strerror() on platforms lacking it. That's
been dead code for nigh twenty years now, since strerror() was
already required by C89.
We should likewise cause strerror_r to use this behavior, but
I'll tackle that separately.
Patch by me, reviewed by Michael Paquier
Discussion: https://postgr.es/m/2975.1526862605@sss.pgh.pa.us
Apple's latest rearrangements of the system-supplied headers have broken
building of PL/Perl and PL/Tcl. The only practical way to fix PL/Tcl is to
start using the "-isysroot" compiler flag to point to SDK-supplied headers,
as Apple expects. We must also start distinguishing where to find Perl's
headers from where to find its shared library; but that seems like good
cleanup anyway.
Extensions that formerly did something like -I$(perl_archlibexp)/CORE
should now do -I$(perl_includedir)/CORE instead. perl_archlibexp
is still the place to look for libperl.so, though.
If for some reason you don't like the default -isysroot setting, you can
override that by setting PG_SYSROOT in configure's arguments. I don't
currently think people would need to do so, unless maybe for cross-version
build purposes.
In addition, teach configure where to find tclConfig.sh. Our traditional
method of searching $auto_path hasn't worked for the last couple of macOS
releases, and it now seems clear that Apple's not going to change that.
The workaround of manually specifying --with-tclconfig was annoying
already, but Mojave's made it a lot more so because the sysroot path now
has to be included as well. Let's just wire the knowledge into configure
instead. To avoid breaking builds against non-default Tcl installations
(e.g. MacPorts) wherein the $auto_path method probably still works,
arrange to try the additional case only after all else has failed.
Back-patch to all supported versions, since at least the buildfarm
cares about that. The changes are set up to not do anything on macOS
releases that are old enough to not have functional sysroot trees.
Neither plperl nor plpython installed sufficient header files to
permit transform modules to be built out-of-tree using PGXS. Fix that
by installing all plperl and plpython header files (other than those
with special purposes such as generated data tables), and also install
plpython's special .mk file for mangling regression tests.
(This commit does not fix the windows install, which does not
currently install _any_ plperl or plpython headers.)
Also fix the existing transform modules for hstore and ltree so that
their cross-module #include directives work as anticipated by commit
df163230b9 et seq. This allows them to serve as working examples of
how to reference other modules when doing separate out-of-tree builds.
Discussion: https://postgr.es/m/87o9ej8bgl.fsf%40news-spur.riddles.org.uk
The simple slicing API (sq_slice, sq_ass_slice) has been deprecated
since Python 2.0 and has been removed altogether in Python 3, so remove
those functions from the PLyResult class. Instead, the non-slice
mapping functions mp_subscript and mp_ass_subscript can take slice
objects as an index. Since we just pass the index through to the
underlying list object, we already support that. Test coverage was
already in place.
The problem arises with the combination of CALL with output parameters
and doing a COMMIT inside the procedure. When a CALL has output
parameters, the portal uses the strategy PORTAL_UTIL_SELECT instead of
PORTAL_MULTI_QUERY. Using PORTAL_UTIL_SELECT causes the portal's
snapshot to be registered with the current resource
owner (portal->holdSnapshot); see
9ee1cf04ab for the reason.
Normally, PortalDrop() unregisters the snapshot. If not, then
ResourceOwnerRelease() will print a warning about a snapshot leak on
transaction commit. A transaction commit normally drops all
portals (PreCommit_Portals()), except the active portal. So in case of
the active portal, we need to manually release the snapshot to avoid the
warning.
Reported-by: Prabhat Sahu <prabhat.sahu@enterprisedb.com>
Reviewed-by: Jonathan S. Katz <jkatz@postgresql.org>
This test was supposed to check the interaction of INOUT and default
parameters in a procedure call, but it only checked the case where the
parameter was not supplied. Now it also checks the case where the
parameter was supplied. It was already working correctly, so no code
changes required.
We suppressed one of these test cases in commit feb1cc559 because
it was failing to produce the expected results on CLOBBER_CACHE_ALWAYS
buildfarm members. But now we need another test with similar behavior,
so let's set up a test file that is expected to vary between regular and
CLOBBER_CACHE_ALWAYS cases, and provide variant expected files.
Someday we should fix plpgsql's failure for change-of-field-type, and
then the discrepancy will go away and we can fold these tests back
into plpgsql_record.sql. But today is not that day.
Discussion: https://postgr.es/m/87wotkfju1.fsf@news-spur.riddles.org.uk
Until now shadowed_variables was the only plpgsql check supported by
plpgsql.extra_warnings and plpgsql.extra_errors. This patch introduces
two new checks - strict_multi_assignment and too_many_rows. Unlike
shadowed_variables, these new checks are enforced at run-time.
strict_multi_assignment checks that commands allowing multi-assignment
(for example SELECT INTO) have the same number of sources and targets.
too_many_rows checks that queries with an INTO clause return one row
exactly.
These checks are aimed at cases that are technically valid and allowed,
but are often a sign of a bug. Therefore those checks are expected to
be enabled primarily in development and testing environments.
Author: Pavel Stehule
Reviewed-by: Stephen Frost, Tomas Vondra
Discussion: https://www.postgresql.org/message-id/flat/CAFj8pRA2kKRDKpUNwLY0GeG1OqOp+tLS2yQA1V41gzuSz-hCng@mail.gmail.com
Previously a lot of the error messages referenced the type in the
error message itself. That requires that the message is translated
separately for each type.
Note that currently a few smallint cases continue to reference the
integer, rather than smallint, type. A later patch will create a
separate routine for 16bit input.
Author: Andres Freund
Discussion: https://postgr.es/m/20180707200158.wpqkd7rjr4jxq5g7@alap3.anarazel.de
A collection of typos I happened to spot while reading code, as well as
grepping for common mistakes.
Backpatch to all supported versions, as applicable, to avoid conflicts
when backporting other commits in the future.
Starting and aborting transactions in security definer procedures
doesn't work. StartTransaction() insists that the security context
stack is empty, so this would currently cause a crash, and
AbortTransaction() resets it. This could be made to work by
reorganizing the code, but right now we just prohibit it.
Reported-by: amul sul <sulamul@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/CAAJ_b96Gupt_LFL7uNyy3c50-wbhA68NUjiK5%3DrF6_w%3Dpq_T%3DQ%40mail.gmail.com
When executing CALL in PL/pgSQL, we need to set a snapshot before
invoking the to-be-called procedure. Otherwise, the to-be-called
procedure might end up running without a snapshot. For LANGUAGE SQL
procedures, this would result in an assertion failure. (For most other
languages, this is usually not a problem, because those use SPI and SPI
sets snapshots in most cases.) Setting the snapshot restores the
behavior of how CALL worked when it was handled as a generic SQL
statement in PL/pgSQL (exec_stmt_execsql()).
This change revealed another problem: In SPI_commit(), we popped the
active snapshot before committing the transaction, to avoid "snapshot %p
still active" errors. However, there is no particular reason why only
at most one snapshot should be on the stack. So change this to pop all
active snapshots instead of only one.
The previous message for SPI_ERROR_TRANSACTION claimed "cannot begin/end
transactions in PL/pgSQL", but that is no longer true. Nevertheless,
the error can still happen, so reword the messages. The error cases in
exec_prepare_plan() could never happen, so remove them.
There seems little reason for the policy of throwing error if we
find a ref to something other than a hash or array. Recursively
look through the ref, instead. This makes the behavior in non-transform
cases comparable to what was already instantiated for jsonb_plperl.
Note that because we invoke any available transform function before
considering the ref case, it's up to each transform function whether
it wants to play along with this behavior or do something different.
Because the previous behavior was just to throw a useless error,
this seems unlikely to create any compatibility issues. Still, given
the lack of field complaints so far, seems best not to back-patch.
Discussion: https://postgr.es/m/28336.1528393969@sss.pgh.pa.us
This complies with the perlcritic policy
Subroutines::RequireFinalReturn, which is a severity 4 policy. Since we
only currently check at severity level 5, the policy is raised to that
level until we move to level 4 or lower, so that any new infringements
will be caught.
A small cosmetic piece of tidying of the pgperlcritic script is
included.
Mike Blackwell
Discussion: https://postgr.es/m/CAESHdJpfFm_9wQnQ3koY3c91FoRQsO-fh02za9R3OEMndOn84A@mail.gmail.com
To distinguish SQL statements that are INSERT/UPDATE/DELETE from other
ones, exec_stmt_execsql looked at the post-rewrite form of the statement
rather than the original. This is problematic because it did that only
during first execution of the statement (in a session), but the correct
answer could change later due to addition or removal of DO INSTEAD rules
during the session. That could lead to an Assert failure, as reported
by Tushar Ahuja and Robert Haas. In non-assert builds, there's a hazard
that we would fail to enforce STRICT behavior when we'd be expected to.
That would happen if an initially present DO INSTEAD, that replaced the
original statement with one of a different type, were removed; after that
the statement should act "normally", including strictness enforcement, but
it didn't. (The converse case of enforcing strictness when we shouldn't
doesn't seem to be a hazard, as addition of a DO INSTEAD that changes the
statement type would always lead to acting as though the statement returned
zero rows, so that the strictness error could not fire.)
To fix, inspect the original form of the statement not the post-rewrite
form, making it valid to assume the answer can't change intra-session.
This should lead to the same answer in every case except when there is a
DO INSTEAD that changes the statement type; we will now set mod_stmt=true
anyway, while we would not have done so before. That breaks the Assert
in the SPI_OK_REWRITTEN code path, which expected the latter behavior.
It might be all right to assert mod_stmt rather than !mod_stmt there,
but I'm not entirely convinced that that'd always hold, so just remove
the assertion altogether.
This has been broken for a long time, so back-patch to all supported
branches.
Discussion: https://postgr.es/m/CA+TgmoZUrRN4xvZe_BbBn_Xp0BDwuMEue-0OyF0fJpfvU2Yc7Q@mail.gmail.com
Use DISCARD PLANS instead of a reconnect to force reconstruction of
a cached plan; this corresponds more nearly to what people might
actually do in practice.
Up to now, it's been safe for plpgsql to store TOAST pointers in its
variables because the ActiveSnapshot for whatever query called the plpgsql
function will surely protect such TOAST values from being vacuumed away,
even if the owning table rows are committed dead. With the introduction of
procedures, that assumption is no longer good in "non atomic" executions
of plpgsql code. We adopt the slightly brute-force solution of detoasting
all TOAST pointers at the time they are stored into variables, if we're in
a non-atomic context, just in case the owning row goes away.
Some care is needed to avoid long-term memory leaks, since plpgsql tends
to run with CurrentMemoryContext pointing to its call-lifespan context,
but we shouldn't assume that no memory is leaked by heap_tuple_fetch_attr.
In plpgsql proper, we can do the detoasting work in the "eval_mcontext".
Most of the code thrashing here is due to the need to add this capability
to expandedrecord.c as well as plpgsql proper. In expandedrecord.c,
we can't assume that the caller's context is short-lived, so make use of
the short-term sub-context that was already invented for checking domain
constraints. In view of this repurposing, it seems good to rename that
variable and associated code from "domain_check_cxt" to "short_term_cxt".
Peter Eisentraut and Tom Lane
Discussion: https://postgr.es/m/5AC06865.9050005@anastigmatix.net
In Catalog.pm, mark eval of a string instead of a block as allowed.
Disallow perlcritic completely in Gen_dummy_probes.pl, as it's
generated code.
Protect a couple of lines in plperl code from perltidy, so that the
annotation for perlcritic stays on the same line as the construct it
would otherwise object to.
Python 3.7 removes the trailing comma in the repr() of
BaseException (see <https://bugs.python.org/issue30399>), leading to
test output differences. Work around that by composing the equivalent
test output in a more manual way.
Recent gcc can warn about switch-case fall throughs that are not
explicitly labeled as intentional. This seems like a good thing,
so clean up the warnings exposed thereby by labeling all such
cases with comments that gcc will recognize.
In files that already had one or more suitable comments, I generally
matched the existing style of those. Otherwise I went with
/* FALLTHROUGH */, which is one of the spellings approved at the
more-restrictive-than-default level -Wimplicit-fallthrough=4.
(At the default level you can also spell it /* FALL ?THRU */,
and it's not picky about case. What you can't do is include
additional text in the same comment, so some existing comments
containing versions of this aren't good enough.)
Testing with gcc 8.0.1 (Fedora 28's current version), I found that
I also had to put explicit "break"s after elog(ERROR) or ereport(ERROR);
apparently, for this purpose gcc doesn't recognize that those don't
return. That seems like possibly a gcc bug, but it's fine because
in most places we did that anyway; so this amounts to a visit from the
style police.
Discussion: https://postgr.es/m/15083.1525207729@sss.pgh.pa.us
The code previously undefined isnan because of a compiler warning on
MinGW. Since we now need to use isnan, we can't do that anymore.
We might need a different solution if the compiler warning is too
annoying.
We need to call expand_function_arguments() to expand named and default
arguments.
In PL/pgSQL, we also need to deal with named and default INOUT arguments
when receiving the output values into variables.
Author: Pavel Stehule <pavel.stehule@gmail.com>
This reverts commits d204ef6377,
83454e3c2b and a few more commits thereafter
(complete list at the end) related to MERGE feature.
While the feature was fully functional, with sufficient test coverage and
necessary documentation, it was felt that some parts of the executor and
parse-analyzer can use a different design and it wasn't possible to do that in
the available time. So it was decided to revert the patch for PG11 and retry
again in the future.
Thanks again to all reviewers and bug reporters.
List of commits reverted, in reverse chronological order:
f1464c5380 Improve parse representation for MERGE
ddb4158579 MERGE syntax diagram correction
530e69e59b Allow cpluspluscheck to pass by renaming variable
01b88b4df5 MERGE minor errata
3af7b2b0d4 MERGE fix variable warning in non-assert builds
a5d86181ec MERGE INSERT allows only one VALUES clause
4b2d44031f MERGE post-commit review
4923550c20 Tab completion for MERGE
aa3faa3c7a WITH support in MERGE
83454e3c2b New files for MERGE
d204ef6377 MERGE SQL Command following SQL:2016
Author: Pavan Deolasee
Reviewed-by: Michael Paquier
I'd hoped that commit 3b8f6e75f was sufficient to ensure parallel safety
even when a build started in a subdirectory requires rebuilding of
generated headers. This isn't so, because making submake-generated-headers
a prerequisite of "all" isn't enough to ensure it's completed before
starting on "all"'s other prerequisites. The explicit dependencies we put
on the recursive make targets ensure safe ordering before we recurse into
child directories, but they don't protect targets to be made in the current
directory. Hence, put back some ordering dependencies in directories that
we've traditionally expected to be starting points for "standalone" builds,
to wit src/pl/plpython and src/test/regress. (The former needs this in
order to minimize the work involved in building for both python 2 and
python 3; the latter to support packagings that make the regression tests
available for out-of-build-tree execution.) Adjust some other dependencies
so that these two cases work correctly even at high -j settings.
I'm not terribly happy with this partial solution, but I don't see a
way to do better without massive makefile restructuring, which we surely
aren't doing at this point in the development cycle. In any case, it's
little if any worse than what we had in prior releases.
Discussion: https://postgr.es/m/1523353963.8169.26.camel@gunduz.org
Commit 372728b0d created some problems for usages like building a
subdirectory without having first done "make all" at the top level,
or for proceeding directly to "make install" without "make all".
The only reasonably clean way to fix this seems to be to force the
submake-generated-headers rule to fire in *any* "make all" or "make
install" command anywhere in the tree. To avoid lots of redundant work,
as well as parallel make jobs possibly clobbering each others' output, we
still need to be sure that the rule fires only once in a recursive build.
For that, adopt the same MAKELEVEL hack previously used for "temp-install".
But try to document it a bit better.
The submake-errcodes mechanism previously used in src/port/ and src/common/
is subsumed by this, so we can get rid of those special cases. It was
inadequate for src/common/ anyway after the aforesaid commit, and it always
risked parallel attempts to build errcodes.h.
Discussion: https://postgr.es/m/E1f5FAB-0006LU-MB@gemulon.postgresql.org
Traditionally, include/catalog/pg_foo.h contains extern declarations
for functions in backend/catalog/pg_foo.c, in addition to its function
as the authoritative definition of the pg_foo catalog's rowtype.
In some cases, we'd been forced to split out those extern declarations
into separate pg_foo_fn.h headers so that the catalog definitions
could be #include'd by frontend code. That problem is gone as of
commit 9c0a0de4c, so let's undo the splits to make things less
confusing.
Discussion: https://postgr.es/m/23690.1523031777@sss.pgh.pa.us
A normal SQL command run inside PL/pgSQL acquires a snapshot, but SET
TRANSACTION does not work anymore if a snapshot is set. So we have to
handle this separately.
Reviewed-by: Alexander Korotkov <a.korotkov@postgrespro.ru>
Reviewed-by: Tomas Vondra <tomas.vondra@2ndquadrant.com>
If we are not going to save the plan, then we need to unset expr->plan
after we are done, also in error cases. Otherwise, we get a dangling
pointer next time around.
This is not the ideal solution. It would be better if we could convince
SPI not to associate a cached plan with a resource owner, and then we
could just save the plan in all cases. But that would require bigger
surgery.
Reported-by: Pavel Stehule <pavel.stehule@gmail.com>
MERGE performs actions that modify rows in the target table
using a source table or query. MERGE provides a single SQL
statement that can conditionally INSERT/UPDATE/DELETE rows
a task that would other require multiple PL statements.
e.g.
MERGE INTO target AS t
USING source AS s
ON t.tid = s.sid
WHEN MATCHED AND t.balance > s.delta THEN
UPDATE SET balance = t.balance - s.delta
WHEN MATCHED THEN
DELETE
WHEN NOT MATCHED AND s.delta > 0 THEN
INSERT VALUES (s.sid, s.delta)
WHEN NOT MATCHED THEN
DO NOTHING;
MERGE works with regular and partitioned tables, including
column and row security enforcement, as well as support for
row, statement and transition triggers.
MERGE is optimized for OLTP and is parameterizable, though
also useful for large scale ETL/ELT. MERGE is not intended
to be used in preference to existing single SQL commands
for INSERT, UPDATE or DELETE since there is some overhead.
MERGE can be used statically from PL/pgSQL.
MERGE does not yet support inheritance, write rules,
RETURNING clauses, updatable views or foreign tables.
MERGE follows SQL Standard per the most recent SQL:2016.
Includes full tests and documentation, including full
isolation tests to demonstrate the concurrent behavior.
This version written from scratch in 2017 by Simon Riggs,
using docs and tests originally written in 2009. Later work
from Pavan Deolasee has been both complex and deep, leaving
the lead author credit now in his hands.
Extensive discussion of concurrency from Peter Geoghegan,
with thanks for the time and effort contributed.
Various issues reported via sqlsmith by Andreas Seltenreich
Authors: Pavan Deolasee, Simon Riggs
Reviewer: Peter Geoghegan, Amit Langote, Tomas Vondra, Simon Riggs
Discussion:
https://postgr.es/m/CANP8+jKitBSrB7oTgT9CY2i1ObfOt36z0XMraQc+Xrz8QB0nXA@mail.gmail.comhttps://postgr.es/m/CAH2-WzkJdBuxj9PO=2QaO9-3h3xGbQPZ34kJH=HukRekwM-GZg@mail.gmail.com
Tom Lane
Andres Freund
Andrew Gierth
Peter Eisentraut
Tomas Vondra
Heikki Linnakangas
Andrew Dunstan
Simon Riggs