Shulou(Shulou.com)05/31 Report--

This article introduces the relevant knowledge of "what is the role of User subroutines in PostgreSQL". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

The Flex input file consists of four parts:

% {Declarations%} Definitions%%Rules%%User subroutinesUser subroutines

After the rule comes the custom routine. The routines defined in scan.l are mainly to parse the input SQL statements and perform initialization and clean-up work.

/ * LCOV_EXCL_STOP * / * * Arrange access to yyextra for subroutines of the main yylex () function. * We expect each subroutine to have a yyscanner parameter. Rather than * use the yyget_xxx functions, which might or might not get inlined by the * compiler, we cheat just a bit and cast yyscanner to the right type. * provide yyextra access to the main yylex () function. * We expect every subroutine to have a parameter: yyscanner. * instead of using the yyget_xxx function (which may or may not be inlined by the compiler), we force yyscanner to be the correct type. * / # undef yyextra#define yyextra ((struct yyguts_t *) yyscanner)-> yyextra_r) / * Likewise for a couple of other things we need. * / / define other things you need: yylloc/yyleng#undef yylloc#define yylloc ((struct yyguts_t *) yyscanner)-> yylloc_r) # undef yyleng#define yyleng (struct yyguts_t *) yyscanner)-> yyleng_r) / * * scanner_errposition * Report a lexer or grammar error cursor position, if possible. * scanner_errposition: if possible, report the lexical or grammatical error location * * This is expected to be used within an ereport () call. The return value * is a dummy (always 0, in fact). * this routine is used in the ereport () call. The return value is a pseudo column (usually 0 in fact). * * Note that this can only be used for messages emitted during raw parsing * (essentially, scan.l and gram.y), since it requires the yyscanner struct * to still be available. Note that this can only be used for messages generated during the original parsing (scan.l & gram.y), * because it requires that the yyscanner structure is still available. * / intscanner_errposition (int location, core_yyscan_t yyscanner) {int pos; if (location)

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