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Our previous validator used a traditional algorithm that performed comparison and branching one byte at a time. It's useful in that we always know exactly how many bytes we have validated, but that precision comes at a cost. Input validation can show up prominently in profiles of COPY FROM, and future improvements to COPY FROM such as parallelism or faster line parsing will put more pressure on input validation. Hence, add fast paths for both ASCII and multibyte UTF-8: Use bitwise operations to check 16 bytes at a time for ASCII. If that fails, use a "shift-based" DFA on those bytes to handle the general case, including multibyte. These paths are relatively free of branches and thus robust against all kinds of byte patterns. With these algorithms, UTF-8 validation is several times faster, depending on platform and the input byte distribution. The previous coding in pg_utf8_verifystr() is retained for short strings and for when the fast path returns an error. Review, performance testing, and additional hacking by: Heikki Linakangas, Vladimir Sitnikov, Amit Khandekar, Thomas Munro, and Greg Stark Discussion: https://www.postgresql.org/message-id/CAFBsxsEV_SzH%2BOLyCiyon%3DiwggSyMh_eF6A3LU2tiWf3Cy2ZQg%40mail.gmail.com |
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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/.