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Up to now, we remembered the definition of a capturing parenthesis subexpression by storing a pointer to the associated subRE node. That was okay before, because that subRE didn't get modified anymore while parsing the rest of the regexp. However, in the wake of commit ea1268f63, that's no longer true: the outer invocation of parseqatom() feels free to scribble on that subRE. This seems to work anyway, because the states we jam into the child atom in the "prepare a general-purpose state skeleton" stanza aren't really semantically different from the original endpoints of the child atom. But that would be mighty easy to break, and it's definitely not how things worked before. Between this and the issue fixed in the prior commit, it seems best to get rid of this dependence on subRE nodes entirely. We don't need the whole child subRE for future backrefs, only its starting and ending NFA states; so let's just store pointers to those. Also, in the corner case where we make an extra subRE to handle immediately-nested capturing parentheses, it seems like it'd be smart to have the extra subRE have the same begin/end states as the original child subRE does (s/s2 not lp/rp). I think that linking it from lp to rp might actually be semantically wrong, though since Spencer's original code did it that way, I'm not totally certain. Using s/s2 is certainly not wrong, in any case. Per report from Mark Dilger. Back-patch to v14 where the problematic patches came in. Discussion: https://postgr.es/m/0203588E-E609-43AF-9F4F-902854231EE7@enterprisedb.com
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/.