Clean up parsing of ltree and lquery some more.

Fix lquery parsing to handle repeated flag characters correctly,
and to enforce the max label length correctly in some cases where
it did not before, and to detect empty labels in some cases where
it did not before.

In a more cosmetic vein, use a switch rather than if-then chains to
handle the different states, and avoid unnecessary checks on charlen
when looking for ASCII characters, and factor out multiple copies of
the label length checking code.

Tom Lane and Dmitry Belyavsky

Discussion: https://postgr.es/m/CADqLbzLVkBuPX0812o+z=c3i6honszsZZ6VQOSKR3VPbB56P3w@mail.gmail.com

3 files changed, 362 insertions, 278 deletions

diff --git a/contrib/ltree/expected/ltree.out b/contrib/ltree/expected/ltree.out
index 5d9102cb6c9..c6d8f3ef75e 100644
--- a/contrib/ltree/expected/ltree.out
+++ b/contrib/ltree/expected/ltree.out
@@ -31,6 +31,29 @@ SELECT '1.2._3'::ltree;
  1.2._3
 (1 row)
 
+-- empty labels not allowed
+SELECT '.2.3'::ltree;
+ERROR:  ltree syntax error at character 1
+LINE 1: SELECT '.2.3'::ltree;
+               ^
+SELECT '1..3'::ltree;
+ERROR:  ltree syntax error at character 3
+LINE 1: SELECT '1..3'::ltree;
+               ^
+SELECT '1.2.'::ltree;
+ERROR:  ltree syntax error
+LINE 1: SELECT '1.2.'::ltree;
+               ^
+DETAIL:  Unexpected end of input.
+SELECT repeat('x', 255)::ltree;
+                                                                                                                             repeat                                                                                                                              
+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+ xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+(1 row)
+
+SELECT repeat('x', 256)::ltree;
+ERROR:  label string is too long
+DETAIL:  Label length is 256, must be at most 255, at character 257.
 SELECT ltree2text('1.2.3.34.sdf');
   ltree2text  
 --------------
@@ -451,12 +474,81 @@ SELECT 'foo.bar{,}.!a*|b{1,}.c{,44}.d{3,4}'::lquery;
  foo.bar{,}.!a*|b{1,}.c{,44}.d{3,4}
 (1 row)
 
+SELECT 'foo*@@*'::lquery;
+ lquery 
+--------
+ foo@*
+(1 row)
+
 SELECT 'qwerty%@*.tu'::lquery;
     lquery    
 --------------
  qwerty%@*.tu
 (1 row)
 
+-- empty labels not allowed
+SELECT '.2.3'::lquery;
+ERROR:  lquery syntax error at character 1
+LINE 1: SELECT '.2.3'::lquery;
+               ^
+SELECT '1..3'::lquery;
+ERROR:  lquery syntax error at character 3
+LINE 1: SELECT '1..3'::lquery;
+               ^
+SELECT '1.2.'::lquery;
+ERROR:  lquery syntax error
+LINE 1: SELECT '1.2.'::lquery;
+               ^
+DETAIL:  Unexpected end of input.
+SELECT '@.2.3'::lquery;
+ERROR:  lquery syntax error at character 1
+LINE 1: SELECT '@.2.3'::lquery;
+               ^
+SELECT '1.@.3'::lquery;
+ERROR:  lquery syntax error at character 3
+LINE 1: SELECT '1.@.3'::lquery;
+               ^
+SELECT '1.2.@'::lquery;
+ERROR:  lquery syntax error at character 5
+LINE 1: SELECT '1.2.@'::lquery;
+               ^
+SELECT '!.2.3'::lquery;
+ERROR:  lquery syntax error at character 2
+LINE 1: SELECT '!.2.3'::lquery;
+               ^
+DETAIL:  Empty labels are not allowed.
+SELECT '1.!.3'::lquery;
+ERROR:  lquery syntax error at character 4
+LINE 1: SELECT '1.!.3'::lquery;
+               ^
+DETAIL:  Empty labels are not allowed.
+SELECT '1.2.!'::lquery;
+ERROR:  lquery syntax error at character 6
+LINE 1: SELECT '1.2.!'::lquery;
+               ^
+DETAIL:  Empty labels are not allowed.
+SELECT '1.2.3|@.4'::lquery;
+ERROR:  lquery syntax error at character 7
+LINE 1: SELECT '1.2.3|@.4'::lquery;
+               ^
+SELECT (repeat('x', 255) || '*@@*')::lquery;
+                                                                                                                              lquery                                                                                                                               
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+ xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx@*
+(1 row)
+
+SELECT (repeat('x', 256) || '*@@*')::lquery;
+ERROR:  label string is too long
+DETAIL:  Label length is 256, must be at most 255, at character 257.
+SELECT ('!' || repeat('x', 255))::lquery;
+                                                                                                                              lquery                                                                                                                              
+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+ !xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+(1 row)
+
+SELECT ('!' || repeat('x', 256))::lquery;
+ERROR:  label string is too long
+DETAIL:  Label length is 256, must be at most 255, at character 258.
 SELECT nlevel('1.2.3.4');
  nlevel 
 --------
@@ -1072,6 +1164,12 @@ SELECT 'QWER_TY'::ltree ~ 'q%@*';
  t
 (1 row)
 
+SELECT 'QWER_TY'::ltree ~ 'q%@*%@*';
+ ?column? 
+----------
+ t
+(1 row)
+
 SELECT 'QWER_TY'::ltree ~ 'Q_t%@*';
  ?column? 
 ----------
diff --git a/contrib/ltree/ltree_io.c b/contrib/ltree/ltree_io.c
index b928b82d624..15115cb29f3 100644
--- a/contrib/ltree/ltree_io.c
+++ b/contrib/ltree/ltree_io.c
@@ -24,6 +24,10 @@ typedef struct
 #define LTPRS_WAITNAME	0
 #define LTPRS_WAITDELIM 1
 
+static void finish_nodeitem(nodeitem *lptr, const char *ptr,
+							bool is_lquery, int pos);
+
+
 /*
  * expects a null terminated string
  * returns an ltree
@@ -51,7 +55,7 @@ parse_ltree(const char *buf)
 	while (*ptr)
 	{
 		charlen = pg_mblen(ptr);
-		if (charlen == 1 && t_iseq(ptr, '.'))
+		if (t_iseq(ptr, '.'))
 			num++;
 		ptr += charlen;
 	}
@@ -67,40 +71,32 @@ parse_ltree(const char *buf)
 	{
 		charlen = pg_mblen(ptr);
 
-		if (state == LTPRS_WAITNAME)
+		switch (state)
 		{
-			if (ISALNUM(ptr))
-			{
-				lptr->start = ptr;
-				lptr->wlen = 0;
-				state = LTPRS_WAITDELIM;
-			}
-			else
-				UNCHAR;
-		}
-		else if (state == LTPRS_WAITDELIM)
-		{
-			if (charlen == 1 && t_iseq(ptr, '.'))
-			{
-				lptr->len = ptr - lptr->start;
-				if (lptr->wlen > LTREE_LABEL_MAX_CHARS)
-					ereport(ERROR,
-							(errcode(ERRCODE_NAME_TOO_LONG),
-							 errmsg("label string is too long"),
-							 errdetail("Label length is %d, must be at most %d, at character %d.",
-									   lptr->wlen, LTREE_LABEL_MAX_CHARS,
-									   pos)));
-
-				totallen += MAXALIGN(lptr->len + LEVEL_HDRSIZE);
-				lptr++;
-				state = LTPRS_WAITNAME;
-			}
-			else if (!ISALNUM(ptr))
-				UNCHAR;
+			case LTPRS_WAITNAME:
+				if (ISALNUM(ptr))
+				{
+					lptr->start = ptr;
+					lptr->wlen = 0;
+					state = LTPRS_WAITDELIM;
+				}
+				else
+					UNCHAR;
+				break;
+			case LTPRS_WAITDELIM:
+				if (t_iseq(ptr, '.'))
+				{
+					finish_nodeitem(lptr, ptr, false, pos);
+					totallen += MAXALIGN(lptr->len + LEVEL_HDRSIZE);
+					lptr++;
+					state = LTPRS_WAITNAME;
+				}
+				else if (!ISALNUM(ptr))
+					UNCHAR;
+				break;
+			default:
+				elog(ERROR, "internal error in ltree parser");
 		}
-		else
-			/* internal error */
-			elog(ERROR, "internal error in parser");
 
 		ptr += charlen;
 		lptr->wlen++;
@@ -109,14 +105,7 @@ parse_ltree(const char *buf)
 
 	if (state == LTPRS_WAITDELIM)
 	{
-		lptr->len = ptr - lptr->start;
-		if (lptr->wlen > LTREE_LABEL_MAX_CHARS)
-			ereport(ERROR,
-					(errcode(ERRCODE_NAME_TOO_LONG),
-					 errmsg("label string is too long"),
-					 errdetail("Label length is %d, must be at most %d, at character %d.",
-							   lptr->wlen, LTREE_LABEL_MAX_CHARS, pos)));
-
+		finish_nodeitem(lptr, ptr, false, pos);
 		totallen += MAXALIGN(lptr->len + LEVEL_HDRSIZE);
 		lptr++;
 	}
@@ -298,13 +287,10 @@ parse_lquery(const char *buf)
 	{
 		charlen = pg_mblen(ptr);
 
-		if (charlen == 1)
-		{
-			if (t_iseq(ptr, '.'))
-				num++;
-			else if (t_iseq(ptr, '|'))
-				numOR++;
-		}
+		if (t_iseq(ptr, '.'))
+			num++;
+		else if (t_iseq(ptr, '|'))
+			numOR++;
 
 		ptr += charlen;
 	}
@@ -321,220 +307,176 @@ parse_lquery(const char *buf)
 	{
 		charlen = pg_mblen(ptr);
 
-		if (state == LQPRS_WAITLEVEL)
-		{
-			if (ISALNUM(ptr))
-			{
-				GETVAR(curqlevel) = lptr = (nodeitem *) palloc0(sizeof(nodeitem) * (numOR + 1));
-				lptr->start = ptr;
-				state = LQPRS_WAITDELIM;
-				curqlevel->numvar = 1;
-			}
-			else if (charlen == 1 && t_iseq(ptr, '!'))
-			{
-				GETVAR(curqlevel) = lptr = (nodeitem *) palloc0(sizeof(nodeitem) * (numOR + 1));
-				lptr->start = ptr + 1;
-				state = LQPRS_WAITDELIM;
-				curqlevel->numvar = 1;
-				curqlevel->flag |= LQL_NOT;
-				hasnot = true;
-			}
-			else if (charlen == 1 && t_iseq(ptr, '*'))
-				state = LQPRS_WAITOPEN;
-			else
-				UNCHAR;
-		}
-		else if (state == LQPRS_WAITVAR)
-		{
-			if (ISALNUM(ptr))
-			{
-				lptr++;
-				lptr->start = ptr;
-				state = LQPRS_WAITDELIM;
-				curqlevel->numvar++;
-			}
-			else
-				UNCHAR;
-		}
-		else if (state == LQPRS_WAITDELIM)
+		switch (state)
 		{
-			if (charlen == 1 && t_iseq(ptr, '@'))
-			{
-				if (lptr->start == ptr)
+			case LQPRS_WAITLEVEL:
+				if (ISALNUM(ptr))
+				{
+					GETVAR(curqlevel) = lptr = (nodeitem *) palloc0(sizeof(nodeitem) * (numOR + 1));
+					lptr->start = ptr;
+					state = LQPRS_WAITDELIM;
+					curqlevel->numvar = 1;
+				}
+				else if (t_iseq(ptr, '!'))
+				{
+					GETVAR(curqlevel) = lptr = (nodeitem *) palloc0(sizeof(nodeitem) * (numOR + 1));
+					lptr->start = ptr + 1;
+					lptr->wlen = -1;	/* compensate for counting ! below */
+					state = LQPRS_WAITDELIM;
+					curqlevel->numvar = 1;
+					curqlevel->flag |= LQL_NOT;
+					hasnot = true;
+				}
+				else if (t_iseq(ptr, '*'))
+					state = LQPRS_WAITOPEN;
+				else
 					UNCHAR;
-				lptr->flag |= LVAR_INCASE;
-				curqlevel->flag |= LVAR_INCASE;
-			}
-			else if (charlen == 1 && t_iseq(ptr, '*'))
-			{
-				if (lptr->start == ptr)
+				break;
+			case LQPRS_WAITVAR:
+				if (ISALNUM(ptr))
+				{
+					lptr++;
+					lptr->start = ptr;
+					state = LQPRS_WAITDELIM;
+					curqlevel->numvar++;
+				}
+				else
 					UNCHAR;
-				lptr->flag |= LVAR_ANYEND;
-				curqlevel->flag |= LVAR_ANYEND;
-			}
-			else if (charlen == 1 && t_iseq(ptr, '%'))
-			{
-				if (lptr->start == ptr)
+				break;
+			case LQPRS_WAITDELIM:
+				if (t_iseq(ptr, '@'))
+				{
+					lptr->flag |= LVAR_INCASE;
+					curqlevel->flag |= LVAR_INCASE;
+				}
+				else if (t_iseq(ptr, '*'))
+				{
+					lptr->flag |= LVAR_ANYEND;
+					curqlevel->flag |= LVAR_ANYEND;
+				}
+				else if (t_iseq(ptr, '%'))
+				{
+					lptr->flag |= LVAR_SUBLEXEME;
+					curqlevel->flag |= LVAR_SUBLEXEME;
+				}
+				else if (t_iseq(ptr, '|'))
+				{
+					finish_nodeitem(lptr, ptr, true, pos);
+					state = LQPRS_WAITVAR;
+				}
+				else if (t_iseq(ptr, '{'))
+				{
+					finish_nodeitem(lptr, ptr, true, pos);
+					curqlevel->flag |= LQL_COUNT;
+					state = LQPRS_WAITFNUM;
+				}
+				else if (t_iseq(ptr, '.'))
+				{
+					finish_nodeitem(lptr, ptr, true, pos);
+					state = LQPRS_WAITLEVEL;
+					curqlevel = NEXTLEV(curqlevel);
+				}
+				else if (ISALNUM(ptr))
+				{
+					/* disallow more chars after a flag */
+					if (lptr->flag)
+						UNCHAR;
+				}
+				else
 					UNCHAR;
-				lptr->flag |= LVAR_SUBLEXEME;
-				curqlevel->flag |= LVAR_SUBLEXEME;
-			}
-			else if (charlen == 1 && t_iseq(ptr, '|'))
-			{
-				lptr->len = ptr - lptr->start -
-					((lptr->flag & LVAR_SUBLEXEME) ? 1 : 0) -
-					((lptr->flag & LVAR_INCASE) ? 1 : 0) -
-					((lptr->flag & LVAR_ANYEND) ? 1 : 0);
-				if (lptr->wlen > LTREE_LABEL_MAX_CHARS)
-					ereport(ERROR,
-							(errcode(ERRCODE_NAME_TOO_LONG),
-							 errmsg("label string is too long"),
-							 errdetail("Label length is %d, must be at most %d, at character %d.",
-									   lptr->wlen, LTREE_LABEL_MAX_CHARS,
-									   pos)));
-
-				state = LQPRS_WAITVAR;
-			}
-			else if (charlen == 1 && t_iseq(ptr, '{'))
-			{
-				lptr->len = ptr - lptr->start -
-					((lptr->flag & LVAR_SUBLEXEME) ? 1 : 0) -
-					((lptr->flag & LVAR_INCASE) ? 1 : 0) -
-					((lptr->flag & LVAR_ANYEND) ? 1 : 0);
-				if (lptr->wlen > LTREE_LABEL_MAX_CHARS)
-					ereport(ERROR,
-							(errcode(ERRCODE_NAME_TOO_LONG),
-							 errmsg("label string is too long"),
-							 errdetail("Label length is %d, must be at most %d, at character %d.",
-									   lptr->wlen, LTREE_LABEL_MAX_CHARS,
-									   pos)));
-
-				curqlevel->flag |= LQL_COUNT;
-				state = LQPRS_WAITFNUM;
-			}
-			else if (charlen == 1 && t_iseq(ptr, '.'))
-			{
-				lptr->len = ptr - lptr->start -
-					((lptr->flag & LVAR_SUBLEXEME) ? 1 : 0) -
-					((lptr->flag & LVAR_INCASE) ? 1 : 0) -
-					((lptr->flag & LVAR_ANYEND) ? 1 : 0);
-				if (lptr->wlen > LTREE_LABEL_MAX_CHARS)
-					ereport(ERROR,
-							(errcode(ERRCODE_NAME_TOO_LONG),
-							 errmsg("label string is too long"),
-							 errdetail("Label length is %d, must be at most %d, at character %d.",
-									   lptr->wlen, LTREE_LABEL_MAX_CHARS,
-									   pos)));
-
-				state = LQPRS_WAITLEVEL;
-				curqlevel = NEXTLEV(curqlevel);
-			}
-			else if (ISALNUM(ptr))
-			{
-				if (lptr->flag)
+				break;
+			case LQPRS_WAITOPEN:
+				if (t_iseq(ptr, '{'))
+					state = LQPRS_WAITFNUM;
+				else if (t_iseq(ptr, '.'))
+				{
+					/* We only get here for '*', so these are correct defaults */
+					curqlevel->low = 0;
+					curqlevel->high = LTREE_MAX_LEVELS;
+					curqlevel = NEXTLEV(curqlevel);
+					state = LQPRS_WAITLEVEL;
+				}
+				else
 					UNCHAR;
-			}
-			else
-				UNCHAR;
-		}
-		else if (state == LQPRS_WAITOPEN)
-		{
-			if (charlen == 1 && t_iseq(ptr, '{'))
-				state = LQPRS_WAITFNUM;
-			else if (charlen == 1 && t_iseq(ptr, '.'))
-			{
-				/* We only get here for '*', so these are correct defaults */
-				curqlevel->low = 0;
-				curqlevel->high = LTREE_MAX_LEVELS;
-				curqlevel = NEXTLEV(curqlevel);
-				state = LQPRS_WAITLEVEL;
-			}
-			else
-				UNCHAR;
-		}
-		else if (state == LQPRS_WAITFNUM)
-		{
-			if (charlen == 1 && t_iseq(ptr, ','))
-				state = LQPRS_WAITSNUM;
-			else if (t_isdigit(ptr))
-			{
-				int			low = atoi(ptr);
+				break;
+			case LQPRS_WAITFNUM:
+				if (t_iseq(ptr, ','))
+					state = LQPRS_WAITSNUM;
+				else if (t_isdigit(ptr))
+				{
+					int			low = atoi(ptr);
 
-				if (low < 0 || low > LTREE_MAX_LEVELS)
-					ereport(ERROR,
-							(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
-							 errmsg("lquery syntax error"),
-							 errdetail("Low limit (%d) exceeds the maximum allowed (%d), at character %d.",
-									   low, LTREE_MAX_LEVELS, pos)));
+					if (low < 0 || low > LTREE_MAX_LEVELS)
+						ereport(ERROR,
+								(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+								 errmsg("lquery syntax error"),
+								 errdetail("Low limit (%d) exceeds the maximum allowed (%d), at character %d.",
+										   low, LTREE_MAX_LEVELS, pos)));
 
-				curqlevel->low = (uint16) low;
-				state = LQPRS_WAITND;
-			}
-			else
-				UNCHAR;
-		}
-		else if (state == LQPRS_WAITSNUM)
-		{
-			if (t_isdigit(ptr))
-			{
-				int			high = atoi(ptr);
-
-				if (high < 0 || high > LTREE_MAX_LEVELS)
-					ereport(ERROR,
-							(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
-							 errmsg("lquery syntax error"),
-							 errdetail("High limit (%d) exceeds the maximum allowed (%d), at character %d.",
-									   high, LTREE_MAX_LEVELS, pos)));
-				else if (curqlevel->low > high)
-					ereport(ERROR,
-							(errcode(ERRCODE_SYNTAX_ERROR),
-							 errmsg("lquery syntax error"),
-							 errdetail("Low limit (%d) is greater than high limit (%d), at character %d.",
-									   curqlevel->low, high, pos)));
-
-				curqlevel->high = (uint16) high;
-				state = LQPRS_WAITCLOSE;
-			}
-			else if (charlen == 1 && t_iseq(ptr, '}'))
-			{
-				curqlevel->high = LTREE_MAX_LEVELS;
-				state = LQPRS_WAITEND;
-			}
-			else
-				UNCHAR;
-		}
-		else if (state == LQPRS_WAITCLOSE)
-		{
-			if (charlen == 1 && t_iseq(ptr, '}'))
-				state = LQPRS_WAITEND;
-			else if (!t_isdigit(ptr))
-				UNCHAR;
-		}
-		else if (state == LQPRS_WAITND)
-		{
-			if (charlen == 1 && t_iseq(ptr, '}'))
-			{
-				curqlevel->high = curqlevel->low;
-				state = LQPRS_WAITEND;
-			}
-			else if (charlen == 1 && t_iseq(ptr, ','))
-				state = LQPRS_WAITSNUM;
-			else if (!t_isdigit(ptr))
-				UNCHAR;
-		}
-		else if (state == LQPRS_WAITEND)
-		{
-			if (charlen == 1 && t_iseq(ptr, '.'))
-			{
-				state = LQPRS_WAITLEVEL;
-				curqlevel = NEXTLEV(curqlevel);
-			}
-			else
-				UNCHAR;
+					curqlevel->low = (uint16) low;
+					state = LQPRS_WAITND;
+				}
+				else
+					UNCHAR;
+				break;
+			case LQPRS_WAITSNUM:
+				if (t_isdigit(ptr))
+				{
+					int			high = atoi(ptr);
+
+					if (high < 0 || high > LTREE_MAX_LEVELS)
+						ereport(ERROR,
+								(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+								 errmsg("lquery syntax error"),
+								 errdetail("High limit (%d) exceeds the maximum allowed (%d), at character %d.",
+										   high, LTREE_MAX_LEVELS, pos)));
+					else if (curqlevel->low > high)
+						ereport(ERROR,
+								(errcode(ERRCODE_SYNTAX_ERROR),
+								 errmsg("lquery syntax error"),
+								 errdetail("Low limit (%d) is greater than high limit (%d), at character %d.",
+										   curqlevel->low, high, pos)));
+
+					curqlevel->high = (uint16) high;
+					state = LQPRS_WAITCLOSE;
+				}
+				else if (t_iseq(ptr, '}'))
+				{
+					curqlevel->high = LTREE_MAX_LEVELS;
+					state = LQPRS_WAITEND;
+				}
+				else
+					UNCHAR;
+				break;
+			case LQPRS_WAITCLOSE:
+				if (t_iseq(ptr, '}'))
+					state = LQPRS_WAITEND;
+				else if (!t_isdigit(ptr))
+					UNCHAR;
+				break;
+			case LQPRS_WAITND:
+				if (t_iseq(ptr, '}'))
+				{
+					curqlevel->high = curqlevel->low;
+					state = LQPRS_WAITEND;
+				}
+				else if (t_iseq(ptr, ','))
+					state = LQPRS_WAITSNUM;
+				else if (!t_isdigit(ptr))
+					UNCHAR;
+				break;
+			case LQPRS_WAITEND:
+				if (t_iseq(ptr, '.'))
+				{
+					state = LQPRS_WAITLEVEL;
+					curqlevel = NEXTLEV(curqlevel);
+				}
+				else
+					UNCHAR;
+				break;
+			default:
+				elog(ERROR, "internal error in lquery parser");
 		}
-		else
-			/* internal error */
-			elog(ERROR, "internal error in parser");
 
 		ptr += charlen;
 		if (state == LQPRS_WAITDELIM)
@@ -543,30 +485,7 @@ parse_lquery(const char *buf)
 	}
 
 	if (state == LQPRS_WAITDELIM)
-	{
-		if (lptr->start == ptr)
-			ereport(ERROR,
-					(errcode(ERRCODE_SYNTAX_ERROR),
-					 errmsg("lquery syntax error"),
-					 errdetail("Unexpected end of input.")));
-
-		lptr->len = ptr - lptr->start -
-			((lptr->flag & LVAR_SUBLEXEME) ? 1 : 0) -
-			((lptr->flag & LVAR_INCASE) ? 1 : 0) -
-			((lptr->flag & LVAR_ANYEND) ? 1 : 0);
-		if (lptr->len == 0)
-			ereport(ERROR,
-					(errcode(ERRCODE_SYNTAX_ERROR),
-					 errmsg("lquery syntax error"),
-					 errdetail("Unexpected end of input.")));
-
-		if (lptr->wlen > LTREE_LABEL_MAX_CHARS)
-			ereport(ERROR,
-					(errcode(ERRCODE_NAME_TOO_LONG),
-					 errmsg("label string is too long"),
-					 errdetail("Label length is %d, must be at most %d, at character %d.",
-							   lptr->wlen, LTREE_LABEL_MAX_CHARS, pos)));
-	}
+		finish_nodeitem(lptr, ptr, true, pos);
 	else if (state == LQPRS_WAITOPEN)
 		curqlevel->high = LTREE_MAX_LEVELS;
 	else if (state != LQPRS_WAITEND)
@@ -647,6 +566,46 @@ parse_lquery(const char *buf)
 }
 
 /*
+ * Close out parsing an ltree or lquery nodeitem:
+ * compute the correct length, and complain if it's not OK
+ */
+static void
+finish_nodeitem(nodeitem *lptr, const char *ptr, bool is_lquery, int pos)
+{
+	if (is_lquery)
+	{
+		/*
+		 * Back up over any flag characters, and discount them from length and
+		 * position.
+		 */
+		while (ptr > lptr->start && strchr("@*%", ptr[-1]) != NULL)
+		{
+			ptr--;
+			lptr->wlen--;
+			pos--;
+		}
+	}
+
+	/* Now compute the byte length, which we weren't tracking before. */
+	lptr->len = ptr - lptr->start;
+
+	/* Complain if it's empty or too long */
+	if (lptr->len == 0)
+		ereport(ERROR,
+				(errcode(ERRCODE_SYNTAX_ERROR),
+				 is_lquery ?
+				 errmsg("lquery syntax error at character %d", pos) :
+				 errmsg("ltree syntax error at character %d", pos),
+				 errdetail("Empty labels are not allowed.")));
+	if (lptr->wlen > LTREE_LABEL_MAX_CHARS)
+		ereport(ERROR,
+				(errcode(ERRCODE_NAME_TOO_LONG),
+				 errmsg("label string is too long"),
+				 errdetail("Label length is %d, must be at most %d, at character %d.",
+						   lptr->wlen, LTREE_LABEL_MAX_CHARS, pos)));
+}
+
+/*
  * expects an lquery
  * returns a null terminated string
  */
diff --git a/contrib/ltree/sql/ltree.sql b/contrib/ltree/sql/ltree.sql
index 0cf3dd61366..bf733ed17b9 100644
--- a/contrib/ltree/sql/ltree.sql
+++ b/contrib/ltree/sql/ltree.sql
@@ -10,6 +10,14 @@ SELECT '1'::ltree;
 SELECT '1.2'::ltree;
 SELECT '1.2._3'::ltree;
 
+-- empty labels not allowed
+SELECT '.2.3'::ltree;
+SELECT '1..3'::ltree;
+SELECT '1.2.'::ltree;
+
+SELECT repeat('x', 255)::ltree;
+SELECT repeat('x', 256)::ltree;
+
 SELECT ltree2text('1.2.3.34.sdf');
 SELECT text2ltree('1.2.3.34.sdf');
 
@@ -88,8 +96,26 @@ SELECT '1.*.4|3|2.*{,4}'::lquery;
 SELECT '1.*.4|3|2.*{1,}'::lquery;
 SELECT '1.*.4|3|2.*{1}'::lquery;
 SELECT 'foo.bar{,}.!a*|b{1,}.c{,44}.d{3,4}'::lquery;
+SELECT 'foo*@@*'::lquery;
 SELECT 'qwerty%@*.tu'::lquery;
 
+-- empty labels not allowed
+SELECT '.2.3'::lquery;
+SELECT '1..3'::lquery;
+SELECT '1.2.'::lquery;
+SELECT '@.2.3'::lquery;
+SELECT '1.@.3'::lquery;
+SELECT '1.2.@'::lquery;
+SELECT '!.2.3'::lquery;
+SELECT '1.!.3'::lquery;
+SELECT '1.2.!'::lquery;
+SELECT '1.2.3|@.4'::lquery;
+
+SELECT (repeat('x', 255) || '*@@*')::lquery;
+SELECT (repeat('x', 256) || '*@@*')::lquery;
+SELECT ('!' || repeat('x', 255))::lquery;
+SELECT ('!' || repeat('x', 256))::lquery;
+
 SELECT nlevel('1.2.3.4');
 SELECT nlevel(('1' || repeat('.1', 65534))::ltree);
 SELECT nlevel(('1' || repeat('.1', 65535))::ltree);
@@ -200,6 +226,7 @@ SELECT 'a.b.c.d.e'::ltree ~ '!c{0,3}.!a{2,}';
 SELECT 'a.b.c.d.e'::ltree ~ '!c{0,3}.!d{2,}.*';
 
 SELECT 'QWER_TY'::ltree ~ 'q%@*';
+SELECT 'QWER_TY'::ltree ~ 'q%@*%@*';
 SELECT 'QWER_TY'::ltree ~ 'Q_t%@*';
 SELECT 'QWER_GY'::ltree ~ 'q_t%@*';