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Prevent duplicate escape-string warnings when using pg_stat_statements. 

contrib/pg_stat_statements will sometimes run the core lexer a second time
on submitted statements.  Formerly, if you had standard_conforming_strings
turned off, this led to sometimes getting two copies of any warnings
enabled by escape_string_warning.  While this is probably no longer a big
deal in the field, it's a pain for regression testing.

To fix, change the lexer so it doesn't consult the escape_string_warning
GUC variable directly, but looks at a copy in the core_yy_extra_type state
struct.  Then, pg_stat_statements can change that copy to disable warnings
while it's redoing the lexing.

It seemed like a good idea to make this happen for all three of the GUCs
consulted by the lexer, not just escape_string_warning.  There's not an
immediate use-case for callers to adjust the other two AFAIK, but making
it possible is easy enough and seems like good future-proofing.

Arguably this is a bug fix, but there doesn't seem to be enough interest to
justify a back-patch.  We'd not be able to back-patch exactly as-is anyway,
for fear of breaking ABI compatibility of the struct.  (We could perhaps
back-patch the addition of only escape_string_warning by adding it at the
end of the struct, where there's currently alignment padding space.)
This commit is contained in:
Tom Lane 2015-01-22 18:10:47 -05:00
parent f5f2c2de16
commit eb213acfe2
3 changed files with 24 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
contrib/pg_stat_statements/pg_stat_statements.c
View File

@ -2816,6 +2816,9 @@ fill_in_constant_lengths(pgssJumbleState *jstate, const char *query)
ScanKeywords,
NumScanKeywords);
/* we don't want to re-emit any escape string warnings */
yyextra.escape_string_warning = false;
/* Search for each constant, in sequence */
for (i = 0; i < jstate->clocations_count; i++)
{

18
src/backend/parser/scan.l
View File

@ -505,7 +505,7 @@ other .
yyextra->warn_on_first_escape = true;
yyextra->saw_non_ascii = false;
SET_YYLLOC();
if (standard_conforming_strings)
if (yyextra->standard_conforming_strings)
BEGIN(xq);
else
BEGIN(xe);
@ -520,7 +520,7 @@ other .
}
{xusstart} {
SET_YYLLOC();
if (!standard_conforming_strings)
if (!yyextra->standard_conforming_strings)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("unsafe use of string constant with Unicode escapes"),
@ -622,8 +622,8 @@ other .
<xe>{xeescape} {
if (yytext[1] == '\'')
{
if (backslash_quote == BACKSLASH_QUOTE_OFF ||
(backslash_quote == BACKSLASH_QUOTE_SAFE_ENCODING &&
if (yyextra->backslash_quote == BACKSLASH_QUOTE_OFF ||
(yyextra->backslash_quote == BACKSLASH_QUOTE_SAFE_ENCODING &&
PG_ENCODING_IS_CLIENT_ONLY(pg_get_client_encoding())))
ereport(ERROR,
(errcode(ERRCODE_NONSTANDARD_USE_OF_ESCAPE_CHARACTER),
@ -1074,6 +1074,10 @@ scanner_init(const char *str,
yyext->keywords = keywords;
yyext->num_keywords = num_keywords;
yyext->backslash_quote = backslash_quote;
yyext->escape_string_warning = escape_string_warning;
yyext->standard_conforming_strings = standard_conforming_strings;
/*
* Make a scan buffer with special termination needed by flex.
*/
@ -1433,7 +1437,7 @@ check_string_escape_warning(unsigned char ychar, core_yyscan_t yyscanner)
{
if (ychar == '\'')
{
if (yyextra->warn_on_first_escape && escape_string_warning)
if (yyextra->warn_on_first_escape && yyextra->escape_string_warning)
ereport(WARNING,
(errcode(ERRCODE_NONSTANDARD_USE_OF_ESCAPE_CHARACTER),
errmsg("nonstandard use of \\' in a string literal"),
@ -1443,7 +1447,7 @@ check_string_escape_warning(unsigned char ychar, core_yyscan_t yyscanner)
}
else if (ychar == '\\')
{
if (yyextra->warn_on_first_escape && escape_string_warning)
if (yyextra->warn_on_first_escape && yyextra->escape_string_warning)
ereport(WARNING,
(errcode(ERRCODE_NONSTANDARD_USE_OF_ESCAPE_CHARACTER),
errmsg("nonstandard use of \\\\ in a string literal"),
@ -1458,7 +1462,7 @@ check_string_escape_warning(unsigned char ychar, core_yyscan_t yyscanner)
static void
check_escape_warning(core_yyscan_t yyscanner)
{
if (yyextra->warn_on_first_escape && escape_string_warning)
if (yyextra->warn_on_first_escape && yyextra->escape_string_warning)
ereport(WARNING,
(errcode(ERRCODE_NONSTANDARD_USE_OF_ESCAPE_CHARACTER),
errmsg("nonstandard use of escape in a string literal"),

10
src/include/parser/scanner.h
View File

@ -77,6 +77,16 @@ typedef struct core_yy_extra_type
const ScanKeyword *keywords;
int num_keywords;
/*
* Scanner settings to use. These are initialized from the corresponding
* GUC variables by scanner_init(). Callers can modify them after
* scanner_init() if they don't want the scanner's behavior to follow the
* prevailing GUC settings.
*/
int backslash_quote;
bool escape_string_warning;
bool standard_conforming_strings;
/*
* literalbuf is used to accumulate literal values when multiple rules are
* needed to parse a single literal. Call startlit() to reset buffer to