4aea704a5b
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
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| .. | ||
| brin | ||
| commit_ts | ||
| delay_execution | ||
| dummy_index_am | ||
| dummy_seclabel | ||
| plsample | ||
| snapshot_too_old | ||
| ssl_passphrase_callback | ||
| test_bloomfilter | ||
| test_ddl_deparse | ||
| test_extensions | ||
| test_ginpostinglist | ||
| test_integerset | ||
| test_misc | ||
| test_parser | ||
| test_pg_dump | ||
| test_predtest | ||
| test_rbtree | ||
| test_regex | ||
| test_rls_hooks | ||
| test_shm_mq | ||
| unsafe_tests | ||
| worker_spi | ||
| Makefile | ||
| README | ||
README
Test extensions and libraries ============================= src/test/modules contains PostgreSQL extensions that are primarily or entirely intended for testing PostgreSQL and/or to serve as example code. The extensions here aren't intended to be installed in a production server and aren't suitable for "real work". Furthermore, while you can do "make install" and "make installcheck" in this directory or its children, it is NOT ADVISABLE to do so with a server containing valuable data. Some of these tests may have undesirable side-effects on roles or other global objects within the tested server. "make installcheck-world" at the top level does not recurse into this directory. Most extensions have their own pg_regress tests or isolationtester specs. Some are also used by tests elsewhere in the tree. If you're adding new hooks or other functionality exposed as C-level API this is where to add the tests for it.