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Expose helper functions scan_quoted_identifier and scan_identifier.

Browse source 
Previously, this logic was embedded within SplitIdentifierString,
SplitDirectoriesString, and SplitGUCList. Factoring it out saves
a bit of duplicated code, and also makes it available to extensions
that might want to do similar things without necessarily wanting to
do exactly the same thing.

Reviewed-by: Matheus Alcantara <matheusssilv97@gmail.com>
Reviewed-by: Lukas Fittl <lukas@fittl.com>
Discussion: http://postgr.es/m/CA+Tgmob-0W8306mvrJX5Urtqt1AAasu8pi4yLrZ1XfwZU-Uj1w@mail.gmail.com
This commit is contained in:
Robert Haas 2026-04-06 11:13:25 -04:00
parent ca2b5443e2
commit e0e819cc08
2 changed files with 102 additions and 90 deletions
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189
src/backend/utils/adt/varlena.c
View file

@ -2750,6 +2750,96 @@ textToQualifiedNameList(text *textval)
return result;
}
/*
* scan_quoted_identifier - In-place scanner for quoted identifiers.
*
* *nextp should point to the opening double-quote character, and will be
* updated to point just past the end. *endp is set to the position of
* the closing quote. The return value is the identifier, or NULL if the
* matching close-quote cannot be found.
*
* If we find two consecutive double quote characters, that doesn't end the
* identifier: instead, we collapse them into a double quote and include them
* in the resulting token. Note that this requires overwriting the rest of the
* string in place, including the portion beyond the final value of *nextp.
*/
char *
scan_quoted_identifier(char **endp, char **nextp)
{
char *token = *nextp + 1;
for (;;)
{
*endp = strchr(*nextp + 1, '"');
if (*endp == NULL)
return NULL; /* mismatched quotes */
if ((*endp)[1] != '"')
break; /* found end of quoted identifier */
/* Collapse adjacent quotes into one quote, and look again */
memmove(*endp, *endp + 1, strlen(*endp));
*nextp = *endp;
}
/* *endp now points at the terminating quote */
*nextp = *endp + 1;
return token;
}
/*
* scan_identifier - In-place scanner for quoted or unquoted identifiers.
*
* On success, *endp is set to the position where the caller should write '\0'
* to null-terminate the token, and *nextp is advanced past the token (and past
* the closing quote, if any). The return value is the token content, or NULL
* if there is a syntax error (mismatched quotes or empty unquoted token).
*
* Unquoted identifiers are terminated by whitespace or the first occurrence
* of the separator character. Additionally, if downcase_unquoted = true,
* unquoted identifiers are downcased in place. See scan_quoted_identifier for
* an additional way in which we modify the string in place.
*/
char *
scan_identifier(char **endp, char **nextp, char separator, bool downcase_unquoted)
{
char *token;
if (**nextp == '"')
return scan_quoted_identifier(endp, nextp);
/* Unquoted identifier --- extends to separator or whitespace */
token = *nextp;
while (**nextp && **nextp != separator && !scanner_isspace(**nextp))
(*nextp)++;
if (*nextp == token)
return NULL; /* empty token */
*endp = *nextp;
if (downcase_unquoted)
{
/*
* Downcase the identifier, using same code as main lexer does.
*
* XXX because we want to overwrite the input in-place, we cannot
* support a downcasing transformation that increases the string
* length. This is not a problem given the current implementation of
* downcase_truncate_identifier, but we'll probably have to do
* something about this someday.
*/
int len = *endp - token;
char *downname = downcase_truncate_identifier(token, len, false);
Assert(strlen(downname) <= len);
strncpy(token, downname, len); /* strncpy is required here */
pfree(downname);
}
return token;
}
/*
* SplitIdentifierString --- parse a string containing identifiers
*
@ -2794,53 +2884,9 @@ SplitIdentifierString(char *rawstring, char separator,
char *curname;
char *endp;
if (*nextp == '"')
{
/* Quoted name --- collapse quote-quote pairs, no downcasing */
curname = nextp + 1;
for (;;)
{
endp = strchr(nextp + 1, '"');
if (endp == NULL)
return false; /* mismatched quotes */
if (endp[1] != '"')
break; /* found end of quoted name */
/* Collapse adjacent quotes into one quote, and look again */
memmove(endp, endp + 1, strlen(endp));
nextp = endp;
}
/* endp now points at the terminating quote */
nextp = endp + 1;
}
else
{
/* Unquoted name --- extends to separator or whitespace */
char *downname;
int len;
curname = nextp;
while (*nextp && *nextp != separator &&
!scanner_isspace(*nextp))
nextp++;
endp = nextp;
if (curname == nextp)
return false; /* empty unquoted name not allowed */
/*
* Downcase the identifier, using same code as main lexer does.
*
* XXX because we want to overwrite the input in-place, we cannot
* support a downcasing transformation that increases the string
* length. This is not a problem given the current implementation
* of downcase_truncate_identifier, but we'll probably have to do
* something about this someday.
*/
len = endp - curname;
downname = downcase_truncate_identifier(curname, len, false);
Assert(strlen(downname) <= len);
strncpy(curname, downname, len); /* strncpy is required here */
pfree(downname);
}
curname = scan_identifier(&endp, &nextp, separator, true);
if (curname == NULL)
return false; /* mismatched quotes or empty name */
while (scanner_isspace(*nextp))
nextp++; /* skip trailing whitespace */
@ -2924,20 +2970,9 @@ SplitDirectoriesString(char *rawstring, char separator,
if (*nextp == '"')
{
/* Quoted name --- collapse quote-quote pairs */
curname = nextp + 1;
for (;;)
{
endp = strchr(nextp + 1, '"');
if (endp == NULL)
return false; /* mismatched quotes */
if (endp[1] != '"')
break; /* found end of quoted name */
/* Collapse adjacent quotes into one quote, and look again */
memmove(endp, endp + 1, strlen(endp));
nextp = endp;
}
/* endp now points at the terminating quote */
nextp = endp + 1;
curname = scan_quoted_identifier(&endp, &nextp);
if (curname == NULL)
return false; /* mismatched quotes */
}
else
{
@ -3042,35 +3077,9 @@ SplitGUCList(char *rawstring, char separator,
char *curname;
char *endp;
if (*nextp == '"')
{
/* Quoted name --- collapse quote-quote pairs */
curname = nextp + 1;
for (;;)
{
endp = strchr(nextp + 1, '"');
if (endp == NULL)
return false; /* mismatched quotes */
if (endp[1] != '"')
break; /* found end of quoted name */
/* Collapse adjacent quotes into one quote, and look again */
memmove(endp, endp + 1, strlen(endp));
nextp = endp;
}
/* endp now points at the terminating quote */
nextp = endp + 1;
}
else
{
/* Unquoted name --- extends to separator or whitespace */
curname = nextp;
while (*nextp && *nextp != separator &&
!scanner_isspace(*nextp))
nextp++;
endp = nextp;
if (curname == nextp)
return false; /* empty unquoted name not allowed */
}
curname = scan_identifier(&endp, &nextp, separator, false);
if (curname == NULL)
return false; /* mismatched quotes or empty name */
while (scanner_isspace(*nextp))
nextp++; /* skip trailing whitespace */

3
src/include/utils/varlena.h
View file

@ -27,6 +27,9 @@ extern int varstr_levenshtein_less_equal(const char *source, int slen,
int ins_c, int del_c, int sub_c,
int max_d, bool trusted);
extern List *textToQualifiedNameList(text *textval);
extern char *scan_quoted_identifier(char **endp, char **nextp);
extern char *scan_identifier(char **endp, char **nextp, char separator,
bool downcase_unquoted);
extern bool SplitIdentifierString(char *rawstring, char separator,
List **namelist);
extern bool SplitDirectoriesString(char *rawstring, char separator,