Some regular-expression performance hacking

diff --git a/contrib/pg_trgm/trgm_regexp.c b/contrib/pg_trgm/trgm_regexp.c
index 1e4f0121f3..fcf03de32d 100644
--- a/contrib/pg_trgm/trgm_regexp.c
+++ b/contrib/pg_trgm/trgm_regexp.c
@@ -282,8 +282,8 @@ typedef struct
 typedef int TrgmColor;
 
 /* We assume that colors returned by the regexp engine cannot be these: */
-#define COLOR_UNKNOWN	(-1)
-#define COLOR_BLANK		(-2)
+#define COLOR_UNKNOWN	(-3)
+#define COLOR_BLANK		(-4)
 
 typedef struct
 {
@@ -780,7 +780,8 @@ getColorInfo(regex_t *regex, TrgmNFA *trgmNFA)
 		palloc0(colorsCount * sizeof(TrgmColorInfo));
 
 	/*
-	 * Loop over colors, filling TrgmColorInfo about each.
+	 * Loop over colors, filling TrgmColorInfo about each.  Note we include
+	 * WHITE (0) even though we know it'll be reported as non-expandable.
 	 */
 	for (i = 0; i < colorsCount; i++)
 	{
@@ -1098,9 +1099,9 @@ addKey(TrgmNFA *trgmNFA, TrgmState *state, TrgmStateKey *key)
 			/* Add enter key to this state */
 			addKeyToQueue(trgmNFA, &destKey);
 		}
-		else
+		else if (arc->co >= 0)
 		{
-			/* Regular color */
+			/* Regular color (including WHITE) */
 			TrgmColorInfo *colorInfo = &trgmNFA->colorInfo[arc->co];
 
 			if (colorInfo->expandable)
@@ -1156,6 +1157,14 @@ addKey(TrgmNFA *trgmNFA, TrgmState *state, TrgmStateKey *key)
 				addKeyToQueue(trgmNFA, &destKey);
 			}
 		}
+		else
+		{
+			/* RAINBOW: treat as unexpandable color */
+			destKey.prefix.colors[0] = COLOR_UNKNOWN;
+			destKey.prefix.colors[1] = COLOR_UNKNOWN;
+			destKey.nstate = arc->to;
+			addKeyToQueue(trgmNFA, &destKey);
+		}
 	}
 
 	pfree(arcs);
@@ -1216,10 +1225,10 @@ addArcs(TrgmNFA *trgmNFA, TrgmState *state)
 			/*
 			 * Ignore non-expandable colors; addKey already handled the case.
 			 *
-			 * We need no special check for begin/end pseudocolors here.  We
-			 * don't need to do any processing for them, and they will be
-			 * marked non-expandable since the regex engine will have reported
-			 * them that way.
+			 * We need no special check for WHITE or begin/end pseudocolors
+			 * here.  We don't need to do any processing for them, and they
+			 * will be marked non-expandable since the regex engine will have
+			 * reported them that way.
 			 */
 			if (!colorInfo->expandable)
 				continue;
diff --git a/src/backend/regex/README b/src/backend/regex/README
index f08aab69e3..cc1834b89c 100644
--- a/src/backend/regex/README
+++ b/src/backend/regex/README
@@ -261,6 +261,18 @@ and the NFA has these arcs:
 	states 4 -> 5 on color 2 ("x" only)
 which can be seen to be a correct representation of the regex.
 
+There is one more complexity, which is how to handle ".", that is a
+match-anything atom.  We used to do that by generating a "rainbow"
+of arcs of all live colors between the two NFA states before and after
+the dot.  That's expensive in itself when there are lots of colors,
+and it also typically adds lots of follow-on arc-splitting work for the
+color splitting logic.  Now we handle this case by generating a single arc
+labeled with the special color RAINBOW, meaning all colors.  Such arcs
+never need to be split, so they help keep NFAs small in this common case.
+(Note: this optimization doesn't help in REG_NLSTOP mode, where "." is
+not supposed to match newline.  In that case we still handle "." by
+generating an almost-rainbow of all colors except newline's color.)
+
 Given this summary, we can see we need the following operations for
 colors:
 
@@ -349,6 +361,8 @@ The possible arc types are:
 
     PLAIN arcs, which specify matching of any character of a given "color"
     (see above).  These are dumped as "[color_number]->to_state".
+    In addition there can be "rainbow" PLAIN arcs, which are dumped as
+    "[*]->to_state".
 
     EMPTY arcs, which specify a no-op transition to another state.  These
     are dumped as "->to_state".
@@ -356,11 +370,11 @@ The possible arc types are:
     AHEAD constraints, which represent a "next character must be of this
     color" constraint.  AHEAD differs from a PLAIN arc in that the input
     character is not consumed when crossing the arc.  These are dumped as
-    ">color_number>->to_state".
+    ">color_number>->to_state", or possibly ">*>->to_state".
 
     BEHIND constraints, which represent a "previous character must be of
     this color" constraint, which likewise consumes no input.  These are
-    dumped as "<color_number<->to_state".
+    dumped as "<color_number<->to_state", or possibly "<*<->to_state".
 
     '^' arcs, which specify a beginning-of-input constraint.  These are
     dumped as "^0->to_state" or "^1->to_state" for beginning-of-string and
diff --git a/src/backend/regex/regc_color.c b/src/backend/regex/regc_color.c
index f5a4151757..0864011cce 100644
--- a/src/backend/regex/regc_color.c
+++ b/src/backend/regex/regc_color.c
@@ -977,6 +977,7 @@ colorchain(struct colormap *cm,
 {
 	struct colordesc *cd = &cm->cd[a->co];
 
+	assert(a->co >= 0);
 	if (cd->arcs != NULL)
 		cd->arcs->colorchainRev = a;
 	a->colorchain = cd->arcs;
@@ -994,6 +995,7 @@ uncolorchain(struct colormap *cm,
 	struct colordesc *cd = &cm->cd[a->co];
 	struct arc *aa = a->colorchainRev;
 
+	assert(a->co >= 0);
 	if (aa == NULL)
 	{
 		assert(cd->arcs == a);
@@ -1012,6 +1014,9 @@ uncolorchain(struct colormap *cm,
 
 /*
  * rainbow - add arcs of all full colors (but one) between specified states
+ *
+ * If there isn't an exception color, we now generate just a single arc
+ * labeled RAINBOW, saving lots of arc-munging later on.
  */
 static void
 rainbow(struct nfa *nfa,
@@ -1025,6 +1030,13 @@ rainbow(struct nfa *nfa,
 	struct colordesc *end = CDEND(cm);
 	color		co;
 
+	if (but == COLORLESS)
+	{
+		newarc(nfa, type, RAINBOW, from, to);
+		return;
+	}
+
+	/* Gotta do it the hard way.  Skip subcolors, pseudocolors, and "but" */
 	for (cd = cm->cd, co = 0; cd < end && !CISERR(); cd++, co++)
 		if (!UNUSEDCOLOR(cd) && cd->sub != co && co != but &&
 			!(cd->flags & PSEUDO))
@@ -1034,13 +1046,16 @@ rainbow(struct nfa *nfa,
 /*
  * colorcomplement - add arcs of complementary colors
  *
+ * We add arcs of all colors that are not pseudocolors and do not match
+ * any of the "of" state's PLAIN outarcs.
+ *
  * The calling sequence ought to be reconciled with cloneouts().
  */
 static void
 colorcomplement(struct nfa *nfa,
 				struct colormap *cm,
 				int type,
-				struct state *of,	/* complements of this guy's PLAIN outarcs */
+				struct state *of,
 				struct state *from,
 				struct state *to)
 {
@@ -1049,6 +1064,11 @@ colorcomplement(struct nfa *nfa,
 	color		co;
 
 	assert(of != from);
+
+	/* A RAINBOW arc matches all colors, making the complement empty */
+	if (findarc(of, PLAIN, RAINBOW) != NULL)
+		return;
+
 	for (cd = cm->cd, co = 0; cd < end && !CISERR(); cd++, co++)
 		if (!UNUSEDCOLOR(cd) && !(cd->flags & PSEUDO))
 			if (findarc(of, PLAIN, co) == NULL)
diff --git a/src/backend/regex/regc_nfa.c b/src/backend/regex/regc_nfa.c
index 92c9c4d795..1ac030570d 100644
--- a/src/backend/regex/regc_nfa.c
+++ b/src/backend/regex/regc_nfa.c
@@ -271,6 +271,11 @@ destroystate(struct nfa *nfa,
  *
  * This function checks to make sure that no duplicate arcs are created.
  * In general we never want duplicates.
+ *
+ * However: in principle, a RAINBOW arc is redundant with any plain arc
+ * (unless that arc is for a pseudocolor).  But we don't try to recognize
+ * that redundancy, either here or in allied operations such as moveins().
+ * The pseudocolor consideration makes that more costly than it seems worth.
  */
 static void
 newarc(struct nfa *nfa,
@@ -1170,6 +1175,9 @@ copyouts(struct nfa *nfa,
 
 /*
  * cloneouts - copy out arcs of a state to another state pair, modifying type
+ *
+ * This is only used to convert PLAIN arcs to AHEAD/BEHIND arcs, which share
+ * the same interpretation of "co".  It wouldn't be sensible with LACONs.
  */
 static void
 cloneouts(struct nfa *nfa,
@@ -1181,9 +1189,13 @@ cloneouts(struct nfa *nfa,
 	struct arc *a;
 
 	assert(old != from);
+	assert(type == AHEAD || type == BEHIND);
 
 	for (a = old->outs; a != NULL; a = a->outchain)
+	{
+		assert(a->type == PLAIN);
 		newarc(nfa, type, a->co, from, to);
+	}
 }
 
 /*
@@ -1597,7 +1609,7 @@ pull(struct nfa *nfa,
 	for (a = from->ins; a != NULL && !NISERR(); a = nexta)
 	{
 		nexta = a->inchain;
-		switch (combine(con, a))
+		switch (combine(nfa, con, a))
 		{
 			case INCOMPATIBLE:	/* destroy the arc */
 				freearc(nfa, a);
@@ -1624,6 +1636,10 @@ pull(struct nfa *nfa,
 				cparc(nfa, a, s, to);
 				freearc(nfa, a);
 				break;
+			case REPLACEARC:	/* replace arc's color */
+				newarc(nfa, a->type, con->co, a->from, to);
+				freearc(nfa, a);
+				break;
 			default:
 				assert(NOTREACHED);
 				break;
@@ -1764,7 +1780,7 @@ push(struct nfa *nfa,
 	for (a = to->outs; a != NULL && !NISERR(); a = nexta)
 	{
 		nexta = a->outchain;
-		switch (combine(con, a))
+		switch (combine(nfa, con, a))
 		{
 			case INCOMPATIBLE:	/* destroy the arc */
 				freearc(nfa, a);
@@ -1791,6 +1807,10 @@ push(struct nfa *nfa,
 				cparc(nfa, a, from, s);
 				freearc(nfa, a);
 				break;
+			case REPLACEARC:	/* replace arc's color */
+				newarc(nfa, a->type, con->co, from, a->to);
+				freearc(nfa, a);
+				break;
 			default:
 				assert(NOTREACHED);
 				break;
@@ -1810,9 +1830,11 @@ push(struct nfa *nfa,
  * #def INCOMPATIBLE	1	// destroys arc
  * #def SATISFIED		2	// constraint satisfied
  * #def COMPATIBLE		3	// compatible but not satisfied yet
+ * #def REPLACEARC		4	// replace arc's color with constraint color
  */
 static int
-combine(struct arc *con,
+combine(struct nfa *nfa,
+		struct arc *con,
 		struct arc *a)
 {
 #define  CA(ct,at)	 (((ct)<<CHAR_BIT) | (at))
@@ -1827,14 +1849,46 @@ combine(struct arc *con,
 		case CA(BEHIND, PLAIN):
 			if (con->co == a->co)
 				return SATISFIED;
+			if (con->co == RAINBOW)
+			{
+				/* con is satisfied unless arc's color is a pseudocolor */
+				if (!(nfa->cm->cd[a->co].flags & PSEUDO))
+					return SATISFIED;
+			}
+			else if (a->co == RAINBOW)
+			{
+				/* con is incompatible if it's for a pseudocolor */
+				if (nfa->cm->cd[con->co].flags & PSEUDO)
+					return INCOMPATIBLE;
+				/* otherwise, constraint constrains arc to be only its color */
+				return REPLACEARC;
+			}
 			return INCOMPATIBLE;
 			break;
 		case CA('^', '^'):		/* collision, similar constraints */
 		case CA('$', '$'):
-		case CA(AHEAD, AHEAD):
+			if (con->co == a->co)	/* true duplication */
+				return SATISFIED;
+			return INCOMPATIBLE;
+			break;
+		case CA(AHEAD, AHEAD):	/* collision, similar constraints */
 		case CA(BEHIND, BEHIND):
 			if (con->co == a->co)	/* true duplication */
 				return SATISFIED;
+			if (con->co == RAINBOW)
+			{
+				/* con is satisfied unless arc's color is a pseudocolor */
+				if (!(nfa->cm->cd[a->co].flags & PSEUDO))
+					return SATISFIED;
+			}
+			else if (a->co == RAINBOW)
+			{
+				/* con is incompatible if it's for a pseudocolor */
+				if (nfa->cm->cd[con->co].flags & PSEUDO)
+					return INCOMPATIBLE;
+				/* otherwise, constraint constrains arc to be only its color */
+				return REPLACEARC;
+			}
 			return INCOMPATIBLE;
 			break;
 		case CA('^', BEHIND):	/* collision, dissimilar constraints */
@@ -2895,6 +2949,7 @@ compact(struct nfa *nfa,
 					break;
 				case LACON:
 					assert(s->no != cnfa->pre);
+					assert(a->co >= 0);
 					ca->co = (color) (cnfa->ncolors + a->co);
 					ca->to = a->to->no;
 					ca++;
@@ -2902,7 +2957,7 @@ compact(struct nfa *nfa,
 					break;
 				default:
 					NERR(REG_ASSERT);
-					break;
+					return;
 			}
 		carcsort(first, ca - first);
 		ca->co = COLORLESS;
@@ -3068,13 +3123,22 @@ dumparc(struct arc *a,
 	switch (a->type)
 	{
 		case PLAIN:
-			fprintf(f, "[%ld]", (long) a->co);
+			if (a->co == RAINBOW)
+				fprintf(f, "[*]");
+			else
+				fprintf(f, "[%ld]", (long) a->co);
 			break;
 		case AHEAD:
-			fprintf(f, ">%ld>", (long) a->co);
+			if (a->co == RAINBOW)
+				fprintf(f, ">*>");
+			else
+				fprintf(f, ">%ld>", (long) a->co);
 			break;
 		case BEHIND:
-			fprintf(f, "<%ld<", (long) a->co);
+			if (a->co == RAINBOW)
+				fprintf(f, "<*<");
+			else
+				fprintf(f, "<%ld<", (long) a->co);
 			break;
 		case LACON:
 			fprintf(f, ":%ld:", (long) a->co);
@@ -3161,7 +3225,9 @@ dumpcstate(int st,
 	pos = 1;
 	for (ca = cnfa->states[st]; ca->co != COLORLESS; ca++)
 	{
-		if (ca->co < cnfa->ncolors)
+		if (ca->co == RAINBOW)
+			fprintf(f, "\t[*]->%d", ca->to);
+		else if (ca->co < cnfa->ncolors)
 			fprintf(f, "\t[%ld]->%d", (long) ca->co, ca->to);
 		else
 			fprintf(f, "\t:%ld:->%d", (long) (ca->co - cnfa->ncolors), ca->to);
diff --git a/src/backend/regex/regcomp.c b/src/backend/regex/regcomp.c
index 91078dcd80..5956b86026 100644
--- a/src/backend/regex/regcomp.c
+++ b/src/backend/regex/regcomp.c
@@ -158,7 +158,8 @@ static int	push(struct nfa *, struct arc *, struct state **);
 #define INCOMPATIBLE	1		/* destroys arc */
 #define SATISFIED	2			/* constraint satisfied */
 #define COMPATIBLE	3			/* compatible but not satisfied yet */
-static int	combine(struct arc *, struct arc *);
+#define REPLACEARC	4			/* replace arc's color with constraint color */
+static int	combine(struct nfa *nfa, struct arc *con, struct arc *a);
 static void fixempties(struct nfa *, FILE *);
 static struct state *emptyreachable(struct nfa *, struct state *,
 									struct state *, struct arc **);
@@ -289,9 +290,11 @@ struct vars
 #define SBEGIN	'A'				/* beginning of string (even if not BOL) */
 #define SEND	'Z'				/* end of string (even if not EOL) */
 
-/* is an arc colored, and hence on a color chain? */
+/* is an arc colored, and hence should belong to a color chain? */
+/* the test on "co" eliminates RAINBOW arcs, which we don't bother to chain */
 #define COLORED(a) \
-	((a)->type == PLAIN || (a)->type == AHEAD || (a)->type == BEHIND)
+	((a)->co >= 0 && \
+	 ((a)->type == PLAIN || (a)->type == AHEAD || (a)->type == BEHIND))
 
 
 /* static function list */
@@ -1390,7 +1393,8 @@ bracket(struct vars *v,
  * cbracket - handle complemented bracket expression
  * We do it by calling bracket() with dummy endpoints, and then complementing
  * the result.  The alternative would be to invoke rainbow(), and then delete
- * arcs as the b.e. is seen... but that gets messy.
+ * arcs as the b.e. is seen... but that gets messy, and is really quite
+ * infeasible now that rainbow() just puts out one RAINBOW arc.
  */
 static void
 cbracket(struct vars *v,
diff --git a/src/backend/regex/rege_dfa.c b/src/backend/regex/rege_dfa.c
index 5695e158a5..32be2592c5 100644
--- a/src/backend/regex/rege_dfa.c
+++ b/src/backend/regex/rege_dfa.c
@@ -612,6 +612,7 @@ miss(struct vars *v,
 	unsigned	h;
 	struct carc *ca;
 	struct sset *p;
+	int			ispseudocolor;
 	int			ispost;
 	int			noprogress;
 	int			gotstate;
@@ -643,13 +644,15 @@ miss(struct vars *v,
 	 */
 	for (i = 0; i < d->wordsper; i++)
 		d->work[i] = 0;			/* build new stateset bitmap in d->work */
+	ispseudocolor = d->cm->cd[co].flags & PSEUDO;
 	ispost = 0;
 	noprogress = 1;
 	gotstate = 0;
 	for (i = 0; i < d->nstates; i++)
 		if (ISBSET(css->states, i))
 			for (ca = cnfa->states[i]; ca->co != COLORLESS; ca++)
-				if (ca->co == co)
+				if (ca->co == co ||
+					(ca->co == RAINBOW && !ispseudocolor))
 				{
 					BSET(d->work, ca->to);
 					gotstate = 1;
diff --git a/src/backend/regex/regexport.c b/src/backend/regex/regexport.c
index d4f940b8c3..a493dbe88c 100644
--- a/src/backend/regex/regexport.c
+++ b/src/backend/regex/regexport.c
@@ -222,7 +222,8 @@ pg_reg_colorisend(const regex_t *regex, int co)
  * Get number of member chrs of color number "co".
  *
  * Note: we return -1 if the color number is invalid, or if it is a special
- * color (WHITE or a pseudocolor), or if the number of members is uncertain.
+ * color (WHITE, RAINBOW, or a pseudocolor), or if the number of members is
+ * uncertain.
  * Callers should not try to extract the members if -1 is returned.
  */
 int
@@ -233,7 +234,7 @@ pg_reg_getnumcharacters(const regex_t *regex, int co)
 	assert(regex != NULL && regex->re_magic == REMAGIC);
 	cm = &((struct guts *) regex->re_guts)->cmap;
 
-	if (co <= 0 || co > cm->max)	/* we reject 0 which is WHITE */
+	if (co <= 0 || co > cm->max)	/* <= 0 rejects WHITE and RAINBOW */
 		return -1;
 	if (cm->cd[co].flags & PSEUDO)	/* also pseudocolors (BOS etc) */
 		return -1;
@@ -257,7 +258,7 @@ pg_reg_getnumcharacters(const regex_t *regex, int co)
  * whose length chars_len must be at least as long as indicated by
  * pg_reg_getnumcharacters(), else not all chars will be returned.
  *
- * Fetching the members of WHITE or a pseudocolor is not supported.
+ * Fetching the members of WHITE, RAINBOW, or a pseudocolor is not supported.
  *
  * Caution: this is a relatively expensive operation.
  */
diff --git a/src/backend/regex/regprefix.c b/src/backend/regex/regprefix.c
index 1d4593ac94..e2fbad7a8a 100644
--- a/src/backend/regex/regprefix.c
+++ b/src/backend/regex/regprefix.c
@@ -165,9 +165,13 @@ findprefix(struct cnfa *cnfa,
 			/* We can ignore BOS/BOL arcs */
 			if (ca->co == cnfa->bos[0] || ca->co == cnfa->bos[1])
 				continue;
-			/* ... but EOS/EOL arcs terminate the search, as do LACONs */
+
+			/*
+			 * ... but EOS/EOL arcs terminate the search, as do RAINBOW arcs
+			 * and LACONs
+			 */
 			if (ca->co == cnfa->eos[0] || ca->co == cnfa->eos[1] ||
-				ca->co >= cnfa->ncolors)
+				ca->co == RAINBOW || ca->co >= cnfa->ncolors)
 			{
 				thiscolor = COLORLESS;
 				break;
diff --git a/src/include/regex/regexport.h b/src/include/regex/regexport.h
index e6209463f7..99c4fb854e 100644
--- a/src/include/regex/regexport.h
+++ b/src/include/regex/regexport.h
@@ -30,6 +30,10 @@
 
 #include "regex/regex.h"
 
+/* These macros must match corresponding ones in regguts.h: */
+#define COLOR_WHITE		0		/* color for chars not appearing in regex */
+#define COLOR_RAINBOW	(-2)	/* represents all colors except pseudocolors */
+
 /* information about one arc of a regex's NFA */
 typedef struct
 {
diff --git a/src/include/regex/regguts.h b/src/include/regex/regguts.h
index 5d0e7a961c..5bcd669d59 100644
--- a/src/include/regex/regguts.h
+++ b/src/include/regex/regguts.h
@@ -130,11 +130,16 @@
 /*
  * As soon as possible, we map chrs into equivalence classes -- "colors" --
  * which are of much more manageable number.
+ *
+ * To further reduce the number of arcs in NFAs and DFAs, we also have a
+ * special RAINBOW "color" that can be assigned to an arc.  This is not a
+ * real color, in that it has no entry in color maps.
  */
 typedef short color;			/* colors of characters */
 
 #define MAX_COLOR	32767		/* max color (must fit in 'color' datatype) */
 #define COLORLESS	(-1)		/* impossible color */
+#define RAINBOW		(-2)		/* represents all colors except pseudocolors */
 #define WHITE		0			/* default color, parent of all others */
 /* Note: various places in the code know that WHITE is zero */
 
@@ -276,7 +281,7 @@ struct state;
 struct arc
 {
 	int			type;			/* 0 if free, else an NFA arc type code */
-	color		co;
+	color		co;				/* color the arc matches (possibly RAINBOW) */
 	struct state *from;			/* where it's from (and contained within) */
 	struct state *to;			/* where it's to */
 	struct arc *outchain;		/* link in *from's outs chain or free chain */
@@ -284,6 +289,7 @@ struct arc
 #define  freechain	outchain	/* we do not maintain "freechainRev" */
 	struct arc *inchain;		/* link in *to's ins chain */
 	struct arc *inchainRev;		/* back-link in *to's ins chain */
+	/* these fields are not used when co == RAINBOW: */
 	struct arc *colorchain;		/* link in color's arc chain */
 	struct arc *colorchainRev;	/* back-link in color's arc chain */
 };
@@ -344,6 +350,9 @@ struct nfa
  * Plain arcs just store the transition color number as "co".  LACON arcs
  * store the lookaround constraint number plus cnfa.ncolors as "co".  LACON
  * arcs can be distinguished from plain by testing for co >= cnfa.ncolors.
+ *
+ * Note that in a plain arc, "co" can be RAINBOW; since that's negative,
+ * it doesn't break the rule about how to recognize LACON arcs.
  */
 struct carc
 {

diff --git a/src/backend/regex/README b/src/backend/regex/README
index cc1834b89c..a83ab5074d 100644
--- a/src/backend/regex/README
+++ b/src/backend/regex/README
@@ -410,14 +410,20 @@ substring, or an imaginary following EOS character if the substring is at
 the end of the input.
 3. If the NFA is (or can be) in the goal state at this point, it matches.
 
+This definition is necessary to support regexes that begin or end with
+constraints such as \m and \M, which imply requirements on the adjacent
+character if any.  The executor implements that by checking if the
+adjacent character (or BOS/BOL/EOS/EOL pseudo-character) is of the
+right color, and it does that in the same loop that checks characters
+within the match.
+
 So one can mentally execute an untransformed NFA by taking ^ and $ as
 ordinary constraints that match at start and end of input; but plain
 arcs out of the start state should be taken as matches for the character
 before the target substring, and similarly, plain arcs leading to the
 post state are matches for the character after the target substring.
-This definition is necessary to support regexes that begin or end with
-constraints such as \m and \M, which imply requirements on the adjacent
-character if any.  NFAs for simple unanchored patterns will usually have
-pre-state outarcs for all possible character colors as well as BOS and
-BOL, and post-state inarcs for all possible character colors as well as
-EOS and EOL, so that the executor's behavior will work.
+After the optimize() transformation, there are explicit arcs mentioning
+BOS/BOL/EOS/EOL adjacent to the pre-state and post-state.  So a finished
+NFA for a pattern without anchors or adjacent-character constraints will
+have pre-state outarcs for RAINBOW (all possible character colors) as well
+as BOS and BOL, and likewise post-state inarcs for RAINBOW, EOS, and EOL.
diff --git a/src/backend/regex/regc_nfa.c b/src/backend/regex/regc_nfa.c
index 1ac030570d..e5c5c65d84 100644
--- a/src/backend/regex/regc_nfa.c
+++ b/src/backend/regex/regc_nfa.c
@@ -65,6 +65,8 @@ newnfa(struct vars *v,
 	nfa->v = v;
 	nfa->bos[0] = nfa->bos[1] = COLORLESS;
 	nfa->eos[0] = nfa->eos[1] = COLORLESS;
+	nfa->flags = 0;
+	nfa->minmatchall = nfa->maxmatchall = -1;
 	nfa->parent = parent;		/* Precedes newfstate so parent is valid. */
 	nfa->post = newfstate(nfa, '@');	/* number 0 */
 	nfa->pre = newfstate(nfa, '>'); /* number 1 */
@@ -2875,8 +2877,14 @@ analyze(struct nfa *nfa)
 	if (NISERR())
 		return 0;
 
+	/* Detect whether NFA can't match anything */
 	if (nfa->pre->outs == NULL)
 		return REG_UIMPOSSIBLE;
+
+	/* Detect whether NFA matches all strings (possibly with length bounds) */
+	checkmatchall(nfa);
+
+	/* Detect whether NFA can possibly match a zero-length string */
 	for (a = nfa->pre->outs; a != NULL; a = a->outchain)
 		for (aa = a->to->outs; aa != NULL; aa = aa->outchain)
 			if (aa->to == nfa->post)
@@ -2884,6 +2892,279 @@ analyze(struct nfa *nfa)
 	return 0;
 }
 
+/*
+ * checkmatchall - does the NFA represent no more than a string length test?
+ *
+ * If so, set nfa->minmatchall and nfa->maxmatchall correctly (they are -1
+ * to begin with) and set the MATCHALL bit in nfa->flags.
+ *
+ * To succeed, we require all arcs to be PLAIN RAINBOW arcs, except for those
+ * for pseudocolors (i.e., BOS/BOL/EOS/EOL).  We must be able to reach the
+ * post state via RAINBOW arcs, and if there are any loops in the graph, they
+ * must be loop-to-self arcs, ensuring that each loop iteration consumes
+ * exactly one character.  (Longer loops are problematic because they create
+ * non-consecutive possible match lengths; we have no good way to represent
+ * that situation for lengths beyond the DUPINF limit.)
+ *
+ * Pseudocolor arcs complicate things a little.  We know that they can only
+ * appear as pre-state outarcs (for BOS/BOL) or post-state inarcs (for
+ * EOS/EOL).  There, they must exactly replicate the parallel RAINBOW arcs,
+ * e.g. if the pre state has one RAINBOW outarc to state 2, it must have BOS
+ * and BOL outarcs to state 2, and no others.  Missing or extra pseudocolor
+ * arcs can occur, meaning that the NFA involves some constraint on the
+ * adjacent characters, which makes it not a matchall NFA.
+ */
+static void
+checkmatchall(struct nfa *nfa)
+{
+	bool		hasmatch[DUPINF + 1];
+	int			minmatch,
+				maxmatch,
+				morematch;
+
+	/*
+	 * hasmatch[i] will be set true if a match of length i is feasible, for i
+	 * from 0 to DUPINF-1.  hasmatch[DUPINF] will be set true if every match
+	 * length of DUPINF or more is feasible.
+	 */
+	memset(hasmatch, 0, sizeof(hasmatch));
+
+	/*
+	 * Recursively search the graph for all-RAINBOW paths to the "post" state,
+	 * starting at the "pre" state.  The -1 initial depth accounts for the
+	 * fact that transitions out of the "pre" state are not part of the
+	 * matched string.  We likewise don't count the final transition to the
+	 * "post" state as part of the match length.  (But we still insist that
+	 * those transitions have RAINBOW arcs, otherwise there are lookbehind or
+	 * lookahead constraints at the start/end of the pattern.)
+	 */
+	if (!checkmatchall_recurse(nfa, nfa->pre, false, -1, hasmatch))
+		return;
+
+	/*
+	 * We found some all-RAINBOW paths, and not anything that we couldn't
+	 * handle.  Now verify that pseudocolor arcs adjacent to the pre and post
+	 * states match the RAINBOW arcs there.  (We could do this while
+	 * recursing, but it's expensive and unlikely to fail, so do it last.)
+	 */
+	if (!check_out_colors_match(nfa->pre, RAINBOW, nfa->bos[0]) ||
+		!check_out_colors_match(nfa->pre, nfa->bos[0], RAINBOW) ||
+		!check_out_colors_match(nfa->pre, RAINBOW, nfa->bos[1]) ||
+		!check_out_colors_match(nfa->pre, nfa->bos[1], RAINBOW))
+		return;
+	if (!check_in_colors_match(nfa->post, RAINBOW, nfa->eos[0]) ||
+		!check_in_colors_match(nfa->post, nfa->eos[0], RAINBOW) ||
+		!check_in_colors_match(nfa->post, RAINBOW, nfa->eos[1]) ||
+		!check_in_colors_match(nfa->post, nfa->eos[1], RAINBOW))
+		return;
+
+	/*
+	 * hasmatch[] now represents the set of possible match lengths; but we
+	 * want to reduce that to a min and max value, because it doesn't seem
+	 * worth complicating regexec.c to deal with nonconsecutive possible match
+	 * lengths.  Find min and max of first run of lengths, then verify there
+	 * are no nonconsecutive lengths.
+	 */
+	for (minmatch = 0; minmatch <= DUPINF; minmatch++)
+	{
+		if (hasmatch[minmatch])
+			break;
+	}
+	assert(minmatch <= DUPINF); /* else checkmatchall_recurse lied */
+	for (maxmatch = minmatch; maxmatch < DUPINF; maxmatch++)
+	{
+		if (!hasmatch[maxmatch + 1])
+			break;
+	}
+	for (morematch = maxmatch + 1; morematch <= DUPINF; morematch++)
+	{
+		if (hasmatch[morematch])
+			return;				/* fail, there are nonconsecutive lengths */
+	}
+
+	/* Success, so record the info */
+	nfa->minmatchall = minmatch;
+	nfa->maxmatchall = maxmatch;
+	nfa->flags |= MATCHALL;
+}
+
+/*
+ * checkmatchall_recurse - recursive search for checkmatchall
+ *
+ * s is the current state
+ * foundloop is true if any predecessor state has a loop-to-self
+ * depth is the current recursion depth (starting at -1)
+ * hasmatch[] is the output area for recording feasible match lengths
+ *
+ * We return true if there is at least one all-RAINBOW path to the "post"
+ * state and no non-matchall paths; otherwise false.  Note we assume that
+ * any dead-end paths have already been removed, else we might return
+ * false unnecessarily.
+ */
+static bool
+checkmatchall_recurse(struct nfa *nfa, struct state *s,
+					  bool foundloop, int depth,
+					  bool *hasmatch)
+{
+	bool		result = false;
+	struct arc *a;
+
+	/*
+	 * Since this is recursive, it could be driven to stack overflow.  But we
+	 * need not treat that as a hard failure; just deem the NFA non-matchall.
+	 */
+	if (STACK_TOO_DEEP(nfa->v->re))
+		return false;
+
+	/*
+	 * Likewise, if we get to a depth too large to represent correctly in
+	 * maxmatchall, fail quietly.
+	 */
+	if (depth >= DUPINF)
+		return false;
+
+	/*
+	 * Scan the outarcs to detect cases we can't handle, and to see if there
+	 * is a loop-to-self here.  We need to know about any such loop before we
+	 * recurse, so it's hard to avoid making two passes over the outarcs.  In
+	 * any case, checking for showstoppers before we recurse is probably best.
+	 */
+	for (a = s->outs; a != NULL; a = a->outchain)
+	{
+		if (a->type != PLAIN)
+			return false;		/* any LACONs make it non-matchall */
+		if (a->co != RAINBOW)
+		{
+			if (nfa->cm->cd[a->co].flags & PSEUDO)
+			{
+				/*
+				 * Pseudocolor arc: verify it's in a valid place (this seems
+				 * quite unlikely to fail, but let's be sure).
+				 */
+				if (s == nfa->pre &&
+					(a->co == nfa->bos[0] || a->co == nfa->bos[1]))
+					 /* okay BOS/BOL arc */ ;
+				else if (a->to == nfa->post &&
+						 (a->co == nfa->eos[0] || a->co == nfa->eos[1]))
+					 /* okay EOS/EOL arc */ ;
+				else
+					return false;	/* unexpected pseudocolor arc */
+				/* We'll finish checking these arcs after the recursion */
+				continue;
+			}
+			return false;		/* any other color makes it non-matchall */
+		}
+		if (a->to == s)
+		{
+			/*
+			 * We found a cycle of length 1, so remember that to pass down to
+			 * successor states.  (It doesn't matter if there was also such a
+			 * loop at a predecessor state.)
+			 */
+			foundloop = true;
+		}
+		else if (a->to->tmp)
+		{
+			/* We found a cycle of length > 1, so fail. */
+			return false;
+		}
+	}
+
+	/* We need to recurse, so mark state as under consideration */
+	assert(s->tmp == NULL);
+	s->tmp = s;
+
+	for (a = s->outs; a != NULL; a = a->outchain)
+	{
+		if (a->co != RAINBOW)
+			continue;			/* ignore pseudocolor arcs */
+		if (a->to == nfa->post)
+		{
+			/* We found an all-RAINBOW path to the post state */
+			result = true;
+			/* Record potential match lengths */
+			assert(depth >= 0);
+			hasmatch[depth] = true;
+			if (foundloop)
+			{
+				/* A predecessor loop makes all larger lengths match, too */
+				int			i;
+
+				for (i = depth + 1; i <= DUPINF; i++)
+					hasmatch[i] = true;
+			}
+		}
+		else if (a->to != s)
+		{
+			/* This is a new path forward; recurse to investigate */
+			result = checkmatchall_recurse(nfa, a->to,
+										   foundloop, depth + 1,
+										   hasmatch);
+			/* Fail if any recursive path fails */
+			if (!result)
+				break;
+		}
+	}
+
+	s->tmp = NULL;
+	return result;
+}
+
+/*
+ * check_out_colors_match - subroutine for checkmatchall
+ *
+ * Check if every s outarc of color co1 has a matching outarc of color co2.
+ * (checkmatchall_recurse already verified that all of the outarcs are PLAIN,
+ * so we need not examine arc types here.)
+ */
+static bool
+check_out_colors_match(struct state *s, color co1, color co2)
+{
+	struct arc *a1;
+	struct arc *a2;
+
+	for (a1 = s->outs; a1 != NULL; a1 = a1->outchain)
+	{
+		if (a1->co != co1)
+			continue;
+		for (a2 = s->outs; a2 != NULL; a2 = a2->outchain)
+		{
+			if (a2->co == co2 && a2->to == a1->to)
+				break;
+		}
+		if (a2 == NULL)
+			return false;
+	}
+	return true;
+}
+
+/*
+ * check_in_colors_match - subroutine for checkmatchall
+ *
+ * Check if every s inarc of color co1 has a matching inarc of color co2.
+ * (For paranoia's sake, ignore any non-PLAIN arcs here.)
+ */
+static bool
+check_in_colors_match(struct state *s, color co1, color co2)
+{
+	struct arc *a1;
+	struct arc *a2;
+
+	for (a1 = s->ins; a1 != NULL; a1 = a1->inchain)
+	{
+		if (a1->type != PLAIN || a1->co != co1)
+			continue;
+		for (a2 = s->ins; a2 != NULL; a2 = a2->inchain)
+		{
+			if (a2->type == PLAIN && a2->co == co2 && a2->from == a1->from)
+				break;
+		}
+		if (a2 == NULL)
+			return false;
+	}
+	return true;
+}
+
 /*
  * compact - construct the compact representation of an NFA
  */
@@ -2930,7 +3211,9 @@ compact(struct nfa *nfa,
 	cnfa->eos[0] = nfa->eos[0];
 	cnfa->eos[1] = nfa->eos[1];
 	cnfa->ncolors = maxcolor(nfa->cm) + 1;
-	cnfa->flags = 0;
+	cnfa->flags = nfa->flags;
+	cnfa->minmatchall = nfa->minmatchall;
+	cnfa->maxmatchall = nfa->maxmatchall;
 
 	ca = cnfa->arcs;
 	for (s = nfa->states; s != NULL; s = s->next)
@@ -3034,6 +3317,11 @@ dumpnfa(struct nfa *nfa,
 		fprintf(f, ", eos [%ld]", (long) nfa->eos[0]);
 	if (nfa->eos[1] != COLORLESS)
 		fprintf(f, ", eol [%ld]", (long) nfa->eos[1]);
+	if (nfa->flags & HASLACONS)
+		fprintf(f, ", haslacons");
+	if (nfa->flags & MATCHALL)
+		fprintf(f, ", minmatchall %d, maxmatchall %d",
+				nfa->minmatchall, nfa->maxmatchall);
 	fprintf(f, "\n");
 	for (s = nfa->states; s != NULL; s = s->next)
 	{
@@ -3201,6 +3489,9 @@ dumpcnfa(struct cnfa *cnfa,
 		fprintf(f, ", eol [%ld]", (long) cnfa->eos[1]);
 	if (cnfa->flags & HASLACONS)
 		fprintf(f, ", haslacons");
+	if (cnfa->flags & MATCHALL)
+		fprintf(f, ", minmatchall %d, maxmatchall %d",
+				cnfa->minmatchall, 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 5956b86026..17e79ad0fb 100644
--- a/src/backend/regex/regcomp.c
+++ b/src/backend/regex/regcomp.c
@@ -175,6 +175,11 @@ static void cleanup(struct nfa *);
 static void markreachable(struct nfa *, struct state *, struct state *, struct state *);
 static void markcanreach(struct nfa *, struct state *, struct state *, struct state *);
 static long analyze(struct nfa *);
+static void checkmatchall(struct nfa *);
+static bool checkmatchall_recurse(struct nfa *, struct state *,
+								  bool, int, bool *);
+static bool check_out_colors_match(struct state *, color, color);
+static bool check_in_colors_match(struct state *, color, color);
 static void compact(struct nfa *, struct cnfa *);
 static void carcsort(struct carc *, size_t);
 static int	carc_cmp(const void *, const void *);
diff --git a/src/backend/regex/rege_dfa.c b/src/backend/regex/rege_dfa.c
index 32be2592c5..20ec463204 100644
--- a/src/backend/regex/rege_dfa.c
+++ b/src/backend/regex/rege_dfa.c
@@ -58,6 +58,29 @@ longest(struct vars *v,
 	if (hitstopp != NULL)
 		*hitstopp = 0;
 
+	/* fast path for matchall NFAs */
+	if (d->cnfa->flags & MATCHALL)
+	{
+		size_t		nchr = stop - start;
+		size_t		maxmatchall = d->cnfa->maxmatchall;
+
+		if (nchr < d->cnfa->minmatchall)
+			return NULL;
+		if (maxmatchall == DUPINF)
+		{
+			if (stop == v->stop && hitstopp != NULL)
+				*hitstopp = 1;
+		}
+		else
+		{
+			if (stop == v->stop && nchr <= maxmatchall + 1 && hitstopp != NULL)
+				*hitstopp = 1;
+			if (nchr > maxmatchall)
+				return start + maxmatchall;
+		}
+		return stop;
+	}
+
 	/* initialize */
 	css = initialize(v, d, start);
 	if (css == NULL)
@@ -187,6 +210,24 @@ shortest(struct vars *v,
 	if (hitstopp != NULL)
 		*hitstopp = 0;
 
+	/* fast path for matchall NFAs */
+	if (d->cnfa->flags & MATCHALL)
+	{
+		size_t		nchr = min - start;
+
+		if (d->cnfa->maxmatchall != DUPINF &&
+			nchr > d->cnfa->maxmatchall)
+			return NULL;
+		if ((max - start) < d->cnfa->minmatchall)
+			return NULL;
+		if (nchr < d->cnfa->minmatchall)
+			min = start + d->cnfa->minmatchall;
+		if (coldp != NULL)
+			*coldp = start;
+		/* there is no case where we should set *hitstopp */
+		return min;
+	}
+
 	/* initialize */
 	css = initialize(v, d, start);
 	if (css == NULL)
@@ -312,6 +353,22 @@ matchuntil(struct vars *v,
 	struct sset *ss;
 	struct colormap *cm = d->cm;
 
+	/* fast path for matchall NFAs */
+	if (d->cnfa->flags & MATCHALL)
+	{
+		size_t		nchr = probe - v->start;
+
+		/*
+		 * It might seem that we should check maxmatchall too, but the
+		 * implicit .* at the front of the pattern absorbs any extra
+		 * characters.  Thus, we should always match as long as there are at
+		 * least minmatchall characters.
+		 */
+		if (nchr < d->cnfa->minmatchall)
+			return 0;
+		return 1;
+	}
+
 	/* initialize and startup, or restart, if necessary */
 	if (cp == NULL || cp > probe)
 	{
diff --git a/src/backend/regex/regprefix.c b/src/backend/regex/regprefix.c
index e2fbad7a8a..ec435b6f5f 100644
--- a/src/backend/regex/regprefix.c
+++ b/src/backend/regex/regprefix.c
@@ -77,6 +77,10 @@ pg_regprefix(regex_t *re,
 	assert(g->tree != NULL);
 	cnfa = &g->tree->cnfa;
 
+	/* matchall NFAs never have a fixed prefix */
+	if (cnfa->flags & MATCHALL)
+		return REG_NOMATCH;
+
 	/*
 	 * Since a correct NFA should never contain any exit-free loops, it should
 	 * not be possible for our traversal to return to a previously visited NFA
diff --git a/src/include/regex/regguts.h b/src/include/regex/regguts.h
index 5bcd669d59..956b37b72d 100644
--- a/src/include/regex/regguts.h
+++ b/src/include/regex/regguts.h
@@ -331,6 +331,9 @@ struct nfa
 	struct colormap *cm;		/* the color map */
 	color		bos[2];			/* colors, if any, assigned to BOS and BOL */
 	color		eos[2];			/* colors, if any, assigned to EOS and EOL */
+	int			flags;			/* flags to pass forward to cNFA */
+	int			minmatchall;	/* min number of chrs to match, if matchall */
+	int			maxmatchall;	/* max number of chrs to match, or DUPINF */
 	struct vars *v;				/* simplifies compile error reporting */
 	struct nfa *parent;			/* parent NFA, if any */
 };
@@ -353,6 +356,14 @@ struct nfa
  *
  * Note that in a plain arc, "co" can be RAINBOW; since that's negative,
  * it doesn't break the rule about how to recognize LACON arcs.
+ *
+ * We have special markings for "trivial" NFAs that can match any string
+ * (possibly with limits on the number of characters therein).  In such a
+ * case, flags & MATCHALL is set (and HASLACONS can't be set).  Then the
+ * fields minmatchall and maxmatchall give the minimum and maximum numbers
+ * of characters to match.  For example, ".*" produces minmatchall = 0
+ * and maxmatchall = DUPINF, while ".+" produces minmatchall = 1 and
+ * maxmatchall = DUPINF.
  */
 struct carc
 {
@@ -366,6 +377,7 @@ struct cnfa
 	int			ncolors;		/* number of colors (max color in use + 1) */
 	int			flags;
 #define  HASLACONS	01			/* uses lookaround constraints */
+#define  MATCHALL	02			/* matches all strings of a range of lengths */
 	int			pre;			/* setup state number */
 	int			post;			/* teardown state number */
 	color		bos[2];			/* colors, if any, assigned to BOS and BOL */
@@ -375,6 +387,9 @@ struct cnfa
 	struct carc **states;		/* vector of pointers to outarc lists */
 	/* states[n] are pointers into a single malloc'd array of arcs */
 	struct carc *arcs;			/* the area for the lists */
+	/* these fields are used only in a MATCHALL NFA (else they're -1): */
+	int			minmatchall;	/* min number of chrs to match */
+	int			maxmatchall;	/* max number of chrs to match, or DUPINF */
 };
 
 #define ZAPCNFA(cnfa)	((cnfa).nstates = 0)
diff --git a/src/test/modules/test_regex/expected/test_regex.out b/src/test/modules/test_regex/expected/test_regex.out
index 0dc2265d8b..f01ca071d9 100644
--- a/src/test/modules/test_regex/expected/test_regex.out
+++ b/src/test/modules/test_regex/expected/test_regex.out
@@ -3315,6 +3315,21 @@ select * from test_regex('(?=b)b', 'a', 'HP');
  {0,REG_ULOOKAROUND,REG_UNONPOSIX}
 (1 row)
 
+-- expectMatch	23.9 HP		...(?!.)	abcde	cde
+select * from test_regex('...(?!.)', 'abcde', 'HP');
+            test_regex             
+-----------------------------------
+ {0,REG_ULOOKAROUND,REG_UNONPOSIX}
+ {cde}
+(2 rows)
+
+-- expectNomatch	23.10 HP	...(?=.)	abc
+select * from test_regex('...(?=.)', 'abc', 'HP');
+            test_regex             
+-----------------------------------
+ {0,REG_ULOOKAROUND,REG_UNONPOSIX}
+(1 row)
+
 -- Postgres addition: lookbehind constraints
 -- expectMatch	23.11 HPN		(?<=a)b*	ab	b
 select * from test_regex('(?<=a)b*', 'ab', 'HPN');
@@ -3376,6 +3391,39 @@ select * from test_regex('(?<=b)b', 'b', 'HP');
  {0,REG_ULOOKAROUND,REG_UNONPOSIX}
 (1 row)
 
+-- expectMatch	23.19 HP		(?<=.)..	abcde	bc
+select * from test_regex('(?<=.)..', 'abcde', 'HP');
+            test_regex             
+-----------------------------------
+ {0,REG_ULOOKAROUND,REG_UNONPOSIX}
+ {bc}
+(2 rows)
+
+-- expectMatch	23.20 HP		(?<=..)a*	aaabb	a
+select * from test_regex('(?<=..)a*', 'aaabb', 'HP');
+            test_regex             
+-----------------------------------
+ {0,REG_ULOOKAROUND,REG_UNONPOSIX}
+ {a}
+(2 rows)
+
+-- expectMatch	23.21 HP		(?<=..)b*	aaabb	{}
+-- Note: empty match here is correct, it matches after the first 2 characters
+select * from test_regex('(?<=..)b*', 'aaabb', 'HP');
+            test_regex             
+-----------------------------------
+ {0,REG_ULOOKAROUND,REG_UNONPOSIX}
+ {""}
+(2 rows)
+
+-- expectMatch	23.22 HP		(?<=..)b+	aaabb	bb
+select * from test_regex('(?<=..)b+', 'aaabb', 'HP');
+            test_regex             
+-----------------------------------
+ {0,REG_ULOOKAROUND,REG_UNONPOSIX}
+ {bb}
+(2 rows)
+
 -- doing 24 "non-greedy quantifiers"
 -- expectMatch	24.1  PT	ab+?		abb	ab
 select * from test_regex('ab+?', 'abb', 'PT');
diff --git a/src/test/modules/test_regex/sql/test_regex.sql b/src/test/modules/test_regex/sql/test_regex.sql
index 1a2bfa6235..ae7d6b43e4 100644
--- a/src/test/modules/test_regex/sql/test_regex.sql
+++ b/src/test/modules/test_regex/sql/test_regex.sql
@@ -1049,6 +1049,10 @@ select * from test_regex('a(?!b)b*', 'a', 'HP');
 select * from test_regex('(?=b)b', 'b', 'HP');
 -- expectNomatch	23.8 HP		(?=b)b		a
 select * from test_regex('(?=b)b', 'a', 'HP');
+-- expectMatch	23.9 HP		...(?!.)	abcde	cde
+select * from test_regex('...(?!.)', 'abcde', 'HP');
+-- expectNomatch	23.10 HP	...(?=.)	abc
+select * from test_regex('...(?=.)', 'abc', 'HP');
 
 -- Postgres addition: lookbehind constraints
 
@@ -1068,6 +1072,15 @@ select * from test_regex('a(?<!b)b*', 'a', 'HP');
 select * from test_regex('(?<=b)b', 'bb', 'HP');
 -- expectNomatch	23.18 HP		(?<=b)b		b
 select * from test_regex('(?<=b)b', 'b', 'HP');
+-- expectMatch	23.19 HP		(?<=.)..	abcde	bc
+select * from test_regex('(?<=.)..', 'abcde', 'HP');
+-- expectMatch	23.20 HP		(?<=..)a*	aaabb	a
+select * from test_regex('(?<=..)a*', 'aaabb', 'HP');
+-- expectMatch	23.21 HP		(?<=..)b*	aaabb	{}
+-- Note: empty match here is correct, it matches after the first 2 characters
+select * from test_regex('(?<=..)b*', 'aaabb', 'HP');
+-- expectMatch	23.22 HP		(?<=..)b+	aaabb	bb
+select * from test_regex('(?<=..)b+', 'aaabb', 'HP');
 
 -- doing 24 "non-greedy quantifiers"
 

diff --git a/contrib/pg_trgm/trgm_regexp.c b/contrib/pg_trgm/trgm_regexp.c
index 1e4f0121f3..fcf03de32d 100644
--- a/contrib/pg_trgm/trgm_regexp.c
+++ b/contrib/pg_trgm/trgm_regexp.c
@@ -282,8 +282,8 @@ typedef struct
 typedef int TrgmColor;
 
 /* We assume that colors returned by the regexp engine cannot be these: */
-#define COLOR_UNKNOWN	(-1)
-#define COLOR_BLANK		(-2)
+#define COLOR_UNKNOWN	(-3)
+#define COLOR_BLANK		(-4)
 
 typedef struct
 {
@@ -780,7 +780,8 @@ getColorInfo(regex_t *regex, TrgmNFA *trgmNFA)
 		palloc0(colorsCount * sizeof(TrgmColorInfo));
 
 	/*
-	 * Loop over colors, filling TrgmColorInfo about each.
+	 * Loop over colors, filling TrgmColorInfo about each.  Note we include
+	 * WHITE (0) even though we know it'll be reported as non-expandable.
 	 */
 	for (i = 0; i < colorsCount; i++)
 	{
@@ -1098,9 +1099,9 @@ addKey(TrgmNFA *trgmNFA, TrgmState *state, TrgmStateKey *key)
 			/* Add enter key to this state */
 			addKeyToQueue(trgmNFA, &destKey);
 		}
-		else
+		else if (arc->co >= 0)
 		{
-			/* Regular color */
+			/* Regular color (including WHITE) */
 			TrgmColorInfo *colorInfo = &trgmNFA->colorInfo[arc->co];
 
 			if (colorInfo->expandable)
@@ -1156,6 +1157,14 @@ addKey(TrgmNFA *trgmNFA, TrgmState *state, TrgmStateKey *key)
 				addKeyToQueue(trgmNFA, &destKey);
 			}
 		}
+		else
+		{
+			/* RAINBOW: treat as unexpandable color */
+			destKey.prefix.colors[0] = COLOR_UNKNOWN;
+			destKey.prefix.colors[1] = COLOR_UNKNOWN;
+			destKey.nstate = arc->to;
+			addKeyToQueue(trgmNFA, &destKey);
+		}
 	}
 
 	pfree(arcs);
@@ -1216,10 +1225,10 @@ addArcs(TrgmNFA *trgmNFA, TrgmState *state)
 			/*
 			 * Ignore non-expandable colors; addKey already handled the case.
 			 *
-			 * We need no special check for begin/end pseudocolors here.  We
-			 * don't need to do any processing for them, and they will be
-			 * marked non-expandable since the regex engine will have reported
-			 * them that way.
+			 * We need no special check for WHITE or begin/end pseudocolors
+			 * here.  We don't need to do any processing for them, and they
+			 * will be marked non-expandable since the regex engine will have
+			 * reported them that way.
 			 */
 			if (!colorInfo->expandable)
 				continue;
diff --git a/src/backend/regex/README b/src/backend/regex/README
index f08aab69e3..cc1834b89c 100644
--- a/src/backend/regex/README
+++ b/src/backend/regex/README
@@ -261,6 +261,18 @@ and the NFA has these arcs:
 	states 4 -> 5 on color 2 ("x" only)
 which can be seen to be a correct representation of the regex.
 
+There is one more complexity, which is how to handle ".", that is a
+match-anything atom.  We used to do that by generating a "rainbow"
+of arcs of all live colors between the two NFA states before and after
+the dot.  That's expensive in itself when there are lots of colors,
+and it also typically adds lots of follow-on arc-splitting work for the
+color splitting logic.  Now we handle this case by generating a single arc
+labeled with the special color RAINBOW, meaning all colors.  Such arcs
+never need to be split, so they help keep NFAs small in this common case.
+(Note: this optimization doesn't help in REG_NLSTOP mode, where "." is
+not supposed to match newline.  In that case we still handle "." by
+generating an almost-rainbow of all colors except newline's color.)
+
 Given this summary, we can see we need the following operations for
 colors:
 
@@ -349,6 +361,8 @@ The possible arc types are:
 
     PLAIN arcs, which specify matching of any character of a given "color"
     (see above).  These are dumped as "[color_number]->to_state".
+    In addition there can be "rainbow" PLAIN arcs, which are dumped as
+    "[*]->to_state".
 
     EMPTY arcs, which specify a no-op transition to another state.  These
     are dumped as "->to_state".
@@ -356,11 +370,11 @@ The possible arc types are:
     AHEAD constraints, which represent a "next character must be of this
     color" constraint.  AHEAD differs from a PLAIN arc in that the input
     character is not consumed when crossing the arc.  These are dumped as
-    ">color_number>->to_state".
+    ">color_number>->to_state", or possibly ">*>->to_state".
 
     BEHIND constraints, which represent a "previous character must be of
     this color" constraint, which likewise consumes no input.  These are
-    dumped as "<color_number<->to_state".
+    dumped as "<color_number<->to_state", or possibly "<*<->to_state".
 
     '^' arcs, which specify a beginning-of-input constraint.  These are
     dumped as "^0->to_state" or "^1->to_state" for beginning-of-string and
diff --git a/src/backend/regex/regc_color.c b/src/backend/regex/regc_color.c
index f5a4151757..0864011cce 100644
--- a/src/backend/regex/regc_color.c
+++ b/src/backend/regex/regc_color.c
@@ -977,6 +977,7 @@ colorchain(struct colormap *cm,
 {
 	struct colordesc *cd = &cm->cd[a->co];
 
+	assert(a->co >= 0);
 	if (cd->arcs != NULL)
 		cd->arcs->colorchainRev = a;
 	a->colorchain = cd->arcs;
@@ -994,6 +995,7 @@ uncolorchain(struct colormap *cm,
 	struct colordesc *cd = &cm->cd[a->co];
 	struct arc *aa = a->colorchainRev;
 
+	assert(a->co >= 0);
 	if (aa == NULL)
 	{
 		assert(cd->arcs == a);
@@ -1012,6 +1014,9 @@ uncolorchain(struct colormap *cm,
 
 /*
  * rainbow - add arcs of all full colors (but one) between specified states
+ *
+ * If there isn't an exception color, we now generate just a single arc
+ * labeled RAINBOW, saving lots of arc-munging later on.
  */
 static void
 rainbow(struct nfa *nfa,
@@ -1025,6 +1030,13 @@ rainbow(struct nfa *nfa,
 	struct colordesc *end = CDEND(cm);
 	color		co;
 
+	if (but == COLORLESS)
+	{
+		newarc(nfa, type, RAINBOW, from, to);
+		return;
+	}
+
+	/* Gotta do it the hard way.  Skip subcolors, pseudocolors, and "but" */
 	for (cd = cm->cd, co = 0; cd < end && !CISERR(); cd++, co++)
 		if (!UNUSEDCOLOR(cd) && cd->sub != co && co != but &&
 			!(cd->flags & PSEUDO))
@@ -1034,13 +1046,16 @@ rainbow(struct nfa *nfa,
 /*
  * colorcomplement - add arcs of complementary colors
  *
+ * We add arcs of all colors that are not pseudocolors and do not match
+ * any of the "of" state's PLAIN outarcs.
+ *
  * The calling sequence ought to be reconciled with cloneouts().
  */
 static void
 colorcomplement(struct nfa *nfa,
 				struct colormap *cm,
 				int type,
-				struct state *of,	/* complements of this guy's PLAIN outarcs */
+				struct state *of,
 				struct state *from,
 				struct state *to)
 {
@@ -1049,6 +1064,11 @@ colorcomplement(struct nfa *nfa,
 	color		co;
 
 	assert(of != from);
+
+	/* A RAINBOW arc matches all colors, making the complement empty */
+	if (findarc(of, PLAIN, RAINBOW) != NULL)
+		return;
+
 	for (cd = cm->cd, co = 0; cd < end && !CISERR(); cd++, co++)
 		if (!UNUSEDCOLOR(cd) && !(cd->flags & PSEUDO))
 			if (findarc(of, PLAIN, co) == NULL)
diff --git a/src/backend/regex/regc_nfa.c b/src/backend/regex/regc_nfa.c
index cde82625c8..ff98bfd694 100644
--- a/src/backend/regex/regc_nfa.c
+++ b/src/backend/regex/regc_nfa.c
@@ -271,6 +271,11 @@ destroystate(struct nfa *nfa,
  *
  * This function checks to make sure that no duplicate arcs are created.
  * In general we never want duplicates.
+ *
+ * However: in principle, a RAINBOW arc is redundant with any plain arc
+ * (unless that arc is for a pseudocolor).  But we don't try to recognize
+ * that redundancy, either here or in allied operations such as moveins().
+ * The pseudocolor consideration makes that more costly than it seems worth.
  */
 static void
 newarc(struct nfa *nfa,
@@ -1170,6 +1175,9 @@ copyouts(struct nfa *nfa,
 
 /*
  * cloneouts - copy out arcs of a state to another state pair, modifying type
+ *
+ * This is only used to convert PLAIN arcs to AHEAD/BEHIND arcs, which share
+ * the same interpretation of "co".  It wouldn't be sensible with LACONs.
  */
 static void
 cloneouts(struct nfa *nfa,
@@ -1181,9 +1189,13 @@ cloneouts(struct nfa *nfa,
 	struct arc *a;
 
 	assert(old != from);
+	assert(type == AHEAD || type == BEHIND);
 
 	for (a = old->outs; a != NULL; a = a->outchain)
+	{
+		assert(a->type == PLAIN);
 		newarc(nfa, type, a->co, from, to);
+	}
 }
 
 /*
@@ -1597,7 +1609,7 @@ pull(struct nfa *nfa,
 	for (a = from->ins; a != NULL && !NISERR(); a = nexta)
 	{
 		nexta = a->inchain;
-		switch (combine(con, a))
+		switch (combine(nfa, con, a))
 		{
 			case INCOMPATIBLE:	/* destroy the arc */
 				freearc(nfa, a);
@@ -1624,6 +1636,10 @@ pull(struct nfa *nfa,
 				cparc(nfa, a, s, to);
 				freearc(nfa, a);
 				break;
+			case REPLACEARC:	/* replace arc's color */
+				newarc(nfa, a->type, con->co, a->from, to);
+				freearc(nfa, a);
+				break;
 			default:
 				assert(NOTREACHED);
 				break;
@@ -1764,7 +1780,7 @@ push(struct nfa *nfa,
 	for (a = to->outs; a != NULL && !NISERR(); a = nexta)
 	{
 		nexta = a->outchain;
-		switch (combine(con, a))
+		switch (combine(nfa, con, a))
 		{
 			case INCOMPATIBLE:	/* destroy the arc */
 				freearc(nfa, a);
@@ -1791,6 +1807,10 @@ push(struct nfa *nfa,
 				cparc(nfa, a, from, s);
 				freearc(nfa, a);
 				break;
+			case REPLACEARC:	/* replace arc's color */
+				newarc(nfa, a->type, con->co, from, a->to);
+				freearc(nfa, a);
+				break;
 			default:
 				assert(NOTREACHED);
 				break;
@@ -1810,9 +1830,11 @@ push(struct nfa *nfa,
  * #def INCOMPATIBLE	1	// destroys arc
  * #def SATISFIED		2	// constraint satisfied
  * #def COMPATIBLE		3	// compatible but not satisfied yet
+ * #def REPLACEARC		4	// replace arc's color with constraint color
  */
 static int
-combine(struct arc *con,
+combine(struct nfa *nfa,
+		struct arc *con,
 		struct arc *a)
 {
 #define  CA(ct,at)	 (((ct)<<CHAR_BIT) | (at))
@@ -1827,14 +1849,46 @@ combine(struct arc *con,
 		case CA(BEHIND, PLAIN):
 			if (con->co == a->co)
 				return SATISFIED;
+			if (con->co == RAINBOW)
+			{
+				/* con is satisfied unless arc's color is a pseudocolor */
+				if (!(nfa->cm->cd[a->co].flags & PSEUDO))
+					return SATISFIED;
+			}
+			else if (a->co == RAINBOW)
+			{
+				/* con is incompatible if it's for a pseudocolor */
+				if (nfa->cm->cd[con->co].flags & PSEUDO)
+					return INCOMPATIBLE;
+				/* otherwise, constraint constrains arc to be only its color */
+				return REPLACEARC;
+			}
 			return INCOMPATIBLE;
 			break;
 		case CA('^', '^'):		/* collision, similar constraints */
 		case CA('$', '$'):
-		case CA(AHEAD, AHEAD):
+			if (con->co == a->co)	/* true duplication */
+				return SATISFIED;
+			return INCOMPATIBLE;
+			break;
+		case CA(AHEAD, AHEAD):	/* collision, similar constraints */
 		case CA(BEHIND, BEHIND):
 			if (con->co == a->co)	/* true duplication */
 				return SATISFIED;
+			if (con->co == RAINBOW)
+			{
+				/* con is satisfied unless arc's color is a pseudocolor */
+				if (!(nfa->cm->cd[a->co].flags & PSEUDO))
+					return SATISFIED;
+			}
+			else if (a->co == RAINBOW)
+			{
+				/* con is incompatible if it's for a pseudocolor */
+				if (nfa->cm->cd[con->co].flags & PSEUDO)
+					return INCOMPATIBLE;
+				/* otherwise, constraint constrains arc to be only its color */
+				return REPLACEARC;
+			}
 			return INCOMPATIBLE;
 			break;
 		case CA('^', BEHIND):	/* collision, dissimilar constraints */
@@ -2895,6 +2949,7 @@ compact(struct nfa *nfa,
 					break;
 				case LACON:
 					assert(s->no != cnfa->pre);
+					assert(a->co >= 0);
 					ca->co = (color) (cnfa->ncolors + a->co);
 					ca->to = a->to->no;
 					ca++;
@@ -2902,7 +2957,7 @@ compact(struct nfa *nfa,
 					break;
 				default:
 					NERR(REG_ASSERT);
-					break;
+					return;
 			}
 		carcsort(first, ca - first);
 		ca->co = COLORLESS;
@@ -3068,13 +3123,22 @@ dumparc(struct arc *a,
 	switch (a->type)
 	{
 		case PLAIN:
-			fprintf(f, "[%ld]", (long) a->co);
+			if (a->co == RAINBOW)
+				fprintf(f, "[*]");
+			else
+				fprintf(f, "[%ld]", (long) a->co);
 			break;
 		case AHEAD:
-			fprintf(f, ">%ld>", (long) a->co);
+			if (a->co == RAINBOW)
+				fprintf(f, ">*>");
+			else
+				fprintf(f, ">%ld>", (long) a->co);
 			break;
 		case BEHIND:
-			fprintf(f, "<%ld<", (long) a->co);
+			if (a->co == RAINBOW)
+				fprintf(f, "<*<");
+			else
+				fprintf(f, "<%ld<", (long) a->co);
 			break;
 		case LACON:
 			fprintf(f, ":%ld:", (long) a->co);
@@ -3161,7 +3225,9 @@ dumpcstate(int st,
 	pos = 1;
 	for (ca = cnfa->states[st]; ca->co != COLORLESS; ca++)
 	{
-		if (ca->co < cnfa->ncolors)
+		if (ca->co == RAINBOW)
+			fprintf(f, "\t[*]->%d", ca->to);
+		else if (ca->co < cnfa->ncolors)
 			fprintf(f, "\t[%ld]->%d", (long) ca->co, ca->to);
 		else
 			fprintf(f, "\t:%ld:->%d", (long) (ca->co - cnfa->ncolors), ca->to);
diff --git a/src/backend/regex/regcomp.c b/src/backend/regex/regcomp.c
index f0896d2db1..e73476040d 100644
--- a/src/backend/regex/regcomp.c
+++ b/src/backend/regex/regcomp.c
@@ -158,7 +158,8 @@ static int	push(struct nfa *, struct arc *, struct state **);
 #define INCOMPATIBLE	1		/* destroys arc */
 #define SATISFIED	2			/* constraint satisfied */
 #define COMPATIBLE	3			/* compatible but not satisfied yet */
-static int	combine(struct arc *, struct arc *);
+#define REPLACEARC	4			/* replace arc's color with constraint color */
+static int	combine(struct nfa *nfa, struct arc *con, struct arc *a);
 static void fixempties(struct nfa *, FILE *);
 static struct state *emptyreachable(struct nfa *, struct state *,
 									struct state *, struct arc **);
@@ -289,9 +290,11 @@ struct vars
 #define SBEGIN	'A'				/* beginning of string (even if not BOL) */
 #define SEND	'Z'				/* end of string (even if not EOL) */
 
-/* is an arc colored, and hence on a color chain? */
+/* is an arc colored, and hence should belong to a color chain? */
+/* the test on "co" eliminates RAINBOW arcs, which we don't bother to chain */
 #define COLORED(a) \
-	((a)->type == PLAIN || (a)->type == AHEAD || (a)->type == BEHIND)
+	((a)->co >= 0 && \
+	 ((a)->type == PLAIN || (a)->type == AHEAD || (a)->type == BEHIND))
 
 
 /* static function list */
@@ -1393,7 +1396,8 @@ bracket(struct vars *v,
  * cbracket - handle complemented bracket expression
  * We do it by calling bracket() with dummy endpoints, and then complementing
  * the result.  The alternative would be to invoke rainbow(), and then delete
- * arcs as the b.e. is seen... but that gets messy.
+ * arcs as the b.e. is seen... but that gets messy, and is really quite
+ * infeasible now that rainbow() just puts out one RAINBOW arc.
  */
 static void
 cbracket(struct vars *v,
diff --git a/src/backend/regex/rege_dfa.c b/src/backend/regex/rege_dfa.c
index 5695e158a5..32be2592c5 100644
--- a/src/backend/regex/rege_dfa.c
+++ b/src/backend/regex/rege_dfa.c
@@ -612,6 +612,7 @@ miss(struct vars *v,
 	unsigned	h;
 	struct carc *ca;
 	struct sset *p;
+	int			ispseudocolor;
 	int			ispost;
 	int			noprogress;
 	int			gotstate;
@@ -643,13 +644,15 @@ miss(struct vars *v,
 	 */
 	for (i = 0; i < d->wordsper; i++)
 		d->work[i] = 0;			/* build new stateset bitmap in d->work */
+	ispseudocolor = d->cm->cd[co].flags & PSEUDO;
 	ispost = 0;
 	noprogress = 1;
 	gotstate = 0;
 	for (i = 0; i < d->nstates; i++)
 		if (ISBSET(css->states, i))
 			for (ca = cnfa->states[i]; ca->co != COLORLESS; ca++)
-				if (ca->co == co)
+				if (ca->co == co ||
+					(ca->co == RAINBOW && !ispseudocolor))
 				{
 					BSET(d->work, ca->to);
 					gotstate = 1;
diff --git a/src/backend/regex/regexport.c b/src/backend/regex/regexport.c
index d4f940b8c3..a493dbe88c 100644
--- a/src/backend/regex/regexport.c
+++ b/src/backend/regex/regexport.c
@@ -222,7 +222,8 @@ pg_reg_colorisend(const regex_t *regex, int co)
  * Get number of member chrs of color number "co".
  *
  * Note: we return -1 if the color number is invalid, or if it is a special
- * color (WHITE or a pseudocolor), or if the number of members is uncertain.
+ * color (WHITE, RAINBOW, or a pseudocolor), or if the number of members is
+ * uncertain.
  * Callers should not try to extract the members if -1 is returned.
  */
 int
@@ -233,7 +234,7 @@ pg_reg_getnumcharacters(const regex_t *regex, int co)
 	assert(regex != NULL && regex->re_magic == REMAGIC);
 	cm = &((struct guts *) regex->re_guts)->cmap;
 
-	if (co <= 0 || co > cm->max)	/* we reject 0 which is WHITE */
+	if (co <= 0 || co > cm->max)	/* <= 0 rejects WHITE and RAINBOW */
 		return -1;
 	if (cm->cd[co].flags & PSEUDO)	/* also pseudocolors (BOS etc) */
 		return -1;
@@ -257,7 +258,7 @@ pg_reg_getnumcharacters(const regex_t *regex, int co)
  * whose length chars_len must be at least as long as indicated by
  * pg_reg_getnumcharacters(), else not all chars will be returned.
  *
- * Fetching the members of WHITE or a pseudocolor is not supported.
+ * Fetching the members of WHITE, RAINBOW, or a pseudocolor is not supported.
  *
  * Caution: this is a relatively expensive operation.
  */
diff --git a/src/backend/regex/regprefix.c b/src/backend/regex/regprefix.c
index 1d4593ac94..e2fbad7a8a 100644
--- a/src/backend/regex/regprefix.c
+++ b/src/backend/regex/regprefix.c
@@ -165,9 +165,13 @@ findprefix(struct cnfa *cnfa,
 			/* We can ignore BOS/BOL arcs */
 			if (ca->co == cnfa->bos[0] || ca->co == cnfa->bos[1])
 				continue;
-			/* ... but EOS/EOL arcs terminate the search, as do LACONs */
+
+			/*
+			 * ... but EOS/EOL arcs terminate the search, as do RAINBOW arcs
+			 * and LACONs
+			 */
 			if (ca->co == cnfa->eos[0] || ca->co == cnfa->eos[1] ||
-				ca->co >= cnfa->ncolors)
+				ca->co == RAINBOW || ca->co >= cnfa->ncolors)
 			{
 				thiscolor = COLORLESS;
 				break;
diff --git a/src/include/regex/regexport.h b/src/include/regex/regexport.h
index e6209463f7..99c4fb854e 100644
--- a/src/include/regex/regexport.h
+++ b/src/include/regex/regexport.h
@@ -30,6 +30,10 @@
 
 #include "regex/regex.h"
 
+/* These macros must match corresponding ones in regguts.h: */
+#define COLOR_WHITE		0		/* color for chars not appearing in regex */
+#define COLOR_RAINBOW	(-2)	/* represents all colors except pseudocolors */
+
 /* information about one arc of a regex's NFA */
 typedef struct
 {
diff --git a/src/include/regex/regguts.h b/src/include/regex/regguts.h
index 0a616562d0..6d39108319 100644
--- a/src/include/regex/regguts.h
+++ b/src/include/regex/regguts.h
@@ -130,11 +130,16 @@
 /*
  * As soon as possible, we map chrs into equivalence classes -- "colors" --
  * which are of much more manageable number.
+ *
+ * To further reduce the number of arcs in NFAs and DFAs, we also have a
+ * special RAINBOW "color" that can be assigned to an arc.  This is not a
+ * real color, in that it has no entry in color maps.
  */
 typedef short color;			/* colors of characters */
 
 #define MAX_COLOR	32767		/* max color (must fit in 'color' datatype) */
 #define COLORLESS	(-1)		/* impossible color */
+#define RAINBOW		(-2)		/* represents all colors except pseudocolors */
 #define WHITE		0			/* default color, parent of all others */
 /* Note: various places in the code know that WHITE is zero */
 
@@ -276,7 +281,7 @@ struct state;
 struct arc
 {
 	int			type;			/* 0 if free, else an NFA arc type code */
-	color		co;
+	color		co;				/* color the arc matches (possibly RAINBOW) */
 	struct state *from;			/* where it's from (and contained within) */
 	struct state *to;			/* where it's to */
 	struct arc *outchain;		/* link in *from's outs chain or free chain */
@@ -284,6 +289,7 @@ struct arc
 #define  freechain	outchain	/* we do not maintain "freechainRev" */
 	struct arc *inchain;		/* link in *to's ins chain */
 	struct arc *inchainRev;		/* back-link in *to's ins chain */
+	/* these fields are not used when co == RAINBOW: */
 	struct arc *colorchain;		/* link in color's arc chain */
 	struct arc *colorchainRev;	/* back-link in color's arc chain */
 };
@@ -344,6 +350,9 @@ struct nfa
  * Plain arcs just store the transition color number as "co".  LACON arcs
  * store the lookaround constraint number plus cnfa.ncolors as "co".  LACON
  * arcs can be distinguished from plain by testing for co >= cnfa.ncolors.
+ *
+ * Note that in a plain arc, "co" can be RAINBOW; since that's negative,
+ * it doesn't break the rule about how to recognize LACON arcs.
  */
 struct carc
 {

diff --git a/src/backend/regex/README b/src/backend/regex/README
index cc1834b89c..a83ab5074d 100644
--- a/src/backend/regex/README
+++ b/src/backend/regex/README
@@ -410,14 +410,20 @@ substring, or an imaginary following EOS character if the substring is at
 the end of the input.
 3. If the NFA is (or can be) in the goal state at this point, it matches.
 
+This definition is necessary to support regexes that begin or end with
+constraints such as \m and \M, which imply requirements on the adjacent
+character if any.  The executor implements that by checking if the
+adjacent character (or BOS/BOL/EOS/EOL pseudo-character) is of the
+right color, and it does that in the same loop that checks characters
+within the match.
+
 So one can mentally execute an untransformed NFA by taking ^ and $ as
 ordinary constraints that match at start and end of input; but plain
 arcs out of the start state should be taken as matches for the character
 before the target substring, and similarly, plain arcs leading to the
 post state are matches for the character after the target substring.
-This definition is necessary to support regexes that begin or end with
-constraints such as \m and \M, which imply requirements on the adjacent
-character if any.  NFAs for simple unanchored patterns will usually have
-pre-state outarcs for all possible character colors as well as BOS and
-BOL, and post-state inarcs for all possible character colors as well as
-EOS and EOL, so that the executor's behavior will work.
+After the optimize() transformation, there are explicit arcs mentioning
+BOS/BOL/EOS/EOL adjacent to the pre-state and post-state.  So a finished
+NFA for a pattern without anchors or adjacent-character constraints will
+have pre-state outarcs for RAINBOW (all possible character colors) as well
+as BOS and BOL, and likewise post-state inarcs for RAINBOW, EOS, and EOL.
diff --git a/src/backend/regex/regc_nfa.c b/src/backend/regex/regc_nfa.c
index ff98bfd694..b403bb250d 100644
--- a/src/backend/regex/regc_nfa.c
+++ b/src/backend/regex/regc_nfa.c
@@ -65,6 +65,8 @@ newnfa(struct vars *v,
 	nfa->v = v;
 	nfa->bos[0] = nfa->bos[1] = COLORLESS;
 	nfa->eos[0] = nfa->eos[1] = COLORLESS;
+	nfa->flags = 0;
+	nfa->minmatchall = nfa->maxmatchall = -1;
 	nfa->parent = parent;		/* Precedes newfstate so parent is valid. */
 	nfa->post = newfstate(nfa, '@');	/* number 0 */
 	nfa->pre = newfstate(nfa, '>'); /* number 1 */
@@ -2875,8 +2877,14 @@ analyze(struct nfa *nfa)
 	if (NISERR())
 		return 0;
 
+	/* Detect whether NFA can't match anything */
 	if (nfa->pre->outs == NULL)
 		return REG_UIMPOSSIBLE;
+
+	/* Detect whether NFA matches all strings (possibly with length bounds) */
+	checkmatchall(nfa);
+
+	/* Detect whether NFA can possibly match a zero-length string */
 	for (a = nfa->pre->outs; a != NULL; a = a->outchain)
 		for (aa = a->to->outs; aa != NULL; aa = aa->outchain)
 			if (aa->to == nfa->post)
@@ -2884,6 +2892,279 @@ analyze(struct nfa *nfa)
 	return 0;
 }
 
+/*
+ * checkmatchall - does the NFA represent no more than a string length test?
+ *
+ * If so, set nfa->minmatchall and nfa->maxmatchall correctly (they are -1
+ * to begin with) and set the MATCHALL bit in nfa->flags.
+ *
+ * To succeed, we require all arcs to be PLAIN RAINBOW arcs, except for those
+ * for pseudocolors (i.e., BOS/BOL/EOS/EOL).  We must be able to reach the
+ * post state via RAINBOW arcs, and if there are any loops in the graph, they
+ * must be loop-to-self arcs, ensuring that each loop iteration consumes
+ * exactly one character.  (Longer loops are problematic because they create
+ * non-consecutive possible match lengths; we have no good way to represent
+ * that situation for lengths beyond the DUPINF limit.)
+ *
+ * Pseudocolor arcs complicate things a little.  We know that they can only
+ * appear as pre-state outarcs (for BOS/BOL) or post-state inarcs (for
+ * EOS/EOL).  There, they must exactly replicate the parallel RAINBOW arcs,
+ * e.g. if the pre state has one RAINBOW outarc to state 2, it must have BOS
+ * and BOL outarcs to state 2, and no others.  Missing or extra pseudocolor
+ * arcs can occur, meaning that the NFA involves some constraint on the
+ * adjacent characters, which makes it not a matchall NFA.
+ */
+static void
+checkmatchall(struct nfa *nfa)
+{
+	bool		hasmatch[DUPINF + 1];
+	int			minmatch,
+				maxmatch,
+				morematch;
+
+	/*
+	 * hasmatch[i] will be set true if a match of length i is feasible, for i
+	 * from 0 to DUPINF-1.  hasmatch[DUPINF] will be set true if every match
+	 * length of DUPINF or more is feasible.
+	 */
+	memset(hasmatch, 0, sizeof(hasmatch));
+
+	/*
+	 * Recursively search the graph for all-RAINBOW paths to the "post" state,
+	 * starting at the "pre" state.  The -1 initial depth accounts for the
+	 * fact that transitions out of the "pre" state are not part of the
+	 * matched string.  We likewise don't count the final transition to the
+	 * "post" state as part of the match length.  (But we still insist that
+	 * those transitions have RAINBOW arcs, otherwise there are lookbehind or
+	 * lookahead constraints at the start/end of the pattern.)
+	 */
+	if (!checkmatchall_recurse(nfa, nfa->pre, false, -1, hasmatch))
+		return;
+
+	/*
+	 * We found some all-RAINBOW paths, and not anything that we couldn't
+	 * handle.  Now verify that pseudocolor arcs adjacent to the pre and post
+	 * states match the RAINBOW arcs there.  (We could do this while
+	 * recursing, but it's expensive and unlikely to fail, so do it last.)
+	 */
+	if (!check_out_colors_match(nfa->pre, RAINBOW, nfa->bos[0]) ||
+		!check_out_colors_match(nfa->pre, nfa->bos[0], RAINBOW) ||
+		!check_out_colors_match(nfa->pre, RAINBOW, nfa->bos[1]) ||
+		!check_out_colors_match(nfa->pre, nfa->bos[1], RAINBOW))
+		return;
+	if (!check_in_colors_match(nfa->post, RAINBOW, nfa->eos[0]) ||
+		!check_in_colors_match(nfa->post, nfa->eos[0], RAINBOW) ||
+		!check_in_colors_match(nfa->post, RAINBOW, nfa->eos[1]) ||
+		!check_in_colors_match(nfa->post, nfa->eos[1], RAINBOW))
+		return;
+
+	/*
+	 * hasmatch[] now represents the set of possible match lengths; but we
+	 * want to reduce that to a min and max value, because it doesn't seem
+	 * worth complicating regexec.c to deal with nonconsecutive possible match
+	 * lengths.  Find min and max of first run of lengths, then verify there
+	 * are no nonconsecutive lengths.
+	 */
+	for (minmatch = 0; minmatch <= DUPINF; minmatch++)
+	{
+		if (hasmatch[minmatch])
+			break;
+	}
+	assert(minmatch <= DUPINF); /* else checkmatchall_recurse lied */
+	for (maxmatch = minmatch; maxmatch < DUPINF; maxmatch++)
+	{
+		if (!hasmatch[maxmatch + 1])
+			break;
+	}
+	for (morematch = maxmatch + 1; morematch <= DUPINF; morematch++)
+	{
+		if (hasmatch[morematch])
+			return;				/* fail, there are nonconsecutive lengths */
+	}
+
+	/* Success, so record the info */
+	nfa->minmatchall = minmatch;
+	nfa->maxmatchall = maxmatch;
+	nfa->flags |= MATCHALL;
+}
+
+/*
+ * checkmatchall_recurse - recursive search for checkmatchall
+ *
+ * s is the current state
+ * foundloop is true if any predecessor state has a loop-to-self
+ * depth is the current recursion depth (starting at -1)
+ * hasmatch[] is the output area for recording feasible match lengths
+ *
+ * We return true if there is at least one all-RAINBOW path to the "post"
+ * state and no non-matchall paths; otherwise false.  Note we assume that
+ * any dead-end paths have already been removed, else we might return
+ * false unnecessarily.
+ */
+static bool
+checkmatchall_recurse(struct nfa *nfa, struct state *s,
+					  bool foundloop, int depth,
+					  bool *hasmatch)
+{
+	bool		result = false;
+	struct arc *a;
+
+	/*
+	 * Since this is recursive, it could be driven to stack overflow.  But we
+	 * need not treat that as a hard failure; just deem the NFA non-matchall.
+	 */
+	if (STACK_TOO_DEEP(nfa->v->re))
+		return false;
+
+	/*
+	 * Likewise, if we get to a depth too large to represent correctly in
+	 * maxmatchall, fail quietly.
+	 */
+	if (depth >= DUPINF)
+		return false;
+
+	/*
+	 * Scan the outarcs to detect cases we can't handle, and to see if there
+	 * is a loop-to-self here.  We need to know about any such loop before we
+	 * recurse, so it's hard to avoid making two passes over the outarcs.  In
+	 * any case, checking for showstoppers before we recurse is probably best.
+	 */
+	for (a = s->outs; a != NULL; a = a->outchain)
+	{
+		if (a->type != PLAIN)
+			return false;		/* any LACONs make it non-matchall */
+		if (a->co != RAINBOW)
+		{
+			if (nfa->cm->cd[a->co].flags & PSEUDO)
+			{
+				/*
+				 * Pseudocolor arc: verify it's in a valid place (this seems
+				 * quite unlikely to fail, but let's be sure).
+				 */
+				if (s == nfa->pre &&
+					(a->co == nfa->bos[0] || a->co == nfa->bos[1]))
+					 /* okay BOS/BOL arc */ ;
+				else if (a->to == nfa->post &&
+						 (a->co == nfa->eos[0] || a->co == nfa->eos[1]))
+					 /* okay EOS/EOL arc */ ;
+				else
+					return false;	/* unexpected pseudocolor arc */
+				/* We'll finish checking these arcs after the recursion */
+				continue;
+			}
+			return false;		/* any other color makes it non-matchall */
+		}
+		if (a->to == s)
+		{
+			/*
+			 * We found a cycle of length 1, so remember that to pass down to
+			 * successor states.  (It doesn't matter if there was also such a
+			 * loop at a predecessor state.)
+			 */
+			foundloop = true;
+		}
+		else if (a->to->tmp)
+		{
+			/* We found a cycle of length > 1, so fail. */
+			return false;
+		}
+	}
+
+	/* We need to recurse, so mark state as under consideration */
+	assert(s->tmp == NULL);
+	s->tmp = s;
+
+	for (a = s->outs; a != NULL; a = a->outchain)
+	{
+		if (a->co != RAINBOW)
+			continue;			/* ignore pseudocolor arcs */
+		if (a->to == nfa->post)
+		{
+			/* We found an all-RAINBOW path to the post state */
+			result = true;
+			/* Record potential match lengths */
+			assert(depth >= 0);
+			hasmatch[depth] = true;
+			if (foundloop)
+			{
+				/* A predecessor loop makes all larger lengths match, too */
+				int			i;
+
+				for (i = depth + 1; i <= DUPINF; i++)
+					hasmatch[i] = true;
+			}
+		}
+		else if (a->to != s)
+		{
+			/* This is a new path forward; recurse to investigate */
+			result = checkmatchall_recurse(nfa, a->to,
+										   foundloop, depth + 1,
+										   hasmatch);
+			/* Fail if any recursive path fails */
+			if (!result)
+				break;
+		}
+	}
+
+	s->tmp = NULL;
+	return result;
+}
+
+/*
+ * check_out_colors_match - subroutine for checkmatchall
+ *
+ * Check if every s outarc of color co1 has a matching outarc of color co2.
+ * (checkmatchall_recurse already verified that all of the outarcs are PLAIN,
+ * so we need not examine arc types here.)
+ */
+static bool
+check_out_colors_match(struct state *s, color co1, color co2)
+{
+	struct arc *a1;
+	struct arc *a2;
+
+	for (a1 = s->outs; a1 != NULL; a1 = a1->outchain)
+	{
+		if (a1->co != co1)
+			continue;
+		for (a2 = s->outs; a2 != NULL; a2 = a2->outchain)
+		{
+			if (a2->co == co2 && a2->to == a1->to)
+				break;
+		}
+		if (a2 == NULL)
+			return false;
+	}
+	return true;
+}
+
+/*
+ * check_in_colors_match - subroutine for checkmatchall
+ *
+ * Check if every s inarc of color co1 has a matching inarc of color co2.
+ * (For paranoia's sake, ignore any non-PLAIN arcs here.)
+ */
+static bool
+check_in_colors_match(struct state *s, color co1, color co2)
+{
+	struct arc *a1;
+	struct arc *a2;
+
+	for (a1 = s->ins; a1 != NULL; a1 = a1->inchain)
+	{
+		if (a1->type != PLAIN || a1->co != co1)
+			continue;
+		for (a2 = s->ins; a2 != NULL; a2 = a2->inchain)
+		{
+			if (a2->type == PLAIN && a2->co == co2 && a2->from == a1->from)
+				break;
+		}
+		if (a2 == NULL)
+			return false;
+	}
+	return true;
+}
+
 /*
  * compact - construct the compact representation of an NFA
  */
@@ -2930,7 +3211,9 @@ compact(struct nfa *nfa,
 	cnfa->eos[0] = nfa->eos[0];
 	cnfa->eos[1] = nfa->eos[1];
 	cnfa->ncolors = maxcolor(nfa->cm) + 1;
-	cnfa->flags = 0;
+	cnfa->flags = nfa->flags;
+	cnfa->minmatchall = nfa->minmatchall;
+	cnfa->maxmatchall = nfa->maxmatchall;
 
 	ca = cnfa->arcs;
 	for (s = nfa->states; s != NULL; s = s->next)
@@ -3034,6 +3317,11 @@ dumpnfa(struct nfa *nfa,
 		fprintf(f, ", eos [%ld]", (long) nfa->eos[0]);
 	if (nfa->eos[1] != COLORLESS)
 		fprintf(f, ", eol [%ld]", (long) nfa->eos[1]);
+	if (nfa->flags & HASLACONS)
+		fprintf(f, ", haslacons");
+	if (nfa->flags & MATCHALL)
+		fprintf(f, ", minmatchall %d, maxmatchall %d",
+				nfa->minmatchall, nfa->maxmatchall);
 	fprintf(f, "\n");
 	for (s = nfa->states; s != NULL; s = s->next)
 	{
@@ -3201,6 +3489,9 @@ dumpcnfa(struct cnfa *cnfa,
 		fprintf(f, ", eol [%ld]", (long) cnfa->eos[1]);
 	if (cnfa->flags & HASLACONS)
 		fprintf(f, ", haslacons");
+	if (cnfa->flags & MATCHALL)
+		fprintf(f, ", minmatchall %d, maxmatchall %d",
+				cnfa->minmatchall, 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 e73476040d..b228aedbd9 100644
--- a/src/backend/regex/regcomp.c
+++ b/src/backend/regex/regcomp.c
@@ -175,6 +175,11 @@ static void cleanup(struct nfa *);
 static void markreachable(struct nfa *, struct state *, struct state *, struct state *);
 static void markcanreach(struct nfa *, struct state *, struct state *, struct state *);
 static long analyze(struct nfa *);
+static void checkmatchall(struct nfa *);
+static bool checkmatchall_recurse(struct nfa *, struct state *,
+								  bool, int, bool *);
+static bool check_out_colors_match(struct state *, color, color);
+static bool check_in_colors_match(struct state *, color, color);
 static void compact(struct nfa *, struct cnfa *);
 static void carcsort(struct carc *, size_t);
 static int	carc_cmp(const void *, const void *);
diff --git a/src/backend/regex/rege_dfa.c b/src/backend/regex/rege_dfa.c
index 32be2592c5..20ec463204 100644
--- a/src/backend/regex/rege_dfa.c
+++ b/src/backend/regex/rege_dfa.c
@@ -58,6 +58,29 @@ longest(struct vars *v,
 	if (hitstopp != NULL)
 		*hitstopp = 0;
 
+	/* fast path for matchall NFAs */
+	if (d->cnfa->flags & MATCHALL)
+	{
+		size_t		nchr = stop - start;
+		size_t		maxmatchall = d->cnfa->maxmatchall;
+
+		if (nchr < d->cnfa->minmatchall)
+			return NULL;
+		if (maxmatchall == DUPINF)
+		{
+			if (stop == v->stop && hitstopp != NULL)
+				*hitstopp = 1;
+		}
+		else
+		{
+			if (stop == v->stop && nchr <= maxmatchall + 1 && hitstopp != NULL)
+				*hitstopp = 1;
+			if (nchr > maxmatchall)
+				return start + maxmatchall;
+		}
+		return stop;
+	}
+
 	/* initialize */
 	css = initialize(v, d, start);
 	if (css == NULL)
@@ -187,6 +210,24 @@ shortest(struct vars *v,
 	if (hitstopp != NULL)
 		*hitstopp = 0;
 
+	/* fast path for matchall NFAs */
+	if (d->cnfa->flags & MATCHALL)
+	{
+		size_t		nchr = min - start;
+
+		if (d->cnfa->maxmatchall != DUPINF &&
+			nchr > d->cnfa->maxmatchall)
+			return NULL;
+		if ((max - start) < d->cnfa->minmatchall)
+			return NULL;
+		if (nchr < d->cnfa->minmatchall)
+			min = start + d->cnfa->minmatchall;
+		if (coldp != NULL)
+			*coldp = start;
+		/* there is no case where we should set *hitstopp */
+		return min;
+	}
+
 	/* initialize */
 	css = initialize(v, d, start);
 	if (css == NULL)
@@ -312,6 +353,22 @@ matchuntil(struct vars *v,
 	struct sset *ss;
 	struct colormap *cm = d->cm;
 
+	/* fast path for matchall NFAs */
+	if (d->cnfa->flags & MATCHALL)
+	{
+		size_t		nchr = probe - v->start;
+
+		/*
+		 * It might seem that we should check maxmatchall too, but the
+		 * implicit .* at the front of the pattern absorbs any extra
+		 * characters.  Thus, we should always match as long as there are at
+		 * least minmatchall characters.
+		 */
+		if (nchr < d->cnfa->minmatchall)
+			return 0;
+		return 1;
+	}
+
 	/* initialize and startup, or restart, if necessary */
 	if (cp == NULL || cp > probe)
 	{
diff --git a/src/backend/regex/regprefix.c b/src/backend/regex/regprefix.c
index e2fbad7a8a..ec435b6f5f 100644
--- a/src/backend/regex/regprefix.c
+++ b/src/backend/regex/regprefix.c
@@ -77,6 +77,10 @@ pg_regprefix(regex_t *re,
 	assert(g->tree != NULL);
 	cnfa = &g->tree->cnfa;
 
+	/* matchall NFAs never have a fixed prefix */
+	if (cnfa->flags & MATCHALL)
+		return REG_NOMATCH;
+
 	/*
 	 * Since a correct NFA should never contain any exit-free loops, it should
 	 * not be possible for our traversal to return to a previously visited NFA
diff --git a/src/include/regex/regguts.h b/src/include/regex/regguts.h
index 6d39108319..82e761bfe5 100644
--- a/src/include/regex/regguts.h
+++ b/src/include/regex/regguts.h
@@ -331,6 +331,9 @@ struct nfa
 	struct colormap *cm;		/* the color map */
 	color		bos[2];			/* colors, if any, assigned to BOS and BOL */
 	color		eos[2];			/* colors, if any, assigned to EOS and EOL */
+	int			flags;			/* flags to pass forward to cNFA */
+	int			minmatchall;	/* min number of chrs to match, if matchall */
+	int			maxmatchall;	/* max number of chrs to match, or DUPINF */
 	struct vars *v;				/* simplifies compile error reporting */
 	struct nfa *parent;			/* parent NFA, if any */
 };
@@ -353,6 +356,14 @@ struct nfa
  *
  * Note that in a plain arc, "co" can be RAINBOW; since that's negative,
  * it doesn't break the rule about how to recognize LACON arcs.
+ *
+ * We have special markings for "trivial" NFAs that can match any string
+ * (possibly with limits on the number of characters therein).  In such a
+ * case, flags & MATCHALL is set (and HASLACONS can't be set).  Then the
+ * fields minmatchall and maxmatchall give the minimum and maximum numbers
+ * of characters to match.  For example, ".*" produces minmatchall = 0
+ * and maxmatchall = DUPINF, while ".+" produces minmatchall = 1 and
+ * maxmatchall = DUPINF.
  */
 struct carc
 {
@@ -366,6 +377,7 @@ struct cnfa
 	int			ncolors;		/* number of colors (max color in use + 1) */
 	int			flags;
 #define  HASLACONS	01			/* uses lookaround constraints */
+#define  MATCHALL	02			/* matches all strings of a range of lengths */
 	int			pre;			/* setup state number */
 	int			post;			/* teardown state number */
 	color		bos[2];			/* colors, if any, assigned to BOS and BOL */
@@ -375,6 +387,9 @@ struct cnfa
 	struct carc **states;		/* vector of pointers to outarc lists */
 	/* states[n] are pointers into a single malloc'd array of arcs */
 	struct carc *arcs;			/* the area for the lists */
+	/* these fields are used only in a MATCHALL NFA (else they're -1): */
+	int			minmatchall;	/* min number of chrs to match */
+	int			maxmatchall;	/* max number of chrs to match, or DUPINF */
 };
 
 /*
diff --git a/src/test/modules/test_regex/expected/test_regex.out b/src/test/modules/test_regex/expected/test_regex.out
index 0dc2265d8b..f01ca071d9 100644
--- a/src/test/modules/test_regex/expected/test_regex.out
+++ b/src/test/modules/test_regex/expected/test_regex.out
@@ -3315,6 +3315,21 @@ select * from test_regex('(?=b)b', 'a', 'HP');
  {0,REG_ULOOKAROUND,REG_UNONPOSIX}
 (1 row)
 
+-- expectMatch	23.9 HP		...(?!.)	abcde	cde
+select * from test_regex('...(?!.)', 'abcde', 'HP');
+            test_regex             
+-----------------------------------
+ {0,REG_ULOOKAROUND,REG_UNONPOSIX}
+ {cde}
+(2 rows)
+
+-- expectNomatch	23.10 HP	...(?=.)	abc
+select * from test_regex('...(?=.)', 'abc', 'HP');
+            test_regex             
+-----------------------------------
+ {0,REG_ULOOKAROUND,REG_UNONPOSIX}
+(1 row)
+
 -- Postgres addition: lookbehind constraints
 -- expectMatch	23.11 HPN		(?<=a)b*	ab	b
 select * from test_regex('(?<=a)b*', 'ab', 'HPN');
@@ -3376,6 +3391,39 @@ select * from test_regex('(?<=b)b', 'b', 'HP');
  {0,REG_ULOOKAROUND,REG_UNONPOSIX}
 (1 row)
 
+-- expectMatch	23.19 HP		(?<=.)..	abcde	bc
+select * from test_regex('(?<=.)..', 'abcde', 'HP');
+            test_regex             
+-----------------------------------
+ {0,REG_ULOOKAROUND,REG_UNONPOSIX}
+ {bc}
+(2 rows)
+
+-- expectMatch	23.20 HP		(?<=..)a*	aaabb	a
+select * from test_regex('(?<=..)a*', 'aaabb', 'HP');
+            test_regex             
+-----------------------------------
+ {0,REG_ULOOKAROUND,REG_UNONPOSIX}
+ {a}
+(2 rows)
+
+-- expectMatch	23.21 HP		(?<=..)b*	aaabb	{}
+-- Note: empty match here is correct, it matches after the first 2 characters
+select * from test_regex('(?<=..)b*', 'aaabb', 'HP');
+            test_regex             
+-----------------------------------
+ {0,REG_ULOOKAROUND,REG_UNONPOSIX}
+ {""}
+(2 rows)
+
+-- expectMatch	23.22 HP		(?<=..)b+	aaabb	bb
+select * from test_regex('(?<=..)b+', 'aaabb', 'HP');
+            test_regex             
+-----------------------------------
+ {0,REG_ULOOKAROUND,REG_UNONPOSIX}
+ {bb}
+(2 rows)
+
 -- doing 24 "non-greedy quantifiers"
 -- expectMatch	24.1  PT	ab+?		abb	ab
 select * from test_regex('ab+?', 'abb', 'PT');
diff --git a/src/test/modules/test_regex/sql/test_regex.sql b/src/test/modules/test_regex/sql/test_regex.sql
index 1a2bfa6235..ae7d6b43e4 100644
--- a/src/test/modules/test_regex/sql/test_regex.sql
+++ b/src/test/modules/test_regex/sql/test_regex.sql
@@ -1049,6 +1049,10 @@ select * from test_regex('a(?!b)b*', 'a', 'HP');
 select * from test_regex('(?=b)b', 'b', 'HP');
 -- expectNomatch	23.8 HP		(?=b)b		a
 select * from test_regex('(?=b)b', 'a', 'HP');
+-- expectMatch	23.9 HP		...(?!.)	abcde	cde
+select * from test_regex('...(?!.)', 'abcde', 'HP');
+-- expectNomatch	23.10 HP	...(?=.)	abc
+select * from test_regex('...(?=.)', 'abc', 'HP');
 
 -- Postgres addition: lookbehind constraints
 
@@ -1068,6 +1072,15 @@ select * from test_regex('a(?<!b)b*', 'a', 'HP');
 select * from test_regex('(?<=b)b', 'bb', 'HP');
 -- expectNomatch	23.18 HP		(?<=b)b		b
 select * from test_regex('(?<=b)b', 'b', 'HP');
+-- expectMatch	23.19 HP		(?<=.)..	abcde	bc
+select * from test_regex('(?<=.)..', 'abcde', 'HP');
+-- expectMatch	23.20 HP		(?<=..)a*	aaabb	a
+select * from test_regex('(?<=..)a*', 'aaabb', 'HP');
+-- expectMatch	23.21 HP		(?<=..)b*	aaabb	{}
+-- Note: empty match here is correct, it matches after the first 2 characters
+select * from test_regex('(?<=..)b*', 'aaabb', 'HP');
+-- expectMatch	23.22 HP		(?<=..)b+	aaabb	bb
+select * from test_regex('(?<=..)b+', 'aaabb', 'HP');
 
 -- doing 24 "non-greedy quantifiers"
 

diff --git a/src/backend/regex/regcomp.c b/src/backend/regex/regcomp.c
index b228aedbd9..6cf4209d30 100644
--- a/src/backend/regex/regcomp.c
+++ b/src/backend/regex/regcomp.c
@@ -1123,14 +1123,24 @@ parseqatom(struct vars *v,
 	t->left = atom;
 	atomp = &t->left;
 
-	/* here we should recurse... but we must postpone that to the end */
+	/*
+	 * Here we should recurse to fill t->right ... but we must postpone that
+	 * to the end.
+	 */
 
-	/* split top into prefix and remaining */
+	/*
+	 * Convert top node to a concatenation of the prefix (top->left, covering
+	 * whatever we parsed previously) and remaining (t).  Note that the prefix
+	 * could be empty, in which case this concatenation node is unnecessary.
+	 * To keep things simple, we operate in a general way for now, and get rid
+	 * of unnecessary subres below.
+	 */
 	assert(top->op == '=' && top->left == NULL && top->right == NULL);
 	top->left = subre(v, '=', top->flags, top->begin, lp);
 	NOERR();
 	top->op = '.';
 	top->right = t;
+	/* top->flags will get updated later */
 
 	/* if it's a backref, now is the time to replicate the subNFA */
 	if (atomtype == BACKREF)
@@ -1220,16 +1230,75 @@ parseqatom(struct vars *v,
 	/* and finally, look after that postponed recursion */
 	t = top->right;
 	if (!(SEE('|') || SEE(stopper) || SEE(EOS)))
+	{
+		/* parse all the rest of the branch, and insert in t->right */
 		t->right = parsebranch(v, stopper, type, s2, rp, 1);
+		NOERR();
+		assert(SEE('|') || SEE(stopper) || SEE(EOS));
+
+		/* here's the promised update of the flags */
+		t->flags |= COMBINE(t->flags, t->right->flags);
+		top->flags |= COMBINE(top->flags, t->flags);
+
+		/*
+		 * At this point both top and t are concatenation (op == '.') subres,
+		 * and we have top->left = prefix of branch, top->right = t, t->left =
+		 * messy atom (with quantification superstructure if needed), t->right
+		 * = rest of branch.
+		 *
+		 * If the messy atom was the first thing in the branch, then top->left
+		 * is vacuous and we can get rid of one level of concatenation.  Since
+		 * the caller is holding a pointer to the top node, we can't remove
+		 * that node; but we're allowed to change its properties.
+		 */
+		assert(top->left->op == '=');
+		if (top->left->begin == top->left->end)
+		{
+			assert(!MESSY(top->left->flags));
+			freesubre(v, top->left);
+			top->left = t->left;
+			top->right = t->right;
+			t->left = t->right = NULL;
+			freesubre(v, t);
+		}
+	}
 	else
 	{
+		/*
+		 * There's nothing left in the branch, so we don't need the second
+		 * concatenation node 't'.  Just link s2 straight to rp.
+		 */
 		EMPTYARC(s2, rp);
-		t->right = subre(v, '=', 0, s2, rp);
+		top->right = t->left;
+		top->flags |= COMBINE(top->flags, top->right->flags);
+		t->left = t->right = NULL;
+		freesubre(v, t);
+
+		/*
+		 * Again, it could be that top->left is vacuous (if the messy atom was
+		 * in fact the only thing in the branch).  In that case we need no
+		 * concatenation at all; just replace top with top->right.
+		 */
+		assert(top->left->op == '=');
+		if (top->left->begin == top->left->end)
+		{
+			assert(!MESSY(top->left->flags));
+			freesubre(v, top->left);
+			t = top->right;
+			top->op = t->op;
+			top->flags = t->flags;
+			top->id = t->id;
+			top->subno = t->subno;
+			top->min = t->min;
+			top->max = t->max;
+			top->left = t->left;
+			top->right = t->right;
+			top->begin = t->begin;
+			top->end = t->end;
+			t->left = t->right = NULL;
+			freesubre(v, t);
+		}
 	}
-	NOERR();
-	assert(SEE('|') || SEE(stopper) || SEE(EOS));
-	t->flags |= COMBINE(t->flags, t->right->flags);
-	top->flags |= COMBINE(top->flags, t->flags);
 }
 
 /*

diff --git a/src/backend/regex/regcomp.c b/src/backend/regex/regcomp.c
index 6cf4209d30..c688806992 100644
--- a/src/backend/regex/regcomp.c
+++ b/src/backend/regex/regcomp.c
@@ -58,6 +58,7 @@ static void processlacon(struct vars *, struct state *, struct state *, int,
 						 struct state *, struct state *);
 static struct subre *subre(struct vars *, int, int, struct state *, struct state *);
 static void freesubre(struct vars *, struct subre *);
+static void freesubreandsiblings(struct vars *, struct subre *);
 static void freesrnode(struct vars *, struct subre *);
 static void optst(struct vars *, struct subre *);
 static int	numst(struct subre *, int);
@@ -652,8 +653,8 @@ makesearch(struct vars *v,
  * parse - parse an RE
  *
  * This is actually just the top level, which parses a bunch of branches
- * tied together with '|'.  They appear in the tree as the left children
- * of a chain of '|' subres.
+ * tied together with '|'.  If there's more than one, they appear in the
+ * tree as the children of a '|' subre.
  */
 static struct subre *
 parse(struct vars *v,
@@ -662,41 +663,34 @@ parse(struct vars *v,
 	  struct state *init,		/* initial state */
 	  struct state *final)		/* final state */
 {
-	struct state *left;			/* scaffolding for branch */
-	struct state *right;
 	struct subre *branches;		/* top level */
-	struct subre *branch;		/* current branch */
-	struct subre *t;			/* temporary */
-	int			firstbranch;	/* is this the first branch? */
+	struct subre *lastbranch;	/* latest branch */
 
 	assert(stopper == ')' || stopper == EOS);
 
 	branches = subre(v, '|', LONGER, init, final);
 	NOERRN();
-	branch = branches;
-	firstbranch = 1;
+	lastbranch = NULL;
 	do
 	{							/* a branch */
-		if (!firstbranch)
-		{
-			/* need a place to hang it */
-			branch->right = subre(v, '|', LONGER, init, final);
-			NOERRN();
-			branch = branch->right;
-		}
-		firstbranch = 0;
+		struct subre *branch;
+		struct state *left;		/* scaffolding for branch */
+		struct state *right;
+
 		left = newstate(v->nfa);
 		right = newstate(v->nfa);
 		NOERRN();
 		EMPTYARC(init, left);
 		EMPTYARC(right, final);
 		NOERRN();
-		branch->left = parsebranch(v, stopper, type, left, right, 0);
+		branch = parsebranch(v, stopper, type, left, right, 0);
 		NOERRN();
-		branch->flags |= UP(branch->flags | branch->left->flags);
-		if ((branch->flags & ~branches->flags) != 0)	/* new flags */
-			for (t = branches; t != branch; t = t->right)
-				t->flags |= branch->flags;
+		if (lastbranch)
+			lastbranch->sibling = branch;
+		else
+			branches->child = branch;
+		branches->flags |= UP(branches->flags | branch->flags);
+		lastbranch = branch;
 	} while (EAT('|'));
 	assert(SEE(stopper) || SEE(EOS));
 
@@ -707,20 +701,16 @@ parse(struct vars *v,
 	}
 
 	/* optimize out simple cases */
-	if (branch == branches)
+	if (lastbranch == branches->child)
 	{							/* only one branch */
-		assert(branch->right == NULL);
-		t = branch->left;
-		branch->left = NULL;
-		freesubre(v, branches);
-		branches = t;
+		assert(lastbranch->sibling == NULL);
+		freesrnode(v, branches);
+		branches = lastbranch;
 	}
 	else if (!MESSY(branches->flags))
 	{							/* no interesting innards */
-		freesubre(v, branches->left);
-		branches->left = NULL;
-		freesubre(v, branches->right);
-		branches->right = NULL;
+		freesubreandsiblings(v, branches->child);
+		branches->child = NULL;
 		branches->op = '=';
 	}
 
@@ -972,7 +962,7 @@ parseqatom(struct vars *v,
 				t = subre(v, '(', atom->flags | CAP, lp, rp);
 				NOERR();
 				t->subno = subno;
-				t->left = atom;
+				t->child = atom;
 				atom = t;
 			}
 			/* postpone everything else pending possible {0} */
@@ -1120,26 +1110,27 @@ parseqatom(struct vars *v,
 	/* break remaining subRE into x{...} and what follows */
 	t = subre(v, '.', COMBINE(qprefer, atom->flags), lp, rp);
 	NOERR();
-	t->left = atom;
-	atomp = &t->left;
+	t->child = atom;
+	atomp = &t->child;
 
 	/*
-	 * Here we should recurse to fill t->right ... but we must postpone that
-	 * to the end.
+	 * Here we should recurse to fill t->child->sibling ... but we must
+	 * postpone that to the end.  One reason is that t->child may be replaced
+	 * below, and we don't want to worry about its sibling link.
 	 */
 
 	/*
-	 * Convert top node to a concatenation of the prefix (top->left, covering
+	 * Convert top node to a concatenation of the prefix (top->child, covering
 	 * whatever we parsed previously) and remaining (t).  Note that the prefix
 	 * could be empty, in which case this concatenation node is unnecessary.
 	 * To keep things simple, we operate in a general way for now, and get rid
 	 * of unnecessary subres below.
 	 */
-	assert(top->op == '=' && top->left == NULL && top->right == NULL);
-	top->left = subre(v, '=', top->flags, top->begin, lp);
+	assert(top->op == '=' && top->child == NULL);
+	top->child = subre(v, '=', top->flags, top->begin, lp);
 	NOERR();
 	top->op = '.';
-	top->right = t;
+	top->child->sibling = t;
 	/* top->flags will get updated later */
 
 	/* if it's a backref, now is the time to replicate the subNFA */
@@ -1201,9 +1192,9 @@ parseqatom(struct vars *v,
 		f = COMBINE(qprefer, atom->flags);
 		t = subre(v, '.', f, s, atom->end); /* prefix and atom */
 		NOERR();
-		t->left = subre(v, '=', PREF(f), s, atom->begin);
+		t->child = subre(v, '=', PREF(f), s, atom->begin);
 		NOERR();
-		t->right = atom;
+		t->child->sibling = atom;
 		*atomp = t;
 		/* rest of branch can be strung starting from atom->end */
 		s2 = atom->end;
@@ -1222,44 +1213,43 @@ parseqatom(struct vars *v,
 		NOERR();
 		t->min = (short) m;
 		t->max = (short) n;
-		t->left = atom;
+		t->child = atom;
 		*atomp = t;
 		/* rest of branch is to be strung from iteration's end state */
 	}
 
 	/* and finally, look after that postponed recursion */
-	t = top->right;
+	t = top->child->sibling;
 	if (!(SEE('|') || SEE(stopper) || SEE(EOS)))
 	{
-		/* parse all the rest of the branch, and insert in t->right */
-		t->right = parsebranch(v, stopper, type, s2, rp, 1);
+		/* parse all the rest of the branch, and insert in t->child->sibling */
+		t->child->sibling = parsebranch(v, stopper, type, s2, rp, 1);
 		NOERR();
 		assert(SEE('|') || SEE(stopper) || SEE(EOS));
 
 		/* here's the promised update of the flags */
-		t->flags |= COMBINE(t->flags, t->right->flags);
+		t->flags |= COMBINE(t->flags, t->child->sibling->flags);
 		top->flags |= COMBINE(top->flags, t->flags);
 
 		/*
 		 * At this point both top and t are concatenation (op == '.') subres,
-		 * and we have top->left = prefix of branch, top->right = t, t->left =
-		 * messy atom (with quantification superstructure if needed), t->right
-		 * = rest of branch.
+		 * and we have top->child = prefix of branch, top->child->sibling = t,
+		 * t->child = messy atom (with quantification superstructure if
+		 * needed), t->child->sibling = rest of branch.
 		 *
-		 * If the messy atom was the first thing in the branch, then top->left
-		 * is vacuous and we can get rid of one level of concatenation.  Since
-		 * the caller is holding a pointer to the top node, we can't remove
-		 * that node; but we're allowed to change its properties.
+		 * If the messy atom was the first thing in the branch, then
+		 * top->child is vacuous and we can get rid of one level of
+		 * concatenation.  Since the caller is holding a pointer to the top
+		 * node, we can't remove that node; but we're allowed to change its
+		 * properties.
 		 */
-		assert(top->left->op == '=');
-		if (top->left->begin == top->left->end)
+		assert(top->child->op == '=');
+		if (top->child->begin == top->child->end)
 		{
-			assert(!MESSY(top->left->flags));
-			freesubre(v, top->left);
-			top->left = t->left;
-			top->right = t->right;
-			t->left = t->right = NULL;
-			freesubre(v, t);
+			assert(!MESSY(top->child->flags));
+			freesubre(v, top->child);
+			top->child = t->child;
+			freesrnode(v, t);
 		}
 	}
 	else
@@ -1269,34 +1259,31 @@ parseqatom(struct vars *v,
 		 * concatenation node 't'.  Just link s2 straight to rp.
 		 */
 		EMPTYARC(s2, rp);
-		top->right = t->left;
-		top->flags |= COMBINE(top->flags, top->right->flags);
-		t->left = t->right = NULL;
-		freesubre(v, t);
+		top->child->sibling = t->child;
+		top->flags |= COMBINE(top->flags, top->child->sibling->flags);
+		freesrnode(v, t);
 
 		/*
-		 * Again, it could be that top->left is vacuous (if the messy atom was
-		 * in fact the only thing in the branch).  In that case we need no
-		 * concatenation at all; just replace top with top->right.
+		 * Again, it could be that top->child is vacuous (if the messy atom
+		 * was in fact the only thing in the branch).  In that case we need no
+		 * concatenation at all; just replace top with top->child->sibling.
 		 */
-		assert(top->left->op == '=');
-		if (top->left->begin == top->left->end)
+		assert(top->child->op == '=');
+		if (top->child->begin == top->child->end)
 		{
-			assert(!MESSY(top->left->flags));
-			freesubre(v, top->left);
-			t = top->right;
+			assert(!MESSY(top->child->flags));
+			t = top->child->sibling;
+			freesubre(v, top->child);
 			top->op = t->op;
 			top->flags = t->flags;
 			top->id = t->id;
 			top->subno = t->subno;
 			top->min = t->min;
 			top->max = t->max;
-			top->left = t->left;
-			top->right = t->right;
+			top->child = t->child;
 			top->begin = t->begin;
 			top->end = t->end;
-			t->left = t->right = NULL;
-			freesubre(v, t);
+			freesrnode(v, t);
 		}
 	}
 }
@@ -1786,7 +1773,7 @@ subre(struct vars *v,
 	}
 
 	if (ret != NULL)
-		v->treefree = ret->left;
+		v->treefree = ret->child;
 	else
 	{
 		ret = (struct subre *) MALLOC(sizeof(struct subre));
@@ -1806,8 +1793,8 @@ subre(struct vars *v,
 	ret->id = 0;				/* will be assigned later */
 	ret->subno = 0;
 	ret->min = ret->max = 1;
-	ret->left = NULL;
-	ret->right = NULL;
+	ret->child = NULL;
+	ret->sibling = NULL;
 	ret->begin = begin;
 	ret->end = end;
 	ZAPCNFA(ret->cnfa);
@@ -1817,6 +1804,9 @@ subre(struct vars *v,
 
 /*
  * freesubre - free a subRE subtree
+ *
+ * This frees child node(s) of the given subRE too,
+ * but not its siblings.
  */
 static void
 freesubre(struct vars *v,		/* might be NULL */
@@ -1825,14 +1815,31 @@ freesubre(struct vars *v,		/* might be NULL */
 	if (sr == NULL)
 		return;
 
-	if (sr->left != NULL)
-		freesubre(v, sr->left);
-	if (sr->right != NULL)
-		freesubre(v, sr->right);
+	if (sr->child != NULL)
+		freesubreandsiblings(v, sr->child);
 
 	freesrnode(v, sr);
 }
 
+/*
+ * freesubreandsiblings - free a subRE subtree
+ *
+ * This frees child node(s) of the given subRE too,
+ * as well as any following siblings.
+ */
+static void
+freesubreandsiblings(struct vars *v,	/* might be NULL */
+					 struct subre *sr)
+{
+	while (sr != NULL)
+	{
+		struct subre *next = sr->sibling;
+
+		freesubre(v, sr);
+		sr = next;
+	}
+}
+
 /*
  * freesrnode - free one node in a subRE subtree
  */
@@ -1850,7 +1857,7 @@ freesrnode(struct vars *v,		/* might be NULL */
 	if (v != NULL && v->treechain != NULL)
 	{
 		/* we're still parsing, maybe we can reuse the subre */
-		sr->left = v->treefree;
+		sr->child = v->treefree;
 		v->treefree = sr;
 	}
 	else
@@ -1881,15 +1888,14 @@ numst(struct subre *t,
 	  int start)				/* starting point for subtree numbers */
 {
 	int			i;
+	struct subre *t2;
 
 	assert(t != NULL);
 
 	i = start;
 	t->id = (short) i++;
-	if (t->left != NULL)
-		i = numst(t->left, i);
-	if (t->right != NULL)
-		i = numst(t->right, i);
+	for (t2 = t->child; t2 != NULL; t2 = t2->sibling)
+		i = numst(t2, i);
 	return i;
 }
 
@@ -1913,13 +1919,13 @@ numst(struct subre *t,
 static void
 markst(struct subre *t)
 {
+	struct subre *t2;
+
 	assert(t != NULL);
 
 	t->flags |= INUSE;
-	if (t->left != NULL)
-		markst(t->left);
-	if (t->right != NULL)
-		markst(t->right);
+	for (t2 = t->child; t2 != NULL; t2 = t2->sibling)
+		markst(t2);
 }
 
 /*
@@ -1949,12 +1955,12 @@ nfatree(struct vars *v,
 		struct subre *t,
 		FILE *f)				/* for debug output */
 {
+	struct subre *t2;
+
 	assert(t != NULL && t->begin != NULL);
 
-	if (t->left != NULL)
-		(DISCARD) nfatree(v, t->left, f);
-	if (t->right != NULL)
-		(DISCARD) nfatree(v, t->right, f);
+	for (t2 = t->child; t2 != NULL; t2 = t2->sibling)
+		(DISCARD) nfatree(v, t2, f);
 
 	return nfanode(v, t, 0, f);
 }
@@ -2206,6 +2212,7 @@ stdump(struct subre *t,
 	   int nfapresent)			/* is the original NFA still around? */
 {
 	char		idbuf[50];
+	struct subre *t2;
 
 	fprintf(f, "%s. `%c'", stid(t, idbuf, sizeof(idbuf)), t->op);
 	if (t->flags & LONGER)
@@ -2231,20 +2238,18 @@ stdump(struct subre *t,
 	}
 	if (nfapresent)
 		fprintf(f, " %ld-%ld", (long) t->begin->no, (long) t->end->no);
-	if (t->left != NULL)
-		fprintf(f, " L:%s", stid(t->left, idbuf, sizeof(idbuf)));
-	if (t->right != NULL)
-		fprintf(f, " R:%s", stid(t->right, idbuf, sizeof(idbuf)));
+	if (t->child != NULL)
+		fprintf(f, " C:%s", stid(t->child, idbuf, sizeof(idbuf)));
+	if (t->sibling != NULL)
+		fprintf(f, " S:%s", stid(t->sibling, idbuf, sizeof(idbuf)));
 	if (!NULLCNFA(t->cnfa))
 	{
 		fprintf(f, "\n");
 		dumpcnfa(&t->cnfa, f);
 	}
 	fprintf(f, "\n");
-	if (t->left != NULL)
-		stdump(t->left, f, nfapresent);
-	if (t->right != NULL)
-		stdump(t->right, f, nfapresent);
+	for (t2 = t->child; t2 != NULL; t2 = t2->sibling)
+		stdump(t2, f, nfapresent);
 }
 
 /*
diff --git a/src/backend/regex/regexec.c b/src/backend/regex/regexec.c
index f7eaa76b02..4b65e38329 100644
--- a/src/backend/regex/regexec.c
+++ b/src/backend/regex/regexec.c
@@ -635,6 +635,8 @@ static void
 zaptreesubs(struct vars *v,
 			struct subre *t)
 {
+	struct subre *t2;
+
 	if (t->op == '(')
 	{
 		int			n = t->subno;
@@ -647,10 +649,8 @@ zaptreesubs(struct vars *v,
 		}
 	}
 
-	if (t->left != NULL)
-		zaptreesubs(v, t->left);
-	if (t->right != NULL)
-		zaptreesubs(v, t->right);
+	for (t2 = t->child; t2 != NULL; t2 = t2->sibling)
+		zaptreesubs(v, t2);
 }
 
 /*
@@ -709,35 +709,35 @@ cdissect(struct vars *v,
 	switch (t->op)
 	{
 		case '=':				/* terminal node */
-			assert(t->left == NULL && t->right == NULL);
+			assert(t->child == NULL);
 			er = REG_OKAY;		/* no action, parent did the work */
 			break;
 		case 'b':				/* back reference */
-			assert(t->left == NULL && t->right == NULL);
+			assert(t->child == NULL);
 			er = cbrdissect(v, t, begin, end);
 			break;
 		case '.':				/* concatenation */
-			assert(t->left != NULL && t->right != NULL);
-			if (t->left->flags & SHORTER)	/* reverse scan */
+			assert(t->child != NULL);
+			if (t->child->flags & SHORTER)	/* reverse scan */
 				er = crevcondissect(v, t, begin, end);
 			else
 				er = ccondissect(v, t, begin, end);
 			break;
 		case '|':				/* alternation */
-			assert(t->left != NULL);
+			assert(t->child != NULL);
 			er = caltdissect(v, t, begin, end);
 			break;
 		case '*':				/* iteration */
-			assert(t->left != NULL);
-			if (t->left->flags & SHORTER)	/* reverse scan */
+			assert(t->child != NULL);
+			if (t->child->flags & SHORTER)	/* reverse scan */
 				er = creviterdissect(v, t, begin, end);
 			else
 				er = citerdissect(v, t, begin, end);
 			break;
 		case '(':				/* capturing */
-			assert(t->left != NULL && t->right == NULL);
+			assert(t->child != NULL);
 			assert(t->subno > 0);
-			er = cdissect(v, t->left, begin, end);
+			er = cdissect(v, t->child, begin, end);
 			if (er == REG_OKAY)
 				subset(v, t, begin, end);
 			break;
@@ -765,19 +765,22 @@ ccondissect(struct vars *v,
 			chr *begin,			/* beginning of relevant substring */
 			chr *end)			/* end of same */
 {
+	struct subre *left = t->child;
+	struct subre *right = left->sibling;
 	struct dfa *d;
 	struct dfa *d2;
 	chr		   *mid;
 	int			er;
 
 	assert(t->op == '.');
-	assert(t->left != NULL && t->left->cnfa.nstates > 0);
-	assert(t->right != NULL && t->right->cnfa.nstates > 0);
-	assert(!(t->left->flags & SHORTER));
+	assert(left != NULL && left->cnfa.nstates > 0);
+	assert(right != NULL && right->cnfa.nstates > 0);
+	assert(right->sibling == NULL);
+	assert(!(left->flags & SHORTER));
 
-	d = getsubdfa(v, t->left);
+	d = getsubdfa(v, left);
 	NOERR();
-	d2 = getsubdfa(v, t->right);
+	d2 = getsubdfa(v, right);
 	NOERR();
 	MDEBUG(("cconcat %d\n", t->id));
 
@@ -794,10 +797,10 @@ ccondissect(struct vars *v,
 		/* try this midpoint on for size */
 		if (longest(v, d2, mid, end, (int *) NULL) == end)
 		{
-			er = cdissect(v, t->left, begin, mid);
+			er = cdissect(v, left, begin, mid);
 			if (er == REG_OKAY)
 			{
-				er = cdissect(v, t->right, mid, end);
+				er = cdissect(v, right, mid, end);
 				if (er == REG_OKAY)
 				{
 					/* satisfaction */
@@ -826,8 +829,8 @@ ccondissect(struct vars *v,
 			return REG_NOMATCH;
 		}
 		MDEBUG(("%d: new midpoint %ld\n", t->id, LOFF(mid)));
-		zaptreesubs(v, t->left);
-		zaptreesubs(v, t->right);
+		zaptreesubs(v, left);
+		zaptreesubs(v, right);
 	}
 
 	/* can't get here */
@@ -843,19 +846,22 @@ crevcondissect(struct vars *v,
 			   chr *begin,		/* beginning of relevant substring */
 			   chr *end)		/* end of same */
 {
+	struct subre *left = t->child;
+	struct subre *right = left->sibling;
 	struct dfa *d;
 	struct dfa *d2;
 	chr		   *mid;
 	int			er;
 
 	assert(t->op == '.');
-	assert(t->left != NULL && t->left->cnfa.nstates > 0);
-	assert(t->right != NULL && t->right->cnfa.nstates > 0);
-	assert(t->left->flags & SHORTER);
+	assert(left != NULL && left->cnfa.nstates > 0);
+	assert(right != NULL && right->cnfa.nstates > 0);
+	assert(right->sibling == NULL);
+	assert(left->flags & SHORTER);
 
-	d = getsubdfa(v, t->left);
+	d = getsubdfa(v, left);
 	NOERR();
-	d2 = getsubdfa(v, t->right);
+	d2 = getsubdfa(v, right);
 	NOERR();
 	MDEBUG(("crevcon %d\n", t->id));
 
@@ -872,10 +878,10 @@ crevcondissect(struct vars *v,
 		/* try this midpoint on for size */
 		if (longest(v, d2, mid, end, (int *) NULL) == end)
 		{
-			er = cdissect(v, t->left, begin, mid);
+			er = cdissect(v, left, begin, mid);
 			if (er == REG_OKAY)
 			{
-				er = cdissect(v, t->right, mid, end);
+				er = cdissect(v, right, mid, end);
 				if (er == REG_OKAY)
 				{
 					/* satisfaction */
@@ -904,8 +910,8 @@ crevcondissect(struct vars *v,
 			return REG_NOMATCH;
 		}
 		MDEBUG(("%d: new midpoint %ld\n", t->id, LOFF(mid)));
-		zaptreesubs(v, t->left);
-		zaptreesubs(v, t->right);
+		zaptreesubs(v, left);
+		zaptreesubs(v, right);
 	}
 
 	/* can't get here */
@@ -1005,26 +1011,30 @@ caltdissect(struct vars *v,
 	struct dfa *d;
 	int			er;
 
-	/* We loop, rather than tail-recurse, to handle a chain of alternatives */
+	assert(t->op == '|');
+
+	t = t->child;
+	/* there should be at least 2 alternatives */
+	assert(t != NULL && t->sibling != NULL);
+
 	while (t != NULL)
 	{
-		assert(t->op == '|');
-		assert(t->left != NULL && t->left->cnfa.nstates > 0);
+		assert(t->cnfa.nstates > 0);
 
 		MDEBUG(("calt n%d\n", t->id));
 
-		d = getsubdfa(v, t->left);
+		d = getsubdfa(v, t);
 		NOERR();
 		if (longest(v, d, begin, end, (int *) NULL) == end)
 		{
 			MDEBUG(("calt matched\n"));
-			er = cdissect(v, t->left, begin, end);
+			er = cdissect(v, t, begin, end);
 			if (er != REG_NOMATCH)
 				return er;
 		}
 		NOERR();
 
-		t = t->right;
+		t = t->sibling;
 	}
 
 	return REG_NOMATCH;
@@ -1050,8 +1060,8 @@ citerdissect(struct vars *v,
 	int			er;
 
 	assert(t->op == '*');
-	assert(t->left != NULL && t->left->cnfa.nstates > 0);
-	assert(!(t->left->flags & SHORTER));
+	assert(t->child != NULL && t->child->cnfa.nstates > 0);
+	assert(!(t->child->flags & SHORTER));
 	assert(begin <= end);
 
 	/*
@@ -1086,7 +1096,7 @@ citerdissect(struct vars *v,
 		return REG_ESPACE;
 	endpts[0] = begin;
 
-	d = getsubdfa(v, t->left);
+	d = getsubdfa(v, t->child);
 	if (ISERR())
 	{
 		FREE(endpts);
@@ -1165,8 +1175,8 @@ citerdissect(struct vars *v,
 
 		for (i = nverified + 1; i <= k; i++)
 		{
-			zaptreesubs(v, t->left);
-			er = cdissect(v, t->left, endpts[i - 1], endpts[i]);
+			zaptreesubs(v, t->child);
+			er = cdissect(v, t->child, endpts[i - 1], endpts[i]);
 			if (er == REG_OKAY)
 			{
 				nverified = i;
@@ -1251,8 +1261,8 @@ creviterdissect(struct vars *v,
 	int			er;
 
 	assert(t->op == '*');
-	assert(t->left != NULL && t->left->cnfa.nstates > 0);
-	assert(t->left->flags & SHORTER);
+	assert(t->child != NULL && t->child->cnfa.nstates > 0);
+	assert(t->child->flags & SHORTER);
 	assert(begin <= end);
 
 	/*
@@ -1287,7 +1297,7 @@ creviterdissect(struct vars *v,
 		return REG_ESPACE;
 	endpts[0] = begin;
 
-	d = getsubdfa(v, t->left);
+	d = getsubdfa(v, t->child);
 	if (ISERR())
 	{
 		FREE(endpts);
@@ -1372,8 +1382,8 @@ creviterdissect(struct vars *v,
 
 		for (i = nverified + 1; i <= k; i++)
 		{
-			zaptreesubs(v, t->left);
-			er = cdissect(v, t->left, endpts[i - 1], endpts[i]);
+			zaptreesubs(v, t->child);
+			er = cdissect(v, t->child, endpts[i - 1], endpts[i]);
 			if (er == REG_OKAY)
 			{
 				nverified = i;
diff --git a/src/include/regex/regguts.h b/src/include/regex/regguts.h
index 82e761bfe5..249c44982f 100644
--- a/src/include/regex/regguts.h
+++ b/src/include/regex/regguts.h
@@ -423,15 +423,17 @@ struct cnfa
  *		'='  plain regex without interesting substructure (implemented as DFA)
  *		'b'  back-reference (has no substructure either)
  *		'('  capture node: captures the match of its single child
- *		'.'  concatenation: matches a match for left, then a match for right
- *		'|'  alternation: matches a match for left or a match for right
+ *		'.'  concatenation: matches a match for first child, then second child
+ *		'|'  alternation: matches a match for any of its children
  *		'*'  iteration: matches some number of matches of its single child
  *
- * Note: the right child of an alternation must be another alternation or
- * NULL; hence, an N-way branch requires N alternation nodes, not N-1 as you
- * might expect.  This could stand to be changed.  Actually I'd rather see
- * a single alternation node with N children, but that will take revising
- * the representation of struct subre.
+ * An alternation node can have any number of children (but at least two),
+ * linked through their sibling fields.
+ *
+ * A concatenation node must have exactly two children.  It might be useful
+ * to support more, but that would complicate the executor.  Note that it is
+ * the first child's greediness that determines the node's preference for
+ * where to split a match.
  *
  * Note: when a backref is directly quantified, we stick the min/max counts
  * into the backref rather than plastering an iteration node on top.  This is
@@ -460,8 +462,8 @@ struct subre
 								 * LATYPE code for lookaround constraint */
 	short		min;			/* min repetitions for iteration or backref */
 	short		max;			/* max repetitions for iteration or backref */
-	struct subre *left;			/* left child, if any (also freelist chain) */
-	struct subre *right;		/* right child, if any */
+	struct subre *child;		/* first child, if any (also freelist chain) */
+	struct subre *sibling;		/* next child of same parent, if any */
 	struct state *begin;		/* outarcs from here... */
 	struct state *end;			/* ...ending in inarcs here */
 	struct cnfa cnfa;			/* compacted NFA, if any */

diff --git a/contrib/pg_trgm/trgm_regexp.c b/contrib/pg_trgm/trgm_regexp.c
index 1e4f0121f3..fcf03de32d 100644
--- a/contrib/pg_trgm/trgm_regexp.c
+++ b/contrib/pg_trgm/trgm_regexp.c
@@ -282,8 +282,8 @@ typedef struct
 typedef int TrgmColor;
 
 /* We assume that colors returned by the regexp engine cannot be these: */
-#define COLOR_UNKNOWN	(-1)
-#define COLOR_BLANK		(-2)
+#define COLOR_UNKNOWN	(-3)
+#define COLOR_BLANK		(-4)
 
 typedef struct
 {
@@ -780,7 +780,8 @@ getColorInfo(regex_t *regex, TrgmNFA *trgmNFA)
 		palloc0(colorsCount * sizeof(TrgmColorInfo));
 
 	/*
-	 * Loop over colors, filling TrgmColorInfo about each.
+	 * Loop over colors, filling TrgmColorInfo about each.  Note we include
+	 * WHITE (0) even though we know it'll be reported as non-expandable.
 	 */
 	for (i = 0; i < colorsCount; i++)
 	{
@@ -1098,9 +1099,9 @@ addKey(TrgmNFA *trgmNFA, TrgmState *state, TrgmStateKey *key)
 			/* Add enter key to this state */
 			addKeyToQueue(trgmNFA, &destKey);
 		}
-		else
+		else if (arc->co >= 0)
 		{
-			/* Regular color */
+			/* Regular color (including WHITE) */
 			TrgmColorInfo *colorInfo = &trgmNFA->colorInfo[arc->co];
 
 			if (colorInfo->expandable)
@@ -1156,6 +1157,14 @@ addKey(TrgmNFA *trgmNFA, TrgmState *state, TrgmStateKey *key)
 				addKeyToQueue(trgmNFA, &destKey);
 			}
 		}
+		else
+		{
+			/* RAINBOW: treat as unexpandable color */
+			destKey.prefix.colors[0] = COLOR_UNKNOWN;
+			destKey.prefix.colors[1] = COLOR_UNKNOWN;
+			destKey.nstate = arc->to;
+			addKeyToQueue(trgmNFA, &destKey);
+		}
 	}
 
 	pfree(arcs);
@@ -1216,10 +1225,10 @@ addArcs(TrgmNFA *trgmNFA, TrgmState *state)
 			/*
 			 * Ignore non-expandable colors; addKey already handled the case.
 			 *
-			 * We need no special check for begin/end pseudocolors here.  We
-			 * don't need to do any processing for them, and they will be
-			 * marked non-expandable since the regex engine will have reported
-			 * them that way.
+			 * We need no special check for WHITE or begin/end pseudocolors
+			 * here.  We don't need to do any processing for them, and they
+			 * will be marked non-expandable since the regex engine will have
+			 * reported them that way.
 			 */
 			if (!colorInfo->expandable)
 				continue;
diff --git a/src/backend/regex/README b/src/backend/regex/README
index f08aab69e3..a83ab5074d 100644
--- a/src/backend/regex/README
+++ b/src/backend/regex/README
@@ -261,6 +261,18 @@ and the NFA has these arcs:
 	states 4 -> 5 on color 2 ("x" only)
 which can be seen to be a correct representation of the regex.
 
+There is one more complexity, which is how to handle ".", that is a
+match-anything atom.  We used to do that by generating a "rainbow"
+of arcs of all live colors between the two NFA states before and after
+the dot.  That's expensive in itself when there are lots of colors,
+and it also typically adds lots of follow-on arc-splitting work for the
+color splitting logic.  Now we handle this case by generating a single arc
+labeled with the special color RAINBOW, meaning all colors.  Such arcs
+never need to be split, so they help keep NFAs small in this common case.
+(Note: this optimization doesn't help in REG_NLSTOP mode, where "." is
+not supposed to match newline.  In that case we still handle "." by
+generating an almost-rainbow of all colors except newline's color.)
+
 Given this summary, we can see we need the following operations for
 colors:
 
@@ -349,6 +361,8 @@ The possible arc types are:
 
     PLAIN arcs, which specify matching of any character of a given "color"
     (see above).  These are dumped as "[color_number]->to_state".
+    In addition there can be "rainbow" PLAIN arcs, which are dumped as
+    "[*]->to_state".
 
     EMPTY arcs, which specify a no-op transition to another state.  These
     are dumped as "->to_state".
@@ -356,11 +370,11 @@ The possible arc types are:
     AHEAD constraints, which represent a "next character must be of this
     color" constraint.  AHEAD differs from a PLAIN arc in that the input
     character is not consumed when crossing the arc.  These are dumped as
-    ">color_number>->to_state".
+    ">color_number>->to_state", or possibly ">*>->to_state".
 
     BEHIND constraints, which represent a "previous character must be of
     this color" constraint, which likewise consumes no input.  These are
-    dumped as "<color_number<->to_state".
+    dumped as "<color_number<->to_state", or possibly "<*<->to_state".
 
     '^' arcs, which specify a beginning-of-input constraint.  These are
     dumped as "^0->to_state" or "^1->to_state" for beginning-of-string and
@@ -396,14 +410,20 @@ substring, or an imaginary following EOS character if the substring is at
 the end of the input.
 3. If the NFA is (or can be) in the goal state at this point, it matches.
 
+This definition is necessary to support regexes that begin or end with
+constraints such as \m and \M, which imply requirements on the adjacent
+character if any.  The executor implements that by checking if the
+adjacent character (or BOS/BOL/EOS/EOL pseudo-character) is of the
+right color, and it does that in the same loop that checks characters
+within the match.
+
 So one can mentally execute an untransformed NFA by taking ^ and $ as
 ordinary constraints that match at start and end of input; but plain
 arcs out of the start state should be taken as matches for the character
 before the target substring, and similarly, plain arcs leading to the
 post state are matches for the character after the target substring.
-This definition is necessary to support regexes that begin or end with
-constraints such as \m and \M, which imply requirements on the adjacent
-character if any.  NFAs for simple unanchored patterns will usually have
-pre-state outarcs for all possible character colors as well as BOS and
-BOL, and post-state inarcs for all possible character colors as well as
-EOS and EOL, so that the executor's behavior will work.
+After the optimize() transformation, there are explicit arcs mentioning
+BOS/BOL/EOS/EOL adjacent to the pre-state and post-state.  So a finished
+NFA for a pattern without anchors or adjacent-character constraints will
+have pre-state outarcs for RAINBOW (all possible character colors) as well
+as BOS and BOL, and likewise post-state inarcs for RAINBOW, EOS, and EOL.
diff --git a/src/backend/regex/regc_color.c b/src/backend/regex/regc_color.c
index f5a4151757..0864011cce 100644
--- a/src/backend/regex/regc_color.c
+++ b/src/backend/regex/regc_color.c
@@ -977,6 +977,7 @@ colorchain(struct colormap *cm,
 {
 	struct colordesc *cd = &cm->cd[a->co];
 
+	assert(a->co >= 0);
 	if (cd->arcs != NULL)
 		cd->arcs->colorchainRev = a;
 	a->colorchain = cd->arcs;
@@ -994,6 +995,7 @@ uncolorchain(struct colormap *cm,
 	struct colordesc *cd = &cm->cd[a->co];
 	struct arc *aa = a->colorchainRev;
 
+	assert(a->co >= 0);
 	if (aa == NULL)
 	{
 		assert(cd->arcs == a);
@@ -1012,6 +1014,9 @@ uncolorchain(struct colormap *cm,
 
 /*
  * rainbow - add arcs of all full colors (but one) between specified states
+ *
+ * If there isn't an exception color, we now generate just a single arc
+ * labeled RAINBOW, saving lots of arc-munging later on.
  */
 static void
 rainbow(struct nfa *nfa,
@@ -1025,6 +1030,13 @@ rainbow(struct nfa *nfa,
 	struct colordesc *end = CDEND(cm);
 	color		co;
 
+	if (but == COLORLESS)
+	{
+		newarc(nfa, type, RAINBOW, from, to);
+		return;
+	}
+
+	/* Gotta do it the hard way.  Skip subcolors, pseudocolors, and "but" */
 	for (cd = cm->cd, co = 0; cd < end && !CISERR(); cd++, co++)
 		if (!UNUSEDCOLOR(cd) && cd->sub != co && co != but &&
 			!(cd->flags & PSEUDO))
@@ -1034,13 +1046,16 @@ rainbow(struct nfa *nfa,
 /*
  * colorcomplement - add arcs of complementary colors
  *
+ * We add arcs of all colors that are not pseudocolors and do not match
+ * any of the "of" state's PLAIN outarcs.
+ *
  * The calling sequence ought to be reconciled with cloneouts().
  */
 static void
 colorcomplement(struct nfa *nfa,
 				struct colormap *cm,
 				int type,
-				struct state *of,	/* complements of this guy's PLAIN outarcs */
+				struct state *of,
 				struct state *from,
 				struct state *to)
 {
@@ -1049,6 +1064,11 @@ colorcomplement(struct nfa *nfa,
 	color		co;
 
 	assert(of != from);
+
+	/* A RAINBOW arc matches all colors, making the complement empty */
+	if (findarc(of, PLAIN, RAINBOW) != NULL)
+		return;
+
 	for (cd = cm->cd, co = 0; cd < end && !CISERR(); cd++, co++)
 		if (!UNUSEDCOLOR(cd) && !(cd->flags & PSEUDO))
 			if (findarc(of, PLAIN, co) == NULL)
diff --git a/src/backend/regex/regc_nfa.c b/src/backend/regex/regc_nfa.c
index 7ed675f88a..ff98bfd694 100644
--- a/src/backend/regex/regc_nfa.c
+++ b/src/backend/regex/regc_nfa.c
@@ -271,6 +271,11 @@ destroystate(struct nfa *nfa,
  *
  * This function checks to make sure that no duplicate arcs are created.
  * In general we never want duplicates.
+ *
+ * However: in principle, a RAINBOW arc is redundant with any plain arc
+ * (unless that arc is for a pseudocolor).  But we don't try to recognize
+ * that redundancy, either here or in allied operations such as moveins().
+ * The pseudocolor consideration makes that more costly than it seems worth.
  */
 static void
 newarc(struct nfa *nfa,
@@ -1170,6 +1175,9 @@ copyouts(struct nfa *nfa,
 
 /*
  * cloneouts - copy out arcs of a state to another state pair, modifying type
+ *
+ * This is only used to convert PLAIN arcs to AHEAD/BEHIND arcs, which share
+ * the same interpretation of "co".  It wouldn't be sensible with LACONs.
  */
 static void
 cloneouts(struct nfa *nfa,
@@ -1181,9 +1189,13 @@ cloneouts(struct nfa *nfa,
 	struct arc *a;
 
 	assert(old != from);
+	assert(type == AHEAD || type == BEHIND);
 
 	for (a = old->outs; a != NULL; a = a->outchain)
+	{
+		assert(a->type == PLAIN);
 		newarc(nfa, type, a->co, from, to);
+	}
 }
 
 /*
@@ -1597,7 +1609,7 @@ pull(struct nfa *nfa,
 	for (a = from->ins; a != NULL && !NISERR(); a = nexta)
 	{
 		nexta = a->inchain;
-		switch (combine(con, a))
+		switch (combine(nfa, con, a))
 		{
 			case INCOMPATIBLE:	/* destroy the arc */
 				freearc(nfa, a);
@@ -1624,6 +1636,10 @@ pull(struct nfa *nfa,
 				cparc(nfa, a, s, to);
 				freearc(nfa, a);
 				break;
+			case REPLACEARC:	/* replace arc's color */
+				newarc(nfa, a->type, con->co, a->from, to);
+				freearc(nfa, a);
+				break;
 			default:
 				assert(NOTREACHED);
 				break;
@@ -1764,7 +1780,7 @@ push(struct nfa *nfa,
 	for (a = to->outs; a != NULL && !NISERR(); a = nexta)
 	{
 		nexta = a->outchain;
-		switch (combine(con, a))
+		switch (combine(nfa, con, a))
 		{
 			case INCOMPATIBLE:	/* destroy the arc */
 				freearc(nfa, a);
@@ -1791,6 +1807,10 @@ push(struct nfa *nfa,
 				cparc(nfa, a, from, s);
 				freearc(nfa, a);
 				break;
+			case REPLACEARC:	/* replace arc's color */
+				newarc(nfa, a->type, con->co, from, a->to);
+				freearc(nfa, a);
+				break;
 			default:
 				assert(NOTREACHED);
 				break;
@@ -1810,9 +1830,11 @@ push(struct nfa *nfa,
  * #def INCOMPATIBLE	1	// destroys arc
  * #def SATISFIED		2	// constraint satisfied
  * #def COMPATIBLE		3	// compatible but not satisfied yet
+ * #def REPLACEARC		4	// replace arc's color with constraint color
  */
 static int
-combine(struct arc *con,
+combine(struct nfa *nfa,
+		struct arc *con,
 		struct arc *a)
 {
 #define  CA(ct,at)	 (((ct)<<CHAR_BIT) | (at))
@@ -1827,14 +1849,46 @@ combine(struct arc *con,
 		case CA(BEHIND, PLAIN):
 			if (con->co == a->co)
 				return SATISFIED;
+			if (con->co == RAINBOW)
+			{
+				/* con is satisfied unless arc's color is a pseudocolor */
+				if (!(nfa->cm->cd[a->co].flags & PSEUDO))
+					return SATISFIED;
+			}
+			else if (a->co == RAINBOW)
+			{
+				/* con is incompatible if it's for a pseudocolor */
+				if (nfa->cm->cd[con->co].flags & PSEUDO)
+					return INCOMPATIBLE;
+				/* otherwise, constraint constrains arc to be only its color */
+				return REPLACEARC;
+			}
 			return INCOMPATIBLE;
 			break;
 		case CA('^', '^'):		/* collision, similar constraints */
 		case CA('$', '$'):
-		case CA(AHEAD, AHEAD):
+			if (con->co == a->co)	/* true duplication */
+				return SATISFIED;
+			return INCOMPATIBLE;
+			break;
+		case CA(AHEAD, AHEAD):	/* collision, similar constraints */
 		case CA(BEHIND, BEHIND):
 			if (con->co == a->co)	/* true duplication */
 				return SATISFIED;
+			if (con->co == RAINBOW)
+			{
+				/* con is satisfied unless arc's color is a pseudocolor */
+				if (!(nfa->cm->cd[a->co].flags & PSEUDO))
+					return SATISFIED;
+			}
+			else if (a->co == RAINBOW)
+			{
+				/* con is incompatible if it's for a pseudocolor */
+				if (nfa->cm->cd[con->co].flags & PSEUDO)
+					return INCOMPATIBLE;
+				/* otherwise, constraint constrains arc to be only its color */
+				return REPLACEARC;
+			}
 			return INCOMPATIBLE;
 			break;
 		case CA('^', BEHIND):	/* collision, dissimilar constraints */
@@ -2895,6 +2949,7 @@ compact(struct nfa *nfa,
 					break;
 				case LACON:
 					assert(s->no != cnfa->pre);
+					assert(a->co >= 0);
 					ca->co = (color) (cnfa->ncolors + a->co);
 					ca->to = a->to->no;
 					ca++;
@@ -3068,13 +3123,22 @@ dumparc(struct arc *a,
 	switch (a->type)
 	{
 		case PLAIN:
-			fprintf(f, "[%ld]", (long) a->co);
+			if (a->co == RAINBOW)
+				fprintf(f, "[*]");
+			else
+				fprintf(f, "[%ld]", (long) a->co);
 			break;
 		case AHEAD:
-			fprintf(f, ">%ld>", (long) a->co);
+			if (a->co == RAINBOW)
+				fprintf(f, ">*>");
+			else
+				fprintf(f, ">%ld>", (long) a->co);
 			break;
 		case BEHIND:
-			fprintf(f, "<%ld<", (long) a->co);
+			if (a->co == RAINBOW)
+				fprintf(f, "<*<");
+			else
+				fprintf(f, "<%ld<", (long) a->co);
 			break;
 		case LACON:
 			fprintf(f, ":%ld:", (long) a->co);
@@ -3161,7 +3225,9 @@ dumpcstate(int st,
 	pos = 1;
 	for (ca = cnfa->states[st]; ca->co != COLORLESS; ca++)
 	{
-		if (ca->co < cnfa->ncolors)
+		if (ca->co == RAINBOW)
+			fprintf(f, "\t[*]->%d", ca->to);
+		else if (ca->co < cnfa->ncolors)
 			fprintf(f, "\t[%ld]->%d", (long) ca->co, ca->to);
 		else
 			fprintf(f, "\t:%ld:->%d", (long) (ca->co - cnfa->ncolors), ca->to);
diff --git a/src/backend/regex/regcomp.c b/src/backend/regex/regcomp.c
index cd0caaa2d0..ae8dbe5819 100644
--- a/src/backend/regex/regcomp.c
+++ b/src/backend/regex/regcomp.c
@@ -158,7 +158,8 @@ static int	push(struct nfa *, struct arc *, struct state **);
 #define INCOMPATIBLE	1		/* destroys arc */
 #define SATISFIED	2			/* constraint satisfied */
 #define COMPATIBLE	3			/* compatible but not satisfied yet */
-static int	combine(struct arc *, struct arc *);
+#define REPLACEARC	4			/* replace arc's color with constraint color */
+static int	combine(struct nfa *nfa, struct arc *con, struct arc *a);
 static void fixempties(struct nfa *, FILE *);
 static struct state *emptyreachable(struct nfa *, struct state *,
 									struct state *, struct arc **);
@@ -289,9 +290,11 @@ struct vars
 #define SBEGIN	'A'				/* beginning of string (even if not BOL) */
 #define SEND	'Z'				/* end of string (even if not EOL) */
 
-/* is an arc colored, and hence on a color chain? */
+/* is an arc colored, and hence should belong to a color chain? */
+/* the test on "co" eliminates RAINBOW arcs, which we don't bother to chain */
 #define COLORED(a) \
-	((a)->type == PLAIN || (a)->type == AHEAD || (a)->type == BEHIND)
+	((a)->co >= 0 && \
+	 ((a)->type == PLAIN || (a)->type == AHEAD || (a)->type == BEHIND))
 
 
 /* static function list */
@@ -1393,7 +1396,8 @@ bracket(struct vars *v,
  * cbracket - handle complemented bracket expression
  * We do it by calling bracket() with dummy endpoints, and then complementing
  * the result.  The alternative would be to invoke rainbow(), and then delete
- * arcs as the b.e. is seen... but that gets messy.
+ * arcs as the b.e. is seen... but that gets messy, and is really quite
+ * infeasible now that rainbow() just puts out one RAINBOW arc.
  */
 static void
 cbracket(struct vars *v,
diff --git a/src/backend/regex/rege_dfa.c b/src/backend/regex/rege_dfa.c
index 5695e158a5..32be2592c5 100644
--- a/src/backend/regex/rege_dfa.c
+++ b/src/backend/regex/rege_dfa.c
@@ -612,6 +612,7 @@ miss(struct vars *v,
 	unsigned	h;
 	struct carc *ca;
 	struct sset *p;
+	int			ispseudocolor;
 	int			ispost;
 	int			noprogress;
 	int			gotstate;
@@ -643,13 +644,15 @@ miss(struct vars *v,
 	 */
 	for (i = 0; i < d->wordsper; i++)
 		d->work[i] = 0;			/* build new stateset bitmap in d->work */
+	ispseudocolor = d->cm->cd[co].flags & PSEUDO;
 	ispost = 0;
 	noprogress = 1;
 	gotstate = 0;
 	for (i = 0; i < d->nstates; i++)
 		if (ISBSET(css->states, i))
 			for (ca = cnfa->states[i]; ca->co != COLORLESS; ca++)
-				if (ca->co == co)
+				if (ca->co == co ||
+					(ca->co == RAINBOW && !ispseudocolor))
 				{
 					BSET(d->work, ca->to);
 					gotstate = 1;
diff --git a/src/backend/regex/regexport.c b/src/backend/regex/regexport.c
index d4f940b8c3..a493dbe88c 100644
--- a/src/backend/regex/regexport.c
+++ b/src/backend/regex/regexport.c
@@ -222,7 +222,8 @@ pg_reg_colorisend(const regex_t *regex, int co)
  * Get number of member chrs of color number "co".
  *
  * Note: we return -1 if the color number is invalid, or if it is a special
- * color (WHITE or a pseudocolor), or if the number of members is uncertain.
+ * color (WHITE, RAINBOW, or a pseudocolor), or if the number of members is
+ * uncertain.
  * Callers should not try to extract the members if -1 is returned.
  */
 int
@@ -233,7 +234,7 @@ pg_reg_getnumcharacters(const regex_t *regex, int co)
 	assert(regex != NULL && regex->re_magic == REMAGIC);
 	cm = &((struct guts *) regex->re_guts)->cmap;
 
-	if (co <= 0 || co > cm->max)	/* we reject 0 which is WHITE */
+	if (co <= 0 || co > cm->max)	/* <= 0 rejects WHITE and RAINBOW */
 		return -1;
 	if (cm->cd[co].flags & PSEUDO)	/* also pseudocolors (BOS etc) */
 		return -1;
@@ -257,7 +258,7 @@ pg_reg_getnumcharacters(const regex_t *regex, int co)
  * whose length chars_len must be at least as long as indicated by
  * pg_reg_getnumcharacters(), else not all chars will be returned.
  *
- * Fetching the members of WHITE or a pseudocolor is not supported.
+ * Fetching the members of WHITE, RAINBOW, or a pseudocolor is not supported.
  *
  * Caution: this is a relatively expensive operation.
  */
diff --git a/src/backend/regex/regprefix.c b/src/backend/regex/regprefix.c
index 1d4593ac94..e2fbad7a8a 100644
--- a/src/backend/regex/regprefix.c
+++ b/src/backend/regex/regprefix.c
@@ -165,9 +165,13 @@ findprefix(struct cnfa *cnfa,
 			/* We can ignore BOS/BOL arcs */
 			if (ca->co == cnfa->bos[0] || ca->co == cnfa->bos[1])
 				continue;
-			/* ... but EOS/EOL arcs terminate the search, as do LACONs */
+
+			/*
+			 * ... but EOS/EOL arcs terminate the search, as do RAINBOW arcs
+			 * and LACONs
+			 */
 			if (ca->co == cnfa->eos[0] || ca->co == cnfa->eos[1] ||
-				ca->co >= cnfa->ncolors)
+				ca->co == RAINBOW || ca->co >= cnfa->ncolors)
 			{
 				thiscolor = COLORLESS;
 				break;
diff --git a/src/include/regex/regexport.h b/src/include/regex/regexport.h
index e6209463f7..99c4fb854e 100644
--- a/src/include/regex/regexport.h
+++ b/src/include/regex/regexport.h
@@ -30,6 +30,10 @@
 
 #include "regex/regex.h"
 
+/* These macros must match corresponding ones in regguts.h: */
+#define COLOR_WHITE		0		/* color for chars not appearing in regex */
+#define COLOR_RAINBOW	(-2)	/* represents all colors except pseudocolors */
+
 /* information about one arc of a regex's NFA */
 typedef struct
 {
diff --git a/src/include/regex/regguts.h b/src/include/regex/regguts.h
index 0a616562d0..6d39108319 100644
--- a/src/include/regex/regguts.h
+++ b/src/include/regex/regguts.h
@@ -130,11 +130,16 @@
 /*
  * As soon as possible, we map chrs into equivalence classes -- "colors" --
  * which are of much more manageable number.
+ *
+ * To further reduce the number of arcs in NFAs and DFAs, we also have a
+ * special RAINBOW "color" that can be assigned to an arc.  This is not a
+ * real color, in that it has no entry in color maps.
  */
 typedef short color;			/* colors of characters */
 
 #define MAX_COLOR	32767		/* max color (must fit in 'color' datatype) */
 #define COLORLESS	(-1)		/* impossible color */
+#define RAINBOW		(-2)		/* represents all colors except pseudocolors */
 #define WHITE		0			/* default color, parent of all others */
 /* Note: various places in the code know that WHITE is zero */
 
@@ -276,7 +281,7 @@ struct state;
 struct arc
 {
 	int			type;			/* 0 if free, else an NFA arc type code */
-	color		co;
+	color		co;				/* color the arc matches (possibly RAINBOW) */
 	struct state *from;			/* where it's from (and contained within) */
 	struct state *to;			/* where it's to */
 	struct arc *outchain;		/* link in *from's outs chain or free chain */
@@ -284,6 +289,7 @@ struct arc
 #define  freechain	outchain	/* we do not maintain "freechainRev" */
 	struct arc *inchain;		/* link in *to's ins chain */
 	struct arc *inchainRev;		/* back-link in *to's ins chain */
+	/* these fields are not used when co == RAINBOW: */
 	struct arc *colorchain;		/* link in color's arc chain */
 	struct arc *colorchainRev;	/* back-link in color's arc chain */
 };
@@ -344,6 +350,9 @@ struct nfa
  * Plain arcs just store the transition color number as "co".  LACON arcs
  * store the lookaround constraint number plus cnfa.ncolors as "co".  LACON
  * arcs can be distinguished from plain by testing for co >= cnfa.ncolors.
+ *
+ * Note that in a plain arc, "co" can be RAINBOW; since that's negative,
+ * it doesn't break the rule about how to recognize LACON arcs.
  */
 struct carc
 {

diff --git a/src/backend/regex/regc_nfa.c b/src/backend/regex/regc_nfa.c
index ff98bfd694..1a6c9ce183 100644
--- a/src/backend/regex/regc_nfa.c
+++ b/src/backend/regex/regc_nfa.c
@@ -65,6 +65,8 @@ newnfa(struct vars *v,
 	nfa->v = v;
 	nfa->bos[0] = nfa->bos[1] = COLORLESS;
 	nfa->eos[0] = nfa->eos[1] = COLORLESS;
+	nfa->flags = 0;
+	nfa->minmatchall = nfa->maxmatchall = -1;
 	nfa->parent = parent;		/* Precedes newfstate so parent is valid. */
 	nfa->post = newfstate(nfa, '@');	/* number 0 */
 	nfa->pre = newfstate(nfa, '>'); /* number 1 */
@@ -2875,8 +2877,14 @@ analyze(struct nfa *nfa)
 	if (NISERR())
 		return 0;
 
+	/* Detect whether NFA can't match anything */
 	if (nfa->pre->outs == NULL)
 		return REG_UIMPOSSIBLE;
+
+	/* Detect whether NFA matches all strings (possibly with length bounds) */
+	checkmatchall(nfa);
+
+	/* Detect whether NFA can possibly match a zero-length string */
 	for (a = nfa->pre->outs; a != NULL; a = a->outchain)
 		for (aa = a->to->outs; aa != NULL; aa = aa->outchain)
 			if (aa->to == nfa->post)
@@ -2884,6 +2892,282 @@ analyze(struct nfa *nfa)
 	return 0;
 }
 
+/*
+ * checkmatchall - does the NFA represent no more than a string length test?
+ *
+ * If so, set nfa->minmatchall and nfa->maxmatchall correctly (they are -1
+ * to begin with) and set the MATCHALL bit in nfa->flags.
+ *
+ * To succeed, we require all arcs to be PLAIN RAINBOW arcs, except for those
+ * for pseudocolors (i.e., BOS/BOL/EOS/EOL).  We must be able to reach the
+ * post state via RAINBOW arcs, and if there are any loops in the graph, they
+ * must be loop-to-self arcs, ensuring that each loop iteration consumes
+ * exactly one character.  (Longer loops are problematic because they create
+ * non-consecutive possible match lengths; we have no good way to represent
+ * that situation for lengths beyond the DUPINF limit.)
+ *
+ * Pseudocolor arcs complicate things a little.  We know that they can only
+ * appear as pre-state outarcs (for BOS/BOL) or post-state inarcs (for
+ * EOS/EOL).  There, they must exactly replicate the parallel RAINBOW arcs,
+ * e.g. if the pre state has one RAINBOW outarc to state 2, it must have BOS
+ * and BOL outarcs to state 2, and no others.  Missing or extra pseudocolor
+ * arcs can occur, meaning that the NFA involves some constraint on the
+ * adjacent characters, which makes it not a matchall NFA.
+ */
+static void
+checkmatchall(struct nfa *nfa)
+{
+	bool		hasmatch[DUPINF + 1];
+	int			minmatch,
+				maxmatch,
+				morematch;
+
+	/*
+	 * hasmatch[i] will be set true if a match of length i is feasible, for i
+	 * from 0 to DUPINF-1.  hasmatch[DUPINF] will be set true if every match
+	 * length of DUPINF or more is feasible.
+	 */
+	memset(hasmatch, 0, sizeof(hasmatch));
+
+	/*
+	 * Recursively search the graph for all-RAINBOW paths to the "post" state,
+	 * starting at the "pre" state.  The -1 initial depth accounts for the
+	 * fact that transitions out of the "pre" state are not part of the
+	 * matched string.  We likewise don't count the final transition to the
+	 * "post" state as part of the match length.  (But we still insist that
+	 * those transitions have RAINBOW arcs, otherwise there are lookbehind or
+	 * lookahead constraints at the start/end of the pattern.)
+	 */
+	if (!checkmatchall_recurse(nfa, nfa->pre, false, -1, hasmatch))
+		return;
+
+	/*
+	 * We found some all-RAINBOW paths, and not anything that we couldn't
+	 * handle.  Now verify that pseudocolor arcs adjacent to the pre and post
+	 * states match the RAINBOW arcs there.  (We could do this while
+	 * recursing, but it's expensive and unlikely to fail, so do it last.)
+	 */
+	if (!check_out_colors_match(nfa->pre, RAINBOW, nfa->bos[0]) ||
+		!check_out_colors_match(nfa->pre, nfa->bos[0], RAINBOW) ||
+		!check_out_colors_match(nfa->pre, RAINBOW, nfa->bos[1]) ||
+		!check_out_colors_match(nfa->pre, nfa->bos[1], RAINBOW))
+		return;
+	if (!check_in_colors_match(nfa->post, RAINBOW, nfa->eos[0]) ||
+		!check_in_colors_match(nfa->post, nfa->eos[0], RAINBOW) ||
+		!check_in_colors_match(nfa->post, RAINBOW, nfa->eos[1]) ||
+		!check_in_colors_match(nfa->post, nfa->eos[1], RAINBOW))
+		return;
+
+	/*
+	 * hasmatch[] now represents the set of possible match lengths; but we
+	 * want to reduce that to a min and max value, because it doesn't seem
+	 * worth complicating regexec.c to deal with nonconsecutive possible match
+	 * lengths.  Find min and max of first run of lengths, then verify there
+	 * are no nonconsecutive lengths.
+	 */
+	for (minmatch = 0; minmatch <= DUPINF; minmatch++)
+	{
+		if (hasmatch[minmatch])
+			break;
+	}
+	assert(minmatch <= DUPINF); /* else checkmatchall_recurse lied */
+	for (maxmatch = minmatch; maxmatch < DUPINF; maxmatch++)
+	{
+		if (!hasmatch[maxmatch + 1])
+			break;
+	}
+	for (morematch = maxmatch + 1; morematch <= DUPINF; morematch++)
+	{
+		if (hasmatch[morematch])
+			return;				/* fail, there are nonconsecutive lengths */
+	}
+
+	/* Success, so record the info */
+	nfa->minmatchall = minmatch;
+	nfa->maxmatchall = maxmatch;
+	nfa->flags |= MATCHALL;
+}
+
+/*
+ * checkmatchall_recurse - recursive search for checkmatchall
+ *
+ * s is the current state
+ * foundloop is true if any predecessor state has a loop-to-self
+ * depth is the current recursion depth (starting at -1)
+ * hasmatch[] is the output area for recording feasible match lengths
+ *
+ * We return true if there is at least one all-RAINBOW path to the "post"
+ * state and no non-matchall paths; otherwise false.  Note we assume that
+ * any dead-end paths have already been removed, else we might return
+ * false unnecessarily.
+ */
+static bool
+checkmatchall_recurse(struct nfa *nfa, struct state *s,
+					  bool foundloop, int depth,
+					  bool *hasmatch)
+{
+	bool		result = false;
+	struct arc *a;
+
+	/*
+	 * Since this is recursive, it could be driven to stack overflow.  But we
+	 * need not treat that as a hard failure; just deem the NFA non-matchall.
+	 */
+	if (STACK_TOO_DEEP(nfa->v->re))
+		return false;
+
+	/*
+	 * Likewise, if we get to a depth too large to represent correctly in
+	 * maxmatchall, fail quietly.
+	 */
+	if (depth >= DUPINF)
+		return false;
+
+	/*
+	 * Scan the outarcs to detect cases we can't handle, and to see if there
+	 * is a loop-to-self here.  We need to know about any such loop before we
+	 * recurse, so it's hard to avoid making two passes over the outarcs.  In
+	 * any case, checking for showstoppers before we recurse is probably best.
+	 */
+	for (a = s->outs; a != NULL; a = a->outchain)
+	{
+		if (a->type != PLAIN)
+			return false;		/* any LACONs make it non-matchall */
+		if (a->co != RAINBOW)
+		{
+			if (nfa->cm->cd[a->co].flags & PSEUDO)
+			{
+				/*
+				 * Pseudocolor arc: verify it's in a valid place (this seems
+				 * quite unlikely to fail, but let's be sure).
+				 */
+				if (s == nfa->pre &&
+					(a->co == nfa->bos[0] || a->co == nfa->bos[1]))
+					 /* okay BOS/BOL arc */ ;
+				else if (a->to == nfa->post &&
+						 (a->co == nfa->eos[0] || a->co == nfa->eos[1]))
+					 /* okay EOS/EOL arc */ ;
+				else
+					return false;	/* unexpected pseudocolor arc */
+				/* We'll finish checking these arcs after the recursion */
+				continue;
+			}
+			return false;		/* any other color makes it non-matchall */
+		}
+		if (a->to == s)
+		{
+			/*
+			 * We found a cycle of length 1, so remember that to pass down to
+			 * successor states.  (It doesn't matter if there was also such a
+			 * loop at a predecessor state.)
+			 */
+			foundloop = true;
+		}
+		else if (a->to->tmp)
+		{
+			/* We found a cycle of length > 1, so fail. */
+			return false;
+		}
+	}
+
+	/* We need to recurse, so mark state as under consideration */
+	assert(s->tmp == NULL);
+	s->tmp = s;
+
+	for (a = s->outs; a != NULL; a = a->outchain)
+	{
+		if (a->co != RAINBOW)
+			continue;			/* ignore pseudocolor arcs */
+		if (a->to == nfa->post)
+		{
+			/* We found an all-RAINBOW path to the post state */
+			result = true;
+			/* Record potential match lengths */
+			assert(depth >= 0);
+			hasmatch[depth] = true;
+			if (foundloop)
+			{
+				/* A predecessor loop makes all larger lengths match, too */
+				int			i;
+
+				for (i = depth + 1; i <= DUPINF; i++)
+					hasmatch[i] = true;
+			}
+		}
+		else if (a->to != s)
+		{
+			/* This is a new path forward; recurse to investigate */
+			result = checkmatchall_recurse(nfa, a->to,
+										   foundloop, depth + 1,
+										   hasmatch);
+			/* Fail if any recursive path fails */
+			if (!result)
+				break;
+		}
+	}
+
+	s->tmp = NULL;
+	return result;
+}
+
+/*
+ * check_out_colors_match - subroutine for checkmatchall
+ *
+ * Check if every s outarc of color co1 has a matching outarc of color co2.
+ * (checkmatchall_recurse already verified that all of the outarcs are PLAIN,
+ * so we need not examine arc types here.  Also, since it verified that there
+ * are only RAINBOW and pseudocolor arcs, there shouldn't be enough arcs for
+ * this brute-force O(N^2) implementation to cause problems.)
+ */
+static bool
+check_out_colors_match(struct state *s, color co1, color co2)
+{
+	struct arc *a1;
+	struct arc *a2;
+
+	for (a1 = s->outs; a1 != NULL; a1 = a1->outchain)
+	{
+		if (a1->co != co1)
+			continue;
+		for (a2 = s->outs; a2 != NULL; a2 = a2->outchain)
+		{
+			if (a2->co == co2 && a2->to == a1->to)
+				break;
+		}
+		if (a2 == NULL)
+			return false;
+	}
+	return true;
+}
+
+/*
+ * check_in_colors_match - subroutine for checkmatchall
+ *
+ * Check if every s inarc of color co1 has a matching inarc of color co2.
+ * (For paranoia's sake, ignore any non-PLAIN arcs here.  But we're still
+ * not expecting very many arcs.)
+ */
+static bool
+check_in_colors_match(struct state *s, color co1, color co2)
+{
+	struct arc *a1;
+	struct arc *a2;
+
+	for (a1 = s->ins; a1 != NULL; a1 = a1->inchain)
+	{
+		if (a1->type != PLAIN || a1->co != co1)
+			continue;
+		for (a2 = s->ins; a2 != NULL; a2 = a2->inchain)
+		{
+			if (a2->type == PLAIN && a2->co == co2 && a2->from == a1->from)
+				break;
+		}
+		if (a2 == NULL)
+			return false;
+	}
+	return true;
+}
+
 /*
  * compact - construct the compact representation of an NFA
  */
@@ -2930,7 +3214,9 @@ compact(struct nfa *nfa,
 	cnfa->eos[0] = nfa->eos[0];
 	cnfa->eos[1] = nfa->eos[1];
 	cnfa->ncolors = maxcolor(nfa->cm) + 1;
-	cnfa->flags = 0;
+	cnfa->flags = nfa->flags;
+	cnfa->minmatchall = nfa->minmatchall;
+	cnfa->maxmatchall = nfa->maxmatchall;
 
 	ca = cnfa->arcs;
 	for (s = nfa->states; s != NULL; s = s->next)
@@ -3034,6 +3320,11 @@ dumpnfa(struct nfa *nfa,
 		fprintf(f, ", eos [%ld]", (long) nfa->eos[0]);
 	if (nfa->eos[1] != COLORLESS)
 		fprintf(f, ", eol [%ld]", (long) nfa->eos[1]);
+	if (nfa->flags & HASLACONS)
+		fprintf(f, ", haslacons");
+	if (nfa->flags & MATCHALL)
+		fprintf(f, ", minmatchall %d, maxmatchall %d",
+				nfa->minmatchall, nfa->maxmatchall);
 	fprintf(f, "\n");
 	for (s = nfa->states; s != NULL; s = s->next)
 	{
@@ -3201,6 +3492,9 @@ dumpcnfa(struct cnfa *cnfa,
 		fprintf(f, ", eol [%ld]", (long) cnfa->eos[1]);
 	if (cnfa->flags & HASLACONS)
 		fprintf(f, ", haslacons");
+	if (cnfa->flags & MATCHALL)
+		fprintf(f, ", minmatchall %d, maxmatchall %d",
+				cnfa->minmatchall, 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 ae8dbe5819..39e837adc2 100644
--- a/src/backend/regex/regcomp.c
+++ b/src/backend/regex/regcomp.c
@@ -175,6 +175,11 @@ static void cleanup(struct nfa *);
 static void markreachable(struct nfa *, struct state *, struct state *, struct state *);
 static void markcanreach(struct nfa *, struct state *, struct state *, struct state *);
 static long analyze(struct nfa *);
+static void checkmatchall(struct nfa *);
+static bool checkmatchall_recurse(struct nfa *, struct state *,
+								  bool, int, bool *);
+static bool check_out_colors_match(struct state *, color, color);
+static bool check_in_colors_match(struct state *, color, color);
 static void compact(struct nfa *, struct cnfa *);
 static void carcsort(struct carc *, size_t);
 static int	carc_cmp(const void *, const void *);
diff --git a/src/backend/regex/rege_dfa.c b/src/backend/regex/rege_dfa.c
index 32be2592c5..89d162ed6a 100644
--- a/src/backend/regex/rege_dfa.c
+++ b/src/backend/regex/rege_dfa.c
@@ -58,6 +58,29 @@ longest(struct vars *v,
 	if (hitstopp != NULL)
 		*hitstopp = 0;
 
+	/* fast path for matchall NFAs */
+	if (d->cnfa->flags & MATCHALL)
+	{
+		size_t		nchr = stop - start;
+		size_t		maxmatchall = d->cnfa->maxmatchall;
+
+		if (nchr < d->cnfa->minmatchall)
+			return NULL;
+		if (maxmatchall == DUPINF)
+		{
+			if (stop == v->stop && hitstopp != NULL)
+				*hitstopp = 1;
+		}
+		else
+		{
+			if (stop == v->stop && nchr <= maxmatchall + 1 && hitstopp != NULL)
+				*hitstopp = 1;
+			if (nchr > maxmatchall)
+				return start + maxmatchall;
+		}
+		return stop;
+	}
+
 	/* initialize */
 	css = initialize(v, d, start);
 	if (css == NULL)
@@ -187,6 +210,24 @@ shortest(struct vars *v,
 	if (hitstopp != NULL)
 		*hitstopp = 0;
 
+	/* fast path for matchall NFAs */
+	if (d->cnfa->flags & MATCHALL)
+	{
+		size_t		nchr = min - start;
+
+		if (d->cnfa->maxmatchall != DUPINF &&
+			nchr > d->cnfa->maxmatchall)
+			return NULL;
+		if ((max - start) < d->cnfa->minmatchall)
+			return NULL;
+		if (nchr < d->cnfa->minmatchall)
+			min = start + d->cnfa->minmatchall;
+		if (coldp != NULL)
+			*coldp = start;
+		/* there is no case where we should set *hitstopp */
+		return min;
+	}
+
 	/* initialize */
 	css = initialize(v, d, start);
 	if (css == NULL)
@@ -312,6 +353,22 @@ matchuntil(struct vars *v,
 	struct sset *ss;
 	struct colormap *cm = d->cm;
 
+	/* fast path for matchall NFAs */
+	if (d->cnfa->flags & MATCHALL)
+	{
+		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;
+		return 1;
+	}
+
 	/* initialize and startup, or restart, if necessary */
 	if (cp == NULL || cp > probe)
 	{
diff --git a/src/backend/regex/regprefix.c b/src/backend/regex/regprefix.c
index e2fbad7a8a..ec435b6f5f 100644
--- a/src/backend/regex/regprefix.c
+++ b/src/backend/regex/regprefix.c
@@ -77,6 +77,10 @@ pg_regprefix(regex_t *re,
 	assert(g->tree != NULL);
 	cnfa = &g->tree->cnfa;
 
+	/* matchall NFAs never have a fixed prefix */
+	if (cnfa->flags & MATCHALL)
+		return REG_NOMATCH;
+
 	/*
 	 * Since a correct NFA should never contain any exit-free loops, it should
 	 * not be possible for our traversal to return to a previously visited NFA
diff --git a/src/include/regex/regguts.h b/src/include/regex/regguts.h
index 6d39108319..82e761bfe5 100644
--- a/src/include/regex/regguts.h
+++ b/src/include/regex/regguts.h
@@ -331,6 +331,9 @@ struct nfa
 	struct colormap *cm;		/* the color map */
 	color		bos[2];			/* colors, if any, assigned to BOS and BOL */
 	color		eos[2];			/* colors, if any, assigned to EOS and EOL */
+	int			flags;			/* flags to pass forward to cNFA */
+	int			minmatchall;	/* min number of chrs to match, if matchall */
+	int			maxmatchall;	/* max number of chrs to match, or DUPINF */
 	struct vars *v;				/* simplifies compile error reporting */
 	struct nfa *parent;			/* parent NFA, if any */
 };
@@ -353,6 +356,14 @@ struct nfa
  *
  * Note that in a plain arc, "co" can be RAINBOW; since that's negative,
  * it doesn't break the rule about how to recognize LACON arcs.
+ *
+ * We have special markings for "trivial" NFAs that can match any string
+ * (possibly with limits on the number of characters therein).  In such a
+ * case, flags & MATCHALL is set (and HASLACONS can't be set).  Then the
+ * fields minmatchall and maxmatchall give the minimum and maximum numbers
+ * of characters to match.  For example, ".*" produces minmatchall = 0
+ * and maxmatchall = DUPINF, while ".+" produces minmatchall = 1 and
+ * maxmatchall = DUPINF.
  */
 struct carc
 {
@@ -366,6 +377,7 @@ struct cnfa
 	int			ncolors;		/* number of colors (max color in use + 1) */
 	int			flags;
 #define  HASLACONS	01			/* uses lookaround constraints */
+#define  MATCHALL	02			/* matches all strings of a range of lengths */
 	int			pre;			/* setup state number */
 	int			post;			/* teardown state number */
 	color		bos[2];			/* colors, if any, assigned to BOS and BOL */
@@ -375,6 +387,9 @@ struct cnfa
 	struct carc **states;		/* vector of pointers to outarc lists */
 	/* states[n] are pointers into a single malloc'd array of arcs */
 	struct carc *arcs;			/* the area for the lists */
+	/* these fields are used only in a MATCHALL NFA (else they're -1): */
+	int			minmatchall;	/* min number of chrs to match */
+	int			maxmatchall;	/* max number of chrs to match, or DUPINF */
 };
 
 /*

diff --git a/src/backend/regex/regcomp.c b/src/backend/regex/regcomp.c
index 39e837adc2..0182e02db1 100644
--- a/src/backend/regex/regcomp.c
+++ b/src/backend/regex/regcomp.c
@@ -1123,14 +1123,24 @@ parseqatom(struct vars *v,
 	t->left = atom;
 	atomp = &t->left;
 
-	/* here we should recurse... but we must postpone that to the end */
+	/*
+	 * Here we should recurse to fill t->right ... but we must postpone that
+	 * to the end.
+	 */
 
-	/* split top into prefix and remaining */
+	/*
+	 * Convert top node to a concatenation of the prefix (top->left, covering
+	 * whatever we parsed previously) and remaining (t).  Note that the prefix
+	 * could be empty, in which case this concatenation node is unnecessary.
+	 * To keep things simple, we operate in a general way for now, and get rid
+	 * of unnecessary subres below.
+	 */
 	assert(top->op == '=' && top->left == NULL && top->right == NULL);
 	top->left = subre(v, '=', top->flags, top->begin, lp);
 	NOERR();
 	top->op = '.';
 	top->right = t;
+	/* top->flags will get updated later */
 
 	/* if it's a backref, now is the time to replicate the subNFA */
 	if (atomtype == BACKREF)
@@ -1220,16 +1230,75 @@ parseqatom(struct vars *v,
 	/* and finally, look after that postponed recursion */
 	t = top->right;
 	if (!(SEE('|') || SEE(stopper) || SEE(EOS)))
+	{
+		/* parse all the rest of the branch, and insert in t->right */
 		t->right = parsebranch(v, stopper, type, s2, rp, 1);
+		NOERR();
+		assert(SEE('|') || SEE(stopper) || SEE(EOS));
+
+		/* here's the promised update of the flags */
+		t->flags |= COMBINE(t->flags, t->right->flags);
+		top->flags |= COMBINE(top->flags, t->flags);
+
+		/*
+		 * At this point both top and t are concatenation (op == '.') subres,
+		 * and we have top->left = prefix of branch, top->right = t, t->left =
+		 * messy atom (with quantification superstructure if needed), t->right
+		 * = rest of branch.
+		 *
+		 * If the messy atom was the first thing in the branch, then top->left
+		 * is vacuous and we can get rid of one level of concatenation.  Since
+		 * the caller is holding a pointer to the top node, we can't remove
+		 * that node; but we're allowed to change its properties.
+		 */
+		assert(top->left->op == '=');
+		if (top->left->begin == top->left->end)
+		{
+			assert(!MESSY(top->left->flags));
+			freesubre(v, top->left);
+			top->left = t->left;
+			top->right = t->right;
+			t->left = t->right = NULL;
+			freesubre(v, t);
+		}
+	}
 	else
 	{
+		/*
+		 * There's nothing left in the branch, so we don't need the second
+		 * concatenation node 't'.  Just link s2 straight to rp.
+		 */
 		EMPTYARC(s2, rp);
-		t->right = subre(v, '=', 0, s2, rp);
+		top->right = t->left;
+		top->flags |= COMBINE(top->flags, top->right->flags);
+		t->left = t->right = NULL;
+		freesubre(v, t);
+
+		/*
+		 * Again, it could be that top->left is vacuous (if the messy atom was
+		 * in fact the only thing in the branch).  In that case we need no
+		 * concatenation at all; just replace top with top->right.
+		 */
+		assert(top->left->op == '=');
+		if (top->left->begin == top->left->end)
+		{
+			assert(!MESSY(top->left->flags));
+			freesubre(v, top->left);
+			t = top->right;
+			top->op = t->op;
+			top->flags = t->flags;
+			top->id = t->id;
+			top->subno = t->subno;
+			top->min = t->min;
+			top->max = t->max;
+			top->left = t->left;
+			top->right = t->right;
+			top->begin = t->begin;
+			top->end = t->end;
+			t->left = t->right = NULL;
+			freesubre(v, t);
+		}
 	}
-	NOERR();
-	assert(SEE('|') || SEE(stopper) || SEE(EOS));
-	t->flags |= COMBINE(t->flags, t->right->flags);
-	top->flags |= COMBINE(top->flags, t->flags);
 }
 
 /*

diff --git a/src/backend/regex/README b/src/backend/regex/README
index a83ab5074d..cafeb3dffb 100644
--- a/src/backend/regex/README
+++ b/src/backend/regex/README
@@ -129,9 +129,9 @@ If not, we can reject the match immediately without iterating through many
 possibilities.
 
 As an example, consider the regex "(a[bc]+)\1".  The compiled
-representation will have a top-level concatenation subre node.  Its left
+representation will have a top-level concatenation subre node.  Its first
 child is a capture node, and the child of that is a plain DFA node for
-"a[bc]+".  The concatenation's right child is a backref node for \1.
+"a[bc]+".  The concatenation's second child is a backref node for \1.
 The DFA associated with the concatenation node will be "a[bc]+a[bc]+",
 where the backref has been replaced by a copy of the DFA for its referent
 expression.  When executed, the concatenation node will have to search for
diff --git a/src/backend/regex/regcomp.c b/src/backend/regex/regcomp.c
index 0182e02db1..4d483e7e53 100644
--- a/src/backend/regex/regcomp.c
+++ b/src/backend/regex/regcomp.c
@@ -58,6 +58,7 @@ static void processlacon(struct vars *, struct state *, struct state *, int,
 						 struct state *, struct state *);
 static struct subre *subre(struct vars *, int, int, struct state *, struct state *);
 static void freesubre(struct vars *, struct subre *);
+static void freesubreandsiblings(struct vars *, struct subre *);
 static void freesrnode(struct vars *, struct subre *);
 static void optst(struct vars *, struct subre *);
 static int	numst(struct subre *, int);
@@ -652,8 +653,8 @@ makesearch(struct vars *v,
  * parse - parse an RE
  *
  * This is actually just the top level, which parses a bunch of branches
- * tied together with '|'.  They appear in the tree as the left children
- * of a chain of '|' subres.
+ * tied together with '|'.  If there's more than one, they appear in the
+ * tree as the children of a '|' subre.
  */
 static struct subre *
 parse(struct vars *v,
@@ -662,41 +663,34 @@ parse(struct vars *v,
 	  struct state *init,		/* initial state */
 	  struct state *final)		/* final state */
 {
-	struct state *left;			/* scaffolding for branch */
-	struct state *right;
 	struct subre *branches;		/* top level */
-	struct subre *branch;		/* current branch */
-	struct subre *t;			/* temporary */
-	int			firstbranch;	/* is this the first branch? */
+	struct subre *lastbranch;	/* latest branch */
 
 	assert(stopper == ')' || stopper == EOS);
 
 	branches = subre(v, '|', LONGER, init, final);
 	NOERRN();
-	branch = branches;
-	firstbranch = 1;
+	lastbranch = NULL;
 	do
 	{							/* a branch */
-		if (!firstbranch)
-		{
-			/* need a place to hang it */
-			branch->right = subre(v, '|', LONGER, init, final);
-			NOERRN();
-			branch = branch->right;
-		}
-		firstbranch = 0;
+		struct subre *branch;
+		struct state *left;		/* scaffolding for branch */
+		struct state *right;
+
 		left = newstate(v->nfa);
 		right = newstate(v->nfa);
 		NOERRN();
 		EMPTYARC(init, left);
 		EMPTYARC(right, final);
 		NOERRN();
-		branch->left = parsebranch(v, stopper, type, left, right, 0);
+		branch = parsebranch(v, stopper, type, left, right, 0);
 		NOERRN();
-		branch->flags |= UP(branch->flags | branch->left->flags);
-		if ((branch->flags & ~branches->flags) != 0)	/* new flags */
-			for (t = branches; t != branch; t = t->right)
-				t->flags |= branch->flags;
+		if (lastbranch)
+			lastbranch->sibling = branch;
+		else
+			branches->child = branch;
+		branches->flags |= UP(branches->flags | branch->flags);
+		lastbranch = branch;
 	} while (EAT('|'));
 	assert(SEE(stopper) || SEE(EOS));
 
@@ -707,20 +701,16 @@ parse(struct vars *v,
 	}
 
 	/* optimize out simple cases */
-	if (branch == branches)
+	if (lastbranch == branches->child)
 	{							/* only one branch */
-		assert(branch->right == NULL);
-		t = branch->left;
-		branch->left = NULL;
-		freesubre(v, branches);
-		branches = t;
+		assert(lastbranch->sibling == NULL);
+		freesrnode(v, branches);
+		branches = lastbranch;
 	}
 	else if (!MESSY(branches->flags))
 	{							/* no interesting innards */
-		freesubre(v, branches->left);
-		branches->left = NULL;
-		freesubre(v, branches->right);
-		branches->right = NULL;
+		freesubreandsiblings(v, branches->child);
+		branches->child = NULL;
 		branches->op = '=';
 	}
 
@@ -972,7 +962,7 @@ parseqatom(struct vars *v,
 				t = subre(v, '(', atom->flags | CAP, lp, rp);
 				NOERR();
 				t->subno = subno;
-				t->left = atom;
+				t->child = atom;
 				atom = t;
 			}
 			/* postpone everything else pending possible {0} */
@@ -1120,26 +1110,27 @@ parseqatom(struct vars *v,
 	/* break remaining subRE into x{...} and what follows */
 	t = subre(v, '.', COMBINE(qprefer, atom->flags), lp, rp);
 	NOERR();
-	t->left = atom;
-	atomp = &t->left;
+	t->child = atom;
+	atomp = &t->child;
 
 	/*
-	 * Here we should recurse to fill t->right ... but we must postpone that
-	 * to the end.
+	 * Here we should recurse to fill t->child->sibling ... but we must
+	 * postpone that to the end.  One reason is that t->child may be replaced
+	 * below, and we don't want to worry about its sibling link.
 	 */
 
 	/*
-	 * Convert top node to a concatenation of the prefix (top->left, covering
+	 * Convert top node to a concatenation of the prefix (top->child, covering
 	 * whatever we parsed previously) and remaining (t).  Note that the prefix
 	 * could be empty, in which case this concatenation node is unnecessary.
 	 * To keep things simple, we operate in a general way for now, and get rid
 	 * of unnecessary subres below.
 	 */
-	assert(top->op == '=' && top->left == NULL && top->right == NULL);
-	top->left = subre(v, '=', top->flags, top->begin, lp);
+	assert(top->op == '=' && top->child == NULL);
+	top->child = subre(v, '=', top->flags, top->begin, lp);
 	NOERR();
 	top->op = '.';
-	top->right = t;
+	top->child->sibling = t;
 	/* top->flags will get updated later */
 
 	/* if it's a backref, now is the time to replicate the subNFA */
@@ -1201,9 +1192,9 @@ parseqatom(struct vars *v,
 		f = COMBINE(qprefer, atom->flags);
 		t = subre(v, '.', f, s, atom->end); /* prefix and atom */
 		NOERR();
-		t->left = subre(v, '=', PREF(f), s, atom->begin);
+		t->child = subre(v, '=', PREF(f), s, atom->begin);
 		NOERR();
-		t->right = atom;
+		t->child->sibling = atom;
 		*atomp = t;
 		/* rest of branch can be strung starting from atom->end */
 		s2 = atom->end;
@@ -1222,44 +1213,43 @@ parseqatom(struct vars *v,
 		NOERR();
 		t->min = (short) m;
 		t->max = (short) n;
-		t->left = atom;
+		t->child = atom;
 		*atomp = t;
 		/* rest of branch is to be strung from iteration's end state */
 	}
 
 	/* and finally, look after that postponed recursion */
-	t = top->right;
+	t = top->child->sibling;
 	if (!(SEE('|') || SEE(stopper) || SEE(EOS)))
 	{
-		/* parse all the rest of the branch, and insert in t->right */
-		t->right = parsebranch(v, stopper, type, s2, rp, 1);
+		/* parse all the rest of the branch, and insert in t->child->sibling */
+		t->child->sibling = parsebranch(v, stopper, type, s2, rp, 1);
 		NOERR();
 		assert(SEE('|') || SEE(stopper) || SEE(EOS));
 
 		/* here's the promised update of the flags */
-		t->flags |= COMBINE(t->flags, t->right->flags);
+		t->flags |= COMBINE(t->flags, t->child->sibling->flags);
 		top->flags |= COMBINE(top->flags, t->flags);
 
 		/*
 		 * At this point both top and t are concatenation (op == '.') subres,
-		 * and we have top->left = prefix of branch, top->right = t, t->left =
-		 * messy atom (with quantification superstructure if needed), t->right
-		 * = rest of branch.
+		 * and we have top->child = prefix of branch, top->child->sibling = t,
+		 * t->child = messy atom (with quantification superstructure if
+		 * needed), t->child->sibling = rest of branch.
 		 *
-		 * If the messy atom was the first thing in the branch, then top->left
-		 * is vacuous and we can get rid of one level of concatenation.  Since
-		 * the caller is holding a pointer to the top node, we can't remove
-		 * that node; but we're allowed to change its properties.
+		 * If the messy atom was the first thing in the branch, then
+		 * top->child is vacuous and we can get rid of one level of
+		 * concatenation.  Since the caller is holding a pointer to the top
+		 * node, we can't remove that node; but we're allowed to change its
+		 * properties.
 		 */
-		assert(top->left->op == '=');
-		if (top->left->begin == top->left->end)
+		assert(top->child->op == '=');
+		if (top->child->begin == top->child->end)
 		{
-			assert(!MESSY(top->left->flags));
-			freesubre(v, top->left);
-			top->left = t->left;
-			top->right = t->right;
-			t->left = t->right = NULL;
-			freesubre(v, t);
+			assert(!MESSY(top->child->flags));
+			freesubre(v, top->child);
+			top->child = t->child;
+			freesrnode(v, t);
 		}
 	}
 	else
@@ -1269,34 +1259,31 @@ parseqatom(struct vars *v,
 		 * concatenation node 't'.  Just link s2 straight to rp.
 		 */
 		EMPTYARC(s2, rp);
-		top->right = t->left;
-		top->flags |= COMBINE(top->flags, top->right->flags);
-		t->left = t->right = NULL;
-		freesubre(v, t);
+		top->child->sibling = t->child;
+		top->flags |= COMBINE(top->flags, top->child->sibling->flags);
+		freesrnode(v, t);
 
 		/*
-		 * Again, it could be that top->left is vacuous (if the messy atom was
-		 * in fact the only thing in the branch).  In that case we need no
-		 * concatenation at all; just replace top with top->right.
+		 * Again, it could be that top->child is vacuous (if the messy atom
+		 * was in fact the only thing in the branch).  In that case we need no
+		 * concatenation at all; just replace top with top->child->sibling.
 		 */
-		assert(top->left->op == '=');
-		if (top->left->begin == top->left->end)
+		assert(top->child->op == '=');
+		if (top->child->begin == top->child->end)
 		{
-			assert(!MESSY(top->left->flags));
-			freesubre(v, top->left);
-			t = top->right;
+			assert(!MESSY(top->child->flags));
+			t = top->child->sibling;
+			freesubre(v, top->child);
 			top->op = t->op;
 			top->flags = t->flags;
 			top->id = t->id;
 			top->subno = t->subno;
 			top->min = t->min;
 			top->max = t->max;
-			top->left = t->left;
-			top->right = t->right;
+			top->child = t->child;
 			top->begin = t->begin;
 			top->end = t->end;
-			t->left = t->right = NULL;
-			freesubre(v, t);
+			freesrnode(v, t);
 		}
 	}
 }
@@ -1786,7 +1773,7 @@ subre(struct vars *v,
 	}
 
 	if (ret != NULL)
-		v->treefree = ret->left;
+		v->treefree = ret->child;
 	else
 	{
 		ret = (struct subre *) MALLOC(sizeof(struct subre));
@@ -1806,8 +1793,8 @@ subre(struct vars *v,
 	ret->id = 0;				/* will be assigned later */
 	ret->subno = 0;
 	ret->min = ret->max = 1;
-	ret->left = NULL;
-	ret->right = NULL;
+	ret->child = NULL;
+	ret->sibling = NULL;
 	ret->begin = begin;
 	ret->end = end;
 	ZAPCNFA(ret->cnfa);
@@ -1817,6 +1804,9 @@ subre(struct vars *v,
 
 /*
  * freesubre - free a subRE subtree
+ *
+ * This frees child node(s) of the given subRE too,
+ * but not its siblings.
  */
 static void
 freesubre(struct vars *v,		/* might be NULL */
@@ -1825,14 +1815,31 @@ freesubre(struct vars *v,		/* might be NULL */
 	if (sr == NULL)
 		return;
 
-	if (sr->left != NULL)
-		freesubre(v, sr->left);
-	if (sr->right != NULL)
-		freesubre(v, sr->right);
+	if (sr->child != NULL)
+		freesubreandsiblings(v, sr->child);
 
 	freesrnode(v, sr);
 }
 
+/*
+ * freesubreandsiblings - free a subRE subtree
+ *
+ * This frees child node(s) of the given subRE too,
+ * as well as any following siblings.
+ */
+static void
+freesubreandsiblings(struct vars *v,	/* might be NULL */
+					 struct subre *sr)
+{
+	while (sr != NULL)
+	{
+		struct subre *next = sr->sibling;
+
+		freesubre(v, sr);
+		sr = next;
+	}
+}
+
 /*
  * freesrnode - free one node in a subRE subtree
  */
@@ -1850,7 +1857,7 @@ freesrnode(struct vars *v,		/* might be NULL */
 	if (v != NULL && v->treechain != NULL)
 	{
 		/* we're still parsing, maybe we can reuse the subre */
-		sr->left = v->treefree;
+		sr->child = v->treefree;
 		v->treefree = sr;
 	}
 	else
@@ -1881,15 +1888,14 @@ numst(struct subre *t,
 	  int start)				/* starting point for subtree numbers */
 {
 	int			i;
+	struct subre *t2;
 
 	assert(t != NULL);
 
 	i = start;
 	t->id = (short) i++;
-	if (t->left != NULL)
-		i = numst(t->left, i);
-	if (t->right != NULL)
-		i = numst(t->right, i);
+	for (t2 = t->child; t2 != NULL; t2 = t2->sibling)
+		i = numst(t2, i);
 	return i;
 }
 
@@ -1913,13 +1919,13 @@ numst(struct subre *t,
 static void
 markst(struct subre *t)
 {
+	struct subre *t2;
+
 	assert(t != NULL);
 
 	t->flags |= INUSE;
-	if (t->left != NULL)
-		markst(t->left);
-	if (t->right != NULL)
-		markst(t->right);
+	for (t2 = t->child; t2 != NULL; t2 = t2->sibling)
+		markst(t2);
 }
 
 /*
@@ -1949,12 +1955,12 @@ nfatree(struct vars *v,
 		struct subre *t,
 		FILE *f)				/* for debug output */
 {
+	struct subre *t2;
+
 	assert(t != NULL && t->begin != NULL);
 
-	if (t->left != NULL)
-		(DISCARD) nfatree(v, t->left, f);
-	if (t->right != NULL)
-		(DISCARD) nfatree(v, t->right, f);
+	for (t2 = t->child; t2 != NULL; t2 = t2->sibling)
+		(DISCARD) nfatree(v, t2, f);
 
 	return nfanode(v, t, 0, f);
 }
@@ -2206,6 +2212,7 @@ stdump(struct subre *t,
 	   int nfapresent)			/* is the original NFA still around? */
 {
 	char		idbuf[50];
+	struct subre *t2;
 
 	fprintf(f, "%s. `%c'", stid(t, idbuf, sizeof(idbuf)), t->op);
 	if (t->flags & LONGER)
@@ -2231,20 +2238,18 @@ stdump(struct subre *t,
 	}
 	if (nfapresent)
 		fprintf(f, " %ld-%ld", (long) t->begin->no, (long) t->end->no);
-	if (t->left != NULL)
-		fprintf(f, " L:%s", stid(t->left, idbuf, sizeof(idbuf)));
-	if (t->right != NULL)
-		fprintf(f, " R:%s", stid(t->right, idbuf, sizeof(idbuf)));
+	if (t->child != NULL)
+		fprintf(f, " C:%s", stid(t->child, idbuf, sizeof(idbuf)));
+	if (t->sibling != NULL)
+		fprintf(f, " S:%s", stid(t->sibling, idbuf, sizeof(idbuf)));
 	if (!NULLCNFA(t->cnfa))
 	{
 		fprintf(f, "\n");
 		dumpcnfa(&t->cnfa, f);
 	}
 	fprintf(f, "\n");
-	if (t->left != NULL)
-		stdump(t->left, f, nfapresent);
-	if (t->right != NULL)
-		stdump(t->right, f, nfapresent);
+	for (t2 = t->child; t2 != NULL; t2 = t2->sibling)
+		stdump(t2, f, nfapresent);
 }
 
 /*
diff --git a/src/backend/regex/regexec.c b/src/backend/regex/regexec.c
index adcbcc0a8e..4541cf9a7e 100644
--- a/src/backend/regex/regexec.c
+++ b/src/backend/regex/regexec.c
@@ -640,6 +640,8 @@ static void
 zaptreesubs(struct vars *v,
 			struct subre *t)
 {
+	struct subre *t2;
+
 	if (t->op == '(')
 	{
 		int			n = t->subno;
@@ -652,10 +654,8 @@ zaptreesubs(struct vars *v,
 		}
 	}
 
-	if (t->left != NULL)
-		zaptreesubs(v, t->left);
-	if (t->right != NULL)
-		zaptreesubs(v, t->right);
+	for (t2 = t->child; t2 != NULL; t2 = t2->sibling)
+		zaptreesubs(v, t2);
 }
 
 /*
@@ -714,35 +714,35 @@ cdissect(struct vars *v,
 	switch (t->op)
 	{
 		case '=':				/* terminal node */
-			assert(t->left == NULL && t->right == NULL);
+			assert(t->child == NULL);
 			er = REG_OKAY;		/* no action, parent did the work */
 			break;
 		case 'b':				/* back reference */
-			assert(t->left == NULL && t->right == NULL);
+			assert(t->child == NULL);
 			er = cbrdissect(v, t, begin, end);
 			break;
 		case '.':				/* concatenation */
-			assert(t->left != NULL && t->right != NULL);
-			if (t->left->flags & SHORTER)	/* reverse scan */
+			assert(t->child != NULL);
+			if (t->child->flags & SHORTER)	/* reverse scan */
 				er = crevcondissect(v, t, begin, end);
 			else
 				er = ccondissect(v, t, begin, end);
 			break;
 		case '|':				/* alternation */
-			assert(t->left != NULL);
+			assert(t->child != NULL);
 			er = caltdissect(v, t, begin, end);
 			break;
 		case '*':				/* iteration */
-			assert(t->left != NULL);
-			if (t->left->flags & SHORTER)	/* reverse scan */
+			assert(t->child != NULL);
+			if (t->child->flags & SHORTER)	/* reverse scan */
 				er = creviterdissect(v, t, begin, end);
 			else
 				er = citerdissect(v, t, begin, end);
 			break;
 		case '(':				/* capturing */
-			assert(t->left != NULL && t->right == NULL);
+			assert(t->child != NULL);
 			assert(t->subno > 0);
-			er = cdissect(v, t->left, begin, end);
+			er = cdissect(v, t->child, begin, end);
 			if (er == REG_OKAY)
 				subset(v, t, begin, end);
 			break;
@@ -770,19 +770,22 @@ ccondissect(struct vars *v,
 			chr *begin,			/* beginning of relevant substring */
 			chr *end)			/* end of same */
 {
+	struct subre *left = t->child;
+	struct subre *right = left->sibling;
 	struct dfa *d;
 	struct dfa *d2;
 	chr		   *mid;
 	int			er;
 
 	assert(t->op == '.');
-	assert(t->left != NULL && t->left->cnfa.nstates > 0);
-	assert(t->right != NULL && t->right->cnfa.nstates > 0);
-	assert(!(t->left->flags & SHORTER));
+	assert(left != NULL && left->cnfa.nstates > 0);
+	assert(right != NULL && right->cnfa.nstates > 0);
+	assert(right->sibling == NULL);
+	assert(!(left->flags & SHORTER));
 
-	d = getsubdfa(v, t->left);
+	d = getsubdfa(v, left);
 	NOERR();
-	d2 = getsubdfa(v, t->right);
+	d2 = getsubdfa(v, right);
 	NOERR();
 	MDEBUG(("%d: ccondissect %ld-%ld\n", t->id, LOFF(begin), LOFF(end)));
 
@@ -799,10 +802,10 @@ ccondissect(struct vars *v,
 		/* try this midpoint on for size */
 		if (longest(v, d2, mid, end, (int *) NULL) == end)
 		{
-			er = cdissect(v, t->left, begin, mid);
+			er = cdissect(v, left, begin, mid);
 			if (er == REG_OKAY)
 			{
-				er = cdissect(v, t->right, mid, end);
+				er = cdissect(v, right, mid, end);
 				if (er == REG_OKAY)
 				{
 					/* satisfaction */
@@ -831,8 +834,8 @@ ccondissect(struct vars *v,
 			return REG_NOMATCH;
 		}
 		MDEBUG(("%d: new midpoint %ld\n", t->id, LOFF(mid)));
-		zaptreesubs(v, t->left);
-		zaptreesubs(v, t->right);
+		zaptreesubs(v, left);
+		zaptreesubs(v, right);
 	}
 
 	/* can't get here */
@@ -848,19 +851,22 @@ crevcondissect(struct vars *v,
 			   chr *begin,		/* beginning of relevant substring */
 			   chr *end)		/* end of same */
 {
+	struct subre *left = t->child;
+	struct subre *right = left->sibling;
 	struct dfa *d;
 	struct dfa *d2;
 	chr		   *mid;
 	int			er;
 
 	assert(t->op == '.');
-	assert(t->left != NULL && t->left->cnfa.nstates > 0);
-	assert(t->right != NULL && t->right->cnfa.nstates > 0);
-	assert(t->left->flags & SHORTER);
+	assert(left != NULL && left->cnfa.nstates > 0);
+	assert(right != NULL && right->cnfa.nstates > 0);
+	assert(right->sibling == NULL);
+	assert(left->flags & SHORTER);
 
-	d = getsubdfa(v, t->left);
+	d = getsubdfa(v, left);
 	NOERR();
-	d2 = getsubdfa(v, t->right);
+	d2 = getsubdfa(v, right);
 	NOERR();
 	MDEBUG(("%d: crevcondissect %ld-%ld\n", t->id, LOFF(begin), LOFF(end)));
 
@@ -877,10 +883,10 @@ crevcondissect(struct vars *v,
 		/* try this midpoint on for size */
 		if (longest(v, d2, mid, end, (int *) NULL) == end)
 		{
-			er = cdissect(v, t->left, begin, mid);
+			er = cdissect(v, left, begin, mid);
 			if (er == REG_OKAY)
 			{
-				er = cdissect(v, t->right, mid, end);
+				er = cdissect(v, right, mid, end);
 				if (er == REG_OKAY)
 				{
 					/* satisfaction */
@@ -909,8 +915,8 @@ crevcondissect(struct vars *v,
 			return REG_NOMATCH;
 		}
 		MDEBUG(("%d: new midpoint %ld\n", t->id, LOFF(mid)));
-		zaptreesubs(v, t->left);
-		zaptreesubs(v, t->right);
+		zaptreesubs(v, left);
+		zaptreesubs(v, right);
 	}
 
 	/* can't get here */
@@ -1011,26 +1017,30 @@ caltdissect(struct vars *v,
 	struct dfa *d;
 	int			er;
 
-	/* We loop, rather than tail-recurse, to handle a chain of alternatives */
+	assert(t->op == '|');
+
+	t = t->child;
+	/* there should be at least 2 alternatives */
+	assert(t != NULL && t->sibling != NULL);
+
 	while (t != NULL)
 	{
-		assert(t->op == '|');
-		assert(t->left != NULL && t->left->cnfa.nstates > 0);
+		assert(t->cnfa.nstates > 0);
 
 		MDEBUG(("%d: caltdissect %ld-%ld\n", t->id, LOFF(begin), LOFF(end)));
 
-		d = getsubdfa(v, t->left);
+		d = getsubdfa(v, t);
 		NOERR();
 		if (longest(v, d, begin, end, (int *) NULL) == end)
 		{
 			MDEBUG(("%d: caltdissect matched\n", t->id));
-			er = cdissect(v, t->left, begin, end);
+			er = cdissect(v, t, begin, end);
 			if (er != REG_NOMATCH)
 				return er;
 		}
 		NOERR();
 
-		t = t->right;
+		t = t->sibling;
 	}
 
 	return REG_NOMATCH;
@@ -1056,8 +1066,8 @@ citerdissect(struct vars *v,
 	int			er;
 
 	assert(t->op == '*');
-	assert(t->left != NULL && t->left->cnfa.nstates > 0);
-	assert(!(t->left->flags & SHORTER));
+	assert(t->child != NULL && t->child->cnfa.nstates > 0);
+	assert(!(t->child->flags & SHORTER));
 	assert(begin <= end);
 
 	MDEBUG(("%d: citerdissect %ld-%ld\n", t->id, LOFF(begin), LOFF(end)));
@@ -1094,7 +1104,7 @@ citerdissect(struct vars *v,
 		return REG_ESPACE;
 	endpts[0] = begin;
 
-	d = getsubdfa(v, t->left);
+	d = getsubdfa(v, t->child);
 	if (ISERR())
 	{
 		FREE(endpts);
@@ -1172,8 +1182,8 @@ citerdissect(struct vars *v,
 
 		for (i = nverified + 1; i <= k; i++)
 		{
-			zaptreesubs(v, t->left);
-			er = cdissect(v, t->left, endpts[i - 1], endpts[i]);
+			zaptreesubs(v, t->child);
+			er = cdissect(v, t->child, endpts[i - 1], endpts[i]);
 			if (er == REG_OKAY)
 			{
 				nverified = i;
@@ -1258,8 +1268,8 @@ creviterdissect(struct vars *v,
 	int			er;
 
 	assert(t->op == '*');
-	assert(t->left != NULL && t->left->cnfa.nstates > 0);
-	assert(t->left->flags & SHORTER);
+	assert(t->child != NULL && t->child->cnfa.nstates > 0);
+	assert(t->child->flags & SHORTER);
 	assert(begin <= end);
 
 	MDEBUG(("%d: creviterdissect %ld-%ld\n", t->id, LOFF(begin), LOFF(end)));
@@ -1299,7 +1309,7 @@ creviterdissect(struct vars *v,
 		return REG_ESPACE;
 	endpts[0] = begin;
 
-	d = getsubdfa(v, t->left);
+	d = getsubdfa(v, t->child);
 	if (ISERR())
 	{
 		FREE(endpts);
@@ -1383,8 +1393,8 @@ creviterdissect(struct vars *v,
 
 		for (i = nverified + 1; i <= k; i++)
 		{
-			zaptreesubs(v, t->left);
-			er = cdissect(v, t->left, endpts[i - 1], endpts[i]);
+			zaptreesubs(v, t->child);
+			er = cdissect(v, t->child, endpts[i - 1], endpts[i]);
 			if (er == REG_OKAY)
 			{
 				nverified = i;
diff --git a/src/include/regex/regguts.h b/src/include/regex/regguts.h
index 82e761bfe5..90ee16957a 100644
--- a/src/include/regex/regguts.h
+++ b/src/include/regex/regguts.h
@@ -423,15 +423,17 @@ struct cnfa
  *		'='  plain regex without interesting substructure (implemented as DFA)
  *		'b'  back-reference (has no substructure either)
  *		'('  capture node: captures the match of its single child
- *		'.'  concatenation: matches a match for left, then a match for right
- *		'|'  alternation: matches a match for left or a match for right
+ *		'.'  concatenation: matches a match for first child, then second child
+ *		'|'  alternation: matches a match for any of its children
  *		'*'  iteration: matches some number of matches of its single child
  *
- * Note: the right child of an alternation must be another alternation or
- * NULL; hence, an N-way branch requires N alternation nodes, not N-1 as you
- * might expect.  This could stand to be changed.  Actually I'd rather see
- * a single alternation node with N children, but that will take revising
- * the representation of struct subre.
+ * An alternation node can have any number of children (but at least two),
+ * linked through their sibling fields.
+ *
+ * A concatenation node must have exactly two children.  It might be useful
+ * to support more, but that would complicate the executor.  Note that it is
+ * the first child's greediness that determines the node's preference for
+ * where to split a match.
  *
  * Note: when a backref is directly quantified, we stick the min/max counts
  * into the backref rather than plastering an iteration node on top.  This is
@@ -460,8 +462,8 @@ struct subre
 								 * LATYPE code for lookaround constraint */
 	short		min;			/* min repetitions for iteration or backref */
 	short		max;			/* max repetitions for iteration or backref */
-	struct subre *left;			/* left child, if any (also freelist chain) */
-	struct subre *right;		/* right child, if any */
+	struct subre *child;		/* first child, if any (also freelist chain) */
+	struct subre *sibling;		/* next child of same parent, if any */
 	struct state *begin;		/* outarcs from here... */
 	struct state *end;			/* ...ending in inarcs here */
 	struct cnfa cnfa;			/* compacted NFA, if any */

diff --git a/src/backend/regex/README b/src/backend/regex/README
index cafeb3dffb..e4b083664f 100644
--- a/src/backend/regex/README
+++ b/src/backend/regex/README
@@ -130,8 +130,8 @@ possibilities.
 
 As an example, consider the regex "(a[bc]+)\1".  The compiled
 representation will have a top-level concatenation subre node.  Its first
-child is a capture node, and the child of that is a plain DFA node for
-"a[bc]+".  The concatenation's second child is a backref node for \1.
+child is a plain DFA node for "a[bc]+" (which is marked as being a capture
+node).  The concatenation's second child is a backref node for \1.
 The DFA associated with the concatenation node will be "a[bc]+a[bc]+",
 where the backref has been replaced by a copy of the DFA for its referent
 expression.  When executed, the concatenation node will have to search for
@@ -147,6 +147,17 @@ run much faster than a pure NFA engine could do.  It is this behavior that
 justifies using the phrase "hybrid DFA/NFA engine" to describe Spencer's
 library.
 
+It's perhaps worth noting that separate capture subre nodes are a rarity:
+normally, we just mark a subre as capturing and that's it.  However, it's
+legal to write a regex like "((x))" in which the same substring has to be
+captured by multiple sets of parentheses.  Since a subre has room for only
+one "capno" field, a single subre can't handle that.  We handle such cases
+by wrapping the base subre (which captures the innermost parens) in a
+no-op capture node, or even more than one for "(((x)))" etc.  This is a
+little bit inefficient because we end up with multiple identical NFAs,
+but since the case is pointless and infrequent, it's not worth working
+harder.
+
 
 Colors and colormapping
 -----------------------
diff --git a/src/backend/regex/regcomp.c b/src/backend/regex/regcomp.c
index 4d483e7e53..891ad15b23 100644
--- a/src/backend/regex/regcomp.c
+++ b/src/backend/regex/regcomp.c
@@ -452,7 +452,7 @@ pg_regcomp(regex_t *re,
 #endif
 
 		/* Prepend .* to pattern if it's a lookbehind LACON */
-		nfanode(v, lasub, !LATYPE_IS_AHEAD(lasub->subno), debug);
+		nfanode(v, lasub, !LATYPE_IS_AHEAD(lasub->latype), debug);
 	}
 	CNOERR();
 	if (v->tree->flags & SHORTER)
@@ -944,7 +944,13 @@ parseqatom(struct vars *v,
 			else
 				atomtype = PLAIN;	/* something that's not '(' */
 			NEXT();
-			/* need new endpoints because tree will contain pointers */
+
+			/*
+			 * Make separate endpoints to ensure we keep this sub-NFA cleanly
+			 * separate from what surrounds it.  We need to be sure that when
+			 * we duplicate the sub-NFA for a backref, we get the right states
+			 * and no others.
+			 */
 			s = newstate(v->nfa);
 			s2 = newstate(v->nfa);
 			NOERR();
@@ -959,11 +965,21 @@ parseqatom(struct vars *v,
 			{
 				assert(v->subs[subno] == NULL);
 				v->subs[subno] = atom;
-				t = subre(v, '(', atom->flags | CAP, lp, rp);
-				NOERR();
-				t->subno = subno;
-				t->child = atom;
-				atom = t;
+				if (atom->capno == 0)
+				{
+					/* normal case: just mark the atom as capturing */
+					atom->flags |= CAP;
+					atom->capno = subno;
+				}
+				else
+				{
+					/* generate no-op wrapper node to handle "((x))" */
+					t = subre(v, '(', atom->flags | CAP, lp, rp);
+					NOERR();
+					t->capno = subno;
+					t->child = atom;
+					atom = t;
+				}
 			}
 			/* postpone everything else pending possible {0} */
 			break;
@@ -976,7 +992,7 @@ parseqatom(struct vars *v,
 			atom = subre(v, 'b', BACKR, lp, rp);
 			NOERR();
 			subno = v->nextvalue;
-			atom->subno = subno;
+			atom->backno = subno;
 			EMPTYARC(lp, rp);	/* temporarily, so there's something */
 			NEXT();
 			break;
@@ -1276,8 +1292,10 @@ parseqatom(struct vars *v,
 			freesubre(v, top->child);
 			top->op = t->op;
 			top->flags = t->flags;
+			top->latype = t->latype;
 			top->id = t->id;
-			top->subno = t->subno;
+			top->capno = t->capno;
+			top->backno = t->backno;
 			top->min = t->min;
 			top->max = t->max;
 			top->child = t->child;
@@ -1790,8 +1808,10 @@ subre(struct vars *v,
 
 	ret->op = op;
 	ret->flags = flags;
+	ret->latype = (char) -1;
 	ret->id = 0;				/* will be assigned later */
-	ret->subno = 0;
+	ret->capno = 0;
+	ret->backno = 0;
 	ret->min = ret->max = 1;
 	ret->child = NULL;
 	ret->sibling = NULL;
@@ -1893,7 +1913,7 @@ numst(struct subre *t,
 	assert(t != NULL);
 
 	i = start;
-	t->id = (short) i++;
+	t->id = i++;
 	for (t2 = t->child; t2 != NULL; t2 = t2->sibling)
 		i = numst(t2, i);
 	return i;
@@ -2040,7 +2060,7 @@ newlacon(struct vars *v,
 	sub = &v->lacons[n];
 	sub->begin = begin;
 	sub->end = end;
-	sub->subno = latype;
+	sub->latype = latype;
 	ZAPCNFA(sub->cnfa);
 	return n;
 }
@@ -2163,7 +2183,7 @@ dump(regex_t *re,
 		struct subre *lasub = &g->lacons[i];
 		const char *latype;
 
-		switch (lasub->subno)
+		switch (lasub->latype)
 		{
 			case LATYPE_AHEAD_POS:
 				latype = "positive lookahead";
@@ -2227,8 +2247,12 @@ stdump(struct subre *t,
 		fprintf(f, " hasbackref");
 	if (!(t->flags & INUSE))
 		fprintf(f, " UNUSED");
-	if (t->subno != 0)
-		fprintf(f, " (#%d)", t->subno);
+	if (t->latype != (char) -1)
+		fprintf(f, " latype(%d)", t->latype);
+	if (t->capno != 0)
+		fprintf(f, " capture(%d)", t->capno);
+	if (t->backno != 0)
+		fprintf(f, " backref(%d)", t->backno);
 	if (t->min != 1 || t->max != 1)
 	{
 		fprintf(f, " {%d,", t->min);
diff --git a/src/backend/regex/rege_dfa.c b/src/backend/regex/rege_dfa.c
index 89d162ed6a..957ceb8137 100644
--- a/src/backend/regex/rege_dfa.c
+++ b/src/backend/regex/rege_dfa.c
@@ -825,12 +825,12 @@ lacon(struct vars *v,
 	d = getladfa(v, n);
 	if (d == NULL)
 		return 0;
-	if (LATYPE_IS_AHEAD(sub->subno))
+	if (LATYPE_IS_AHEAD(sub->latype))
 	{
 		/* used to use longest() here, but shortest() could be much cheaper */
 		end = shortest(v, d, cp, cp, v->stop,
 					   (chr **) NULL, (int *) NULL);
-		satisfied = LATYPE_IS_POS(sub->subno) ? (end != NULL) : (end == NULL);
+		satisfied = LATYPE_IS_POS(sub->latype) ? (end != NULL) : (end == NULL);
 	}
 	else
 	{
@@ -843,7 +843,7 @@ lacon(struct vars *v,
 		 * nominal match.
 		 */
 		satisfied = matchuntil(v, d, cp, &v->lblastcss[n], &v->lblastcp[n]);
-		if (!LATYPE_IS_POS(sub->subno))
+		if (!LATYPE_IS_POS(sub->latype))
 			satisfied = !satisfied;
 	}
 	FDEBUG(("=== lacon %d satisfied %d\n", n, satisfied));
diff --git a/src/backend/regex/regexec.c b/src/backend/regex/regexec.c
index 4541cf9a7e..2a1ef0176a 100644
--- a/src/backend/regex/regexec.c
+++ b/src/backend/regex/regexec.c
@@ -640,13 +640,11 @@ static void
 zaptreesubs(struct vars *v,
 			struct subre *t)
 {
+	int			n = t->capno;
 	struct subre *t2;
 
-	if (t->op == '(')
+	if (n > 0)
 	{
-		int			n = t->subno;
-
-		assert(n > 0);
 		if ((size_t) n < v->nmatch)
 		{
 			v->pmatch[n].rm_so = -1;
@@ -667,7 +665,7 @@ subset(struct vars *v,
 	   chr *begin,
 	   chr *end)
 {
-	int			n = sub->subno;
+	int			n = sub->capno;
 
 	assert(n > 0);
 	if ((size_t) n >= v->nmatch)
@@ -739,12 +737,10 @@ cdissect(struct vars *v,
 			else
 				er = citerdissect(v, t, begin, end);
 			break;
-		case '(':				/* capturing */
+		case '(':				/* no-op capture node */
 			assert(t->child != NULL);
-			assert(t->subno > 0);
+			assert(t->capno > 0);
 			er = cdissect(v, t->child, begin, end);
-			if (er == REG_OKAY)
-				subset(v, t, begin, end);
 			break;
 		default:
 			er = REG_ASSERT;
@@ -758,6 +754,12 @@ cdissect(struct vars *v,
 	 */
 	assert(er != REG_NOMATCH || (t->flags & BACKR));
 
+	/*
+	 * If this node is marked as capturing, save successful match's location.
+	 */
+	if (t->capno > 0 && er == REG_OKAY)
+		subset(v, t, begin, end);
+
 	return er;
 }
 
@@ -932,7 +934,7 @@ cbrdissect(struct vars *v,
 		   chr *begin,			/* beginning of relevant substring */
 		   chr *end)			/* end of same */
 {
-	int			n = t->subno;
+	int			n = t->backno;
 	size_t		numreps;
 	size_t		tlen;
 	size_t		brlen;
diff --git a/src/include/regex/regguts.h b/src/include/regex/regguts.h
index 90ee16957a..306525eb5f 100644
--- a/src/include/regex/regguts.h
+++ b/src/include/regex/regguts.h
@@ -422,7 +422,7 @@ struct cnfa
  * "op" is one of:
  *		'='  plain regex without interesting substructure (implemented as DFA)
  *		'b'  back-reference (has no substructure either)
- *		'('  capture node: captures the match of its single child
+ *		'('  no-op capture node: captures the match of its single child
  *		'.'  concatenation: matches a match for first child, then second child
  *		'|'  alternation: matches a match for any of its children
  *		'*'  iteration: matches some number of matches of its single child
@@ -446,8 +446,8 @@ struct subre
 #define  LONGER  01				/* prefers longer match */
 #define  SHORTER 02				/* prefers shorter match */
 #define  MIXED	 04				/* mixed preference below */
-#define  CAP	 010			/* capturing parens below */
-#define  BACKR	 020			/* back reference below */
+#define  CAP	 010			/* capturing parens here or below */
+#define  BACKR	 020			/* back reference here or below */
 #define  INUSE	 0100			/* in use in final tree */
 #define  NOPROP  03				/* bits which may not propagate up */
 #define  LMIX(f) ((f)<<2)		/* LONGER -> MIXED */
@@ -457,9 +457,10 @@ struct subre
 #define  PREF(f) ((f)&NOPROP)
 #define  PREF2(f1, f2)	 ((PREF(f1) != 0) ? PREF(f1) : PREF(f2))
 #define  COMBINE(f1, f2) (UP((f1)|(f2)) | PREF2(f1, f2))
-	short		id;				/* ID of subre (1..ntree-1) */
-	int			subno;			/* subexpression number for 'b' and '(', or
-								 * LATYPE code for lookaround constraint */
+	char		latype;			/* LATYPE code, if lookaround constraint */
+	int			id;				/* ID of subre (1..ntree-1) */
+	int			capno;			/* if capture node, subno to capture into */
+	int			backno;			/* if backref node, subno it refers to */
 	short		min;			/* min repetitions for iteration or backref */
 	short		max;			/* max repetitions for iteration or backref */
 	struct subre *child;		/* first child, if any (also freelist chain) */

diff --git a/src/backend/regex/regc_nfa.c b/src/backend/regex/regc_nfa.c
index 69929eddfc..3da394b9a5 100644
--- a/src/backend/regex/regc_nfa.c
+++ b/src/backend/regex/regc_nfa.c
@@ -3182,81 +3182,145 @@ compact(struct nfa *nfa,
 {
 	struct state *s;
 	struct arc *a;
-	size_t		nstates;
-	size_t		narcs;
-	struct carc *ca;
-	struct carc *first;
+	size_t		nstates = 0;
+	size_t		nlastates = 0;
+	size_t		nplainarcs = 0;
+	size_t		nlaarcs = 0;
+	struct carc *cpa;
+	struct carc *cla;
 
 	assert(!NISERR());
 
-	nstates = 0;
-	narcs = 0;
 	for (s = nfa->states; s != NULL; s = s->next)
 	{
+		size_t		nthislaarcs = 0;
+
 		nstates++;
-		narcs += s->nouts + 1;	/* need one extra for endmarker */
+		for (a = s->outs; a != NULL; a = a->outchain)
+		{
+			switch (a->type)
+			{
+				case PLAIN:
+					nplainarcs++;
+					break;
+				case LACON:
+					nthislaarcs++;
+					break;
+				default:
+					NERR(REG_ASSERT);
+					return;
+			}
+		}
+		nplainarcs++;			/* each state needs an endmarker arc */
+		if (nthislaarcs > 0)
+		{
+			nlastates++;
+			nlaarcs += nthislaarcs + 1; /* endmarker needed */
+		}
 	}
 
 	cnfa->stflags = (char *) MALLOC(nstates * sizeof(char));
-	cnfa->states = (struct carc **) MALLOC(nstates * sizeof(struct carc *));
-	cnfa->arcs = (struct carc *) MALLOC(narcs * sizeof(struct carc));
-	if (cnfa->stflags == NULL || cnfa->states == NULL || cnfa->arcs == NULL)
+	cnfa->firstarc = (struct carc **) MALLOC(nstates * sizeof(struct carc *));
+	cnfa->arcs = (struct carc *)
+		MALLOC((nplainarcs + nlaarcs) * sizeof(struct carc));
+	if (nlastates > 0)
+	{
+		cnfa->lastates = (int *) MALLOC(nlastates * sizeof(int));
+		cnfa->firstlaarc = (struct carc **)
+			MALLOC(nlastates * sizeof(struct carc *));
+	}
+	else
+	{
+		cnfa->lastates = NULL;
+		cnfa->firstlaarc = NULL;
+	}
+	if (cnfa->stflags == NULL || cnfa->firstarc == NULL || cnfa->arcs == NULL ||
+		(nlastates > 0 && (cnfa->lastates == NULL || cnfa->firstlaarc == NULL)))
 	{
 		if (cnfa->stflags != NULL)
 			FREE(cnfa->stflags);
-		if (cnfa->states != NULL)
-			FREE(cnfa->states);
+		if (cnfa->firstarc != NULL)
+			FREE(cnfa->firstarc);
 		if (cnfa->arcs != NULL)
 			FREE(cnfa->arcs);
+		if (cnfa->lastates != NULL)
+			FREE(cnfa->lastates);
+		if (cnfa->firstlaarc != NULL)
+			FREE(cnfa->firstlaarc);
 		NERR(REG_ESPACE);
 		return;
 	}
+	assert(nstates > 0);
 	cnfa->nstates = nstates;
+	cnfa->ncolors = maxcolor(nfa->cm) + 1;
+	cnfa->flags = nfa->flags;
+	if (nlastates > 0)
+		cnfa->flags |= HASLACONS;
+	cnfa->nlastates = 0;		/* will set below */
 	cnfa->pre = nfa->pre->no;
 	cnfa->post = nfa->post->no;
 	cnfa->bos[0] = nfa->bos[0];
 	cnfa->bos[1] = nfa->bos[1];
 	cnfa->eos[0] = nfa->eos[0];
 	cnfa->eos[1] = nfa->eos[1];
-	cnfa->ncolors = maxcolor(nfa->cm) + 1;
-	cnfa->flags = nfa->flags;
 	cnfa->minmatchall = nfa->minmatchall;
 	cnfa->maxmatchall = nfa->maxmatchall;
 
-	ca = cnfa->arcs;
+	cpa = cnfa->arcs;			/* where to store plain arcs */
+	cla = cnfa->arcs + nplainarcs;	/* where to store LA arcs */
 	for (s = nfa->states; s != NULL; s = s->next)
 	{
+		struct carc *firstp = cpa;
+		struct carc *firstla = cla;
+
 		assert((size_t) s->no < nstates);
 		cnfa->stflags[s->no] = 0;
-		cnfa->states[s->no] = ca;
-		first = ca;
+		cnfa->firstarc[s->no] = cpa;
 		for (a = s->outs; a != NULL; a = a->outchain)
+		{
 			switch (a->type)
 			{
 				case PLAIN:
-					ca->co = a->co;
-					ca->to = a->to->no;
-					ca++;
+					cpa->co = a->co;
+					cpa->to = a->to->no;
+					cpa++;
 					break;
 				case LACON:
 					assert(s->no != cnfa->pre);
 					assert(a->co >= 0);
-					ca->co = (color) (cnfa->ncolors + a->co);
-					ca->to = a->to->no;
-					ca++;
-					cnfa->flags |= HASLACONS;
+					if (cla == firstla)
+					{
+						cnfa->lastates[cnfa->nlastates] = s->no;
+						cnfa->firstlaarc[cnfa->nlastates] = cla;
+						cnfa->nlastates++;
+					}
+					cla->co = a->co;
+					cla->to = a->to->no;
+					cla++;
 					break;
 				default:
 					NERR(REG_ASSERT);
 					return;
 			}
-		carcsort(first, ca - first);
-		ca->co = COLORLESS;
-		ca->to = 0;
-		ca++;
+		}
+		/* sort plain arcs, just for neatness */
+		carcsort(firstp, cpa - firstp);
+		/* add endmarker for plain arcs */
+		cpa->co = COLORLESS;
+		cpa->to = 0;
+		cpa++;
+		/* and the same for LA arcs, if this state has any */
+		if (cla != firstla)
+		{
+			carcsort(firstla, cla - firstla);
+			cla->co = COLORLESS;
+			cla->to = 0;
+			cla++;
+		}
 	}
-	assert(ca == &cnfa->arcs[narcs]);
-	assert(cnfa->nstates != 0);
+	assert(cpa == &cnfa->arcs[nplainarcs]);
+	assert(cla == &cnfa->arcs[nplainarcs + nlaarcs]);
+	assert(nlastates == cnfa->nlastates);
 
 	/* mark no-progress states */
 	for (a = nfa->pre->outs; a != NULL; a = a->outchain)
@@ -3299,7 +3363,11 @@ freecnfa(struct cnfa *cnfa)
 {
 	assert(!NULLCNFA(*cnfa));	/* not empty already */
 	FREE(cnfa->stflags);
-	FREE(cnfa->states);
+	FREE(cnfa->firstarc);
+	if (cnfa->lastates != NULL)
+		FREE(cnfa->lastates);
+	if (cnfa->firstlaarc != NULL)
+		FREE(cnfa->firstlaarc);
 	FREE(cnfa->arcs);
 	ZAPCNFA(*cnfa);
 }
@@ -3518,18 +3586,19 @@ dumpcstate(int st,
 		   FILE *f)
 {
 	struct carc *ca;
+	bool		hasarc = false;
 	int			pos;
+	int			i;
 
 	fprintf(f, "%d%s", st, (cnfa->stflags[st] & CNFA_NOPROGRESS) ? ":" : ".");
 	pos = 1;
-	for (ca = cnfa->states[st]; ca->co != COLORLESS; ca++)
+	/* Dump its plain out-arcs */
+	for (ca = cnfa->firstarc[st]; ca->co != COLORLESS; ca++)
 	{
 		if (ca->co == RAINBOW)
 			fprintf(f, "\t[*]->%d", ca->to);
-		else if (ca->co < cnfa->ncolors)
-			fprintf(f, "\t[%ld]->%d", (long) ca->co, ca->to);
 		else
-			fprintf(f, "\t:%ld:->%d", (long) (ca->co - cnfa->ncolors), ca->to);
+			fprintf(f, "\t[%ld]->%d", (long) ca->co, ca->to);
 		if (pos == 5)
 		{
 			fprintf(f, "\n");
@@ -3537,8 +3606,28 @@ dumpcstate(int st,
 		}
 		else
 			pos++;
+		hasarc = true;
+	}
+	/* Dump its LACON out-arcs, if any */
+	for (i = 0; i < cnfa->nlastates; i++)
+	{
+		if (cnfa->lastates[i] != st)
+			continue;
+		for (ca = cnfa->firstlaarc[i]; ca->co != COLORLESS; ca++)
+		{
+			fprintf(f, "\t:%ld:->%d", (long) ca->co, ca->to);
+			if (pos == 5)
+			{
+				fprintf(f, "\n");
+				pos = 1;
+			}
+			else
+				pos++;
+			hasarc = true;
+		}
+		break;					/* needn't look through rest of lastates[] */
 	}
-	if (ca == cnfa->states[st] || pos != 1)
+	if (pos != 1 || !hasarc)
 		fprintf(f, "\n");
 	fflush(f);
 }
diff --git a/src/backend/regex/rege_dfa.c b/src/backend/regex/rege_dfa.c
index 1db52d1005..ad2c98bd91 100644
--- a/src/backend/regex/rege_dfa.c
+++ b/src/backend/regex/rege_dfa.c
@@ -677,6 +677,8 @@ miss(struct vars *v,
 	int			gotstate;
 	int			dolacons;
 	int			sawlacons;
+	color		lastlacon;
+	int			lastlaresult;
 
 	/* for convenience, we can be called even if it might not be a miss */
 	if (css->outs[co] != NULL)
@@ -709,7 +711,7 @@ miss(struct vars *v,
 	gotstate = 0;
 	for (i = 0; i < d->nstates; i++)
 		if (ISBSET(css->states, i))
-			for (ca = cnfa->states[i]; ca->co != COLORLESS; ca++)
+			for (ca = cnfa->firstarc[i]; ca->co != COLORLESS; ca++)
 				if (ca->co == co ||
 					(ca->co == RAINBOW && !ispseudocolor))
 				{
@@ -725,27 +727,33 @@ miss(struct vars *v,
 		return NULL;			/* character cannot reach any new state */
 	dolacons = (cnfa->flags & HASLACONS);
 	sawlacons = 0;
+	lastlacon = COLORLESS;
+	lastlaresult = 0;			/* doesn't matter */
 	/* outer loop handles transitive closure of reachable-by-LACON states */
 	while (dolacons)
 	{
+		int			j;
+
 		dolacons = 0;
-		for (i = 0; i < d->nstates; i++)
+		for (j = 0; j < cnfa->nlastates; j++)
+		{
+			i = cnfa->lastates[j];
 			if (ISBSET(d->work, i))
-				for (ca = cnfa->states[i]; ca->co != COLORLESS; ca++)
+				for (ca = cnfa->firstlaarc[j]; ca->co != COLORLESS; ca++)
 				{
-					if (ca->co < cnfa->ncolors)
-						continue;	/* not a LACON arc */
 					if (ISBSET(d->work, ca->to))
 						continue;	/* arc would be a no-op anyway */
 					sawlacons = 1;	/* this LACON affects our result */
-					if (!lacon(v, cnfa, cp, ca->co))
+					/* we might have just eval'd this same LACON */
+					if (ca->co != lastlacon)
 					{
+						lastlacon = ca->co;
+						lastlaresult = lacon(v, cnfa, cp, lastlacon);
 						if (ISERR())
 							return NULL;
-						continue;	/* LACON arc cannot be traversed */
 					}
-					if (ISERR())
-						return NULL;
+					if (!lastlaresult)
+						continue;	/* LACON arc cannot be traversed */
 					BSET(d->work, ca->to);
 					dolacons = 1;
 					if (ca->to == cnfa->post)
@@ -754,6 +762,7 @@ miss(struct vars *v,
 						noprogress = 0;
 					FDEBUG(("%d :> %d\n", i, ca->to));
 				}
+		}
 	}
 	h = HASH(d->work, d->wordsper);
 
@@ -805,9 +814,8 @@ static int						/* predicate:  constraint satisfied? */
 lacon(struct vars *v,
 	  struct cnfa *pcnfa,		/* parent cnfa */
 	  chr *cp,
-	  color co)					/* "color" of the lookaround constraint */
+	  int n)					/* index of the lookaround constraint */
 {
-	int			n;
 	struct subre *sub;
 	struct dfa *d;
 	chr		   *end;
@@ -820,7 +828,6 @@ lacon(struct vars *v,
 		return 0;
 	}
 
-	n = co - pcnfa->ncolors;
 	assert(n > 0 && n < v->g->nlacons && v->g->lacons != NULL);
 	FDEBUG(("=== testing lacon %d\n", n));
 	sub = &v->g->lacons[n];
diff --git a/src/backend/regex/regexec.c b/src/backend/regex/regexec.c
index cf95989948..69acc285f7 100644
--- a/src/backend/regex/regexec.c
+++ b/src/backend/regex/regexec.c
@@ -160,7 +160,7 @@ static void freedfa(struct dfa *);
 static unsigned hash(unsigned *, int);
 static struct sset *initialize(struct vars *, struct dfa *, chr *);
 static struct sset *miss(struct vars *, struct dfa *, struct sset *, color, chr *, chr *);
-static int	lacon(struct vars *, struct cnfa *, chr *, color);
+static int	lacon(struct vars *, struct cnfa *, chr *, int);
 static struct sset *getvacant(struct vars *, struct dfa *, chr *, chr *);
 static struct sset *pickss(struct vars *, struct dfa *, chr *, chr *);
 
diff --git a/src/backend/regex/regexport.c b/src/backend/regex/regexport.c
index a493dbe88c..964a017f84 100644
--- a/src/backend/regex/regexport.c
+++ b/src/backend/regex/regexport.c
@@ -95,6 +95,7 @@ traverse_lacons(struct cnfa *cnfa, int st,
 				regex_arc_t *arcs, int arcs_len)
 {
 	struct carc *ca;
+	int			i;
 
 	/*
 	 * Since this function recurses, it could theoretically be driven to stack
@@ -103,20 +104,24 @@ traverse_lacons(struct cnfa *cnfa, int st,
 	 */
 	check_stack_depth();
 
-	for (ca = cnfa->states[st]; ca->co != COLORLESS; ca++)
+	/* Count and possibly emit state's ordinary out-arcs */
+	for (ca = cnfa->firstarc[st]; ca->co != COLORLESS; ca++)
 	{
-		if (ca->co < cnfa->ncolors)
+		int			ndx = (*arcs_count)++;
+
+		if (ndx < arcs_len)
 		{
-			/* Ordinary arc, so count and possibly emit it */
-			int			ndx = (*arcs_count)++;
-
-			if (ndx < arcs_len)
-			{
-				arcs[ndx].co = ca->co;
-				arcs[ndx].to = ca->to;
-			}
+			arcs[ndx].co = ca->co;
+			arcs[ndx].to = ca->to;
 		}
-		else
+	}
+
+	/* Find state's LACON out-arcs, if any */
+	for (i = 0; i < cnfa->nlastates; i++)
+	{
+		if (cnfa->lastates[i] != st)
+			continue;
+		for (ca = cnfa->firstlaarc[i]; ca->co != COLORLESS; ca++)
 		{
 			/* LACON arc --- assume it's satisfied and recurse... */
 			/* ... but first, assert it doesn't lead directly to post state */
@@ -124,6 +129,7 @@ traverse_lacons(struct cnfa *cnfa, int st,
 
 			traverse_lacons(cnfa, ca->to, arcs_count, arcs, arcs_len);
 		}
+		break;					/* needn't look through rest of lastates[] */
 	}
 }
 
diff --git a/src/backend/regex/regprefix.c b/src/backend/regex/regprefix.c
index ec435b6f5f..31e158000f 100644
--- a/src/backend/regex/regprefix.c
+++ b/src/backend/regex/regprefix.c
@@ -131,7 +131,7 @@ findprefix(struct cnfa *cnfa,
 	 */
 	st = cnfa->pre;
 	nextst = -1;
-	for (ca = cnfa->states[st]; ca->co != COLORLESS; ca++)
+	for (ca = cnfa->firstarc[st]; ca->co != COLORLESS; ca++)
 	{
 		if (ca->co == cnfa->bos[0] || ca->co == cnfa->bos[1])
 		{
@@ -146,6 +146,8 @@ findprefix(struct cnfa *cnfa,
 	if (nextst == -1)
 		return REG_NOMATCH;
 
+	/* The "pre" state won't have LACON out-arcs, so don't bother looking */
+
 	/*
 	 * Scan through successive states, stopping as soon as we find one with
 	 * more than one acceptable transition character (either multiple colors
@@ -164,18 +166,14 @@ findprefix(struct cnfa *cnfa,
 		st = nextst;
 		nextst = -1;
 		thiscolor = COLORLESS;
-		for (ca = cnfa->states[st]; ca->co != COLORLESS; ca++)
+		for (ca = cnfa->firstarc[st]; ca->co != COLORLESS; ca++)
 		{
 			/* We can ignore BOS/BOL arcs */
 			if (ca->co == cnfa->bos[0] || ca->co == cnfa->bos[1])
 				continue;
-
-			/*
-			 * ... but EOS/EOL arcs terminate the search, as do RAINBOW arcs
-			 * and LACONs
-			 */
+			/* ... but EOS/EOL arcs terminate the search, as do RAINBOW arcs */
 			if (ca->co == cnfa->eos[0] || ca->co == cnfa->eos[1] ||
-				ca->co == RAINBOW || ca->co >= cnfa->ncolors)
+				ca->co == RAINBOW)
 			{
 				thiscolor = COLORLESS;
 				break;
@@ -198,6 +196,21 @@ findprefix(struct cnfa *cnfa,
 				break;
 			}
 		}
+		/* If good so far, check to see if state has LACON outarcs */
+		if (thiscolor != COLORLESS)
+		{
+			int			i;
+
+			for (i = 0; i < cnfa->nlastates; i++)
+			{
+				if (cnfa->lastates[i] == st)
+				{
+					/* Yes, so terminate the search */
+					thiscolor = COLORLESS;
+					break;
+				}
+			}
+		}
 		/* Done if we didn't find exactly one color on plain outarcs */
 		if (thiscolor == COLORLESS)
 			break;
@@ -235,7 +248,7 @@ findprefix(struct cnfa *cnfa,
 	 * even if the string is of zero length.
 	 */
 	nextst = -1;
-	for (ca = cnfa->states[st]; ca->co != COLORLESS; ca++)
+	for (ca = cnfa->firstarc[st]; ca->co != COLORLESS; ca++)
 	{
 		if (ca->co == cnfa->eos[0] || ca->co == cnfa->eos[1])
 		{
@@ -253,6 +266,20 @@ findprefix(struct cnfa *cnfa,
 			break;
 		}
 	}
+	/* If good so far, check to see if state has LACON outarcs */
+	if (nextst != -1)
+	{
+		int			i;
+
+		for (i = 0; i < cnfa->nlastates; i++)
+		{
+			if (cnfa->lastates[i] == st)
+			{
+				nextst = -1;
+				break;
+			}
+		}
+	}
 	if (nextst == cnfa->post)
 		return REG_EXACT;
 
diff --git a/src/include/regex/regguts.h b/src/include/regex/regguts.h
index 306525eb5f..6b3b399b2c 100644
--- a/src/include/regex/regguts.h
+++ b/src/include/regex/regguts.h
@@ -345,17 +345,15 @@ struct nfa
  *
  * The main space savings in a compacted NFA is from making the arcs as small
  * as possible.  We store only the transition color and next-state number for
- * each arc.  The list of out arcs for each state is an array beginning at
- * cnfa.states[statenumber], and terminated by a dummy carc struct with
- * co == COLORLESS.
+ * each arc.  The list of plain out-arcs for each state is an array beginning
+ * at cnfa.firstarc[statenumber], and terminated by a dummy carc struct with
+ * co == COLORLESS.  If a state has LACON out-arcs (most don't), then its
+ * state number appears in cnfa.lastates[k] for some k, and its first LACON
+ * out-arc is at cnfa.firstlaarc[k].  That array is likewise terminated by a
+ * dummy carc struct with co == COLORLESS.  The "co" values for LACON out-arcs
+ * are lookaround constraint numbers.
  *
- * The non-dummy carc structs are of two types: plain arcs and LACON arcs.
- * Plain arcs just store the transition color number as "co".  LACON arcs
- * store the lookaround constraint number plus cnfa.ncolors as "co".  LACON
- * arcs can be distinguished from plain by testing for co >= cnfa.ncolors.
- *
- * Note that in a plain arc, "co" can be RAINBOW; since that's negative,
- * it doesn't break the rule about how to recognize LACON arcs.
+ * Note that in a plain arc, "co" can be RAINBOW rather than a regular color.
  *
  * We have special markings for "trivial" NFAs that can match any string
  * (possibly with limits on the number of characters therein).  In such a
@@ -375,17 +373,20 @@ struct cnfa
 {
 	int			nstates;		/* number of states */
 	int			ncolors;		/* number of colors (max color in use + 1) */
-	int			flags;
+	int			flags;			/* bitmask of the following flags: */
 #define  HASLACONS	01			/* uses lookaround constraints */
 #define  MATCHALL	02			/* matches all strings of a range of lengths */
+	int			nlastates;		/* number of states with lookaround outarcs */
 	int			pre;			/* setup state number */
 	int			post;			/* teardown state number */
 	color		bos[2];			/* colors, if any, assigned to BOS and BOL */
 	color		eos[2];			/* colors, if any, assigned to EOS and EOL */
 	char	   *stflags;		/* vector of per-state flags bytes */
 #define  CNFA_NOPROGRESS	01	/* flag bit for a no-progress state */
-	struct carc **states;		/* vector of pointers to outarc lists */
-	/* states[n] are pointers into a single malloc'd array of arcs */
+	struct carc **firstarc;		/* per-state pointers to plain outarc lists */
+	int		   *lastates;		/* numbers of states with lookaround outarcs */
+	struct carc **firstlaarc;	/* pointers to LA outarcs for such states */
+	/* firstarc[n] & firstlaarc[n] are pointers into a single array of arcs */
 	struct carc *arcs;			/* the area for the lists */
 	/* these fields are used only in a MATCHALL NFA (else they're -1): */
 	int			minmatchall;	/* min number of chrs to match */

diff --git a/src/backend/regex/regc_nfa.c b/src/backend/regex/regc_nfa.c
index 69929eddfc..411c86f4ff 100644
--- a/src/backend/regex/regc_nfa.c
+++ b/src/backend/regex/regc_nfa.c
@@ -142,9 +142,12 @@ newstate(struct nfa *nfa)
 	{
 		s = nfa->free;
 		nfa->free = s->next;
+		/* the state's free arcs stay as they are */
 	}
 	else
 	{
+		int			i;
+
 		if (nfa->v->spaceused >= REG_MAX_COMPILE_SPACE)
 		{
 			NERR(REG_ETOOBIG);
@@ -157,9 +160,16 @@ newstate(struct nfa *nfa)
 			return NULL;
 		}
 		nfa->v->spaceused += sizeof(struct state);
-		s->oas.next = NULL;
-		s->free = NULL;
-		s->noas = 0;
+		s->lastab = NULL;
+		/* initialize free arcs; this should match allocarc() */
+		for (i = 0; i < NINITARCS - 1; i++)
+		{
+			s->inita[i].type = 0;
+			s->inita[i].freechain = &s->inita[i + 1];
+		}
+		s->inita[i].type = 0;
+		s->inita[i].freechain = NULL;
+		s->free = &s->inita[0];
 	}
 
 	assert(nfa->nstates >= 0);
@@ -255,11 +265,11 @@ destroystate(struct nfa *nfa,
 	struct arcbatch *abnext;
 
 	assert(s->no == FREESTATE);
-	for (ab = s->oas.next; ab != NULL; ab = abnext)
+	for (ab = s->lastab; ab != NULL; ab = abnext)
 	{
 		abnext = ab->next;
+		nfa->v->spaceused -= ARCBATCHSIZE(ab->narcs);
 		FREE(ab);
-		nfa->v->spaceused -= sizeof(struct arcbatch);
 	}
 	s->ins = NULL;
 	s->outs = NULL;
@@ -377,41 +387,39 @@ allocarc(struct nfa *nfa,
 {
 	struct arc *a;
 
-	/* shortcut */
-	if (s->free == NULL && s->noas < ABSIZE)
-	{
-		a = &s->oas.a[s->noas];
-		s->noas++;
-		return a;
-	}
-
 	/* if none at hand, get more */
 	if (s->free == NULL)
 	{
 		struct arcbatch *newAb;
-		int			i;
+		size_t		narcs;
+		size_t		i;
 
 		if (nfa->v->spaceused >= REG_MAX_COMPILE_SPACE)
 		{
 			NERR(REG_ETOOBIG);
 			return NULL;
 		}
-		newAb = (struct arcbatch *) MALLOC(sizeof(struct arcbatch));
+		narcs = (s->lastab != NULL) ? s->lastab->narcs * 2 : FIRSTABSIZE;
+		if (narcs > MAXABSIZE)
+			narcs = MAXABSIZE;
+		newAb = (struct arcbatch *) MALLOC(ARCBATCHSIZE(narcs));
 		if (newAb == NULL)
 		{
 			NERR(REG_ESPACE);
 			return NULL;
 		}
-		nfa->v->spaceused += sizeof(struct arcbatch);
-		newAb->next = s->oas.next;
-		s->oas.next = newAb;
+		nfa->v->spaceused += ARCBATCHSIZE(narcs);
+		newAb->narcs = narcs;
+		newAb->next = s->lastab;
+		s->lastab = newAb;
 
-		for (i = 0; i < ABSIZE; i++)
+		for (i = 0; i < narcs - 1; i++)
 		{
 			newAb->a[i].type = 0;
 			newAb->a[i].freechain = &newAb->a[i + 1];
 		}
-		newAb->a[ABSIZE - 1].freechain = NULL;
+		newAb->a[i].type = 0;
+		newAb->a[i].freechain = NULL;
 		s->free = &newAb->a[0];
 	}
 	assert(s->free != NULL);
@@ -3413,7 +3421,7 @@ dumparc(struct arc *a,
 		FILE *f)
 {
 	struct arc *aa;
-	struct arcbatch *ab;
+	bool		found = false;
 
 	fprintf(f, "\t");
 	switch (a->type)
@@ -3451,15 +3459,29 @@ dumparc(struct arc *a,
 	}
 	if (a->from != s)
 		fprintf(f, "?%d?", a->from->no);
-	for (ab = &a->from->oas; ab != NULL; ab = ab->next)
+
+	/*
+	 * Check that arc belongs to its from-state's arc space.  This is
+	 * approximate, since we don't verify the arc isn't misaligned within the
+	 * space; but it's enough to catch the likely problem of an arc being
+	 * misassigned to a different parent state.
+	 */
+	if (a >= a->from->inita && a < a->from->inita + NINITARCS)
+		found = true;			/* member of initial arcset */
+	else
 	{
-		for (aa = &ab->a[0]; aa < &ab->a[ABSIZE]; aa++)
-			if (aa == a)
+		struct arcbatch *ab;
+
+		for (ab = a->from->lastab; ab != NULL; ab = ab->next)
+		{
+			if (a >= ab->a && a < ab->a + ab->narcs)
+			{
+				found = true;
 				break;			/* NOTE BREAK OUT */
-		if (aa < &ab->a[ABSIZE])	/* propagate break */
-			break;				/* NOTE BREAK OUT */
+			}
+		}
 	}
-	if (ab == NULL)
+	if (!found)
 		fprintf(f, "?!?");		/* not in allocated space */
 	fprintf(f, "->");
 	if (a->to == NULL)
diff --git a/src/include/regex/regguts.h b/src/include/regex/regguts.h
index 306525eb5f..65e6ace9d1 100644
--- a/src/include/regex/regguts.h
+++ b/src/include/regex/regguts.h
@@ -294,12 +294,23 @@ struct arc
 	struct arc *colorchainRev;	/* back-link in color's arc chain */
 };
 
+/*
+ * We include NINITARCS arcs directly in the parent state, to save a separate
+ * malloc for states with few out-arcs.  If more arcs are needed, the first
+ * arcbatch has size FIRSTABSIZE; each succeeding batch doubles in size,
+ * up to MAXABSIZE.
+ */
+#define  NINITARCS		2		/* 2 is enough for about 80% of states */
+#define  FIRSTABSIZE	8		/* 2+8 is enough for 95% of states */
+#define  MAXABSIZE		64		/* don't waste too much space per arcbatch */
+
 struct arcbatch
 {								/* for bulk allocation of arcs */
-	struct arcbatch *next;
-#define  ABSIZE  10
-	struct arc	a[ABSIZE];
+	struct arcbatch *next;		/* chain link */
+	size_t		narcs;			/* number of arcs allocated in this arcbatch */
+	struct arc	a[FLEXIBLE_ARRAY_MEMBER];
 };
+#define  ARCBATCHSIZE(n)  ((n) * sizeof(struct arc) + offsetof(struct arcbatch, a))
 
 struct state
 {
@@ -312,10 +323,10 @@ struct state
 	struct arc *outs;			/* chain of outarcs */
 	struct arc *free;			/* chain of free arcs */
 	struct state *tmp;			/* temporary for traversal algorithms */
-	struct state *next;			/* chain for traversing all */
-	struct state *prev;			/* back chain */
-	struct arcbatch oas;		/* first arcbatch, avoid malloc in easy case */
-	int			noas;			/* number of arcs used in first arcbatch */
+	struct state *next;			/* chain for traversing all live states */
+	struct state *prev;			/* back-link in chain of all live states */
+	struct arcbatch *lastab;	/* chain of associated arcbatches */
+	struct arc	inita[NINITARCS];	/* a few arcs to avoid extra malloc */
 };
 
 struct nfa
@@ -413,7 +424,7 @@ struct cnfa
  */
 #ifndef REG_MAX_COMPILE_SPACE
 #define REG_MAX_COMPILE_SPACE  \
-	(100000 * sizeof(struct state) + 100000 * sizeof(struct arcbatch))
+	(100000 * sizeof(struct state) + 2000000 * sizeof(struct arc))
 #endif
 
 /*

diff --git a/src/backend/regex/regc_nfa.c b/src/backend/regex/regc_nfa.c
index 69929eddfc..df3351b3d0 100644
--- a/src/backend/regex/regc_nfa.c
+++ b/src/backend/regex/regc_nfa.c
@@ -59,7 +59,10 @@ newnfa(struct vars *v,
 
 	nfa->states = NULL;
 	nfa->slast = NULL;
-	nfa->free = NULL;
+	nfa->freestates = NULL;
+	nfa->freearcs = NULL;
+	nfa->lastsb = NULL;
+	nfa->lastab = NULL;
 	nfa->nstates = 0;
 	nfa->cm = cm;
 	nfa->v = v;
@@ -99,23 +102,27 @@ newnfa(struct vars *v,
 static void
 freenfa(struct nfa *nfa)
 {
-	struct state *s;
+	struct statebatch *sb;
+	struct statebatch *sbnext;
+	struct arcbatch *ab;
+	struct arcbatch *abnext;
 
-	while ((s = nfa->states) != NULL)
+	for (sb = nfa->lastsb; sb != NULL; sb = sbnext)
 	{
-		s->nins = s->nouts = 0; /* don't worry about arcs */
-		freestate(nfa, s);
+		sbnext = sb->next;
+		nfa->v->spaceused -= STATEBATCHSIZE(sb->nstates);
+		FREE(sb);
 	}
-	while ((s = nfa->free) != NULL)
+	nfa->lastsb = NULL;
+	for (ab = nfa->lastab; ab != NULL; ab = abnext)
 	{
-		nfa->free = s->next;
-		destroystate(nfa, s);
+		abnext = ab->next;
+		nfa->v->spaceused -= ARCBATCHSIZE(ab->narcs);
+		FREE(ab);
 	}
+	nfa->lastab = NULL;
 
-	nfa->slast = NULL;
 	nfa->nstates = -1;
-	nfa->pre = NULL;
-	nfa->post = NULL;
 	FREE(nfa);
 }
 
@@ -138,29 +145,45 @@ newstate(struct nfa *nfa)
 		return NULL;
 	}
 
-	if (nfa->free != NULL)
-	{
-		s = nfa->free;
-		nfa->free = s->next;
-	}
-	else
+	/* if none at hand, get more */
+	if (nfa->freestates == NULL)
 	{
+		struct statebatch *newSb;
+		size_t		nstates;
+		size_t		i;
+
 		if (nfa->v->spaceused >= REG_MAX_COMPILE_SPACE)
 		{
 			NERR(REG_ETOOBIG);
 			return NULL;
 		}
-		s = (struct state *) MALLOC(sizeof(struct state));
-		if (s == NULL)
+		nstates = (nfa->lastsb != NULL) ? nfa->lastsb->nstates * 2 : FIRSTSBSIZE;
+		if (nstates > MAXSBSIZE)
+			nstates = MAXSBSIZE;
+		newSb = (struct statebatch *) MALLOC(STATEBATCHSIZE(nstates));
+		if (newSb == NULL)
 		{
 			NERR(REG_ESPACE);
 			return NULL;
 		}
-		nfa->v->spaceused += sizeof(struct state);
-		s->oas.next = NULL;
-		s->free = NULL;
-		s->noas = 0;
+		nfa->v->spaceused += STATEBATCHSIZE(nstates);
+		newSb->nstates = nstates;
+		newSb->next = nfa->lastsb;
+		nfa->lastsb = newSb;
+
+		for (i = 0; i < nstates - 1; i++)
+		{
+			newSb->s[i].no = FREESTATE;
+			newSb->s[i].next = &newSb->s[i + 1];
+		}
+		newSb->s[i].no = FREESTATE;
+		newSb->s[i].next = NULL;
+		nfa->freestates = &newSb->s[0];
 	}
+	assert(nfa->freestates != NULL);
+
+	s = nfa->freestates;
+	nfa->freestates = s->next;
 
 	assert(nfa->nstates >= 0);
 	s->no = nfa->nstates++;
@@ -240,32 +263,8 @@ freestate(struct nfa *nfa,
 		nfa->states = s->next;
 	}
 	s->prev = NULL;
-	s->next = nfa->free;		/* don't delete it, put it on the free list */
-	nfa->free = s;
-}
-
-/*
- * destroystate - really get rid of an already-freed state
- */
-static void
-destroystate(struct nfa *nfa,
-			 struct state *s)
-{
-	struct arcbatch *ab;
-	struct arcbatch *abnext;
-
-	assert(s->no == FREESTATE);
-	for (ab = s->oas.next; ab != NULL; ab = abnext)
-	{
-		abnext = ab->next;
-		FREE(ab);
-		nfa->v->spaceused -= sizeof(struct arcbatch);
-	}
-	s->ins = NULL;
-	s->outs = NULL;
-	s->next = NULL;
-	FREE(s);
-	nfa->v->spaceused -= sizeof(struct state);
+	s->next = nfa->freestates;	/* don't delete it, put it on the free list */
+	nfa->freestates = s;
 }
 
 /*
@@ -334,8 +333,7 @@ createarc(struct nfa *nfa,
 {
 	struct arc *a;
 
-	/* the arc is physically allocated within its from-state */
-	a = allocarc(nfa, from);
+	a = allocarc(nfa);
 	if (NISERR())
 		return;
 	assert(a != NULL);
@@ -369,55 +367,52 @@ createarc(struct nfa *nfa,
 }
 
 /*
- * allocarc - allocate a new out-arc within a state
+ * allocarc - allocate a new arc within an NFA
  */
 static struct arc *				/* NULL for failure */
-allocarc(struct nfa *nfa,
-		 struct state *s)
+allocarc(struct nfa *nfa)
 {
 	struct arc *a;
 
-	/* shortcut */
-	if (s->free == NULL && s->noas < ABSIZE)
-	{
-		a = &s->oas.a[s->noas];
-		s->noas++;
-		return a;
-	}
-
 	/* if none at hand, get more */
-	if (s->free == NULL)
+	if (nfa->freearcs == NULL)
 	{
 		struct arcbatch *newAb;
-		int			i;
+		size_t		narcs;
+		size_t		i;
 
 		if (nfa->v->spaceused >= REG_MAX_COMPILE_SPACE)
 		{
 			NERR(REG_ETOOBIG);
 			return NULL;
 		}
-		newAb = (struct arcbatch *) MALLOC(sizeof(struct arcbatch));
+		narcs = (nfa->lastab != NULL) ? nfa->lastab->narcs * 2 : FIRSTABSIZE;
+		if (narcs > MAXABSIZE)
+			narcs = MAXABSIZE;
+		newAb = (struct arcbatch *) MALLOC(ARCBATCHSIZE(narcs));
 		if (newAb == NULL)
 		{
 			NERR(REG_ESPACE);
 			return NULL;
 		}
-		nfa->v->spaceused += sizeof(struct arcbatch);
-		newAb->next = s->oas.next;
-		s->oas.next = newAb;
+		nfa->v->spaceused += ARCBATCHSIZE(narcs);
+		newAb->narcs = narcs;
+		newAb->next = nfa->lastab;
+		nfa->lastab = newAb;
 
-		for (i = 0; i < ABSIZE; i++)
+		for (i = 0; i < narcs - 1; i++)
 		{
 			newAb->a[i].type = 0;
 			newAb->a[i].freechain = &newAb->a[i + 1];
 		}
-		newAb->a[ABSIZE - 1].freechain = NULL;
-		s->free = &newAb->a[0];
+		newAb->a[i].type = 0;
+		newAb->a[i].freechain = NULL;
+		nfa->freearcs = &newAb->a[0];
 	}
-	assert(s->free != NULL);
+	assert(nfa->freearcs != NULL);
 
-	a = s->free;
-	s->free = a->freechain;
+	a = nfa->freearcs;
+	nfa->freearcs = a->freechain;
 	return a;
 }
 
@@ -478,7 +473,7 @@ freearc(struct nfa *nfa,
 	}
 	to->nins--;
 
-	/* clean up and place on from-state's free list */
+	/* clean up and place on NFA's free list */
 	victim->type = 0;
 	victim->from = NULL;		/* precautions... */
 	victim->to = NULL;
@@ -486,8 +481,8 @@ freearc(struct nfa *nfa,
 	victim->inchainRev = NULL;
 	victim->outchain = NULL;
 	victim->outchainRev = NULL;
-	victim->freechain = from->free;
-	from->free = victim;
+	victim->freechain = nfa->freearcs;
+	nfa->freearcs = victim;
 }
 
 /*
@@ -3413,7 +3408,6 @@ dumparc(struct arc *a,
 		FILE *f)
 {
 	struct arc *aa;
-	struct arcbatch *ab;
 
 	fprintf(f, "\t");
 	switch (a->type)
@@ -3451,16 +3445,11 @@ dumparc(struct arc *a,
 	}
 	if (a->from != s)
 		fprintf(f, "?%d?", a->from->no);
-	for (ab = &a->from->oas; ab != NULL; ab = ab->next)
-	{
-		for (aa = &ab->a[0]; aa < &ab->a[ABSIZE]; aa++)
-			if (aa == a)
-				break;			/* NOTE BREAK OUT */
-		if (aa < &ab->a[ABSIZE])	/* propagate break */
+	for (aa = a->from->outs; aa != NULL; aa = aa->outchain)
+		if (aa == a)
 			break;				/* NOTE BREAK OUT */
-	}
-	if (ab == NULL)
-		fprintf(f, "?!?");		/* not in allocated space */
+	if (aa == NULL)
+		fprintf(f, "?!?");		/* missing from out-chain */
 	fprintf(f, "->");
 	if (a->to == NULL)
 	{
diff --git a/src/backend/regex/regcomp.c b/src/backend/regex/regcomp.c
index d3540fdd0f..a51555cfde 100644
--- a/src/backend/regex/regcomp.c
+++ b/src/backend/regex/regcomp.c
@@ -127,10 +127,9 @@ static struct state *newstate(struct nfa *);
 static struct state *newfstate(struct nfa *, int flag);
 static void dropstate(struct nfa *, struct state *);
 static void freestate(struct nfa *, struct state *);
-static void destroystate(struct nfa *, struct state *);
 static void newarc(struct nfa *, int, color, struct state *, struct state *);
 static void createarc(struct nfa *, int, color, struct state *, struct state *);
-static struct arc *allocarc(struct nfa *, struct state *);
+static struct arc *allocarc(struct nfa *);
 static void freearc(struct nfa *, struct arc *);
 static void changearctarget(struct arc *, struct state *);
 static int	hasnonemptyout(struct state *);
diff --git a/src/include/regex/regguts.h b/src/include/regex/regguts.h
index 0e76a828f8..f3e7752171 100644
--- a/src/include/regex/regguts.h
+++ b/src/include/regex/regguts.h
@@ -284,9 +284,6 @@ struct cvec
 
 /*
  * definitions for NFA internal representation
- *
- * Having a "from" pointer within each arc may seem redundant, but it
- * saves a lot of hassle.
  */
 struct state;
 
@@ -294,7 +291,7 @@ struct arc
 {
 	int			type;			/* 0 if free, else an NFA arc type code */
 	color		co;				/* color the arc matches (possibly RAINBOW) */
-	struct state *from;			/* where it's from (and contained within) */
+	struct state *from;			/* where it's from */
 	struct state *to;			/* where it's to */
 	struct arc *outchain;		/* link in *from's outs chain or free chain */
 	struct arc *outchainRev;	/* back-link in *from's outs chain */
@@ -308,28 +305,39 @@ struct arc
 
 struct arcbatch
 {								/* for bulk allocation of arcs */
-	struct arcbatch *next;
-#define  ABSIZE  10
-	struct arc	a[ABSIZE];
+	struct arcbatch *next;		/* chain link */
+	size_t		narcs;			/* number of arcs allocated in this arcbatch */
+	struct arc	a[FLEXIBLE_ARRAY_MEMBER];
 };
+#define  ARCBATCHSIZE(n)  ((n) * sizeof(struct arc) + offsetof(struct arcbatch, a))
+#define  FIRSTABSIZE	64
+#define  MAXABSIZE		1024
 
 struct state
 {
-	int			no;
+	int			no;				/* state number, zero and up; or FREESTATE */
 #define  FREESTATE	 (-1)
 	char		flag;			/* marks special states */
 	int			nins;			/* number of inarcs */
-	struct arc *ins;			/* chain of inarcs */
 	int			nouts;			/* number of outarcs */
+	struct arc *ins;			/* chain of inarcs */
 	struct arc *outs;			/* chain of outarcs */
-	struct arc *free;			/* chain of free arcs */
 	struct state *tmp;			/* temporary for traversal algorithms */
-	struct state *next;			/* chain for traversing all */
-	struct state *prev;			/* back chain */
-	struct arcbatch oas;		/* first arcbatch, avoid malloc in easy case */
-	int			noas;			/* number of arcs used in first arcbatch */
+	struct state *next;			/* chain for traversing all live states */
+	/* the "next" field is also used to chain free states together */
+	struct state *prev;			/* back-link in chain of all live states */
 };
 
+struct statebatch
+{								/* for bulk allocation of states */
+	struct statebatch *next;	/* chain link */
+	size_t		nstates;		/* number of states allocated in this batch */
+	struct state s[FLEXIBLE_ARRAY_MEMBER];
+};
+#define  STATEBATCHSIZE(n)  ((n) * sizeof(struct state) + offsetof(struct statebatch, s))
+#define  FIRSTSBSIZE	32
+#define  MAXSBSIZE		1024
+
 struct nfa
 {
 	struct state *pre;			/* pre-initial state */
@@ -337,9 +345,12 @@ struct nfa
 	struct state *final;		/* final state */
 	struct state *post;			/* post-final state */
 	int			nstates;		/* for numbering states */
-	struct state *states;		/* state-chain header */
+	struct state *states;		/* chain of live states */
 	struct state *slast;		/* tail of the chain */
-	struct state *free;			/* free list */
+	struct state *freestates;	/* chain of free states */
+	struct arc *freearcs;		/* chain of free arcs */
+	struct statebatch *lastsb;	/* chain of statebatches */
+	struct arcbatch *lastab;	/* chain of arcbatches */
 	struct colormap *cm;		/* the color map */
 	color		bos[2];			/* colors, if any, assigned to BOS and BOL */
 	color		eos[2];			/* colors, if any, assigned to EOS and EOL */
@@ -387,7 +398,7 @@ struct cnfa
 {
 	int			nstates;		/* number of states */
 	int			ncolors;		/* number of colors (max color in use + 1) */
-	int			flags;
+	int			flags;			/* bitmask of the following flags: */
 #define  HASLACONS	01			/* uses lookaround constraints */
 #define  MATCHALL	02			/* matches all strings of a range of lengths */
 	int			pre;			/* setup state number */
@@ -422,10 +433,12 @@ struct cnfa
  * transient data is generally not large enough to notice compared to those.
  * Note that we do not charge anything for the final output data structures
  * (the compacted NFA and the colormap).
+ * The scaling here is based on an empirical measurement that very large
+ * NFAs tend to have about 4 arcs/state.
  */
 #ifndef REG_MAX_COMPILE_SPACE
 #define REG_MAX_COMPILE_SPACE  \
-	(100000 * sizeof(struct state) + 100000 * sizeof(struct arcbatch))
+	(500000 * (sizeof(struct state) + 4 * sizeof(struct arc)))
 #endif
 
 /*