diff options
| author | Andrew Gierth | 2018-08-23 19:00:33 +0000 |
|---|---|---|
| committer | Andrew Gierth | 2018-08-23 20:34:42 +0000 |
| commit | 4854ead60a293bb1ca235bd110c6a56c8aaaafd3 (patch) | |
| tree | 75e40f62a12a6de83fdef78ba38ce00ddab61f85 | |
| parent | 90b0f30aea0ee456614ec97f518ffaf8ca6c3b05 (diff) | |
Reduce an unnecessary O(N^3) loop in lexer.
The lexer's handling of operators contained an O(N^3) hazard when
dealing with long strings of + or - characters; it seems hard to
prevent this case from being O(N^2), but the additional N multiplier
was not needed.
Backpatch all the way since this has been there since 7.x, and it
presents at least a mild hazard in that trying to do Bind, PREPARE or
EXPLAIN on a hostile query could take excessive time (without
honouring cancels or timeouts) even if the query was never executed.
| -rw-r--r-- | src/backend/parser/scan.l | 27 | ||||
| -rw-r--r-- | src/fe_utils/psqlscan.l | 27 | ||||
| -rw-r--r-- | src/interfaces/ecpg/preproc/pgc.l | 29 |
3 files changed, 61 insertions, 22 deletions
diff --git a/src/backend/parser/scan.l b/src/backend/parser/scan.l index acd92698057..967b2eaf9b9 100644 --- a/src/backend/parser/scan.l +++ b/src/backend/parser/scan.l @@ -881,20 +881,33 @@ other . * to forbid operator names like '?-' that could not be * sequences of SQL operators. */ - while (nchars > 1 && - (yytext[nchars - 1] == '+' || - yytext[nchars - 1] == '-')) + if (nchars > 1 && + (yytext[nchars - 1] == '+' || + yytext[nchars - 1] == '-')) { int ic; for (ic = nchars - 2; ic >= 0; ic--) { - if (strchr("~!@#^&|`?%", yytext[ic])) + char c = yytext[ic]; + if (c == '~' || c == '!' || c == '@' || + c == '#' || c == '^' || c == '&' || + c == '|' || c == '`' || c == '?' || + c == '%') break; } - if (ic >= 0) - break; /* found a char that makes it OK */ - nchars--; /* else remove the +/-, and check again */ + if (ic < 0) + { + /* + * didn't find a qualifying character, so remove + * all trailing [+-] + */ + do { + nchars--; + } while (nchars > 1 && + (yytext[nchars - 1] == '+' || + yytext[nchars - 1] == '-')); + } } SET_YYLLOC(); diff --git a/src/fe_utils/psqlscan.l b/src/fe_utils/psqlscan.l index 55067b450c2..fe74abc1a6c 100644 --- a/src/fe_utils/psqlscan.l +++ b/src/fe_utils/psqlscan.l @@ -798,20 +798,33 @@ other . * to forbid operator names like '?-' that could not be * sequences of SQL operators. */ - while (nchars > 1 && - (yytext[nchars - 1] == '+' || - yytext[nchars - 1] == '-')) + if (nchars > 1 && + (yytext[nchars - 1] == '+' || + yytext[nchars - 1] == '-')) { int ic; for (ic = nchars - 2; ic >= 0; ic--) { - if (strchr("~!@#^&|`?%", yytext[ic])) + char c = yytext[ic]; + if (c == '~' || c == '!' || c == '@' || + c == '#' || c == '^' || c == '&' || + c == '|' || c == '`' || c == '?' || + c == '%') break; } - if (ic >= 0) - break; /* found a char that makes it OK */ - nchars--; /* else remove the +/-, and check again */ + if (ic < 0) + { + /* + * didn't find a qualifying character, so remove + * all trailing [+-] + */ + do { + nchars--; + } while (nchars > 1 && + (yytext[nchars - 1] == '+' || + yytext[nchars - 1] == '-')); + } } if (nchars < yyleng) diff --git a/src/interfaces/ecpg/preproc/pgc.l b/src/interfaces/ecpg/preproc/pgc.l index 07c722d1d72..bc47c23d038 100644 --- a/src/interfaces/ecpg/preproc/pgc.l +++ b/src/interfaces/ecpg/preproc/pgc.l @@ -687,20 +687,33 @@ cppline {space}*#([^i][A-Za-z]*|{if}|{ifdef}|{ifndef}|{import})((\/\*[^*/]*\*+ * to forbid operator names like '?-' that could not be * sequences of SQL operators. */ - while (nchars > 1 && - (yytext[nchars-1] == '+' || - yytext[nchars-1] == '-')) + if (nchars > 1 && + (yytext[nchars - 1] == '+' || + yytext[nchars - 1] == '-')) { int ic; - for (ic = nchars-2; ic >= 0; ic--) + for (ic = nchars - 2; ic >= 0; ic--) { - if (strchr("~!@#^&|`?%", yytext[ic])) + char c = yytext[ic]; + if (c == '~' || c == '!' || c == '@' || + c == '#' || c == '^' || c == '&' || + c == '|' || c == '`' || c == '?' || + c == '%') break; } - if (ic >= 0) - break; /* found a char that makes it OK */ - nchars--; /* else remove the +/-, and check again */ + if (ic < 0) + { + /* + * didn't find a qualifying character, so remove + * all trailing [+-] + */ + do { + nchars--; + } while (nchars > 1 && + (yytext[nchars - 1] == '+' || + yytext[nchars - 1] == '-')); + } } if (nchars < yyleng) |