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Commitd4a63f8

Browse files
committed
Reduce an unnecessary O(N^3) loop in lexer.
The lexer's handling of operators contained an O(N^3) hazard whendealing with long strings of + or - characters; it seems hard toprevent this case from being O(N^2), but the additional N multiplierwas not needed.Backpatch all the way since this has been there since 7.x, and itpresents at least a mild hazard in that trying to do Bind, PREPARE orEXPLAIN on a hostile query could take excessive time (withouthonouring cancels or timeouts) even if the query was never executed.
1 parent5ca0077 commitd4a63f8

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3 files changed

+61
-22
lines changed

3 files changed

+61
-22
lines changed

‎src/backend/parser/scan.l‎

Lines changed: 20 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -885,20 +885,33 @@ other.
885885
* to forbid operator names like '?-' that could not be
886886
* sequences of SQL operators.
887887
*/
888-
while (nchars >1 &&
889-
(yytext[nchars -1] =='+' ||
890-
yytext[nchars -1] =='-'))
888+
if (nchars >1 &&
889+
(yytext[nchars -1] =='+' ||
890+
yytext[nchars -1] =='-'))
891891
{
892892
intic;
893893

894894
for (ic = nchars -2; ic >=0; ic--)
895895
{
896-
if (strchr("~!@#^&|`?%", yytext[ic]))
896+
char c = yytext[ic];
897+
if (c =='~' || c =='!' || c =='@' ||
898+
c =='#' || c =='^' || c =='&' ||
899+
c =='|' || c =='`' || c =='?' ||
900+
c =='%')
897901
break;
898902
}
899-
if (ic >=0)
900-
break;/* found a char that makes it OK */
901-
nchars--;/* else remove the +/-, and check again */
903+
if (ic <0)
904+
{
905+
/*
906+
* didn't find a qualifying character, so remove
907+
* all trailing [+-]
908+
*/
909+
do {
910+
nchars--;
911+
}while (nchars >1 &&
912+
(yytext[nchars -1] =='+' ||
913+
yytext[nchars -1] =='-'));
914+
}
902915
}
903916

904917
SET_YYLLOC();

‎src/fe_utils/psqlscan.l‎

Lines changed: 20 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -817,20 +817,33 @@ other.
817817
* to forbid operator names like '?-' that could not be
818818
* sequences of SQL operators.
819819
*/
820-
while (nchars >1 &&
821-
(yytext[nchars -1] =='+' ||
822-
yytext[nchars -1] =='-'))
820+
if (nchars >1 &&
821+
(yytext[nchars -1] =='+' ||
822+
yytext[nchars -1] =='-'))
823823
{
824824
intic;
825825

826826
for (ic = nchars -2; ic >=0; ic--)
827827
{
828-
if (strchr("~!@#^&|`?%", yytext[ic]))
828+
char c = yytext[ic];
829+
if (c =='~' || c =='!' || c =='@' ||
830+
c =='#' || c =='^' || c =='&' ||
831+
c =='|' || c =='`' || c =='?' ||
832+
c =='%')
829833
break;
830834
}
831-
if (ic >=0)
832-
break;/* found a char that makes it OK */
833-
nchars--;/* else remove the +/-, and check again */
835+
if (ic <0)
836+
{
837+
/*
838+
* didn't find a qualifying character, so remove
839+
* all trailing [+-]
840+
*/
841+
do {
842+
nchars--;
843+
}while (nchars >1 &&
844+
(yytext[nchars -1] =='+' ||
845+
yytext[nchars -1] =='-'));
846+
}
834847
}
835848

836849
if (nchars < yyleng)

‎src/interfaces/ecpg/preproc/pgc.l‎

Lines changed: 21 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -690,20 +690,33 @@ cppline{space}*#([^i][A-Za-z]*|{if}|{ifdef}|{ifndef}|{import})((\/\*[^*/]*\*+
690690
* to forbid operator names like '?-' that could not be
691691
* sequences of SQL operators.
692692
*/
693-
while (nchars >1 &&
694-
(yytext[nchars-1] =='+' ||
695-
yytext[nchars-1] =='-'))
693+
if (nchars >1 &&
694+
(yytext[nchars -1] =='+' ||
695+
yytext[nchars -1] =='-'))
696696
{
697697
intic;
698698

699-
for (ic = nchars-2; ic >=0; ic--)
699+
for (ic = nchars -2; ic >=0; ic--)
700700
{
701-
if (strchr("~!@#^&|`?%", yytext[ic]))
701+
char c = yytext[ic];
702+
if (c =='~' || c =='!' || c =='@' ||
703+
c =='#' || c =='^' || c =='&' ||
704+
c =='|' || c =='`' || c =='?' ||
705+
c =='%')
702706
break;
703707
}
704-
if (ic >=0)
705-
break;/* found a char that makes it OK */
706-
nchars--;/* else remove the +/-, and check again */
708+
if (ic <0)
709+
{
710+
/*
711+
* didn't find a qualifying character, so remove
712+
* all trailing [+-]
713+
*/
714+
do {
715+
nchars--;
716+
}while (nchars >1 &&
717+
(yytext[nchars -1] =='+' ||
718+
yytext[nchars -1] =='-'));
719+
}
707720
}
708721

709722
if (nchars < yyleng)

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