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Commit2dbfbd6

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 parent6953daf commit2dbfbd6

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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
@@ -881,20 +881,33 @@ other.
881881
* to forbid operator names like '?-' that could not be
882882
* sequences of SQL operators.
883883
*/
884-
while (nchars >1 &&
885-
(yytext[nchars -1] =='+' ||
886-
yytext[nchars -1] =='-'))
884+
if (nchars >1 &&
885+
(yytext[nchars -1] =='+' ||
886+
yytext[nchars -1] =='-'))
887887
{
888888
intic;
889889

890890
for (ic = nchars -2; ic >=0; ic--)
891891
{
892-
if (strchr("~!@#^&|`?%", yytext[ic]))
892+
char c = yytext[ic];
893+
if (c =='~' || c =='!' || c =='@' ||
894+
c =='#' || c =='^' || c =='&' ||
895+
c =='|' || c =='`' || c =='?' ||
896+
c =='%')
893897
break;
894898
}
895-
if (ic >=0)
896-
break;/* found a char that makes it OK */
897-
nchars--;/* else remove the +/-, and check again */
899+
if (ic <0)
900+
{
901+
/*
902+
* didn't find a qualifying character, so remove
903+
* all trailing [+-]
904+
*/
905+
do {
906+
nchars--;
907+
}while (nchars >1 &&
908+
(yytext[nchars -1] =='+' ||
909+
yytext[nchars -1] =='-'));
910+
}
898911
}
899912

900913
SET_YYLLOC();

‎src/fe_utils/psqlscan.l

Lines changed: 20 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -800,20 +800,33 @@ other.
800800
* to forbid operator names like '?-' that could not be
801801
* sequences of SQL operators.
802802
*/
803-
while (nchars >1 &&
804-
(yytext[nchars -1] =='+' ||
805-
yytext[nchars -1] =='-'))
803+
if (nchars >1 &&
804+
(yytext[nchars -1] =='+' ||
805+
yytext[nchars -1] =='-'))
806806
{
807807
intic;
808808

809809
for (ic = nchars -2; ic >=0; ic--)
810810
{
811-
if (strchr("~!@#^&|`?%", yytext[ic]))
811+
char c = yytext[ic];
812+
if (c =='~' || c =='!' || c =='@' ||
813+
c =='#' || c =='^' || c =='&' ||
814+
c =='|' || c =='`' || c =='?' ||
815+
c =='%')
812816
break;
813817
}
814-
if (ic >=0)
815-
break;/* found a char that makes it OK */
816-
nchars--;/* else remove the +/-, and check again */
818+
if (ic <0)
819+
{
820+
/*
821+
* didn't find a qualifying character, so remove
822+
* all trailing [+-]
823+
*/
824+
do {
825+
nchars--;
826+
}while (nchars >1 &&
827+
(yytext[nchars -1] =='+' ||
828+
yytext[nchars -1] =='-'));
829+
}
817830
}
818831

819832
if (nchars < yyleng)

‎src/interfaces/ecpg/preproc/pgc.l

Lines changed: 21 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -686,20 +686,33 @@ cppline{space}*#([^i][A-Za-z]*|{if}|{ifdef}|{ifndef}|{import})((\/\*[^*/]*\*+
686686
* to forbid operator names like '?-' that could not be
687687
* sequences of SQL operators.
688688
*/
689-
while (nchars >1 &&
690-
(yytext[nchars-1] =='+' ||
691-
yytext[nchars-1] =='-'))
689+
if (nchars >1 &&
690+
(yytext[nchars -1] =='+' ||
691+
yytext[nchars -1] =='-'))
692692
{
693693
intic;
694694

695-
for (ic = nchars-2; ic >=0; ic--)
695+
for (ic = nchars -2; ic >=0; ic--)
696696
{
697-
if (strchr("~!@#^&|`?%", yytext[ic]))
697+
char c = yytext[ic];
698+
if (c =='~' || c =='!' || c =='@' ||
699+
c =='#' || c =='^' || c =='&' ||
700+
c =='|' || c =='`' || c =='?' ||
701+
c =='%')
698702
break;
699703
}
700-
if (ic >=0)
701-
break;/* found a char that makes it OK */
702-
nchars--;/* else remove the +/-, and check again */
704+
if (ic <0)
705+
{
706+
/*
707+
* didn't find a qualifying character, so remove
708+
* all trailing [+-]
709+
*/
710+
do {
711+
nchars--;
712+
}while (nchars >1 &&
713+
(yytext[nchars -1] =='+' ||
714+
yytext[nchars -1] =='-'));
715+
}
703716
}
704717

705718
if (nchars < yyleng)

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