[pull] master from postgres:master#805
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POSIX defines the behavior of back-references thus:
The back-reference expression '\n' shall match the same (possibly
empty) string of characters as was matched by a subexpression
enclosed between "\(" and "\)" preceding the '\n'.
As far as I can see, the back-reference is supposed to consider only
the data characters matched by the referenced subexpression. However,
because our engine copies the NFA constructed from the referenced
subexpression, it effectively enforces any constraints therein, too.
As an example, '(^.)\1' ought to match 'xx', or any other string
starting with two occurrences of the same character; but in our code
it does not, and indeed can't match anything, because the '^' anchor
constraint is included in the backref's copied NFA. If POSIX intended
that, you'd think they'd mention it. Perl for one doesn't act that
way, so it's hard to conclude that this isn't a bug.
Fix by modifying the backref's NFA immediately after it's copied from
the reference, replacing all constraint arcs by EMPTY arcs so that the
constraints are treated as automatically satisfied. This still allows
us to enforce matching rules that depend only on the data characters;
for example, in '(^\d+).*\1' the NFA matching step will still know
that the backref can only match strings of digits.
Perhaps surprisingly, this change does not affect the results of any
of a rather large corpus of real-world regexes. Nonetheless, I would
not consider back-patching it, since it's a clear compatibility break.
Patch by me, reviewed by Joel Jacobson
Discussion: https://postgr.es/m/661609.1614560029@sss.pgh.pa.us
In some cases, at the time that we're doing an NFA-based precheck
of whether a backref subexpression can match at a particular place
in the string, we already know which substring the referenced
subexpression matched. If so, we might as well forget about the NFA
and just compare the substring; this is faster and it gives an exact
rather than approximate answer.
In general, this optimization can help while we are prechecking within
the second child expression of a concat node, while the capture was
within the first child expression; then the substring was saved during
cdissect() of the first child and will be available to NFA checks done
while cdissect() recurses into the second child. It can help quite a
lot if the tree looks like
concat
/ \
capture concat
/ \
expensive stuff backref
as we will be able to avoid recursively dissecting the "expensive
stuff" before discovering that the backref isn't satisfied with a
particular midpoint that the lower concat node is testing. This
doesn't help if the concat tree is left-deep, as the capture node
won't get set soon enough (and it's hard to fix that without changing
the engine's match behavior). Fortunately, right-deep concat trees
are the common case.
Patch by me, reviewed by Joel Jacobson
Discussion: https://postgr.es/m/661609.1614560029@sss.pgh.pa.us
This extends the changes made in commit cebc1d3, teaching parseqatom() to generate fewer or cheaper subre nodes in some edge cases. The case of interest here is a quantified atom that is "messy" only because it has greediness opposite to what preceded it (whereas captures and backrefs are intrinsically messy). In this case we don't need an iteration node, since we don't care where the sub-matches of the quantifier are; and we might also not need a second concatenation node. This seems of only marginal real-world use according to my testing, but I wanted to get it in before wrapping up this series of regex performance fixes. Discussion: https://postgr.es/m/1340281.1613018383@sss.pgh.pa.us
On Windows, CMD.EXE allegedly does not run a command that uses forward slashes, so let's convert the path to use backslashes instead. Backpatch to 10. Author: Nitin Jadhav <nitinjadhavpostgres@gmail.com> Reviewed-by: Juan José Santamaría Flecha <juanjo.santamaria@gmail.com> Discussion: https://postgr.es/m/CAMm1aWaNDuaPYFYMAqDeJrZmPtNvLcJRS++CcZWY8LT6KcoBZw@mail.gmail.com
This allows clients to find out the setting at connection time without having to expend a query round trip to do so; which is helpful when trying to identify read/write servers. (One must also look at in_hot_standby, but that's already GUC_REPORT, cf bf8a662.) Modifying libpq to make use of this will come soon, but I felt it cleaner to push the server change separately. Haribabu Kommi, Greg Nancarrow, Vignesh C; reviewed at various times by Laurenz Albe, Takayuki Tsunakawa, Peter Smith. Discussion: https://postgr.es/m/CAF3+xM+8-ztOkaV9gHiJ3wfgENTq97QcjXQt+rbFQ6F7oNzt9A@mail.gmail.com
Adjust some "can't happen" error messages that assumed that the page deletion target page must be a half-dead page. This assumption was wrong in the case of an internal target page. Simply refer to these pages as the target page instead. Internal pages are never marked half-dead. There is exactly one half-dead page for each subtree undergoing deletion. The half-dead page is also the target subtree's leaf-level page. This has been the case since commit efada2b, which totally overhauled nbtree page deletion.
Add documenting assertion. This makes it easier to follow how we maintain the top parent link in target subtree's half-dead/leaf level page.
This option provides REINDEX (TABLESPACE) for reindexdb, applying the tablespace value given by the caller to all the REINDEX queries generated. While on it, this commit adds some tests for REINDEX TABLESPACE, with and without CONCURRENTLY, when run on toast indexes and tables. Such operations are not allowed, and toast relation names are not stable enough to be part of the main regression test suite (even if using a PL function with a TRY/CATCH logic, as CONCURRENTLY could not be tested). Author: Michael Paquier Reviewed-by: Mark Dilger, Daniel Gustafsson Discussion: https://postgr.es/m/YDiaDMnzLICqeukl@paquier.xyz
In addition to the existing options of "any" and "read-write", we now support "read-only", "primary", "standby", and "prefer-standby". "read-write" retains its previous meaning of "transactions are read-write by default", and "read-only" inverts that. The other three modes test specifically for hot-standby status, which is not quite the same thing. (Setting default_transaction_read_only on a primary server renders it read-only to this logic, but not a standby.) Furthermore, if talking to a v14 or later server, no extra network round trip is needed to detect the session's status; the GUC_REPORT variables delivered by the server are enough. When talking to an older server, a SHOW or SELECT query is issued to detect session read-only-ness or server hot-standby state, as needed. Haribabu Kommi, Greg Nancarrow, Vignesh C, Tom Lane; reviewed at various times by Laurenz Albe, Takayuki Tsunakawa, Peter Smith. Discussion: https://postgr.es/m/CAF3+xM+8-ztOkaV9gHiJ3wfgENTq97QcjXQt+rbFQ6F7oNzt9A@mail.gmail.com
…ion_slot. Commit 0aa8a01 extends the output plugin API to allow decoding of prepared xacts and allowed the user to enable/disable the two-phase option via pg_logical_slot_get_changes(). This can lead to a problem such that the first time when it gets changes via pg_logical_slot_get_changes() without two_phase option enabled it will not get the prepared even though prepare is after consistent snapshot. Now next time during getting changes, if the two_phase option is enabled it can skip prepare because by that time start decoding point has been moved. So the user will only get commit prepared. Allow to enable/disable this option at the create slot time and default will be false. It will break the existing slots which is fine in a major release. Author: Ajin Cherian Reviewed-by: Amit Kapila and Vignesh C Discussion: https://postgr.es/m/d0f60d60-133d-bf8d-bd70-47784d8fabf3@enterprisedb.com
Move our qsort implementation into a header that can be used to define specialized functions for better performance and reduced duplication. Reviewed-by: Daniel Gustafsson <daniel@yesql.se> Discussion: https://postgr.es/m/CA%2BhUKGJ2-eaDqAum5bxhpMNhvuJmRDZxB_Tow0n-gse%2BHG0Yig%40mail.gmail.com
Reduce duplication by using the new template. Reviewed-by: Daniel Gustafsson <daniel@yesql.se> Discussion: https://postgr.es/m/CA%2BhUKGJ2-eaDqAum5bxhpMNhvuJmRDZxB_Tow0n-gse%2BHG0Yig%40mail.gmail.com
Replace the Perl code previously used to generate specialized sort functions with sort_template.h. Reviewed-by: Daniel Gustafsson <daniel@yesql.se> Discussion: https://postgr.es/m/CA%2BhUKGJ2-eaDqAum5bxhpMNhvuJmRDZxB_Tow0n-gse%2BHG0Yig%40mail.gmail.com
Per buildfarm; this fix is from Michael Paquier (vignesh C proposed nearly the same). Discussion: https://postgr.es/m/YD8IZ9OKfUf9X1eF@paquier.xyz
It was not clear in the docs that the max_replication_slots is also used to track replication origins on the subscriber side. Author: Paul Martinez Reviewed-by: Amit Kapila Backpatch-through: 10 where logical replication was introduced Discussion: https://postgr.es/m/CACqFVBZgwCN_pHnW6dMNCrOS7tiHCw6Retf_=U2Vvj3aUSeATw@mail.gmail.com
This expands the binary validation in pg_upgrade with a version check per binary to ensure that the target cluster installation only contains binaries from the target version. In order to reduce duplication, validate_exec is exported from port.h and the local copy in pg_upgrade is removed. Author: Daniel Gustafsson <daniel@yesql.se> Discussion: https://www.postgresql.org/message-id/flat/9328.1552952117@sss.pgh.pa.us
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