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Commit 824bf7190 introduced a new search of the NFAs generated by regex compilation. I failed to think hard about the performance characteristics of that search, with the predictable outcome that it's bad: weird regexes can trigger exponential search time. Worse, there's no check-for-interrupt in that code, so you can't even cancel the query if this happens. Fix by introducing memo-ization of the search results, so that any one NFA state need be examined in detail just once. This potentially uses a lot of memory, but we can bound the memory usage by putting a limit on the number of states for which we'll try to prove match-all-ness. That is sane because we already have a limit (DUPINF) on the maximum finite string length that a matchall regex can match; and patterns that involve much more than DUPINF states would probably exceed that limit anyway. Also, rearrange the logic so that we check the basic is-the-graph- all-RAINBOW-arcs property before we start the recursive search to determine path lengths. This will ensure that we fall out quickly whenever the NFA couldn't possibly be matchall. Also stick in a check-for-interrupt, just in case these measures don't completely eliminate the risk of slowness. Discussion: https://postgr.es/m/3483895.1619898362@sss.pgh.pa.us
PostgreSQL Database Management System ===================================== This directory contains the source code distribution of the PostgreSQL database management system. PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings. PostgreSQL has many language interfaces, many of which are listed here: https://www.postgresql.org/download/ See the file INSTALL for instructions on how to build and install PostgreSQL. That file also lists supported operating systems and hardware platforms and contains information regarding any other software packages that are required to build or run the PostgreSQL system. Copyright and license information can be found in the file COPYRIGHT. A comprehensive documentation set is included in this distribution; it can be read as described in the installation instructions. The latest version of this software may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.