repl_scanner.l

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%top{
/*-------------------------------------------------------------------------
 *
 * repl_scanner.l
 *    a lexical scanner for the replication commands
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/replication/repl_scanner.l
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"
 
#include "nodes/parsenodes.h"
#include "utils/builtins.h"
#include "parser/scansup.h"
 
/*
 * NB: include repl_gram.h only AFTER including walsender_private.h, because
 * walsender_private includes headers that define XLogRecPtr.
 */
#include "replication/walsender_private.h"
#include "repl_gram.h"
}
 
%{
/* Avoid exit() on fatal scanner errors (a bit ugly -- see yy_fatal_error) */
#undef fprintf
#define fprintf(file, fmt, msg)  fprintf_to_ereport(fmt, msg)
 
static void
fprintf_to_ereport(const char *fmt, const char *msg)
{
    ereport(ERROR, (errmsg_internal("%s", msg)));
}
 
struct replication_yy_extra_type
{
    /* Pushed-back token (we only handle one) */
    int         repl_pushed_back_token;
 
    /* Work area for collecting literals */
    StringInfoData litbuf;
};
 
static void startlit(yyscan_t yyscanner);
static char *litbufdup(yyscan_t yyscanner);
static void addlit(char *ytext, int yleng, yyscan_t yyscanner);
static void addlitchar(unsigned char ychar, yyscan_t yyscanner);
 
/* LCOV_EXCL_START */
 
%}
 
%option reentrant
%option bison-bridge
%option 8bit
%option never-interactive
%option nodefault
%option noinput
%option nounput
%option noyywrap
%option noyyalloc
%option noyyrealloc
%option noyyfree
%option warn
%option prefix="replication_yy"
%option extra-type="struct replication_yy_extra_type *"
 
/*
 * Exclusive states:
 *  <xd> delimited identifiers (double-quoted identifiers)
 *  <xq> standard single-quoted strings
 */
%x xd
%x xq
 
space           [ \t\n\r\f\v]
 
quote           '
quotestop       {quote}
 
/* Extended quote
 * xqdouble implements embedded quote, ''''
 */
xqstart         {quote}
xqdouble        {quote}{quote}
xqinside        [^']+
 
/* Double quote
 * Allows embedded spaces and other special characters into identifiers.
 */
dquote          \"
xdstart         {dquote}
xdstop          {dquote}
xddouble        {dquote}{dquote}
xdinside        [^"]+
 
digit           [0-9]
hexdigit        [0-9A-Fa-f]
 
ident_start     [A-Za-z\200-\377_]
ident_cont      [A-Za-z\200-\377_0-9\$]
 
identifier      {ident_start}{ident_cont}*
 
%%
 
%{
    /* This code is inserted at the start of replication_yylex() */
 
    /* If we have a pushed-back token, return that. */
    if (yyextra->repl_pushed_back_token)
    {
        int         result = yyextra->repl_pushed_back_token;
 
        yyextra->repl_pushed_back_token = 0;
        return result;
    }
%}
 
BASE_BACKUP         { return K_BASE_BACKUP; }
IDENTIFY_SYSTEM     { return K_IDENTIFY_SYSTEM; }
READ_REPLICATION_SLOT   { return K_READ_REPLICATION_SLOT; }
SHOW        { return K_SHOW; }
TIMELINE            { return K_TIMELINE; }
START_REPLICATION   { return K_START_REPLICATION; }
CREATE_REPLICATION_SLOT     { return K_CREATE_REPLICATION_SLOT; }
DROP_REPLICATION_SLOT       { return K_DROP_REPLICATION_SLOT; }
ALTER_REPLICATION_SLOT      { return K_ALTER_REPLICATION_SLOT; }
TIMELINE_HISTORY    { return K_TIMELINE_HISTORY; }
PHYSICAL            { return K_PHYSICAL; }
RESERVE_WAL         { return K_RESERVE_WAL; }
LOGICAL             { return K_LOGICAL; }
SLOT                { return K_SLOT; }
TEMPORARY           { return K_TEMPORARY; }
TWO_PHASE           { return K_TWO_PHASE; }
EXPORT_SNAPSHOT     { return K_EXPORT_SNAPSHOT; }
NOEXPORT_SNAPSHOT   { return K_NOEXPORT_SNAPSHOT; }
USE_SNAPSHOT        { return K_USE_SNAPSHOT; }
WAIT                { return K_WAIT; }
UPLOAD_MANIFEST     { return K_UPLOAD_MANIFEST; }
 
{space}+        { /* do nothing */ }
 
{digit}+        {
                    yylval->uintval = strtoul(yytext, NULL, 10);
                    return UCONST;
                }
 
{hexdigit}+\/{hexdigit}+        {
                    uint32  hi,
                            lo;
                    if (sscanf(yytext, "%X/%X", &hi, &lo) != 2)
                        replication_yyerror(NULL, yyscanner, "invalid streaming start location");
                    yylval->recptr = ((uint64) hi) << 32 | lo;
                    return RECPTR;
                }
 
{xqstart}       {
                    BEGIN(xq);
                    startlit(yyscanner);
                }
 
<xq>{quotestop} {
                    yyless(1);
                    BEGIN(INITIAL);
                    yylval->str = litbufdup(yyscanner);
                    return SCONST;
                }
 
<xq>{xqdouble}  {
                    addlitchar('\'', yyscanner);
                }
 
<xq>{xqinside}  {
                    addlit(yytext, yyleng, yyscanner);
                }
 
{xdstart}       {
                    BEGIN(xd);
                    startlit(yyscanner);
                }
 
<xd>{xdstop}    {
                    int         len;
 
                    yyless(1);
                    BEGIN(INITIAL);
                    yylval->str = litbufdup(yyscanner);
                    len = strlen(yylval->str);
                    truncate_identifier(yylval->str, len, true);
                    return IDENT;
                }
 
<xd>{xdinside}  {
                    addlit(yytext, yyleng, yyscanner);
                }
 
{identifier}    {
                    int         len = strlen(yytext);
 
                    yylval->str = downcase_truncate_identifier(yytext, len, true);
                    return IDENT;
                }
 
.               {
                    /* Any char not recognized above is returned as itself */
                    return yytext[0];
                }
 
<xq,xd><<EOF>>  { replication_yyerror(NULL, yyscanner, "unterminated quoted string"); }
 
 
<<EOF>>         {
                    yyterminate();
                }
 
%%
 
/* LCOV_EXCL_STOP */
 
/* see scan.l */
#undef yyextra
#define yyextra (((struct yyguts_t *) yyscanner)->yyextra_r)
 
static void
startlit(yyscan_t yyscanner)
{
    initStringInfo(&yyextra->litbuf);
}
 
static char *
litbufdup(yyscan_t yyscanner)
{
    return yyextra->litbuf.data;
}
 
static void
addlit(char *ytext, int yleng, yyscan_t yyscanner)
{
    appendBinaryStringInfo(&yyextra->litbuf, ytext, yleng);
}
 
static void
addlitchar(unsigned char ychar, yyscan_t yyscanner)
{
    appendStringInfoChar(&yyextra->litbuf, ychar);
}
 
/*
  * (The first argument is enforced by Bison to match the first argument of
  * yyparse(), but it is not used here.)
  */
void
replication_yyerror(Node **replication_parse_result_p, yyscan_t yyscanner, const char *message)
{
    ereport(ERROR,
            (errcode(ERRCODE_SYNTAX_ERROR),
             errmsg_internal("%s", message)));
}
 
void
replication_scanner_init(const char *str, yyscan_t *yyscannerp)
{
    yyscan_t    yyscanner;
    struct replication_yy_extra_type *yyext = palloc0_object(struct replication_yy_extra_type);
 
    if (yylex_init(yyscannerp) != 0)
        elog(ERROR, "yylex_init() failed: %m");
 
    yyscanner = *yyscannerp;
 
    yyset_extra(yyext, yyscanner);
 
    yy_scan_string(str, yyscanner);
}
 
void
replication_scanner_finish(yyscan_t yyscanner)
{
    pfree(yyextra);
    yylex_destroy(yyscanner);
}
 
/*
 * Check to see if the first token of a command is a WalSender keyword.
 *
 * To keep repl_scanner.l minimal, we don't ask it to know every construct
 * that the core lexer knows.  Therefore, we daren't lex more than the
 * first token of a general SQL command.  That will usually look like an
 * IDENT token here, although some other cases are possible.
 */
bool
replication_scanner_is_replication_command(yyscan_t yyscanner)
{
    YYSTYPE     dummy;
    int         first_token = replication_yylex(&dummy, yyscanner);
 
    switch (first_token)
    {
        case K_IDENTIFY_SYSTEM:
        case K_BASE_BACKUP:
        case K_START_REPLICATION:
        case K_CREATE_REPLICATION_SLOT:
        case K_DROP_REPLICATION_SLOT:
        case K_ALTER_REPLICATION_SLOT:
        case K_READ_REPLICATION_SLOT:
        case K_TIMELINE_HISTORY:
        case K_UPLOAD_MANIFEST:
        case K_SHOW:
            /* Yes; push back the first token so we can parse later. */
            yyextra->repl_pushed_back_token = first_token;
            return true;
        default:
            /* Nope; we don't bother to push back the token. */
            return false;
    }
}
 
/*
 * Interface functions to make flex use palloc() instead of malloc().
 * It'd be better to make these static, but flex insists otherwise.
 */
 
void *
yyalloc(yy_size_t size, yyscan_t yyscanner)
{
    return palloc(size);
}
 
void *
yyrealloc(void *ptr, yy_size_t size, yyscan_t yyscanner)
{
    if (ptr)
        return repalloc(ptr, size);
    else
        return palloc(size);
}
 
void
yyfree(void *ptr, yyscan_t yyscanner)
{
    if (ptr)
        pfree(ptr);
}