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Commit4854ead

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 parent90b0f30 commit4854ead

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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
@@ -798,20 +798,33 @@ other.
798798
* to forbid operator names like '?-' that could not be
799799
* sequences of SQL operators.
800800
*/
801-
while (nchars >1 &&
802-
(yytext[nchars -1] =='+' ||
803-
yytext[nchars -1] =='-'))
801+
if (nchars >1 &&
802+
(yytext[nchars -1] =='+' ||
803+
yytext[nchars -1] =='-'))
804804
{
805805
intic;
806806

807807
for (ic = nchars -2; ic >=0; ic--)
808808
{
809-
if (strchr("~!@#^&|`?%", yytext[ic]))
809+
char c = yytext[ic];
810+
if (c =='~' || c =='!' || c =='@' ||
811+
c =='#' || c =='^' || c =='&' ||
812+
c =='|' || c =='`' || c =='?' ||
813+
c =='%')
810814
break;
811815
}
812-
if (ic >=0)
813-
break;/* found a char that makes it OK */
814-
nchars--;/* else remove the +/-, and check again */
816+
if (ic <0)
817+
{
818+
/*
819+
* didn't find a qualifying character, so remove
820+
* all trailing [+-]
821+
*/
822+
do {
823+
nchars--;
824+
}while (nchars >1 &&
825+
(yytext[nchars -1] =='+' ||
826+
yytext[nchars -1] =='-'));
827+
}
815828
}
816829

817830
if (nchars < yyleng)

‎src/interfaces/ecpg/preproc/pgc.l‎

Lines changed: 21 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -687,20 +687,33 @@ cppline{space}*#([^i][A-Za-z]*|{if}|{ifdef}|{ifndef}|{import})((\/\*[^*/]*\*+
687687
* to forbid operator names like '?-' that could not be
688688
* sequences of SQL operators.
689689
*/
690-
while (nchars >1 &&
691-
(yytext[nchars-1] =='+' ||
692-
yytext[nchars-1] =='-'))
690+
if (nchars >1 &&
691+
(yytext[nchars -1] =='+' ||
692+
yytext[nchars -1] =='-'))
693693
{
694694
intic;
695695

696-
for (ic = nchars-2; ic >=0; ic--)
696+
for (ic = nchars -2; ic >=0; ic--)
697697
{
698-
if (strchr("~!@#^&|`?%", yytext[ic]))
698+
char c = yytext[ic];
699+
if (c =='~' || c =='!' || c =='@' ||
700+
c =='#' || c =='^' || c =='&' ||
701+
c =='|' || c =='`' || c =='?' ||
702+
c =='%')
699703
break;
700704
}
701-
if (ic >=0)
702-
break;/* found a char that makes it OK */
703-
nchars--;/* else remove the +/-, and check again */
705+
if (ic <0)
706+
{
707+
/*
708+
* didn't find a qualifying character, so remove
709+
* all trailing [+-]
710+
*/
711+
do {
712+
nchars--;
713+
}while (nchars >1 &&
714+
(yytext[nchars -1] =='+' ||
715+
yytext[nchars -1] =='-'));
716+
}
704717
}
705718

706719
if (nchars < yyleng)

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