From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Thu, 25 Aug 2011 18:33:08 +0000 (-0400)
Subject: Fix psql lexer to avoid use of backtracking.
X-Git-Tag: REL9_0_5~34
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=9354f5b76acf37c96ed0173ff8ab3e415bae2b04;p=postgresql

Fix psql lexer to avoid use of backtracking.

Per previous experimentation, backtracking slows down lexing performance
significantly (by about a third).  It's usually pretty easy to avoid, just
need to have rules that accept an incomplete construct and do whatever the
lexer would have done otherwise.

The backtracking was introduced by the patch that added quoted variable
substitution.  Back-patch to 9.0 where that was added.
---

diff --git a/src/bin/psql/psqlscan.l b/src/bin/psql/psqlscan.l
index dfde8db19b..5fefa475af 100644
--- a/src/bin/psql/psqlscan.l
+++ b/src/bin/psql/psqlscan.l
@@ -722,6 +722,23 @@ other			.
 					escape_variable(true);
 				}
 
+	/*
+	 * These rules just avoid the need for scanner backup if one of the
+	 * two rules above fails to match completely.
+	 */
+
+:'[A-Za-z0-9_]*	{
+					/* Throw back everything but the colon */
+					yyless(1);
+					ECHO;
+				}
+
+:\"[A-Za-z0-9_]*	{
+					/* Throw back everything but the colon */
+					yyless(1);
+					ECHO;
+				}
+
 	/*
 	 * Back to backend-compatible rules.
 	 */
@@ -912,7 +929,7 @@ other			.
 					}
 				}
 
-:[A-Za-z0-9_]*	{
+:[A-Za-z0-9_]+	{
 					/* Possible psql variable substitution */
 					if (option_type == OT_VERBATIM)
 						ECHO;
@@ -959,6 +976,20 @@ other			.
 					}
 				}
 
+:'[A-Za-z0-9_]*	{
+					/* Throw back everything but the colon */
+					yyless(1);
+					ECHO;
+					BEGIN(xslashdefaultarg);
+				}
+
+:\"[A-Za-z0-9_]*	{
+					/* Throw back everything but the colon */
+					yyless(1);
+					ECHO;
+					BEGIN(xslashdefaultarg);
+				}
+
 "|"				{
 					ECHO;
 					if (option_type == OT_FILEPIPE)