Commit graph

4972 commits

Author SHA1 Message Date
Bruce Momjian
c44327afa4 Binary upgrade:
Modify pg_dump --binary-upgrade and add backend support routines to
support the preservation of pg_type oids when doing a binary upgrade.
This allows user-defined composite types and arrays to be binary
upgraded.
2009-12-24 22:09:24 +00:00
Tom Lane
d68e08d1fe Allow the index name to be omitted in CREATE INDEX, causing the system to
choose an index name the same as it would do for an unnamed index constraint.
(My recent changes to the index naming logic have helped to ensure that this
will be a reasonable choice.)  Per a suggestion from Peter.

A necessary side-effect is to promote CONCURRENTLY to type_func_name_keyword
status, ie, it can't be a table/column/index name anymore unless quoted.
This is not all bad, since we have heard more than once of people typing
CREATE INDEX CONCURRENTLY ON foo (...) and getting a normal index build of
an index named "concurrently", which was not what they wanted.  Now this
syntax will result in a concurrent build of an index with system-chosen
name; which they can rename afterwards if they want something else.
2009-12-23 17:41:45 +00:00
Tom Lane
cfc5008a51 Adjust naming of indexes and their columns per recent discussion.
Index expression columns are now named after the FigureColname result for
their expressions, rather than always being "pg_expression_N".  Digits are
appended to this name if needed to make the column name unique within the
index.  (That happens for regular columns too, thus fixing the old problem
that CREATE INDEX fooi ON foo (f1, f1) fails.  Before exclusion indexes
there was no real reason to do such a thing, but now maybe there is.)

Default names for indexes and associated constraints now include the column
names of all their columns, not only the first one as in previous practice.
(Of course, this will be truncated as needed to fit in NAMEDATALEN.  Also,
pkey indexes retain the historical behavior of not naming specific columns
at all.)

An example of the results:

regression=# create table foo (f1 int, f2 text,
regression(# exclude (f1 with =, lower(f2) with =));
NOTICE:  CREATE TABLE / EXCLUDE will create implicit index "foo_f1_lower_exclusion" for table "foo"
CREATE TABLE
regression=# \d foo_f1_lower_exclusion
Index "public.foo_f1_lower_exclusion"
 Column |  Type   | Definition
--------+---------+------------
 f1     | integer | f1
 lower  | text    | lower(f2)
btree, for table "public.foo"
2009-12-23 02:35:25 +00:00
Tom Lane
4fca795de4 Bump catversion to reflect the fact that HS patch changed pg_proc
contents, and PG_CONTROL_VERSION to reflect the fact that it changed
pg_control contents.  (I see we did at least remember to change
XLOG_PAGE_MAGIC for the WAL contents changes.)
2009-12-19 04:08:32 +00:00
Simon Riggs
efc16ea520 Allow read only connections during recovery, known as Hot Standby.
Enabled by recovery_connections = on (default) and forcing archive recovery using a recovery.conf. Recovery processing now emulates the original transactions as they are replayed, providing full locking and MVCC behaviour for read only queries. Recovery must enter consistent state before connections are allowed, so there is a delay, typically short, before connections succeed. Replay of recovering transactions can conflict and in some cases deadlock with queries during recovery; these result in query cancellation after max_standby_delay seconds have expired. Infrastructure changes have minor effects on normal running, though introduce four new types of WAL record.

New test mode "make standbycheck" allows regression tests of static command behaviour on a standby server while in recovery. Typical and extreme dynamic behaviours have been checked via code inspection and manual testing. Few port specific behaviours have been utilised, though primary testing has been on Linux only so far.

This commit is the basic patch. Additional changes will follow in this release to enhance some aspects of behaviour, notably improved handling of conflicts, deadlock detection and query cancellation. Changes to VACUUM FULL are also required.

Simon Riggs, with significant and lengthy review by Heikki Linnakangas, including streamlined redesign of snapshot creation and two-phase commit.

Important contributions from Florian Pflug, Mark Kirkwood, Merlin Moncure, Greg Stark, Gianni Ciolli, Gabriele Bartolini, Hannu Krosing, Robert Haas, Tatsuo Ishii, Hiroyuki Yamada plus support and feedback from many other community members.
2009-12-19 01:32:45 +00:00
Peter Eisentraut
d6de43099a Don't unblock SIGQUIT in the SIGQUIT handler
This was possibly linked to a deadlock-like situation in glibc syslog code
invoked by the ereport call in quickdie().  In any case, a signal handler
should not unblock its own signal unless there is a specific reason to.
2009-12-16 23:05:00 +00:00
Peter Eisentraut
b63b967a7e If there is no sigdelset(), define it as a macro.
This removes some duplicate code that recreated the identical workaround
when the newer signal API is missing.
2009-12-16 22:55:34 +00:00
Peter Eisentraut
dd4cd55c15 Python 3 support in PL/Python
Behaves more or less unchanged compared to Python 2, but the new language
variant is called plpython3u.  Documentation describing the naming scheme
is included.
2009-12-15 22:59:55 +00:00
Tom Lane
a5495cd841 Add a hook to let loadable modules get control at ProcessUtility execution,
and use it to extend contrib/pg_stat_statements to track utility commands.

Itagaki Takahiro, reviewed by Euler Taveira de Oliveira.
2009-12-15 20:04:49 +00:00
Tom Lane
34d26872ed Support ORDER BY within aggregate function calls, at long last providing a
non-kluge method for controlling the order in which values are fed to an
aggregate function.  At the same time eliminate the old implementation
restriction that DISTINCT was only supported for single-argument aggregates.

Possibly release-notable behavioral change: formerly, agg(DISTINCT x)
dropped null values of x unconditionally.  Now, it does so only if the
agg transition function is strict; otherwise nulls are treated as DISTINCT
normally would, ie, you get one copy.

Andrew Gierth, reviewed by Hitoshi Harada
2009-12-15 17:57:48 +00:00
Robert Haas
cddca5ec13 Add an EXPLAIN (BUFFERS) option to show buffer-usage statistics.
This patch also removes buffer-usage statistics from the track_counts
output, since this (or the global server statistics) is deemed to be a better
interface to this information.

Itagaki Takahiro, reviewed by Euler Taveira de Oliveira.
2009-12-15 04:57:48 +00:00
Tom Lane
a620d5005d Fix a bug introduced when set-returning SQL functions were made inline-able:
we have to cope with the possibility that the declared result rowtype contains
dropped columns.  This fails in 8.4, as per bug #5240.

While at it, be more paranoid about inserting binary coercions when inlining.
The pre-8.4 code did not really need to worry about that because it could not
inline at all in any case where an added coercion could change the behavior
of the function's statement.  However, when inlining a SRF we allow sorting,
grouping, and set-ops such as UNION.  In these cases, modifying one of the
targetlist entries that the sort/group/setop depends on could conceivably
change the behavior of the function's statement --- so don't inline when
such a case applies.
2009-12-14 02:15:54 +00:00
Magnus Hagander
0182d6f646 Allow LDAP authentication to operate in search+bind mode, meaning it
does a search for the user in the directory first, and then binds with
the DN found for this user.

This allows for LDAP logins in scenarios where the DN of the user cannot
be determined simply by prefix and suffix, such as the case where different
users are located in different containers.

The old way of authentication can be significantly faster, so it's kept
as an option.

Robert Fleming and Magnus Hagander
2009-12-12 21:35:21 +00:00
Robert Haas
02490d4692 Export ExplainBeginOutput() and ExplainEndOutput() for auto_explain.
Without these functions, anyone outside of explain.c can't actually use
ExplainPrintPlan, because the ExplainState won't be initialized properly.
The user-visible result of this was a crash when using auto_explain with
the JSON output format.

Report by Euler Taveira de Oliveira.  Analysis by Tom Lane.  Patch by me.
2009-12-12 00:35:34 +00:00
Itagaki Takahiro
f1325ce213 Add large object access control.
A new system catalog pg_largeobject_metadata manages
ownership and access privileges of large objects.

KaiGai Kohei, reviewed by Jaime Casanova.
2009-12-11 03:34:57 +00:00
Andrew Dunstan
324385d67f Add YAML to list of EXPLAIN formats. Greg Sabino Mullane, reviewed by Takahiro Itagaki. 2009-12-11 01:33:35 +00:00
Tom Lane
62aba76568 Prevent indirect security attacks via changing session-local state within
an allegedly immutable index function.  It was previously recognized that
we had to prevent such a function from executing SET/RESET ROLE/SESSION
AUTHORIZATION, or it could trivially obtain the privileges of the session
user.  However, since there is in general no privilege checking for changes
of session-local state, it is also possible for such a function to change
settings in a way that might subvert later operations in the same session.
Examples include changing search_path to cause an unexpected function to
be called, or replacing an existing prepared statement with another one
that will execute a function of the attacker's choosing.

The present patch secures VACUUM, ANALYZE, and CREATE INDEX/REINDEX against
these threats, which are the same places previously deemed to need protection
against the SET ROLE issue.  GUC changes are still allowed, since there are
many useful cases for that, but we prevent security problems by forcing a
rollback of any GUC change after completing the operation.  Other cases are
handled by throwing an error if any change is attempted; these include temp
table creation, closing a cursor, and creating or deleting a prepared
statement.  (In 7.4, the infrastructure to roll back GUC changes doesn't
exist, so we settle for rejecting changes of "search_path" in these contexts.)

Original report and patch by Gurjeet Singh, additional analysis by
Tom Lane.

Security: CVE-2009-4136
2009-12-09 21:57:51 +00:00
Tom Lane
0cb65564e5 Add exclusion constraints, which generalize the concept of uniqueness to
support any indexable commutative operator, not just equality.  Two rows
violate the exclusion constraint if "row1.col OP row2.col" is TRUE for
each of the columns in the constraint.

Jeff Davis, reviewed by Robert Haas
2009-12-07 05:22:23 +00:00
Tom Lane
8de7472b45 Don't use a duplicate OID for aclexplode(). 2009-12-06 02:55:54 +00:00
Peter Eisentraut
36f887c41c Speed up information schema privilege views
Instead of expensive cross joins to resolve the ACL, add table-returning
function aclexplode() that expands the ACL into a useful form, and join
against that.

Also, implement the role_*_grants views as a thin layer over the respective
*_privileges views instead of essentially repeating the same code twice.

fixes bug #4596

by Joachim Wieland, with cleanup by me
2009-12-05 21:43:36 +00:00
Heikki Linnakangas
ab3148b712 Fix bug in temporary file management with subtransactions. A cursor opened
in a subtransaction stays open even if the subtransaction is aborted, so
any temporary files related to it must stay alive as well. With the patch,
we use ResourceOwners to track open temporary files and don't automatically
close them at subtransaction end (though in the normal case temporary files
are registered with the subtransaction resource owner and will therefore be
closed).

At end of top transaction, we still check that there's no temporary files
marked as close-at-end-of-transaction open, but that's now just a debugging
cross-check as the resource owner cleanup should've closed them already.
2009-12-03 11:03:29 +00:00
Tom Lane
0d32342501 Teach the regular expression functions to do case-insensitive matching and
locale-dependent character classification properly when the database encoding
is UTF8.

The previous coding worked okay in single-byte encodings, or in any case for
ASCII characters, but failed entirely on multibyte characters.  The fix
assumes that the <wctype.h> functions use Unicode code points as the wchar
representation for Unicode, ie, wchar matches pg_wchar.

This is only a partial solution, since we're still stupid about non-ASCII
characters in multibyte encodings other than UTF8.  The practical effect
of that is limited, however, since those cases are generally Far Eastern
glyphs for which concepts like case-folding don't apply anyway.  Certainly
all or nearly all of the field reports of problems have been about UTF8.
A more general solution would require switching to the platform's wchar
representation for all regex operations; which is possible but would have
substantial disadvantages.  Let's try this and see if it's sufficient in
practice.
2009-12-01 21:00:24 +00:00
Bruce Momjian
ef51395e24 Revert due to Tom's concerns:
Add ProcessUtility_hook() to handle all DDL to
contrib/pg_stat_statements.
2009-12-01 02:31:13 +00:00
Bruce Momjian
d85cb27293 ProcessUtility_hook:
Add ProcessUtility_hook() to handle all DDL to contrib/pg_stat_statements.

Itagaki Takahiro
2009-12-01 01:08:46 +00:00
Tom Lane
0c61cff57a Make pg_stat_activity.application_name visible to all users, rather than
being hidden when current_query is.  Relocate it to a column position
more consistent with that behavior.  Per discussion.
2009-11-29 18:14:32 +00:00
Tom Lane
42b2907d12 Add support for anonymous code blocks (DO blocks) to PL/Perl.
Joshua Tolley, reviewed by Brendan Jurd and Tim Bunce
2009-11-29 03:02:27 +00:00
Tom Lane
8217cfbd99 Add support for an application_name parameter, which is displayed in
pg_stat_activity and recorded in log entries.

Dave Page, reviewed by Andres Freund
2009-11-28 23:38:08 +00:00
Tom Lane
1a95f12702 Eliminate a lot of list-management overhead within join_search_one_level
by adding a requirement that build_join_rel add new join RelOptInfos to the
appropriate list immediately at creation.  Per report from Robert Haas,
the list_concat_unique_ptr() calls that this change eliminates were taking
the lion's share of the runtime in larger join problems.  This doesn't do
anything to fix the fundamental combinatorial explosion in large join
problems, but it should push out the threshold of pain a bit further.

Note: because this changes the order in which joinrel lists are built,
it might result in changes in selected plans in cases where different
alternatives have exactly the same costs.  There is one example in the
regression tests.
2009-11-28 00:46:19 +00:00
Heikki Linnakangas
cd87b6f8a5 Fix an old bug in multixact and two-phase commit. Prepared transactions can
be part of multixacts, so allocate a slot for each prepared transaction in
the "oldest member" array in multixact.c. On PREPARE TRANSACTION, transfer
the oldest member value from the current backends slot to the prepared xact
slot. Also save and recover the value from the 2pc state file.

The symptom of the bug was that after a transaction prepared, a shared lock
still held by the prepared transaction was sometimes ignored by other
transactions.

Fix back to 8.1, where both 2PC and multixact were introduced.
2009-11-23 09:58:36 +00:00
Tom Lane
7fc0f06221 Add a WHEN clause to CREATE TRIGGER, allowing a boolean expression to be
checked to determine whether the trigger should be fired.

For BEFORE triggers this is mostly a matter of spec compliance; but for AFTER
triggers it can provide a noticeable performance improvement, since queuing of
a deferred trigger event and re-fetching of the row(s) at end of statement can
be short-circuited if the trigger does not need to be fired.

Takahiro Itagaki, reviewed by KaiGai Kohei.
2009-11-20 20:38:12 +00:00
Tom Lane
c742b795dd Add a hook to CREATE/ALTER ROLE to allow an external module to check the
strength of database passwords, and create a sample implementation of
such a hook as a new contrib module "passwordcheck".

Laurenz Albe, reviewed by Takahiro Itagaki
2009-11-18 21:57:56 +00:00
Tom Lane
5e66a51c2e Provide a parenthesized-options syntax for VACUUM, analogous to that recently
adopted for EXPLAIN.  This will allow additional options to be implemented
in future without having to make them fully-reserved keywords.  The old syntax
remains available for existing options, however.

Itagaki Takahiro
2009-11-16 21:32:07 +00:00
Tom Lane
caf9c830d9 Improve planning of Materialize nodes inserted atop the inner input of a
mergejoin to shield it from doing mark/restore and refetches.  Put an explicit
flag in MergePath so we can centralize the logic that knows about this,
and add costing logic that considers using Materialize even when it's not
forced by the previously-existing considerations.  This is in response to
a discussion back in August that suggested that materializing an inner
indexscan can be helpful when the refetch percentage is high enough.
2009-11-15 02:45:35 +00:00
Magnus Hagander
da8d684d39 Add inheritable ACE when creating a restricted token for execution on
Win32.

Also refactor the code around it to be more clear.

Jesse Morris
2009-11-14 15:39:36 +00:00
Tom Lane
82121aff12 Avoid assuming that enum CreateStmtLikeOption is unsigned. Zdenek Kotala 2009-11-13 23:44:19 +00:00
Tom Lane
19d802767d Remove pg_parse_string_token() --- not needed anymore. 2009-11-12 01:13:12 +00:00
Alvaro Herrera
e7ec022266 Fix longstanding problems in VACUUM caused by untimely interruptions
In VACUUM FULL, an interrupt after the initial transaction has been recorded
as committed can cause postmaster to restart with the following error message:
PANIC: cannot abort transaction NNNN, it was already committed
This problem has been reported many times.

In lazy VACUUM, an interrupt after the table has been truncated by
lazy_truncate_heap causes other backends' relcache to still point to the
removed pages; this can cause future INSERT and UPDATE queries to error out
with the following error message:
could not read block XX of relation 1663/NNN/MMMM: read only 0 of 8192 bytes
The window to this race condition is extremely narrow, but it has been seen in
the wild involving a cancelled autovacuum process.

The solution for both problems is to inhibit interrupts in both operations
until after the respective transactions have been committed.  It's not a
complete solution, because the transaction could theoretically be aborted by
some other error, but at least fixes the most common causes of both problems.
2009-11-10 18:00:06 +00:00
Tom Lane
10bcfa189b Re-refactor the core scanner's API, in order to get out from under the problem
of different parsers having different YYSTYPE unions that they want to use
with it.  I defined a new union core_YYSTYPE that is just the (very short)
list of semantic values returned by the core scanner.  I had originally
worried that this would require an extra interface layer, but actually we can
have parser.c's base_yylex (formerly filtered_base_yylex) take care of that at
no extra cost.  Names associated with the core scanner are now "core_yy_foo",
with "base_yy_foo" being used in the core Bison parser and the parser.c
interface layer.

This solves the last serious stumbling block to eliminating plpgsql's separate
lexer.  One restriction that will still be present is that plpgsql and the
core will have to agree on the token numbers assigned to tokens that can be
returned by the core lexer.  Since Bison doesn't seem willing to accept
external assignments of those numbers, we'll have to live with decreeing that
core and plpgsql grammars declare these tokens first and in the same order.
2009-11-09 18:38:48 +00:00
Andrew Dunstan
b79f49c780 Keep track of language's trusted flag in InlineCodeBlock. Needed to support DO blocks for languages that have both trusted and untrusted variants. 2009-11-06 21:57:57 +00:00
Tom Lane
593f4b854a Don't treat NEW and OLD as reserved words anymore. For the purposes of rules
it works just as well to have them be ordinary identifiers, and this gets rid
of a number of ugly special cases.  Plus we aren't interfering with non-rule
usage of these names.

catversion bump because the names change internally in stored rules.
2009-11-05 23:24:27 +00:00
Tom Lane
6bef82b38a Rename some encoding conversion modules to keep pathnames in our source
tarballs under 100 characters.  This should avoid failures with certain
untarring tools (WinZip and Midnight Commander have been mentioned as
likely suspects).  Per my proposal of yesterday.
catversion bumped since the initial contents of pg_proc change.
2009-11-04 23:47:04 +00:00
Tom Lane
9bedd128d6 Add support for invoking parser callback hooks via SPI and in cached plans.
As proof of concept, modify plpgsql to use the hooks.  plpgsql is still
inserting $n symbols textually, but the "back end" of the parsing process now
goes through the ParamRef hook instead of using a fixed parameter-type array,
and then execution only fetches actually-referenced parameters, using a hook
added to ParamListInfo.

Although there's a lot left to be done in plpgsql, this already cures the
"if (TG_OP = 'INSERT' and NEW.foo ...)"  problem, as illustrated by the
changed regression test.
2009-11-04 22:26:08 +00:00
Tom Lane
7d535ebe5b Dept of second thoughts: after studying index_getnext() a bit more I realize
that it can scribble on scan->xs_ctup.t_self while following HOT chains,
so we can't rely on that to stay valid between hashgettuple() calls.
Introduce a private variable in HashScanOpaque, instead.
2009-11-01 22:30:54 +00:00
Tom Lane
c4afdca4c2 Fix two serious bugs introduced into hash indexes by the 8.4 patch that made
hash indexes keep entries sorted by hash value.  First, the original plans for
concurrency assumed that insertions would happen only at the end of a page,
which is no longer true; this could cause scans to transiently fail to find
index entries in the presence of concurrent insertions.  We can compensate
by teaching scans to re-find their position after re-acquiring read locks.
Second, neither the bucket split nor the bucket compaction logic had been
fixed to preserve hashvalue ordering, so application of either of those
processes could lead to permanent corruption of an index, in the sense
that searches might fail to find entries that are present.

This patch fixes the split and compaction logic to preserve hashvalue
ordering, but it cannot do anything about pre-existing corruption.  We will
need to recommend reindexing all hash indexes in the 8.4.2 release notes.

To buy back the performance loss hereby induced in split and compaction,
fix them to use PageIndexMultiDelete instead of retail PageIndexDelete
operations.  We might later want to do something with qsort'ing the
page contents rather than doing a binary search for each insertion,
but that seemed more invasive than I cared to risk in a back-patch.

Per bug #5157 from Jeff Janes and subsequent investigation.
2009-11-01 21:25:25 +00:00
Tom Lane
fb5d05805b Implement parser hooks for processing ColumnRef and ParamRef nodes, as per my
recent proposal.  As proof of concept, remove knowledge of Params from the
core parser, arranging for them to be handled entirely by parser hook
functions.  It turns out we need an additional hook for that --- I had
forgotten about the code that handles inferring a parameter's type from
context.

This is a preliminary step towards letting plpgsql handle its variables
through parser hooks.  Additional work remains to be done to expose the
facility through SPI, but I think this is all the changes needed in the core
parser.
2009-10-31 01:41:31 +00:00
Tom Lane
cbcd1701f1 Fix AcquireRewriteLocks to be sure that it acquires the right lock strength
when FOR UPDATE is propagated down into a sub-select expanded from a view.
Similar bug to parser's isLockedRel issue that I fixed yesterday; likewise
seems not quite worth the effort to back-patch.
2009-10-28 17:36:50 +00:00
Tom Lane
46e3a16b05 When FOR UPDATE/SHARE is used with LIMIT, put the LockRows plan node
underneath the Limit node, not atop it.  This fixes the old problem that such
a query might unexpectedly return fewer rows than the LIMIT says, due to
LockRows discarding updated rows.

There is a related problem that LockRows might destroy the sort ordering
produced by earlier steps; but fixing that by pushing LockRows below Sort
would create serious performance problems that are unjustified in many
real-world applications, as well as potential deadlock problems from locking
many more rows than expected.  Instead, keep the present semantics of applying
FOR UPDATE after ORDER BY within a single query level; but allow the user to
specify the other way by writing FOR UPDATE in a sub-select.  To make that
work, track whether FOR UPDATE appeared explicitly in sub-selects or got
pushed down from the parent, and don't flatten a sub-select that contained an
explicit FOR UPDATE.
2009-10-28 14:55:47 +00:00
Tom Lane
61e5328208 Make FOR UPDATE/SHARE in the primary query not propagate into WITH queries;
for example in
  WITH w AS (SELECT * FROM foo) SELECT * FROM w, bar ... FOR UPDATE
the FOR UPDATE will now affect bar but not foo.  This is more useful and
consistent than the original 8.4 behavior, which tried to propagate FOR UPDATE
into the WITH query but always failed due to assorted implementation
restrictions.  Even though we are in process of removing those restrictions,
it seems correct on philosophical grounds to not let the outer query's
FOR UPDATE affect the WITH query.

In passing, fix isLockedRel which frequently got things wrong in
nested-subquery cases: "FOR UPDATE OF foo" applies to an alias foo in the
current query level, not subqueries.  This has been broken for a long time,
but it doesn't seem worth back-patching further than 8.4 because the actual
consequences are minimal.  At worst the parser would sometimes get
RowShareLock on a relation when it should be AccessShareLock or vice versa.
That would only make a difference if someone were using ExclusiveLock
concurrently, which no standard operation does, and anyway FOR UPDATE
doesn't result in visible changes so it's not clear that the someone would
notice any problem.  Between that and the fact that FOR UPDATE barely works
with subqueries at all in existing releases, I'm not excited about worrying
about it.
2009-10-27 17:11:18 +00:00
Heikki Linnakangas
2078e384a3 Fix range check in date_recv that tried to limit accepted values to only
those accepted by date_in(). I confused julian day numbers and number of
days since the postgres epoch 2000-01-01 in the original patch.

I just noticed that it's still easy to get such out-of-range values into
the database using to_date or +- operators, but this patch doesn't do
anything about those functions.

Per report from James Pye.
2009-10-26 16:13:11 +00:00
Tom Lane
9f2ee8f287 Re-implement EvalPlanQual processing to improve its performance and eliminate
a lot of strange behaviors that occurred in join cases.  We now identify the
"current" row for every joined relation in UPDATE, DELETE, and SELECT FOR
UPDATE/SHARE queries.  If an EvalPlanQual recheck is necessary, we jam the
appropriate row into each scan node in the rechecking plan, forcing it to emit
only that one row.  The former behavior could rescan the whole of each joined
relation for each recheck, which was terrible for performance, and what's much
worse could result in duplicated output tuples.

Also, the original implementation of EvalPlanQual could not re-use the recheck
execution tree --- it had to go through a full executor init and shutdown for
every row to be tested.  To avoid this overhead, I've associated a special
runtime Param with each LockRows or ModifyTable plan node, and arranged to
make every scan node below such a node depend on that Param.  Thus, by
signaling a change in that Param, the EPQ machinery can just rescan the
already-built test plan.

This patch also adds a prohibition on set-returning functions in the
targetlist of SELECT FOR UPDATE/SHARE.  This is needed to avoid the
duplicate-output-tuple problem.  It seems fairly reasonable since the
other restrictions on SELECT FOR UPDATE are meant to ensure that there
is a unique correspondence between source tuples and result tuples,
which an output SRF destroys as much as anything else does.
2009-10-26 02:26:45 +00:00