From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Fri, 27 Aug 2021 16:18:58 +0000 (-0400)
Subject: Handle interaction of regexp's makesearch and MATCHALL more honestly.
X-Git-Tag: REL_14_RC1~84
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=3068e45799327298a3f4c22b03db2aa48e2ab0da;p=thirdparty%2Fpostgresql.git

Handle interaction of regexp's makesearch and MATCHALL more honestly.

Second thoughts about commit 824bf7190: we apply makesearch() to
an NFA after having determined whether it is a MATCHALL pattern.
Prepending ".*" doesn't make it non-MATCHALL, but it does change the
maximum possible match length, and makesearch() failed to update that.
This has no ill effects given the stylized usage of search NFAs, but
it seems like it's better to keep the data structure consistent.  In
particular, fixing this allows more honest handling of the MATCHALL
check in matchuntil(): we can now assert that maxmatchall is infinity,
instead of lamely assuming that it should act that way.

In passing, improve the code in dump[c]nfa so that infinite maxmatchall
is printed as "inf" not a magic number.
---

diff --git a/src/backend/regex/regc_nfa.c b/src/backend/regex/regc_nfa.c
index 6d77c59e121..0e93c74287e 100644
--- a/src/backend/regex/regc_nfa.c
+++ b/src/backend/regex/regc_nfa.c
@@ -3602,8 +3602,13 @@ dumpnfa(struct nfa *nfa,
 	if (nfa->flags & HASLACONS)
 		fprintf(f, ", haslacons");
 	if (nfa->flags & MATCHALL)
-		fprintf(f, ", minmatchall %d, maxmatchall %d",
-				nfa->minmatchall, nfa->maxmatchall);
+	{
+		fprintf(f, ", minmatchall %d", nfa->minmatchall);
+		if (nfa->maxmatchall == DUPINF)
+			fprintf(f, ", maxmatchall inf");
+		else
+			fprintf(f, ", maxmatchall %d", nfa->maxmatchall);
+	}
 	fprintf(f, "\n");
 	for (s = nfa->states; s != NULL; s = s->next)
 	{
@@ -3766,8 +3771,13 @@ dumpcnfa(struct cnfa *cnfa,
 	if (cnfa->flags & HASLACONS)
 		fprintf(f, ", haslacons");
 	if (cnfa->flags & MATCHALL)
-		fprintf(f, ", minmatchall %d, maxmatchall %d",
-				cnfa->minmatchall, cnfa->maxmatchall);
+	{
+		fprintf(f, ", minmatchall %d", cnfa->minmatchall);
+		if (cnfa->maxmatchall == DUPINF)
+			fprintf(f, ", maxmatchall inf");
+		else
+			fprintf(f, ", maxmatchall %d", cnfa->maxmatchall);
+	}
 	fprintf(f, "\n");
 	for (st = 0; st < cnfa->nstates; st++)
 		dumpcstate(st, cnfa, f);
diff --git a/src/backend/regex/regcomp.c b/src/backend/regex/regcomp.c
index bfe12eb08b3..b735fa6eaff 100644
--- a/src/backend/regex/regcomp.c
+++ b/src/backend/regex/regcomp.c
@@ -598,6 +598,13 @@ makesearch(struct vars *v,
 		/* and ^* and \A* too -- not always necessary, but harmless */
 		newarc(nfa, PLAIN, nfa->bos[0], pre, pre);
 		newarc(nfa, PLAIN, nfa->bos[1], pre, pre);
+
+		/*
+		 * The pattern is still MATCHALL if it was before, but the max match
+		 * length is now infinity.
+		 */
+		if (nfa->flags & MATCHALL)
+			nfa->maxmatchall = DUPINF;
 	}
 
 	/*
diff --git a/src/backend/regex/rege_dfa.c b/src/backend/regex/rege_dfa.c
index 1d79d734468..ba1289c64a9 100644
--- a/src/backend/regex/rege_dfa.c
+++ b/src/backend/regex/rege_dfa.c
@@ -385,14 +385,10 @@ matchuntil(struct vars *v,
 	{
 		size_t		nchr = probe - v->start;
 
-		/*
-		 * It might seem that we should check maxmatchall too, but the .* at
-		 * the front of the pattern absorbs any extra characters (and it was
-		 * tacked on *after* computing minmatchall/maxmatchall).  Thus, we
-		 * should match if there are at least minmatchall characters.
-		 */
 		if (nchr < d->cnfa->minmatchall)
 			return 0;
+		/* maxmatchall will always be infinity, cf. makesearch() */
+		assert(d->cnfa->maxmatchall == DUPINF);
 		return 1;
 	}