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Fix psql lexer to avoid use of backtracking.

Per previous experimentation, backtracking slows down lexing performancesignificantly (by about a third). It's usually pretty easy to avoid, justneed to have rules that accept an incomplete construct and do whatever thelexer would have done otherwise.The backtracking was introduced by the patch that added quoted variablesubstitution. Back-patch to 9.0 where that was added.

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src/bin/psql
- psqlscan.l

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+32

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lines changed

`‎src/bin/psql/psqlscan.l`

Lines changed: 32 additions & 1 deletion

Original file line number	Diff line number	Diff line change
`@@ -722,6 +722,23 @@ other.`
`722`	`722`	`escape_variable(true);`
`723`	`723`	`}`
`724`	`724`
	`725`	`+/*`
	`726`	`+ * These rules just avoid the need for scanner backup if one of the`
	`727`	`+ * two rules above fails to match completely.`
	`728`	`+ */`
	`729`	`+`
	`730`	`+:'[A-Za-z0-9_]*{`
	`731`	`+/* Throw back everything but the colon */`
	`732`	`+yyless(1);`
	`733`	`+ECHO;`
	`734`	`+}`
	`735`	`+`
	`736`	`+:\"[A-Za-z0-9_]*{`
	`737`	`+/* Throw back everything but the colon */`
	`738`	`+yyless(1);`
	`739`	`+ECHO;`
	`740`	`+}`
	`741`	`+`
`725`	`742`	`/*`
`726`	`743`	`* Back to backend-compatible rules.`
`727`	`744`	`*/`
`@@ -912,7 +929,7 @@ other.`
`912`	`929`	`}`
`913`	`930`	`}`
`914`	`931`
`915`		`-:[A-Za-z0-9_]*{`
	`932`	`+:[A-Za-z0-9_]+{`
`916`	`933`	`/* Possible psql variable substitution */`
`917`	`934`	`if (option_type == OT_VERBATIM)`
`918`	`935`	`ECHO;`
`@@ -959,6 +976,20 @@ other.`
`959`	`976`	`}`
`960`	`977`	`}`
`961`	`978`
	`979`	`+:'[A-Za-z0-9_]*{`
	`980`	`+/* Throw back everything but the colon */`
	`981`	`+yyless(1);`
	`982`	`+ECHO;`
	`983`	`+BEGIN(xslashdefaultarg);`
	`984`	`+}`
	`985`	`+`
	`986`	`+:\"[A-Za-z0-9_]*{`
	`987`	`+/* Throw back everything but the colon */`
	`988`	`+yyless(1);`
	`989`	`+ECHO;`
	`990`	`+BEGIN(xslashdefaultarg);`
	`991`	`+}`
	`992`	`+`
`962`	`993`	`"\|"{`
`963`	`994`	`ECHO;`
`964`	`995`	`if (option_type == OT_FILEPIPE)`

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`‎src/bin/psql/psqlscan.l`

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