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This gets us to a point where psqlscan.l can be used by other frontend programs for the same purpose psql uses it for, ie to detect when it's collected a complete SQL command from input that is divided across line boundaries. Moreover, other programs can supply their own lexers for backslash commands of their own choosing. A follow-on patch will use this in pgbench. The end result here is roughly the same as in Kyotaro Horiguchi's 0001-Make-SQL-parser-part-of-psqlscan-independent-from-ps.patch, although the details of the method for switching between lexers are quite different. Basically, in this patch we share the entire PsqlScanState, YY_BUFFER_STATE stack, *and* yyscan_t between different lexers. The only thing we need to do to switch to a different lexer is to make sure the start_state is valid for the new lexer. This works because flex doesn't keep any other persistent state that depends on the specific lexing tables generated for a particular .l file. (We are assuming that both lexers are built with the same flex version, or at least versions that are compatible with respect to the contents of yyscan_t; but that doesn't seem likely to be a big problem in practice, considering how slowly flex changes.) Aside from being more efficient than Horiguchi-san's original solution, this avoids possible corner-case changes in semantics: the original code was capable of popping the input buffer stack while still staying in backslash-related parsing states. I'm not sure that that equates to any useful user-visible behaviors, but I'm not sure it doesn't either, so I'm loath to assume that we only need to consider the topmost buffer when parsing a backslash command. I've attempted to update the MSVC build scripts for the added .l file, but will rely on the buildfarm to see if I missed anything. Kyotaro Horiguchi and Tom Lane
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: http://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 http://www.postgresql.org/download/. For more information look at our web site located at http://www.postgresql.org/.