Underscores in numeric literals

diff --git a/doc/src/sgml/syntax.sgml b/doc/src/sgml/syntax.sgml
new file mode 100644
index 956182e..27e53b4
--- a/doc/src/sgml/syntax.sgml
+++ b/doc/src/sgml/syntax.sgml
@@ -729,6 +729,20 @@ $function$
     </note>
 
     <para>
+     For visual grouping, underscores can be inserted between digits.  These
+     have no further effect on the value of the literal.  For example:
+<literallayout>1_500_000_000
+0b10001000_00000000
+0o_1_755
+0xFFFF_FFFF
+1.618_034
+</literallayout>
+     Underscores are not allowed at the start or end of a numeric constant or
+     a group of digits (that is, immediately before or after a period or the
+     <quote>e</quote>), and more than one underscore in a row is not allowed.
+    </para>
+
+    <para>
      <indexterm><primary>integer</primary></indexterm>
      <indexterm><primary>bigint</primary></indexterm>
      <indexterm><primary>numeric</primary></indexterm>
diff --git a/src/backend/catalog/sql_features.txt b/src/backend/catalog/sql_features.txt
new file mode 100644
index abad216..3766762
--- a/src/backend/catalog/sql_features.txt
+++ b/src/backend/catalog/sql_features.txt
@@ -528,6 +528,7 @@ T653	SQL-schema statements in external r
 T654	SQL-dynamic statements in external routines			NO	
 T655	Cyclically dependent routines			YES	
 T661	Non-decimal integer literals			YES	SQL:202x draft
+T662	Underscores in integer literals			YES	SQL:202x draft
 T811	Basic SQL/JSON constructor functions			NO	
 T812	SQL/JSON: JSON_OBJECTAGG			NO	
 T813	SQL/JSON: JSON_ARRAYAGG with ORDER BY			NO	
diff --git a/src/backend/parser/scan.l b/src/backend/parser/scan.l
new file mode 100644
index 9ad9e0c..a1ea94e
--- a/src/backend/parser/scan.l
+++ b/src/backend/parser/scan.l
@@ -124,6 +124,7 @@ static void addlit(char *ytext, int ylen
 static void addlitchar(unsigned char ychar, core_yyscan_t yyscanner);
 static char *litbufdup(core_yyscan_t yyscanner);
 static unsigned char unescape_single_char(unsigned char c, core_yyscan_t yyscanner);
+static char *strip_underscores(const char *in);
 static int	process_integer_literal(const char *token, YYSTYPE *lval, int base);
 static void addunicode(pg_wchar c, yyscan_t yyscanner);
 
@@ -395,19 +396,19 @@ hexdigit		[0-9A-Fa-f]
 octdigit		[0-7]
 bindigit		[0-1]
 
-decinteger		{decdigit}+
-hexinteger		0[xX]{hexdigit}+
-octinteger		0[oO]{octdigit}+
-bininteger		0[bB]{bindigit}+
+decinteger		{decdigit}(_?{decdigit})*
+hexinteger		0[xX](_?{hexdigit})+
+octinteger		0[oO](_?{octdigit})+
+bininteger		0[bB](_?{bindigit})+
 
-hexfail			0[xX]
-octfail			0[oO]
-binfail			0[bB]
+hexfail			0[xX]_?
+octfail			0[oO]_?
+binfail			0[bB]_?
 
 numeric			(({decinteger}\.{decinteger}?)|(\.{decinteger}))
 numericfail		{decdigit}+\.\.
 
-real			({decinteger}|{numeric})[Ee][-+]?{decdigit}+
+real			({decinteger}|{numeric})[Ee][-+]?{decinteger}+
 realfail		({decinteger}|{numeric})[Ee][-+]
 
 decinteger_junk	{decinteger}{ident_start}
@@ -1028,7 +1029,7 @@ other			.
 				}
 {numeric}		{
 					SET_YYLLOC();
-					yylval->str = pstrdup(yytext);
+					yylval->str = strip_underscores(yytext);
 					return FCONST;
 				}
 {numericfail}	{
@@ -1039,7 +1040,7 @@ other			.
 				}
 {real}			{
 					SET_YYLLOC();
-					yylval->str = pstrdup(yytext);
+					yylval->str = strip_underscores(yytext);
 					return FCONST;
 				}
 {realfail}		{
@@ -1357,6 +1358,30 @@ litbufdup(core_yyscan_t yyscanner)
 	return new;
 }
 
+static char *
+strip_underscores(const char *in)
+{
+	if (strchr(in, '_'))
+	{
+		char	   *out = palloc(strlen(in));
+		const char *p1;
+		char	   *p2;
+
+		p1 = in;
+		p2 = out;
+		while (*p1)
+		{
+			if (*p1 != '_')
+				*p2++ = *p1;
+			p1++;
+		}
+		*p2 = '\0';
+		return out;
+	}
+	else
+		return pstrdup(in);
+}
+
 /*
  * Process {decinteger}, {hexinteger}, etc.  Note this will also do the right
  * thing with {numeric}, ie digits and a decimal point.
@@ -1367,6 +1392,24 @@ process_integer_literal(const char *toke
 	int			val;
 	char	   *endptr;
 
+	if (strchr(token, '_'))
+	{
+		char	   *newtoken = palloc(strlen(token));
+		const char *p1;
+		char	   *p2;
+
+		p1 = token;
+		p2 = newtoken;
+		while (*p1)
+		{
+			if (*p1 != '_')
+				*p2++ = *p1;
+			p1++;
+		}
+		*p2 = '\0';
+		token = newtoken;
+	}
+
 	errno = 0;
 	val = strtoint(base == 10 ? token : token + 2, &endptr, base);
 	if (*endptr != '\0' || errno == ERANGE)
diff --git a/src/backend/utils/adt/numutils.c b/src/backend/utils/adt/numutils.c
new file mode 100644
index 1e1a982..17d573a
--- a/src/backend/utils/adt/numutils.c
+++ b/src/backend/utils/adt/numutils.c
@@ -141,48 +141,99 @@ pg_strtoint16_safe(const char *s, Node *
 	{
 		firstdigit = ptr += 2;
 
-		while (*ptr && isxdigit((unsigned char) *ptr))
+		while (*ptr)
 		{
-			if (unlikely(tmp > -(PG_INT16_MIN / 16)))
-				goto out_of_range;
+			if (isxdigit((unsigned char) *ptr))
+			{
+				if (unlikely(tmp > -(PG_INT16_MIN / 16)))
+					goto out_of_range;
 
-			tmp = tmp * 16 + hexlookup[(unsigned char) *ptr++];
+				tmp = tmp * 16 + hexlookup[(unsigned char) *ptr++];
+			}
+			else if (*ptr == '_')
+			{
+				/* underscore must be followed by more digits */
+				ptr++;
+				if (*ptr == '\0' || !isxdigit((unsigned char) *ptr))
+					goto invalid_syntax;
+			}
+			else
+				break;
 		}
 	}
 	else if (ptr[0] == '0' && (ptr[1] == 'o' || ptr[1] == 'O'))
 	{
 		firstdigit = ptr += 2;
 
-		while (*ptr && (*ptr >= '0' && *ptr <= '7'))
+		while (*ptr)
 		{
-			if (unlikely(tmp > -(PG_INT16_MIN / 8)))
-				goto out_of_range;
+			if (*ptr >= '0' && *ptr <= '7')
+			{
+				if (unlikely(tmp > -(PG_INT16_MIN / 8)))
+					goto out_of_range;
 
-			tmp = tmp * 8 + (*ptr++ - '0');
+				tmp = tmp * 8 + (*ptr++ - '0');
+			}
+			else if (*ptr == '_')
+			{
+				/* underscore must be followed by more digits */
+				ptr++;
+				if (*ptr == '\0' || *ptr < '0' || *ptr > '7')
+					goto invalid_syntax;
+			}
+			else
+				break;
 		}
 	}
 	else if (ptr[0] == '0' && (ptr[1] == 'b' || ptr[1] == 'B'))
 	{
 		firstdigit = ptr += 2;
 
-		while (*ptr && (*ptr >= '0' && *ptr <= '1'))
+		while (*ptr)
 		{
-			if (unlikely(tmp > -(PG_INT16_MIN / 2)))
-				goto out_of_range;
+			if (*ptr >= '0' && *ptr <= '1')
+			{
+				if (unlikely(tmp > -(PG_INT16_MIN / 2)))
+					goto out_of_range;
 
-			tmp = tmp * 2 + (*ptr++ - '0');
+				tmp = tmp * 2 + (*ptr++ - '0');
+			}
+			else if (*ptr == '_')
+			{
+				/* underscore must be followed by more digits */
+				ptr++;
+				if (*ptr == '\0' || *ptr < '0' || *ptr > '1')
+					goto invalid_syntax;
+			}
+			else
+				break;
 		}
 	}
 	else
 	{
 		firstdigit = ptr;
 
-		while (*ptr && isdigit((unsigned char) *ptr))
+		while (*ptr)
 		{
-			if (unlikely(tmp > -(PG_INT16_MIN / 10)))
-				goto out_of_range;
+			if (isdigit((unsigned char) *ptr))
+			{
+				if (unlikely(tmp > -(PG_INT16_MIN / 10)))
+					goto out_of_range;
 
-			tmp = tmp * 10 + (*ptr++ - '0');
+				tmp = tmp * 10 + (*ptr++ - '0');
+			}
+			else if (*ptr == '_')
+			{
+				/* underscore may not be first */
+				if (unlikely(ptr == firstdigit))
+					goto invalid_syntax;
+				/* and it must be followed by more digits */
+				ptr++;
+				if (*ptr == '\0' || !isdigit((unsigned char) *ptr))
+					goto invalid_syntax;
+			}
+			else
+				break;
 		}
 	}
 
@@ -268,48 +319,99 @@ pg_strtoint32_safe(const char *s, Node *
 	{
 		firstdigit = ptr += 2;
 
-		while (*ptr && isxdigit((unsigned char) *ptr))
+		while (*ptr)
 		{
-			if (unlikely(tmp > -(PG_INT32_MIN / 16)))
-				goto out_of_range;
+			if (isxdigit((unsigned char) *ptr))
+			{
+				if (unlikely(tmp > -(PG_INT32_MIN / 16)))
+					goto out_of_range;
 
-			tmp = tmp * 16 + hexlookup[(unsigned char) *ptr++];
+				tmp = tmp * 16 + hexlookup[(unsigned char) *ptr++];
+			}
+			else if (*ptr == '_')
+			{
+				/* underscore must be followed by more digits */
+				ptr++;
+				if (*ptr == '\0' || !isxdigit((unsigned char) *ptr))
+					goto invalid_syntax;
+			}
+			else
+				break;
 		}
 	}
 	else if (ptr[0] == '0' && (ptr[1] == 'o' || ptr[1] == 'O'))
 	{
 		firstdigit = ptr += 2;
 
-		while (*ptr && (*ptr >= '0' && *ptr <= '7'))
+		while (*ptr)
 		{
-			if (unlikely(tmp > -(PG_INT32_MIN / 8)))
-				goto out_of_range;
+			if (*ptr >= '0' && *ptr <= '7')
+			{
+				if (unlikely(tmp > -(PG_INT32_MIN / 8)))
+					goto out_of_range;
 
-			tmp = tmp * 8 + (*ptr++ - '0');
+				tmp = tmp * 8 + (*ptr++ - '0');
+			}
+			else if (*ptr == '_')
+			{
+				/* underscore must be followed by more digits */
+				ptr++;
+				if (*ptr == '\0' || *ptr < '0' || *ptr > '7')
+					goto invalid_syntax;
+			}
+			else
+				break;
 		}
 	}
 	else if (ptr[0] == '0' && (ptr[1] == 'b' || ptr[1] == 'B'))
 	{
 		firstdigit = ptr += 2;
 
-		while (*ptr && (*ptr >= '0' && *ptr <= '1'))
+		while (*ptr)
 		{
-			if (unlikely(tmp > -(PG_INT32_MIN / 2)))
-				goto out_of_range;
+			if (*ptr >= '0' && *ptr <= '1')
+			{
+				if (unlikely(tmp > -(PG_INT32_MIN / 2)))
+					goto out_of_range;
 
-			tmp = tmp * 2 + (*ptr++ - '0');
+				tmp = tmp * 2 + (*ptr++ - '0');
+			}
+			else if (*ptr == '_')
+			{
+				/* underscore must be followed by more digits */
+				ptr++;
+				if (*ptr == '\0' || *ptr < '0' || *ptr > '1')
+					goto invalid_syntax;
+			}
+			else
+				break;
 		}
 	}
 	else
 	{
 		firstdigit = ptr;
 
-		while (*ptr && isdigit((unsigned char) *ptr))
+		while (*ptr)
 		{
-			if (unlikely(tmp > -(PG_INT32_MIN / 10)))
-				goto out_of_range;
+			if (isdigit((unsigned char) *ptr))
+			{
+				if (unlikely(tmp > -(PG_INT32_MIN / 10)))
+					goto out_of_range;
 
-			tmp = tmp * 10 + (*ptr++ - '0');
+				tmp = tmp * 10 + (*ptr++ - '0');
+			}
+			else if (*ptr == '_')
+			{
+				/* underscore may not be first */
+				if (unlikely(ptr == firstdigit))
+					goto invalid_syntax;
+				/* and it must be followed by more digits */
+				ptr++;
+				if (*ptr == '\0' || !isdigit((unsigned char) *ptr))
+					goto invalid_syntax;
+			}
+			else
+				break;
 		}
 	}
 
@@ -395,48 +497,99 @@ pg_strtoint64_safe(const char *s, Node *
 	{
 		firstdigit = ptr += 2;
 
-		while (*ptr && isxdigit((unsigned char) *ptr))
+		while (*ptr)
 		{
-			if (unlikely(tmp > -(PG_INT64_MIN / 16)))
-				goto out_of_range;
+			if (isxdigit((unsigned char) *ptr))
+			{
+				if (unlikely(tmp > -(PG_INT64_MIN / 16)))
+					goto out_of_range;
 
-			tmp = tmp * 16 + hexlookup[(unsigned char) *ptr++];
+				tmp = tmp * 16 + hexlookup[(unsigned char) *ptr++];
+			}
+			else if (*ptr == '_')
+			{
+				/* underscore must be followed by more digits */
+				ptr++;
+				if (*ptr == '\0' || !isxdigit((unsigned char) *ptr))
+					goto invalid_syntax;
+			}
+			else
+				break;
 		}
 	}
 	else if (ptr[0] == '0' && (ptr[1] == 'o' || ptr[1] == 'O'))
 	{
 		firstdigit = ptr += 2;
 
-		while (*ptr && (*ptr >= '0' && *ptr <= '7'))
+		while (*ptr)
 		{
-			if (unlikely(tmp > -(PG_INT64_MIN / 8)))
-				goto out_of_range;
+			if (*ptr >= '0' && *ptr <= '7')
+			{
+				if (unlikely(tmp > -(PG_INT64_MIN / 8)))
+					goto out_of_range;
 
-			tmp = tmp * 8 + (*ptr++ - '0');
+				tmp = tmp * 8 + (*ptr++ - '0');
+			}
+			else if (*ptr == '_')
+			{
+				/* underscore must be followed by more digits */
+				ptr++;
+				if (*ptr == '\0' || *ptr < '0' || *ptr > '7')
+					goto invalid_syntax;
+			}
+			else
+				break;
 		}
 	}
 	else if (ptr[0] == '0' && (ptr[1] == 'b' || ptr[1] == 'B'))
 	{
 		firstdigit = ptr += 2;
 
-		while (*ptr && (*ptr >= '0' && *ptr <= '1'))
+		while (*ptr)
 		{
-			if (unlikely(tmp > -(PG_INT64_MIN / 2)))
-				goto out_of_range;
+			if (*ptr >= '0' && *ptr <= '1')
+			{
+				if (unlikely(tmp > -(PG_INT64_MIN / 2)))
+					goto out_of_range;
 
-			tmp = tmp * 2 + (*ptr++ - '0');
+				tmp = tmp * 2 + (*ptr++ - '0');
+			}
+			else if (*ptr == '_')
+			{
+				/* underscore must be followed by more digits */
+				ptr++;
+				if (*ptr == '\0' || *ptr < '0' || *ptr > '1')
+					goto invalid_syntax;
+			}
+			else
+				break;
 		}
 	}
 	else
 	{
 		firstdigit = ptr;
 
-		while (*ptr && isdigit((unsigned char) *ptr))
+		while (*ptr)
 		{
-			if (unlikely(tmp > -(PG_INT64_MIN / 10)))
-				goto out_of_range;
+			if (isdigit((unsigned char) *ptr))
+			{
+				if (unlikely(tmp > -(PG_INT64_MIN / 10)))
+					goto out_of_range;
 
-			tmp = tmp * 10 + (*ptr++ - '0');
+				tmp = tmp * 10 + (*ptr++ - '0');
+			}
+			else if (*ptr == '_')
+			{
+				/* underscore may not be first */
+				if (unlikely(ptr == firstdigit))
+					goto invalid_syntax;
+				/* and it must be followed by more digits */
+				ptr++;
+				if (*ptr == '\0' || !isdigit((unsigned char) *ptr))
+					goto invalid_syntax;
+			}
+			else
+				break;
 		}
 	}
 
diff --git a/src/fe_utils/psqlscan.l b/src/fe_utils/psqlscan.l
new file mode 100644
index cb1fc52..44f80e4
--- a/src/fe_utils/psqlscan.l
+++ b/src/fe_utils/psqlscan.l
@@ -333,19 +333,19 @@ hexdigit		[0-9A-Fa-f]
 octdigit		[0-7]
 bindigit		[0-1]
 
-decinteger		{decdigit}+
-hexinteger		0[xX]{hexdigit}+
-octinteger		0[oO]{octdigit}+
-bininteger		0[bB]{bindigit}+
+decinteger		{decdigit}(_?{decdigit})*
+hexinteger		0[xX](_?{hexdigit})+
+octinteger		0[oO](_?{octdigit})+
+bininteger		0[bB](_?{bindigit})+
 
-hexfail			0[xX]
-octfail			0[oO]
-binfail			0[bB]
+hexfail			0[xX]_?
+octfail			0[oO]_?
+binfail			0[bB]_?
 
 numeric			(({decinteger}\.{decinteger}?)|(\.{decinteger}))
 numericfail		{decdigit}+\.\.
 
-real			({decinteger}|{numeric})[Ee][-+]?{decdigit}+
+real			({decinteger}|{numeric})[Ee][-+]?{decinteger}
 realfail		({decinteger}|{numeric})[Ee][-+]
 
 decinteger_junk	{decinteger}{ident_start}
diff --git a/src/interfaces/ecpg/preproc/pgc.l b/src/interfaces/ecpg/preproc/pgc.l
new file mode 100644
index 2c09c6c..2761ae3
--- a/src/interfaces/ecpg/preproc/pgc.l
+++ b/src/interfaces/ecpg/preproc/pgc.l
@@ -361,19 +361,19 @@ hexdigit		[0-9A-Fa-f]
 octdigit		[0-7]
 bindigit		[0-1]
 
-decinteger		{decdigit}+
-hexinteger		0[xX]{hexdigit}+
-octinteger		0[oO]{octdigit}+
-bininteger		0[bB]{bindigit}+
+decinteger		{decdigit}(_?{decdigit})*
+hexinteger		0[xX](_?{hexdigit})+
+octinteger		0[oO](_?{octdigit})+
+bininteger		0[bB](_?{bindigit})+
 
-hexfail			0[xX]
-octfail			0[oO]
-binfail			0[bB]
+hexfail			0[xX]_?
+octfail			0[oO]_?
+binfail			0[bB]_?
 
 numeric			(({decinteger}\.{decinteger}?)|(\.{decinteger}))
 numericfail		{decdigit}+\.\.
 
-real			({decinteger}|{numeric})[Ee][-+]?{decdigit}+
+real			({decinteger}|{numeric})[Ee][-+]?{decinteger}
 realfail		({decinteger}|{numeric})[Ee][-+]
 
 decinteger_junk	{decinteger}{ident_start}
diff --git a/src/pl/plpgsql/src/expected/plpgsql_trap.out b/src/pl/plpgsql/src/expected/plpgsql_trap.out
new file mode 100644
index 90cf6c2..62d1679
--- a/src/pl/plpgsql/src/expected/plpgsql_trap.out
+++ b/src/pl/plpgsql/src/expected/plpgsql_trap.out
@@ -141,7 +141,7 @@ begin
   declare x int;
   begin
     -- we assume this will take longer than 1 second:
-    select count(*) into x from generate_series(1, 1000000000000);
+    select count(*) into x from generate_series(1, 1_000_000_000_000);
   exception
     when others then
       raise notice 'caught others?';
diff --git a/src/pl/plpgsql/src/sql/plpgsql_trap.sql b/src/pl/plpgsql/src/sql/plpgsql_trap.sql
new file mode 100644
index c6c1ad8..5459b34
--- a/src/pl/plpgsql/src/sql/plpgsql_trap.sql
+++ b/src/pl/plpgsql/src/sql/plpgsql_trap.sql
@@ -88,7 +88,7 @@ begin
   declare x int;
   begin
     -- we assume this will take longer than 1 second:
-    select count(*) into x from generate_series(1, 1000000000000);
+    select count(*) into x from generate_series(1, 1_000_000_000_000);
   exception
     when others then
       raise notice 'caught others?';
diff --git a/src/test/regress/expected/int2.out b/src/test/regress/expected/int2.out
new file mode 100644
index 08c333b..73b4ee0
--- a/src/test/regress/expected/int2.out
+++ b/src/test/regress/expected/int2.out
@@ -440,3 +440,47 @@ SELECT int2 '-0x8001';
 ERROR:  value "-0x8001" is out of range for type smallint
 LINE 1: SELECT int2 '-0x8001';
                     ^
+-- underscores
+SELECT int2 '1_000';
+ int2 
+------
+ 1000
+(1 row)
+
+SELECT int2 '1_2_3';
+ int2 
+------
+  123
+(1 row)
+
+SELECT int2 '0xE_FF';
+ int2 
+------
+ 3839
+(1 row)
+
+SELECT int2 '0o2_73';
+ int2 
+------
+  187
+(1 row)
+
+SELECT int2 '0b_10_0101';
+ int2 
+------
+   37
+(1 row)
+
+-- error cases
+SELECT int2 '_100';
+ERROR:  invalid input syntax for type smallint: "_100"
+LINE 1: SELECT int2 '_100';
+                    ^
+SELECT int2 '100_';
+ERROR:  invalid input syntax for type smallint: "100_"
+LINE 1: SELECT int2 '100_';
+                    ^
+SELECT int2 '10__000';
+ERROR:  invalid input syntax for type smallint: "10__000"
+LINE 1: SELECT int2 '10__000';
+                    ^
diff --git a/src/test/regress/expected/int4.out b/src/test/regress/expected/int4.out
new file mode 100644
index 8386c7c..9c20574
--- a/src/test/regress/expected/int4.out
+++ b/src/test/regress/expected/int4.out
@@ -548,3 +548,47 @@ SELECT int4 '-0x80000001';
 ERROR:  value "-0x80000001" is out of range for type integer
 LINE 1: SELECT int4 '-0x80000001';
                     ^
+-- underscores
+SELECT int4 '1_000_000';
+  int4   
+---------
+ 1000000
+(1 row)
+
+SELECT int4 '1_2_3';
+ int4 
+------
+  123
+(1 row)
+
+SELECT int4 '0x1EEE_FFFF';
+   int4    
+-----------
+ 518979583
+(1 row)
+
+SELECT int4 '0o2_73';
+ int4 
+------
+  187
+(1 row)
+
+SELECT int4 '0b_10_0101';
+ int4 
+------
+   37
+(1 row)
+
+-- error cases
+SELECT int4 '_100';
+ERROR:  invalid input syntax for type integer: "_100"
+LINE 1: SELECT int4 '_100';
+                    ^
+SELECT int4 '100_';
+ERROR:  invalid input syntax for type integer: "100_"
+LINE 1: SELECT int4 '100_';
+                    ^
+SELECT int4 '100__000';
+ERROR:  invalid input syntax for type integer: "100__000"
+LINE 1: SELECT int4 '100__000';
+                    ^
diff --git a/src/test/regress/expected/int8.out b/src/test/regress/expected/int8.out
new file mode 100644
index 5b62b51..d9dca64
--- a/src/test/regress/expected/int8.out
+++ b/src/test/regress/expected/int8.out
@@ -1044,3 +1044,47 @@ SELECT int8 '-0x8000000000000001';
 ERROR:  value "-0x8000000000000001" is out of range for type bigint
 LINE 1: SELECT int8 '-0x8000000000000001';
                     ^
+-- underscores
+SELECT int8 '1_000_000';
+  int8   
+---------
+ 1000000
+(1 row)
+
+SELECT int8 '1_2_3';
+ int8 
+------
+  123
+(1 row)
+
+SELECT int8 '0x1EEE_FFFF';
+   int8    
+-----------
+ 518979583
+(1 row)
+
+SELECT int8 '0o2_73';
+ int8 
+------
+  187
+(1 row)
+
+SELECT int8 '0b_10_0101';
+ int8 
+------
+   37
+(1 row)
+
+-- error cases
+SELECT int8 '_100';
+ERROR:  invalid input syntax for type bigint: "_100"
+LINE 1: SELECT int8 '_100';
+                    ^
+SELECT int8 '100_';
+ERROR:  invalid input syntax for type bigint: "100_"
+LINE 1: SELECT int8 '100_';
+                    ^
+SELECT int8 '100__000';
+ERROR:  invalid input syntax for type bigint: "100__000"
+LINE 1: SELECT int8 '100__000';
+                    ^
diff --git a/src/test/regress/expected/numerology.out b/src/test/regress/expected/numerology.out
new file mode 100644
index 15cd6b1..6b9b089
--- a/src/test/regress/expected/numerology.out
+++ b/src/test/regress/expected/numerology.out
@@ -166,10 +166,6 @@ SELECT 0x0o;
 ERROR:  trailing junk after numeric literal at or near "0x0o"
 LINE 1: SELECT 0x0o;
                ^
-SELECT 1_2_3;
-ERROR:  trailing junk after numeric literal at or near "1_"
-LINE 1: SELECT 1_2_3;
-               ^
 SELECT 0.a;
 ERROR:  trailing junk after numeric literal at or near "0.a"
 LINE 1: SELECT 0.a;
@@ -234,6 +230,94 @@ SELECT 0x0y;
 ERROR:  trailing junk after numeric literal at or near "0x0y"
 LINE 1: SELECT 0x0y;
                ^
+-- underscores
+SELECT 1_000_000;
+ ?column? 
+----------
+  1000000
+(1 row)
+
+SELECT 1_2_3;
+ ?column? 
+----------
+      123
+(1 row)
+
+SELECT 0x1EEE_FFFF;
+ ?column?  
+-----------
+ 518979583
+(1 row)
+
+SELECT 0o2_73;
+ ?column? 
+----------
+      187
+(1 row)
+
+SELECT 0b_10_0101;
+ ?column? 
+----------
+       37
+(1 row)
+
+SELECT 1_000.000_005;
+  ?column?   
+-------------
+ 1000.000005
+(1 row)
+
+SELECT 1_000.;
+ ?column? 
+----------
+     1000
+(1 row)
+
+SELECT .000_005;
+ ?column? 
+----------
+ 0.000005
+(1 row)
+
+SELECT 1_000.5e0_1;
+ ?column? 
+----------
+    10005
+(1 row)
+
+-- error cases
+SELECT _100;
+ERROR:  column "_100" does not exist
+LINE 1: SELECT _100;
+               ^
+SELECT 100_;
+ERROR:  trailing junk after numeric literal at or near "100_"
+LINE 1: SELECT 100_;
+               ^
+SELECT 100__000;
+ERROR:  trailing junk after numeric literal at or near "100_"
+LINE 1: SELECT 100__000;
+               ^
+SELECT _1_000.5;
+ERROR:  syntax error at or near ".5"
+LINE 1: SELECT _1_000.5;
+                     ^
+SELECT 1_000_.5;
+ERROR:  trailing junk after numeric literal at or near "1_000_"
+LINE 1: SELECT 1_000_.5;
+               ^
+SELECT 1_000._5;
+ERROR:  trailing junk after numeric literal at or near "1_000._"
+LINE 1: SELECT 1_000._5;
+               ^
+SELECT 1_000.5_;
+ERROR:  trailing junk after numeric literal at or near "1_000.5_"
+LINE 1: SELECT 1_000.5_;
+               ^
+SELECT 1_000.5e_1;
+ERROR:  trailing junk after numeric literal at or near "1_000.5e"
+LINE 1: SELECT 1_000.5e_1;
+               ^
 --
 -- Test implicit type conversions
 -- This fails for Postgres v6.1 (and earlier?)
diff --git a/src/test/regress/expected/partition_prune.out b/src/test/regress/expected/partition_prune.out
new file mode 100644
index 7555764..d700c00
--- a/src/test/regress/expected/partition_prune.out
+++ b/src/test/regress/expected/partition_prune.out
@@ -1503,7 +1503,7 @@ explain (costs off) select * from like_o
 create table lparted_by_int2 (a smallint) partition by list (a);
 create table lparted_by_int2_1 partition of lparted_by_int2 for values in (1);
 create table lparted_by_int2_16384 partition of lparted_by_int2 for values in (16384);
-explain (costs off) select * from lparted_by_int2 where a = 100000000000000;
+explain (costs off) select * from lparted_by_int2 where a = 100_000_000_000_000;
         QUERY PLAN        
 --------------------------
  Result
@@ -1514,7 +1514,7 @@ create table rparted_by_int2 (a smallint
 create table rparted_by_int2_1 partition of rparted_by_int2 for values from (1) to (10);
 create table rparted_by_int2_16384 partition of rparted_by_int2 for values from (10) to (16384);
 -- all partitions pruned
-explain (costs off) select * from rparted_by_int2 where a > 100000000000000;
+explain (costs off) select * from rparted_by_int2 where a > 100_000_000_000_000;
         QUERY PLAN        
 --------------------------
  Result
@@ -1523,7 +1523,7 @@ explain (costs off) select * from rparte
 
 create table rparted_by_int2_maxvalue partition of rparted_by_int2 for values from (16384) to (maxvalue);
 -- all partitions but rparted_by_int2_maxvalue pruned
-explain (costs off) select * from rparted_by_int2 where a > 100000000000000;
+explain (costs off) select * from rparted_by_int2 where a > 100_000_000_000_000;
                       QUERY PLAN                      
 ------------------------------------------------------
  Seq Scan on rparted_by_int2_maxvalue rparted_by_int2
diff --git a/src/test/regress/sql/int2.sql b/src/test/regress/sql/int2.sql
new file mode 100644
index a812235..ce8ac97
--- a/src/test/regress/sql/int2.sql
+++ b/src/test/regress/sql/int2.sql
@@ -141,3 +141,17 @@ SELECT int2 '-0o100000';
 SELECT int2 '-0o100001';
 SELECT int2 '-0x8000';
 SELECT int2 '-0x8001';
+
+
+-- underscores
+
+SELECT int2 '1_000';
+SELECT int2 '1_2_3';
+SELECT int2 '0xE_FF';
+SELECT int2 '0o2_73';
+SELECT int2 '0b_10_0101';
+
+-- error cases
+SELECT int2 '_100';
+SELECT int2 '100_';
+SELECT int2 '10__000';
diff --git a/src/test/regress/sql/int4.sql b/src/test/regress/sql/int4.sql
new file mode 100644
index 9e6a404..146963e
--- a/src/test/regress/sql/int4.sql
+++ b/src/test/regress/sql/int4.sql
@@ -196,3 +196,17 @@ SELECT int4 '-0o20000000000';
 SELECT int4 '-0o20000000001';
 SELECT int4 '-0x80000000';
 SELECT int4 '-0x80000001';
+
+
+-- underscores
+
+SELECT int4 '1_000_000';
+SELECT int4 '1_2_3';
+SELECT int4 '0x1EEE_FFFF';
+SELECT int4 '0o2_73';
+SELECT int4 '0b_10_0101';
+
+-- error cases
+SELECT int4 '_100';
+SELECT int4 '100_';
+SELECT int4 '100__000';
diff --git a/src/test/regress/sql/int8.sql b/src/test/regress/sql/int8.sql
new file mode 100644
index 06f273e..c85717c
--- a/src/test/regress/sql/int8.sql
+++ b/src/test/regress/sql/int8.sql
@@ -277,3 +277,17 @@ SELECT int8 '-0o1000000000000000000000';
 SELECT int8 '-0o1000000000000000000001';
 SELECT int8 '-0x8000000000000000';
 SELECT int8 '-0x8000000000000001';
+
+
+-- underscores
+
+SELECT int8 '1_000_000';
+SELECT int8 '1_2_3';
+SELECT int8 '0x1EEE_FFFF';
+SELECT int8 '0o2_73';
+SELECT int8 '0b_10_0101';
+
+-- error cases
+SELECT int8 '_100';
+SELECT int8 '100_';
+SELECT int8 '100__000';
diff --git a/src/test/regress/sql/numerology.sql b/src/test/regress/sql/numerology.sql
new file mode 100644
index 310d9e5..1941c58
--- a/src/test/regress/sql/numerology.sql
+++ b/src/test/regress/sql/numerology.sql
@@ -45,7 +45,6 @@ SELECT -0x8000000000000001;
 -- error cases
 SELECT 123abc;
 SELECT 0x0o;
-SELECT 1_2_3;
 SELECT 0.a;
 SELECT 0.0a;
 SELECT .0a;
@@ -66,6 +65,29 @@ SELECT 0x;
 SELECT 1x;
 SELECT 0x0y;
 
+-- underscores
+SELECT 1_000_000;
+SELECT 1_2_3;
+SELECT 0x1EEE_FFFF;
+SELECT 0o2_73;
+SELECT 0b_10_0101;
+
+SELECT 1_000.000_005;
+SELECT 1_000.;
+SELECT .000_005;
+SELECT 1_000.5e0_1;
+
+-- error cases
+SELECT _100;
+SELECT 100_;
+SELECT 100__000;
+
+SELECT _1_000.5;
+SELECT 1_000_.5;
+SELECT 1_000._5;
+SELECT 1_000.5_;
+SELECT 1_000.5e_1;
+
 
 --
 -- Test implicit type conversions
diff --git a/src/test/regress/sql/partition_prune.sql b/src/test/regress/sql/partition_prune.sql
new file mode 100644
index d70bd86..fb0583f
--- a/src/test/regress/sql/partition_prune.sql
+++ b/src/test/regress/sql/partition_prune.sql
@@ -283,16 +283,16 @@ explain (costs off) select * from like_o
 create table lparted_by_int2 (a smallint) partition by list (a);
 create table lparted_by_int2_1 partition of lparted_by_int2 for values in (1);
 create table lparted_by_int2_16384 partition of lparted_by_int2 for values in (16384);
-explain (costs off) select * from lparted_by_int2 where a = 100000000000000;
+explain (costs off) select * from lparted_by_int2 where a = 100_000_000_000_000;
 
 create table rparted_by_int2 (a smallint) partition by range (a);
 create table rparted_by_int2_1 partition of rparted_by_int2 for values from (1) to (10);
 create table rparted_by_int2_16384 partition of rparted_by_int2 for values from (10) to (16384);
 -- all partitions pruned
-explain (costs off) select * from rparted_by_int2 where a > 100000000000000;
+explain (costs off) select * from rparted_by_int2 where a > 100_000_000_000_000;
 create table rparted_by_int2_maxvalue partition of rparted_by_int2 for values from (16384) to (maxvalue);
 -- all partitions but rparted_by_int2_maxvalue pruned
-explain (costs off) select * from rparted_by_int2 where a > 100000000000000;
+explain (costs off) select * from rparted_by_int2 where a > 100_000_000_000_000;
 
 drop table lp, coll_pruning, rlp, mc3p, mc2p, boolpart, boolrangep, rp, coll_pruning_multi, like_op_noprune, lparted_by_int2, rparted_by_int2;
 

diff --git a/doc/src/sgml/syntax.sgml b/doc/src/sgml/syntax.sgml
new file mode 100644
index 0ccddea..9509d0f
--- a/doc/src/sgml/syntax.sgml
+++ b/doc/src/sgml/syntax.sgml
@@ -729,6 +729,20 @@ $function$
     </note>
 
     <para>
+     For visual grouping, underscores can be inserted between digits.  These
+     have no further effect on the value of the literal.  For example:
+<literallayout>1_500_000_000
+0b10001000_00000000
+0o_1_755
+0xFFFF_FFFF
+1.618_034
+</literallayout>
+     Underscores are not allowed at the start or end of a numeric constant or
+     a group of digits (that is, immediately before or after a period or the
+     <quote>e</quote>), and more than one underscore in a row is not allowed.
+    </para>
+
+    <para>
      <indexterm><primary>integer</primary></indexterm>
      <indexterm><primary>bigint</primary></indexterm>
      <indexterm><primary>numeric</primary></indexterm>
diff --git a/src/backend/catalog/sql_features.txt b/src/backend/catalog/sql_features.txt
new file mode 100644
index abad216..3766762
--- a/src/backend/catalog/sql_features.txt
+++ b/src/backend/catalog/sql_features.txt
@@ -528,6 +528,7 @@ T653	SQL-schema statements in external r
 T654	SQL-dynamic statements in external routines			NO	
 T655	Cyclically dependent routines			YES	
 T661	Non-decimal integer literals			YES	SQL:202x draft
+T662	Underscores in integer literals			YES	SQL:202x draft
 T811	Basic SQL/JSON constructor functions			NO	
 T812	SQL/JSON: JSON_OBJECTAGG			NO	
 T813	SQL/JSON: JSON_ARRAYAGG with ORDER BY			NO	
diff --git a/src/backend/parser/parse_node.c b/src/backend/parser/parse_node.c
new file mode 100644
index f1967a3..5020b9f
--- a/src/backend/parser/parse_node.c
+++ b/src/backend/parser/parse_node.c
@@ -19,6 +19,7 @@
 #include "catalog/pg_type.h"
 #include "mb/pg_wchar.h"
 #include "nodes/makefuncs.h"
+#include "nodes/miscnodes.h"
 #include "nodes/nodeFuncs.h"
 #include "nodes/subscripting.h"
 #include "parser/parse_coerce.h"
@@ -385,47 +386,11 @@ make_const(ParseState *pstate, A_Const *
 			{
 				/* could be an oversize integer as well as a float ... */
 
-				int			base = 10;
-				char	   *startptr;
-				int			sign;
-				char	   *testvalue;
+				ErrorSaveContext escontext = {T_ErrorSaveContext};
 				int64		val64;
-				char	   *endptr;
 
-				startptr = aconst->val.fval.fval;
-				if (startptr[0] == '-')
-				{
-					sign = -1;
-					startptr++;
-				}
-				else
-					sign = +1;
-				if (startptr[0] == '0')
-				{
-					if (startptr[1] == 'b' || startptr[1] == 'B')
-					{
-						base = 2;
-						startptr += 2;
-					}
-					else if (startptr[1] == 'o' || startptr[1] == 'O')
-					{
-						base = 8;
-						startptr += 2;
-					}
-					else if (startptr[1] == 'x' || startptr[1] == 'X')
-					{
-						base = 16;
-						startptr += 2;
-					}
-				}
-
-				if (sign == +1)
-					testvalue = startptr;
-				else
-					testvalue = psprintf("-%s", startptr);
-				errno = 0;
-				val64 = strtoi64(testvalue, &endptr, base);
-				if (errno == 0 && *endptr == '\0')
+				val64 = pg_strtoint64_safe(aconst->val.fval.fval, (Node *) &escontext);
+				if (!escontext.error_occurred)
 				{
 					/*
 					 * It might actually fit in int32. Probably only INT_MIN
diff --git a/src/backend/parser/scan.l b/src/backend/parser/scan.l
new file mode 100644
index 1e821d4..b2216a9
--- a/src/backend/parser/scan.l
+++ b/src/backend/parser/scan.l
@@ -37,10 +37,12 @@
 
 #include "common/string.h"
 #include "gramparse.h"
+#include "nodes/miscnodes.h"
 #include "parser/parser.h"		/* only needed for GUC variables */
 #include "parser/scansup.h"
 #include "port/pg_bitutils.h"
 #include "mb/pg_wchar.h"
+#include "utils/builtins.h"
 }
 
 %{
@@ -395,19 +397,19 @@ hexdigit		[0-9A-Fa-f]
 octdigit		[0-7]
 bindigit		[0-1]
 
-decinteger		{decdigit}+
-hexinteger		0[xX]{hexdigit}+
-octinteger		0[oO]{octdigit}+
-bininteger		0[bB]{bindigit}+
+decinteger		{decdigit}(_?{decdigit})*
+hexinteger		0[xX](_?{hexdigit})+
+octinteger		0[oO](_?{octdigit})+
+bininteger		0[bB](_?{bindigit})+
 
-hexfail			0[xX]
-octfail			0[oO]
-binfail			0[bB]
+hexfail			0[xX]_?
+octfail			0[oO]_?
+binfail			0[bB]_?
 
 numeric			(({decinteger}\.{decinteger}?)|(\.{decinteger}))
 numericfail		{decdigit}+\.\.
 
-real			({decinteger}|{numeric})[Ee][-+]?{decdigit}+
+real			({decinteger}|{numeric})[Ee][-+]?{decinteger}
 realfail		({decinteger}|{numeric})[Ee][-+]
 
 decinteger_junk	{decinteger}{ident_start}
@@ -1364,12 +1366,11 @@ litbufdup(core_yyscan_t yyscanner)
 static int
 process_integer_literal(const char *token, YYSTYPE *lval, int base)
 {
-	int			val;
-	char	   *endptr;
+	ErrorSaveContext escontext = {T_ErrorSaveContext};
+	int32		val;
 
-	errno = 0;
-	val = strtoint(base == 10 ? token : token + 2, &endptr, base);
-	if (*endptr != '\0' || errno == ERANGE)
+	val = pg_strtoint32_safe(token, (Node *) &escontext);
+	if (escontext.error_occurred)
 	{
 		/* integer too large (or contains decimal pt), treat it as a float */
 		lval->str = pstrdup(token);
diff --git a/src/backend/utils/adt/numeric.c b/src/backend/utils/adt/numeric.c
new file mode 100644
index 898c520..a5bc89b
--- a/src/backend/utils/adt/numeric.c
+++ b/src/backend/utils/adt/numeric.c
@@ -6928,10 +6928,7 @@ set_var_from_str(const char *str, const
 	}
 
 	if (!isdigit((unsigned char) *cp))
-		ereturn(escontext, false,
-				(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
-				 errmsg("invalid input syntax for type %s: \"%s\"",
-						"numeric", str)));
+		goto invalid_syntax;
 
 	decdigits = (unsigned char *) palloc(strlen(cp) + DEC_DIGITS * 2);
 
@@ -6952,12 +6949,19 @@ set_var_from_str(const char *str, const
 		else if (*cp == '.')
 		{
 			if (have_dp)
-				ereturn(escontext, false,
-						(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
-						 errmsg("invalid input syntax for type %s: \"%s\"",
-								"numeric", str)));
+				goto invalid_syntax;
 			have_dp = true;
 			cp++;
+			/* decimal point must not be followed by underscore */
+			if (*cp == '_')
+				goto invalid_syntax;
+		}
+		else if (*cp == '_')
+		{
+			/* underscore must be followed by more digits */
+			cp++;
+			if (!isdigit((unsigned char) *cp))
+				goto invalid_syntax;
 		}
 		else
 			break;
@@ -6970,17 +6974,8 @@ set_var_from_str(const char *str, const
 	/* Handle exponent, if any */
 	if (*cp == 'e' || *cp == 'E')
 	{
-		long		exponent;
-		char	   *endptr;
-
-		cp++;
-		exponent = strtol(cp, &endptr, 10);
-		if (endptr == cp)
-			ereturn(escontext, false,
-					(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
-					 errmsg("invalid input syntax for type %s: \"%s\"",
-							"numeric", str)));
-		cp = endptr;
+		int64		exponent = 0;
+		bool		neg = false;
 
 		/*
 		 * At this point, dweight and dscale can't be more than about
@@ -6990,10 +6985,43 @@ set_var_from_str(const char *str, const
 		 * fit in storage format, make_result() will complain about it later;
 		 * for consistency use the same ereport errcode/text as make_result().
 		 */
-		if (exponent >= INT_MAX / 2 || exponent <= -(INT_MAX / 2))
-			ereturn(escontext, false,
-					(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
-					 errmsg("value overflows numeric format")));
+
+		/* exponent sign */
+		cp++;
+		if (*cp == '+')
+			cp++;
+		else if (*cp == '-')
+		{
+			neg = true;
+			cp++;
+		}
+
+		/* exponent digits */
+		if (!isdigit((unsigned char) *cp))
+			goto invalid_syntax;
+
+		while (*cp)
+		{
+			if (isdigit((unsigned char) *cp))
+			{
+				exponent = exponent * 10 + (*cp++ - '0');
+				if (exponent > INT_MAX / 2)
+					goto out_of_range;
+			}
+			else if (*cp == '_')
+			{
+				/* underscore must be followed by more digits */
+				cp++;
+				if (!isdigit((unsigned char) *cp))
+					goto invalid_syntax;
+			}
+			else
+				break;
+		}
+
+		if (neg)
+			exponent = -exponent;
+
 		dweight += (int) exponent;
 		dscale -= (int) exponent;
 		if (dscale < 0)
@@ -7045,6 +7073,17 @@ set_var_from_str(const char *str, const
 	*endptr = cp;
 
 	return true;
+
+out_of_range:
+	ereturn(escontext, false,
+			(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+			 errmsg("value overflows numeric format")));
+
+invalid_syntax:
+	ereturn(escontext, false,
+			(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
+			 errmsg("invalid input syntax for type %s: \"%s\"",
+					"numeric", str)));
 }
 
 
@@ -7127,6 +7166,13 @@ set_var_from_non_decimal_integer_str(con
 				tmp = tmp * 16 + xdigit_value(*cp++);
 				mul = mul * 16;
 			}
+			else if (*cp == '_')
+			{
+				/* Underscore must be followed by more digits */
+				cp++;
+				if (!isxdigit((unsigned char) *cp))
+					goto invalid_syntax;
+			}
 			else
 				break;
 		}
@@ -7157,6 +7203,13 @@ set_var_from_non_decimal_integer_str(con
 				tmp = tmp * 8 + (*cp++ - '0');
 				mul = mul * 8;
 			}
+			else if (*cp == '_')
+			{
+				/* Underscore must be followed by more digits */
+				cp++;
+				if (*cp < '0' || *cp > '7')
+					goto invalid_syntax;
+			}
 			else
 				break;
 		}
@@ -7187,6 +7240,13 @@ set_var_from_non_decimal_integer_str(con
 				tmp = tmp * 2 + (*cp++ - '0');
 				mul = mul * 2;
 			}
+			else if (*cp == '_')
+			{
+				/* Underscore must be followed by more digits */
+				cp++;
+				if (*cp < '0' || *cp > '1')
+					goto invalid_syntax;
+			}
 			else
 				break;
 		}
diff --git a/src/backend/utils/adt/numutils.c b/src/backend/utils/adt/numutils.c
new file mode 100644
index b0e412e..471fbb7
--- a/src/backend/utils/adt/numutils.c
+++ b/src/backend/utils/adt/numutils.c
@@ -141,48 +141,99 @@ pg_strtoint16_safe(const char *s, Node *
 	{
 		firstdigit = ptr += 2;
 
-		while (*ptr && isxdigit((unsigned char) *ptr))
+		while (*ptr)
 		{
-			if (unlikely(tmp > -(PG_INT16_MIN / 16)))
-				goto out_of_range;
+			if (isxdigit((unsigned char) *ptr))
+			{
+				if (unlikely(tmp > -(PG_INT16_MIN / 16)))
+					goto out_of_range;
 
-			tmp = tmp * 16 + hexlookup[(unsigned char) *ptr++];
+				tmp = tmp * 16 + hexlookup[(unsigned char) *ptr++];
+			}
+			else if (*ptr == '_')
+			{
+				/* underscore must be followed by more digits */
+				ptr++;
+				if (*ptr == '\0' || !isxdigit((unsigned char) *ptr))
+					goto invalid_syntax;
+			}
+			else
+				break;
 		}
 	}
 	else if (ptr[0] == '0' && (ptr[1] == 'o' || ptr[1] == 'O'))
 	{
 		firstdigit = ptr += 2;
 
-		while (*ptr && (*ptr >= '0' && *ptr <= '7'))
+		while (*ptr)
 		{
-			if (unlikely(tmp > -(PG_INT16_MIN / 8)))
-				goto out_of_range;
+			if (*ptr >= '0' && *ptr <= '7')
+			{
+				if (unlikely(tmp > -(PG_INT16_MIN / 8)))
+					goto out_of_range;
 
-			tmp = tmp * 8 + (*ptr++ - '0');
+				tmp = tmp * 8 + (*ptr++ - '0');
+			}
+			else if (*ptr == '_')
+			{
+				/* underscore must be followed by more digits */
+				ptr++;
+				if (*ptr == '\0' || *ptr < '0' || *ptr > '7')
+					goto invalid_syntax;
+			}
+			else
+				break;
 		}
 	}
 	else if (ptr[0] == '0' && (ptr[1] == 'b' || ptr[1] == 'B'))
 	{
 		firstdigit = ptr += 2;
 
-		while (*ptr && (*ptr >= '0' && *ptr <= '1'))
+		while (*ptr)
 		{
-			if (unlikely(tmp > -(PG_INT16_MIN / 2)))
-				goto out_of_range;
+			if (*ptr >= '0' && *ptr <= '1')
+			{
+				if (unlikely(tmp > -(PG_INT16_MIN / 2)))
+					goto out_of_range;
 
-			tmp = tmp * 2 + (*ptr++ - '0');
+				tmp = tmp * 2 + (*ptr++ - '0');
+			}
+			else if (*ptr == '_')
+			{
+				/* underscore must be followed by more digits */
+				ptr++;
+				if (*ptr == '\0' || *ptr < '0' || *ptr > '1')
+					goto invalid_syntax;
+			}
+			else
+				break;
 		}
 	}
 	else
 	{
 		firstdigit = ptr;
 
-		while (*ptr && isdigit((unsigned char) *ptr))
+		while (*ptr)
 		{
-			if (unlikely(tmp > -(PG_INT16_MIN / 10)))
-				goto out_of_range;
+			if (isdigit((unsigned char) *ptr))
+			{
+				if (unlikely(tmp > -(PG_INT16_MIN / 10)))
+					goto out_of_range;
 
-			tmp = tmp * 10 + (*ptr++ - '0');
+				tmp = tmp * 10 + (*ptr++ - '0');
+			}
+			else if (*ptr == '_')
+			{
+				/* underscore may not be first */
+				if (unlikely(ptr == firstdigit))
+					goto invalid_syntax;
+				/* and it must be followed by more digits */
+				ptr++;
+				if (*ptr == '\0' || !isdigit((unsigned char) *ptr))
+					goto invalid_syntax;
+			}
+			else
+				break;
 		}
 	}
 
@@ -268,48 +319,99 @@ pg_strtoint32_safe(const char *s, Node *
 	{
 		firstdigit = ptr += 2;
 
-		while (*ptr && isxdigit((unsigned char) *ptr))
+		while (*ptr)
 		{
-			if (unlikely(tmp > -(PG_INT32_MIN / 16)))
-				goto out_of_range;
+			if (isxdigit((unsigned char) *ptr))
+			{
+				if (unlikely(tmp > -(PG_INT32_MIN / 16)))
+					goto out_of_range;
 
-			tmp = tmp * 16 + hexlookup[(unsigned char) *ptr++];
+				tmp = tmp * 16 + hexlookup[(unsigned char) *ptr++];
+			}
+			else if (*ptr == '_')
+			{
+				/* underscore must be followed by more digits */
+				ptr++;
+				if (*ptr == '\0' || !isxdigit((unsigned char) *ptr))
+					goto invalid_syntax;
+			}
+			else
+				break;
 		}
 	}
 	else if (ptr[0] == '0' && (ptr[1] == 'o' || ptr[1] == 'O'))
 	{
 		firstdigit = ptr += 2;
 
-		while (*ptr && (*ptr >= '0' && *ptr <= '7'))
+		while (*ptr)
 		{
-			if (unlikely(tmp > -(PG_INT32_MIN / 8)))
-				goto out_of_range;
+			if (*ptr >= '0' && *ptr <= '7')
+			{
+				if (unlikely(tmp > -(PG_INT32_MIN / 8)))
+					goto out_of_range;
 
-			tmp = tmp * 8 + (*ptr++ - '0');
+				tmp = tmp * 8 + (*ptr++ - '0');
+			}
+			else if (*ptr == '_')
+			{
+				/* underscore must be followed by more digits */
+				ptr++;
+				if (*ptr == '\0' || *ptr < '0' || *ptr > '7')
+					goto invalid_syntax;
+			}
+			else
+				break;
 		}
 	}
 	else if (ptr[0] == '0' && (ptr[1] == 'b' || ptr[1] == 'B'))
 	{
 		firstdigit = ptr += 2;
 
-		while (*ptr && (*ptr >= '0' && *ptr <= '1'))
+		while (*ptr)
 		{
-			if (unlikely(tmp > -(PG_INT32_MIN / 2)))
-				goto out_of_range;
+			if (*ptr >= '0' && *ptr <= '1')
+			{
+				if (unlikely(tmp > -(PG_INT32_MIN / 2)))
+					goto out_of_range;
 
-			tmp = tmp * 2 + (*ptr++ - '0');
+				tmp = tmp * 2 + (*ptr++ - '0');
+			}
+			else if (*ptr == '_')
+			{
+				/* underscore must be followed by more digits */
+				ptr++;
+				if (*ptr == '\0' || *ptr < '0' || *ptr > '1')
+					goto invalid_syntax;
+			}
+			else
+				break;
 		}
 	}
 	else
 	{
 		firstdigit = ptr;
 
-		while (*ptr && isdigit((unsigned char) *ptr))
+		while (*ptr)
 		{
-			if (unlikely(tmp > -(PG_INT32_MIN / 10)))
-				goto out_of_range;
+			if (isdigit((unsigned char) *ptr))
+			{
+				if (unlikely(tmp > -(PG_INT32_MIN / 10)))
+					goto out_of_range;
 
-			tmp = tmp * 10 + (*ptr++ - '0');
+				tmp = tmp * 10 + (*ptr++ - '0');
+			}
+			else if (*ptr == '_')
+			{
+				/* underscore may not be first */
+				if (unlikely(ptr == firstdigit))
+					goto invalid_syntax;
+				/* and it must be followed by more digits */
+				ptr++;
+				if (*ptr == '\0' || !isdigit((unsigned char) *ptr))
+					goto invalid_syntax;
+			}
+			else
+				break;
 		}
 	}
 
@@ -395,48 +497,99 @@ pg_strtoint64_safe(const char *s, Node *
 	{
 		firstdigit = ptr += 2;
 
-		while (*ptr && isxdigit((unsigned char) *ptr))
+		while (*ptr)
 		{
-			if (unlikely(tmp > -(PG_INT64_MIN / 16)))
-				goto out_of_range;
+			if (isxdigit((unsigned char) *ptr))
+			{
+				if (unlikely(tmp > -(PG_INT64_MIN / 16)))
+					goto out_of_range;
 
-			tmp = tmp * 16 + hexlookup[(unsigned char) *ptr++];
+				tmp = tmp * 16 + hexlookup[(unsigned char) *ptr++];
+			}
+			else if (*ptr == '_')
+			{
+				/* underscore must be followed by more digits */
+				ptr++;
+				if (*ptr == '\0' || !isxdigit((unsigned char) *ptr))
+					goto invalid_syntax;
+			}
+			else
+				break;
 		}
 	}
 	else if (ptr[0] == '0' && (ptr[1] == 'o' || ptr[1] == 'O'))
 	{
 		firstdigit = ptr += 2;
 
-		while (*ptr && (*ptr >= '0' && *ptr <= '7'))
+		while (*ptr)
 		{
-			if (unlikely(tmp > -(PG_INT64_MIN / 8)))
-				goto out_of_range;
+			if (*ptr >= '0' && *ptr <= '7')
+			{
+				if (unlikely(tmp > -(PG_INT64_MIN / 8)))
+					goto out_of_range;
 
-			tmp = tmp * 8 + (*ptr++ - '0');
+				tmp = tmp * 8 + (*ptr++ - '0');
+			}
+			else if (*ptr == '_')
+			{
+				/* underscore must be followed by more digits */
+				ptr++;
+				if (*ptr == '\0' || *ptr < '0' || *ptr > '7')
+					goto invalid_syntax;
+			}
+			else
+				break;
 		}
 	}
 	else if (ptr[0] == '0' && (ptr[1] == 'b' || ptr[1] == 'B'))
 	{
 		firstdigit = ptr += 2;
 
-		while (*ptr && (*ptr >= '0' && *ptr <= '1'))
+		while (*ptr)
 		{
-			if (unlikely(tmp > -(PG_INT64_MIN / 2)))
-				goto out_of_range;
+			if (*ptr >= '0' && *ptr <= '1')
+			{
+				if (unlikely(tmp > -(PG_INT64_MIN / 2)))
+					goto out_of_range;
 
-			tmp = tmp * 2 + (*ptr++ - '0');
+				tmp = tmp * 2 + (*ptr++ - '0');
+			}
+			else if (*ptr == '_')
+			{
+				/* underscore must be followed by more digits */
+				ptr++;
+				if (*ptr == '\0' || *ptr < '0' || *ptr > '1')
+					goto invalid_syntax;
+			}
+			else
+				break;
 		}
 	}
 	else
 	{
 		firstdigit = ptr;
 
-		while (*ptr && isdigit((unsigned char) *ptr))
+		while (*ptr)
 		{
-			if (unlikely(tmp > -(PG_INT64_MIN / 10)))
-				goto out_of_range;
+			if (isdigit((unsigned char) *ptr))
+			{
+				if (unlikely(tmp > -(PG_INT64_MIN / 10)))
+					goto out_of_range;
 
-			tmp = tmp * 10 + (*ptr++ - '0');
+				tmp = tmp * 10 + (*ptr++ - '0');
+			}
+			else if (*ptr == '_')
+			{
+				/* underscore may not be first */
+				if (unlikely(ptr == firstdigit))
+					goto invalid_syntax;
+				/* and it must be followed by more digits */
+				ptr++;
+				if (*ptr == '\0' || !isdigit((unsigned char) *ptr))
+					goto invalid_syntax;
+			}
+			else
+				break;
 		}
 	}
 
diff --git a/src/fe_utils/psqlscan.l b/src/fe_utils/psqlscan.l
new file mode 100644
index bec5095..84754ac
--- a/src/fe_utils/psqlscan.l
+++ b/src/fe_utils/psqlscan.l
@@ -333,19 +333,19 @@ hexdigit		[0-9A-Fa-f]
 octdigit		[0-7]
 bindigit		[0-1]
 
-decinteger		{decdigit}+
-hexinteger		0[xX]{hexdigit}+
-octinteger		0[oO]{octdigit}+
-bininteger		0[bB]{bindigit}+
+decinteger		{decdigit}(_?{decdigit})*
+hexinteger		0[xX](_?{hexdigit})+
+octinteger		0[oO](_?{octdigit})+
+bininteger		0[bB](_?{bindigit})+
 
-hexfail			0[xX]
-octfail			0[oO]
-binfail			0[bB]
+hexfail			0[xX]_?
+octfail			0[oO]_?
+binfail			0[bB]_?
 
 numeric			(({decinteger}\.{decinteger}?)|(\.{decinteger}))
 numericfail		{decdigit}+\.\.
 
-real			({decinteger}|{numeric})[Ee][-+]?{decdigit}+
+real			({decinteger}|{numeric})[Ee][-+]?{decinteger}
 realfail		({decinteger}|{numeric})[Ee][-+]
 
 decinteger_junk	{decinteger}{ident_start}
diff --git a/src/interfaces/ecpg/preproc/pgc.l b/src/interfaces/ecpg/preproc/pgc.l
new file mode 100644
index 75815bd..dcd567e
--- a/src/interfaces/ecpg/preproc/pgc.l
+++ b/src/interfaces/ecpg/preproc/pgc.l
@@ -361,19 +361,19 @@ hexdigit		[0-9A-Fa-f]
 octdigit		[0-7]
 bindigit		[0-1]
 
-decinteger		{decdigit}+
-hexinteger		0[xX]{hexdigit}+
-octinteger		0[oO]{octdigit}+
-bininteger		0[bB]{bindigit}+
+decinteger		{decdigit}(_?{decdigit})*
+hexinteger		0[xX](_?{hexdigit})+
+octinteger		0[oO](_?{octdigit})+
+bininteger		0[bB](_?{bindigit})+
 
-hexfail			0[xX]
-octfail			0[oO]
-binfail			0[bB]
+hexfail			0[xX]_?
+octfail			0[oO]_?
+binfail			0[bB]_?
 
 numeric			(({decinteger}\.{decinteger}?)|(\.{decinteger}))
 numericfail		{decdigit}+\.\.
 
-real			({decinteger}|{numeric})[Ee][-+]?{decdigit}+
+real			({decinteger}|{numeric})[Ee][-+]?{decinteger}
 realfail		({decinteger}|{numeric})[Ee][-+]
 
 decinteger_junk	{decinteger}{ident_start}
diff --git a/src/pl/plpgsql/src/expected/plpgsql_trap.out b/src/pl/plpgsql/src/expected/plpgsql_trap.out
new file mode 100644
index 90cf6c2..62d1679
--- a/src/pl/plpgsql/src/expected/plpgsql_trap.out
+++ b/src/pl/plpgsql/src/expected/plpgsql_trap.out
@@ -141,7 +141,7 @@ begin
   declare x int;
   begin
     -- we assume this will take longer than 1 second:
-    select count(*) into x from generate_series(1, 1000000000000);
+    select count(*) into x from generate_series(1, 1_000_000_000_000);
   exception
     when others then
       raise notice 'caught others?';
diff --git a/src/pl/plpgsql/src/sql/plpgsql_trap.sql b/src/pl/plpgsql/src/sql/plpgsql_trap.sql
new file mode 100644
index c6c1ad8..5459b34
--- a/src/pl/plpgsql/src/sql/plpgsql_trap.sql
+++ b/src/pl/plpgsql/src/sql/plpgsql_trap.sql
@@ -88,7 +88,7 @@ begin
   declare x int;
   begin
     -- we assume this will take longer than 1 second:
-    select count(*) into x from generate_series(1, 1000000000000);
+    select count(*) into x from generate_series(1, 1_000_000_000_000);
   exception
     when others then
       raise notice 'caught others?';
diff --git a/src/test/regress/expected/int2.out b/src/test/regress/expected/int2.out
new file mode 100644
index 08c333b..73b4ee0
--- a/src/test/regress/expected/int2.out
+++ b/src/test/regress/expected/int2.out
@@ -440,3 +440,47 @@ SELECT int2 '-0x8001';
 ERROR:  value "-0x8001" is out of range for type smallint
 LINE 1: SELECT int2 '-0x8001';
                     ^
+-- underscores
+SELECT int2 '1_000';
+ int2 
+------
+ 1000
+(1 row)
+
+SELECT int2 '1_2_3';
+ int2 
+------
+  123
+(1 row)
+
+SELECT int2 '0xE_FF';
+ int2 
+------
+ 3839
+(1 row)
+
+SELECT int2 '0o2_73';
+ int2 
+------
+  187
+(1 row)
+
+SELECT int2 '0b_10_0101';
+ int2 
+------
+   37
+(1 row)
+
+-- error cases
+SELECT int2 '_100';
+ERROR:  invalid input syntax for type smallint: "_100"
+LINE 1: SELECT int2 '_100';
+                    ^
+SELECT int2 '100_';
+ERROR:  invalid input syntax for type smallint: "100_"
+LINE 1: SELECT int2 '100_';
+                    ^
+SELECT int2 '10__000';
+ERROR:  invalid input syntax for type smallint: "10__000"
+LINE 1: SELECT int2 '10__000';
+                    ^
diff --git a/src/test/regress/expected/int4.out b/src/test/regress/expected/int4.out
new file mode 100644
index 8386c7c..9c20574
--- a/src/test/regress/expected/int4.out
+++ b/src/test/regress/expected/int4.out
@@ -548,3 +548,47 @@ SELECT int4 '-0x80000001';
 ERROR:  value "-0x80000001" is out of range for type integer
 LINE 1: SELECT int4 '-0x80000001';
                     ^
+-- underscores
+SELECT int4 '1_000_000';
+  int4   
+---------
+ 1000000
+(1 row)
+
+SELECT int4 '1_2_3';
+ int4 
+------
+  123
+(1 row)
+
+SELECT int4 '0x1EEE_FFFF';
+   int4    
+-----------
+ 518979583
+(1 row)
+
+SELECT int4 '0o2_73';
+ int4 
+------
+  187
+(1 row)
+
+SELECT int4 '0b_10_0101';
+ int4 
+------
+   37
+(1 row)
+
+-- error cases
+SELECT int4 '_100';
+ERROR:  invalid input syntax for type integer: "_100"
+LINE 1: SELECT int4 '_100';
+                    ^
+SELECT int4 '100_';
+ERROR:  invalid input syntax for type integer: "100_"
+LINE 1: SELECT int4 '100_';
+                    ^
+SELECT int4 '100__000';
+ERROR:  invalid input syntax for type integer: "100__000"
+LINE 1: SELECT int4 '100__000';
+                    ^
diff --git a/src/test/regress/expected/int8.out b/src/test/regress/expected/int8.out
new file mode 100644
index 5b62b51..d9dca64
--- a/src/test/regress/expected/int8.out
+++ b/src/test/regress/expected/int8.out
@@ -1044,3 +1044,47 @@ SELECT int8 '-0x8000000000000001';
 ERROR:  value "-0x8000000000000001" is out of range for type bigint
 LINE 1: SELECT int8 '-0x8000000000000001';
                     ^
+-- underscores
+SELECT int8 '1_000_000';
+  int8   
+---------
+ 1000000
+(1 row)
+
+SELECT int8 '1_2_3';
+ int8 
+------
+  123
+(1 row)
+
+SELECT int8 '0x1EEE_FFFF';
+   int8    
+-----------
+ 518979583
+(1 row)
+
+SELECT int8 '0o2_73';
+ int8 
+------
+  187
+(1 row)
+
+SELECT int8 '0b_10_0101';
+ int8 
+------
+   37
+(1 row)
+
+-- error cases
+SELECT int8 '_100';
+ERROR:  invalid input syntax for type bigint: "_100"
+LINE 1: SELECT int8 '_100';
+                    ^
+SELECT int8 '100_';
+ERROR:  invalid input syntax for type bigint: "100_"
+LINE 1: SELECT int8 '100_';
+                    ^
+SELECT int8 '100__000';
+ERROR:  invalid input syntax for type bigint: "100__000"
+LINE 1: SELECT int8 '100__000';
+                    ^
diff --git a/src/test/regress/expected/numeric.out b/src/test/regress/expected/numeric.out
new file mode 100644
index 9479652..56a3f36
--- a/src/test/regress/expected/numeric.out
+++ b/src/test/regress/expected/numeric.out
@@ -2144,12 +2144,17 @@ INSERT INTO num_input_test(n1) VALUES ('
 INSERT INTO num_input_test(n1) VALUES (' Infinity ');
 INSERT INTO num_input_test(n1) VALUES (' +inFinity ');
 INSERT INTO num_input_test(n1) VALUES (' -INFINITY ');
+INSERT INTO num_input_test(n1) VALUES ('12_000_000_000');
+INSERT INTO num_input_test(n1) VALUES ('12_000.123_456');
+INSERT INTO num_input_test(n1) VALUES ('23_000_000_000e-1_0');
+INSERT INTO num_input_test(n1) VALUES ('.000_000_000_123e1_0');
+INSERT INTO num_input_test(n1) VALUES ('.000_000_000_123e+1_1');
 INSERT INTO num_input_test(n1) VALUES ('0b10001110111100111100001001010');
-INSERT INTO num_input_test(n1) VALUES ('  -0B1010101101010100101010011000110011101011000111110000101011010010  ');
+INSERT INTO num_input_test(n1) VALUES ('  -0B_1010_1011_0101_0100_1010_1001_1000_1100_1110_1011_0001_1111_0000_1010_1101_0010  ');
 INSERT INTO num_input_test(n1) VALUES ('  +0o112402761777 ');
-INSERT INTO num_input_test(n1) VALUES ('-0O001255245230633431670261');
+INSERT INTO num_input_test(n1) VALUES ('-0O0012_5524_5230_6334_3167_0261');
 INSERT INTO num_input_test(n1) VALUES ('-0x0000000000000000000000000deadbeef');
-INSERT INTO num_input_test(n1) VALUES (' 0X30b1F33a6DF0bD4E64DF9BdA7D15 ');
+INSERT INTO num_input_test(n1) VALUES (' 0X_30b1_F33a_6DF0_bD4E_64DF_9BdA_7D15 ');
 -- bad inputs
 INSERT INTO num_input_test(n1) VALUES ('     ');
 ERROR:  invalid input syntax for type numeric: "     "
@@ -2195,6 +2200,38 @@ INSERT INTO num_input_test(n1) VALUES ('
 ERROR:  invalid input syntax for type numeric: "+ infinity"
 LINE 1: INSERT INTO num_input_test(n1) VALUES ('+ infinity');
                                                ^
+INSERT INTO num_input_test(n1) VALUES ('_123');
+ERROR:  invalid input syntax for type numeric: "_123"
+LINE 1: INSERT INTO num_input_test(n1) VALUES ('_123');
+                                               ^
+INSERT INTO num_input_test(n1) VALUES ('123_');
+ERROR:  invalid input syntax for type numeric: "123_"
+LINE 1: INSERT INTO num_input_test(n1) VALUES ('123_');
+                                               ^
+INSERT INTO num_input_test(n1) VALUES ('12__34');
+ERROR:  invalid input syntax for type numeric: "12__34"
+LINE 1: INSERT INTO num_input_test(n1) VALUES ('12__34');
+                                               ^
+INSERT INTO num_input_test(n1) VALUES ('123_.456');
+ERROR:  invalid input syntax for type numeric: "123_.456"
+LINE 1: INSERT INTO num_input_test(n1) VALUES ('123_.456');
+                                               ^
+INSERT INTO num_input_test(n1) VALUES ('123._456');
+ERROR:  invalid input syntax for type numeric: "123._456"
+LINE 1: INSERT INTO num_input_test(n1) VALUES ('123._456');
+                                               ^
+INSERT INTO num_input_test(n1) VALUES ('1.2e_34');
+ERROR:  invalid input syntax for type numeric: "1.2e_34"
+LINE 1: INSERT INTO num_input_test(n1) VALUES ('1.2e_34');
+                                               ^
+INSERT INTO num_input_test(n1) VALUES ('1.2e34_');
+ERROR:  invalid input syntax for type numeric: "1.2e34_"
+LINE 1: INSERT INTO num_input_test(n1) VALUES ('1.2e34_');
+                                               ^
+INSERT INTO num_input_test(n1) VALUES ('1.2e3__4');
+ERROR:  invalid input syntax for type numeric: "1.2e3__4"
+LINE 1: INSERT INTO num_input_test(n1) VALUES ('1.2e3__4');
+                                               ^
 INSERT INTO num_input_test(n1) VALUES ('0b1112');
 ERROR:  invalid input syntax for type numeric: "0b1112"
 LINE 1: INSERT INTO num_input_test(n1) VALUES ('0b1112');
@@ -2215,6 +2252,18 @@ INSERT INTO num_input_test(n1) VALUES ('
 ERROR:  invalid input syntax for type numeric: "0x12.34"
 LINE 1: INSERT INTO num_input_test(n1) VALUES ('0x12.34');
                                                ^
+INSERT INTO num_input_test(n1) VALUES ('0x__1234');
+ERROR:  invalid input syntax for type numeric: "0x__1234"
+LINE 1: INSERT INTO num_input_test(n1) VALUES ('0x__1234');
+                                               ^
+INSERT INTO num_input_test(n1) VALUES ('0x1234_');
+ERROR:  invalid input syntax for type numeric: "0x1234_"
+LINE 1: INSERT INTO num_input_test(n1) VALUES ('0x1234_');
+                                               ^
+INSERT INTO num_input_test(n1) VALUES ('0x12__34');
+ERROR:  invalid input syntax for type numeric: "0x12__34"
+LINE 1: INSERT INTO num_input_test(n1) VALUES ('0x12__34');
+                                               ^
 SELECT * FROM num_input_test;
                 n1                 
 -----------------------------------
@@ -2231,13 +2280,18 @@ SELECT * FROM num_input_test;
                           Infinity
                           Infinity
                          -Infinity
+                       12000000000
+                      12000.123456
+                      2.3000000000
+                              1.23
+                              12.3
                          299792458
              -12345678901234567890
                         9999999999
              -12345678900987654321
                        -3735928559
  987654321234567898765432123456789
-(19 rows)
+(24 rows)
 
 -- Also try it with non-error-throwing API
 SELECT pg_input_is_valid('34.5', 'numeric');
diff --git a/src/test/regress/expected/numerology.out b/src/test/regress/expected/numerology.out
new file mode 100644
index deb26d3..f662a50
--- a/src/test/regress/expected/numerology.out
+++ b/src/test/regress/expected/numerology.out
@@ -178,10 +178,6 @@ SELECT 0x0o;
 ERROR:  trailing junk after numeric literal at or near "0x0o"
 LINE 1: SELECT 0x0o;
                ^
-SELECT 1_2_3;
-ERROR:  trailing junk after numeric literal at or near "1_"
-LINE 1: SELECT 1_2_3;
-               ^
 SELECT 0.a;
 ERROR:  trailing junk after numeric literal at or near "0.a"
 LINE 1: SELECT 0.a;
@@ -246,6 +242,94 @@ SELECT 0x0y;
 ERROR:  trailing junk after numeric literal at or near "0x0y"
 LINE 1: SELECT 0x0y;
                ^
+-- underscores
+SELECT 1_000_000;
+ ?column? 
+----------
+  1000000
+(1 row)
+
+SELECT 1_2_3;
+ ?column? 
+----------
+      123
+(1 row)
+
+SELECT 0x1EEE_FFFF;
+ ?column?  
+-----------
+ 518979583
+(1 row)
+
+SELECT 0o2_73;
+ ?column? 
+----------
+      187
+(1 row)
+
+SELECT 0b_10_0101;
+ ?column? 
+----------
+       37
+(1 row)
+
+SELECT 1_000.000_005;
+  ?column?   
+-------------
+ 1000.000005
+(1 row)
+
+SELECT 1_000.;
+ ?column? 
+----------
+     1000
+(1 row)
+
+SELECT .000_005;
+ ?column? 
+----------
+ 0.000005
+(1 row)
+
+SELECT 1_000.5e0_1;
+ ?column? 
+----------
+    10005
+(1 row)
+
+-- error cases
+SELECT _100;
+ERROR:  column "_100" does not exist
+LINE 1: SELECT _100;
+               ^
+SELECT 100_;
+ERROR:  trailing junk after numeric literal at or near "100_"
+LINE 1: SELECT 100_;
+               ^
+SELECT 100__000;
+ERROR:  trailing junk after numeric literal at or near "100_"
+LINE 1: SELECT 100__000;
+               ^
+SELECT _1_000.5;
+ERROR:  syntax error at or near ".5"
+LINE 1: SELECT _1_000.5;
+                     ^
+SELECT 1_000_.5;
+ERROR:  trailing junk after numeric literal at or near "1_000_"
+LINE 1: SELECT 1_000_.5;
+               ^
+SELECT 1_000._5;
+ERROR:  trailing junk after numeric literal at or near "1_000._"
+LINE 1: SELECT 1_000._5;
+               ^
+SELECT 1_000.5_;
+ERROR:  trailing junk after numeric literal at or near "1_000.5_"
+LINE 1: SELECT 1_000.5_;
+               ^
+SELECT 1_000.5e_1;
+ERROR:  trailing junk after numeric literal at or near "1_000.5e"
+LINE 1: SELECT 1_000.5e_1;
+               ^
 --
 -- Test implicit type conversions
 -- This fails for Postgres v6.1 (and earlier?)
diff --git a/src/test/regress/expected/partition_prune.out b/src/test/regress/expected/partition_prune.out
new file mode 100644
index 7555764..d700c00
--- a/src/test/regress/expected/partition_prune.out
+++ b/src/test/regress/expected/partition_prune.out
@@ -1503,7 +1503,7 @@ explain (costs off) select * from like_o
 create table lparted_by_int2 (a smallint) partition by list (a);
 create table lparted_by_int2_1 partition of lparted_by_int2 for values in (1);
 create table lparted_by_int2_16384 partition of lparted_by_int2 for values in (16384);
-explain (costs off) select * from lparted_by_int2 where a = 100000000000000;
+explain (costs off) select * from lparted_by_int2 where a = 100_000_000_000_000;
         QUERY PLAN        
 --------------------------
  Result
@@ -1514,7 +1514,7 @@ create table rparted_by_int2 (a smallint
 create table rparted_by_int2_1 partition of rparted_by_int2 for values from (1) to (10);
 create table rparted_by_int2_16384 partition of rparted_by_int2 for values from (10) to (16384);
 -- all partitions pruned
-explain (costs off) select * from rparted_by_int2 where a > 100000000000000;
+explain (costs off) select * from rparted_by_int2 where a > 100_000_000_000_000;
         QUERY PLAN        
 --------------------------
  Result
@@ -1523,7 +1523,7 @@ explain (costs off) select * from rparte
 
 create table rparted_by_int2_maxvalue partition of rparted_by_int2 for values from (16384) to (maxvalue);
 -- all partitions but rparted_by_int2_maxvalue pruned
-explain (costs off) select * from rparted_by_int2 where a > 100000000000000;
+explain (costs off) select * from rparted_by_int2 where a > 100_000_000_000_000;
                       QUERY PLAN                      
 ------------------------------------------------------
  Seq Scan on rparted_by_int2_maxvalue rparted_by_int2
diff --git a/src/test/regress/sql/int2.sql b/src/test/regress/sql/int2.sql
new file mode 100644
index a812235..ce8ac97
--- a/src/test/regress/sql/int2.sql
+++ b/src/test/regress/sql/int2.sql
@@ -141,3 +141,17 @@ SELECT int2 '-0o100000';
 SELECT int2 '-0o100001';
 SELECT int2 '-0x8000';
 SELECT int2 '-0x8001';
+
+
+-- underscores
+
+SELECT int2 '1_000';
+SELECT int2 '1_2_3';
+SELECT int2 '0xE_FF';
+SELECT int2 '0o2_73';
+SELECT int2 '0b_10_0101';
+
+-- error cases
+SELECT int2 '_100';
+SELECT int2 '100_';
+SELECT int2 '10__000';
diff --git a/src/test/regress/sql/int4.sql b/src/test/regress/sql/int4.sql
new file mode 100644
index 9e6a404..146963e
--- a/src/test/regress/sql/int4.sql
+++ b/src/test/regress/sql/int4.sql
@@ -196,3 +196,17 @@ SELECT int4 '-0o20000000000';
 SELECT int4 '-0o20000000001';
 SELECT int4 '-0x80000000';
 SELECT int4 '-0x80000001';
+
+
+-- underscores
+
+SELECT int4 '1_000_000';
+SELECT int4 '1_2_3';
+SELECT int4 '0x1EEE_FFFF';
+SELECT int4 '0o2_73';
+SELECT int4 '0b_10_0101';
+
+-- error cases
+SELECT int4 '_100';
+SELECT int4 '100_';
+SELECT int4 '100__000';
diff --git a/src/test/regress/sql/int8.sql b/src/test/regress/sql/int8.sql
new file mode 100644
index 06f273e..c85717c
--- a/src/test/regress/sql/int8.sql
+++ b/src/test/regress/sql/int8.sql
@@ -277,3 +277,17 @@ SELECT int8 '-0o1000000000000000000000';
 SELECT int8 '-0o1000000000000000000001';
 SELECT int8 '-0x8000000000000000';
 SELECT int8 '-0x8000000000000001';
+
+
+-- underscores
+
+SELECT int8 '1_000_000';
+SELECT int8 '1_2_3';
+SELECT int8 '0x1EEE_FFFF';
+SELECT int8 '0o2_73';
+SELECT int8 '0b_10_0101';
+
+-- error cases
+SELECT int8 '_100';
+SELECT int8 '100_';
+SELECT int8 '100__000';
diff --git a/src/test/regress/sql/numeric.sql b/src/test/regress/sql/numeric.sql
new file mode 100644
index fe93714..2db7656
--- a/src/test/regress/sql/numeric.sql
+++ b/src/test/regress/sql/numeric.sql
@@ -1039,12 +1039,17 @@ INSERT INTO num_input_test(n1) VALUES ('
 INSERT INTO num_input_test(n1) VALUES (' Infinity ');
 INSERT INTO num_input_test(n1) VALUES (' +inFinity ');
 INSERT INTO num_input_test(n1) VALUES (' -INFINITY ');
+INSERT INTO num_input_test(n1) VALUES ('12_000_000_000');
+INSERT INTO num_input_test(n1) VALUES ('12_000.123_456');
+INSERT INTO num_input_test(n1) VALUES ('23_000_000_000e-1_0');
+INSERT INTO num_input_test(n1) VALUES ('.000_000_000_123e1_0');
+INSERT INTO num_input_test(n1) VALUES ('.000_000_000_123e+1_1');
 INSERT INTO num_input_test(n1) VALUES ('0b10001110111100111100001001010');
-INSERT INTO num_input_test(n1) VALUES ('  -0B1010101101010100101010011000110011101011000111110000101011010010  ');
+INSERT INTO num_input_test(n1) VALUES ('  -0B_1010_1011_0101_0100_1010_1001_1000_1100_1110_1011_0001_1111_0000_1010_1101_0010  ');
 INSERT INTO num_input_test(n1) VALUES ('  +0o112402761777 ');
-INSERT INTO num_input_test(n1) VALUES ('-0O001255245230633431670261');
+INSERT INTO num_input_test(n1) VALUES ('-0O0012_5524_5230_6334_3167_0261');
 INSERT INTO num_input_test(n1) VALUES ('-0x0000000000000000000000000deadbeef');
-INSERT INTO num_input_test(n1) VALUES (' 0X30b1F33a6DF0bD4E64DF9BdA7D15 ');
+INSERT INTO num_input_test(n1) VALUES (' 0X_30b1_F33a_6DF0_bD4E_64DF_9BdA_7D15 ');
 
 -- bad inputs
 INSERT INTO num_input_test(n1) VALUES ('     ');
@@ -1058,11 +1063,22 @@ INSERT INTO num_input_test(n1) VALUES ('
 INSERT INTO num_input_test(n1) VALUES ('+NaN');
 INSERT INTO num_input_test(n1) VALUES ('-NaN');
 INSERT INTO num_input_test(n1) VALUES ('+ infinity');
+INSERT INTO num_input_test(n1) VALUES ('_123');
+INSERT INTO num_input_test(n1) VALUES ('123_');
+INSERT INTO num_input_test(n1) VALUES ('12__34');
+INSERT INTO num_input_test(n1) VALUES ('123_.456');
+INSERT INTO num_input_test(n1) VALUES ('123._456');
+INSERT INTO num_input_test(n1) VALUES ('1.2e_34');
+INSERT INTO num_input_test(n1) VALUES ('1.2e34_');
+INSERT INTO num_input_test(n1) VALUES ('1.2e3__4');
 INSERT INTO num_input_test(n1) VALUES ('0b1112');
 INSERT INTO num_input_test(n1) VALUES ('0c1112');
 INSERT INTO num_input_test(n1) VALUES ('0o12345678');
 INSERT INTO num_input_test(n1) VALUES ('0x1eg');
 INSERT INTO num_input_test(n1) VALUES ('0x12.34');
+INSERT INTO num_input_test(n1) VALUES ('0x__1234');
+INSERT INTO num_input_test(n1) VALUES ('0x1234_');
+INSERT INTO num_input_test(n1) VALUES ('0x12__34');
 
 SELECT * FROM num_input_test;
 
diff --git a/src/test/regress/sql/numerology.sql b/src/test/regress/sql/numerology.sql
new file mode 100644
index 310d9e5..1941c58
--- a/src/test/regress/sql/numerology.sql
+++ b/src/test/regress/sql/numerology.sql
@@ -45,7 +45,6 @@ SELECT -0x8000000000000001;
 -- error cases
 SELECT 123abc;
 SELECT 0x0o;
-SELECT 1_2_3;
 SELECT 0.a;
 SELECT 0.0a;
 SELECT .0a;
@@ -66,6 +65,29 @@ SELECT 0x;
 SELECT 1x;
 SELECT 0x0y;
 
+-- underscores
+SELECT 1_000_000;
+SELECT 1_2_3;
+SELECT 0x1EEE_FFFF;
+SELECT 0o2_73;
+SELECT 0b_10_0101;
+
+SELECT 1_000.000_005;
+SELECT 1_000.;
+SELECT .000_005;
+SELECT 1_000.5e0_1;
+
+-- error cases
+SELECT _100;
+SELECT 100_;
+SELECT 100__000;
+
+SELECT _1_000.5;
+SELECT 1_000_.5;
+SELECT 1_000._5;
+SELECT 1_000.5_;
+SELECT 1_000.5e_1;
+
 
 --
 -- Test implicit type conversions
diff --git a/src/test/regress/sql/partition_prune.sql b/src/test/regress/sql/partition_prune.sql
new file mode 100644
index d70bd86..fb0583f
--- a/src/test/regress/sql/partition_prune.sql
+++ b/src/test/regress/sql/partition_prune.sql
@@ -283,16 +283,16 @@ explain (costs off) select * from like_o
 create table lparted_by_int2 (a smallint) partition by list (a);
 create table lparted_by_int2_1 partition of lparted_by_int2 for values in (1);
 create table lparted_by_int2_16384 partition of lparted_by_int2 for values in (16384);
-explain (costs off) select * from lparted_by_int2 where a = 100000000000000;
+explain (costs off) select * from lparted_by_int2 where a = 100_000_000_000_000;
 
 create table rparted_by_int2 (a smallint) partition by range (a);
 create table rparted_by_int2_1 partition of rparted_by_int2 for values from (1) to (10);
 create table rparted_by_int2_16384 partition of rparted_by_int2 for values from (10) to (16384);
 -- all partitions pruned
-explain (costs off) select * from rparted_by_int2 where a > 100000000000000;
+explain (costs off) select * from rparted_by_int2 where a > 100_000_000_000_000;
 create table rparted_by_int2_maxvalue partition of rparted_by_int2 for values from (16384) to (maxvalue);
 -- all partitions but rparted_by_int2_maxvalue pruned
-explain (costs off) select * from rparted_by_int2 where a > 100000000000000;
+explain (costs off) select * from rparted_by_int2 where a > 100_000_000_000_000;
 
 drop table lp, coll_pruning, rlp, mc3p, mc2p, boolpart, boolrangep, rp, coll_pruning_multi, like_op_noprune, lparted_by_int2, rparted_by_int2;