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.

diff --git a/src/backend/parser/scan.l b/src/backend/parser/scan.l
index 30242d343d1502859e982cf289468d329d1886d1..4b2444d3e80b0e47194ba76dbbb9bbc28b75d988 100644 (file)
--- a/src/backend/parser/scan.l
+++ b/src/backend/parser/scan.l
@@ -844,20 +844,33 @@ 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--)
+                                               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/bin/psql/psqlscan.l b/src/bin/psql/psqlscan.l
index 5013b933635bbf20cd2374f14f4df0eaff155a9c..4f9b4bfa0f0aa1313f8686aec33b4e0c500f214c 100644 (file)
--- a/src/bin/psql/psqlscan.l
+++ b/src/bin/psql/psqlscan.l
@@ -811,20 +811,33 @@ 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--)
+                                               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 0dc98f79a85b0470b26b878937ce5a949b28d613..aaaa5885d9074d3a3fcca1749beb6cc3aa19edd1 100644 (file)
--- a/src/interfaces/ecpg/preproc/pgc.l
+++ b/src/interfaces/ecpg/preproc/pgc.l
@@ -675,20 +675,33 @@ cppline                   {space}*#([^i][A-Za-z]*|{if}|{ifdef}|{ifndef}|{import})(.*\\{space})*.
                                                 * 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)