Add +(pg_lsn,numeric) and -(pg_lsn,numeric) operators.

By using these operators, the number of bytes can be added into and
subtracted from LSN.

Bump catalog version.

Author: Fujii Masao
Reviewed-by: Kyotaro Horiguchi, Michael Paquier, Asif Rehman
Discussion: https://postgr.es/m/ed9f7f74-e996-67f8-554a-52ebd3779b3b@oss.nttdata.com

doc/src/sgml/datatype.sgml

@@ -4801,7 +4801,13 @@ SELECT * FROM pg_attribute
     standard comparison operators, like <literal>=</literal> and
     <literal>&gt;</literal>.  Two LSNs can be subtracted using the
     <literal>-</literal> operator; the result is the number of bytes separating
-    those write-ahead log locations.
+    those write-ahead log locations.  Also the number of bytes can be
+    added into and subtracted from LSN using the
+    <literal>+(pg_lsn,numeric)</literal> and
+    <literal>-(pg_lsn,numeric)</literal> operators, respectively. Note that
+    the calculated LSN should be in the range of <type>pg_lsn</type> type,
+    i.e., between <literal>0/0</literal> and
+    <literal>FFFFFFFF/FFFFFFFF</literal>.
    </para>
   </sect1>
 

src/backend/utils/adt/numeric.c

@@ -41,6 +41,7 @@
 #include "utils/guc.h"
 #include "utils/int8.h"
 #include "utils/numeric.h"
+#include "utils/pg_lsn.h"
 #include "utils/sortsupport.h"
 
 /* ----------
@@ -472,6 +473,7 @@ static void apply_typmod(NumericVar *var, int32 typmod);
 static bool numericvar_to_int32(const NumericVar *var, int32 *result);
 static bool numericvar_to_int64(const NumericVar *var, int64 *result);
 static void int64_to_numericvar(int64 val, NumericVar *var);
+static bool numericvar_to_uint64(const NumericVar *var, uint64 *result);
 #ifdef HAVE_INT128
 static bool numericvar_to_int128(const NumericVar *var, int128 *result);
 static void int128_to_numericvar(int128 val, NumericVar *var);
@@ -3692,6 +3694,30 @@ numeric_float4(PG_FUNCTION_ARGS)
 }
 
 
+Datum
+numeric_pg_lsn(PG_FUNCTION_ARGS)
+{
+	Numeric		num = PG_GETARG_NUMERIC(0);
+	NumericVar	x;
+	XLogRecPtr	result;
+
+	if (NUMERIC_IS_NAN(num))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("cannot convert NaN to pg_lsn")));
+
+	/* Convert to variable format and thence to pg_lsn */
+	init_var_from_num(num, &x);
+
+	if (!numericvar_to_uint64(&x, (uint64 *) &result))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("pg_lsn out of range")));
+
+	PG_RETURN_LSN(result);
+}
+
+
 /* ----------------------------------------------------------------------
  *
  * Aggregate functions
@@ -6742,6 +6768,78 @@ int64_to_numericvar(int64 val, NumericVar *var)
 	var->weight = ndigits - 1;
 }
 
+/*
+ * Convert numeric to uint64, rounding if needed.
+ *
+ * If overflow, return false (no error is raised).  Return true if okay.
+ */
+static bool
+numericvar_to_uint64(const NumericVar *var, uint64 *result)
+{
+	NumericDigit *digits;
+	int			ndigits;
+	int			weight;
+	int			i;
+	uint64		val;
+	NumericVar	rounded;
+
+	/* Round to nearest integer */
+	init_var(&rounded);
+	set_var_from_var(var, &rounded);
+	round_var(&rounded, 0);
+
+	/* Check for zero input */
+	strip_var(&rounded);
+	ndigits = rounded.ndigits;
+	if (ndigits == 0)
+	{
+		*result = 0;
+		free_var(&rounded);
+		return true;
+	}
+
+	/* Check for negative input */
+	if (rounded.sign == NUMERIC_NEG)
+	{
+		free_var(&rounded);
+		return false;
+	}
+
+	/*
+	 * For input like 10000000000, we must treat stripped digits as real. So
+	 * the loop assumes there are weight+1 digits before the decimal point.
+	 */
+	weight = rounded.weight;
+	Assert(weight >= 0 && ndigits <= weight + 1);
+
+	/* Construct the result */
+	digits = rounded.digits;
+	val = digits[0];
+	for (i = 1; i <= weight; i++)
+	{
+		if (unlikely(pg_mul_u64_overflow(val, NBASE, &val)))
+		{
+			free_var(&rounded);
+			return false;
+		}
+
+		if (i < ndigits)
+		{
+			if (unlikely(pg_add_u64_overflow(val, digits[i], &val)))
+			{
+				free_var(&rounded);
+				return false;
+			}
+		}
+	}
+
+	free_var(&rounded);
+
+	*result = val;
+
+	return true;
+}
+
 #ifdef HAVE_INT128
 /*
  * Convert numeric to int128, rounding if needed.

src/backend/utils/adt/pg_lsn.c

@@ -16,6 +16,7 @@
 #include "funcapi.h"
 #include "libpq/pqformat.h"
 #include "utils/builtins.h"
+#include "utils/numeric.h"
 #include "utils/pg_lsn.h"
 
 #define MAXPG_LSNLEN			17
@@ -248,3 +249,71 @@ pg_lsn_mi(PG_FUNCTION_ARGS)
 
 	return result;
 }
+
+/*
+ * Add the number of bytes to pg_lsn, giving a new pg_lsn.
+ * Must handle both positive and negative numbers of bytes.
+ */
+Datum
+pg_lsn_pli(PG_FUNCTION_ARGS)
+{
+	XLogRecPtr	lsn = PG_GETARG_LSN(0);
+	Numeric		nbytes = PG_GETARG_NUMERIC(1);
+	Datum		num;
+	Datum		res;
+	char		buf[32];
+
+	if (numeric_is_nan(nbytes))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("cannot add NaN to pg_lsn")));
+
+	/* Convert to numeric */
+	snprintf(buf, sizeof(buf), UINT64_FORMAT, lsn);
+	num = DirectFunctionCall3(numeric_in,
+							  CStringGetDatum(buf),
+							  ObjectIdGetDatum(0),
+							  Int32GetDatum(-1));
+
+	/* Add two numerics */
+	res = DirectFunctionCall2(numeric_add,
+							  NumericGetDatum(num),
+							  NumericGetDatum(nbytes));
+
+	/* Convert to pg_lsn */
+	return DirectFunctionCall1(numeric_pg_lsn, res);
+}
+
+/*
+ * Subtract the number of bytes from pg_lsn, giving a new pg_lsn.
+ * Must handle both positive and negative numbers of bytes.
+ */
+Datum
+pg_lsn_mii(PG_FUNCTION_ARGS)
+{
+	XLogRecPtr	lsn = PG_GETARG_LSN(0);
+	Numeric		nbytes = PG_GETARG_NUMERIC(1);
+	Datum		num;
+	Datum		res;
+	char		buf[32];
+
+	if (numeric_is_nan(nbytes))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("cannot subtract NaN from pg_lsn")));
+
+	/* Convert to numeric */
+	snprintf(buf, sizeof(buf), UINT64_FORMAT, lsn);
+	num = DirectFunctionCall3(numeric_in,
+							  CStringGetDatum(buf),
+							  ObjectIdGetDatum(0),
+							  Int32GetDatum(-1));
+
+	/* Subtract two numerics */
+	res = DirectFunctionCall2(numeric_sub,
+							  NumericGetDatum(num),
+							  NumericGetDatum(nbytes));
+
+	/* Convert to pg_lsn */
+	return DirectFunctionCall1(numeric_pg_lsn, res);
+}

src/include/catalog/catversion.h

@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	202006151
+#define CATALOG_VERSION_NO	202006301
 
 #endif

src/include/catalog/pg_operator.dat

@@ -2909,6 +2909,17 @@
 { oid => '3228', descr => 'minus',
   oprname => '-', oprleft => 'pg_lsn', oprright => 'pg_lsn',
   oprresult => 'numeric', oprcode => 'pg_lsn_mi' },
+{ oid => '5025', descr => 'add',
+  oprname => '+', oprleft => 'pg_lsn', oprright => 'numeric',
+  oprresult => 'pg_lsn', oprcom => '+(numeric,pg_lsn)',
+  oprcode => 'pg_lsn_pli' },
+{ oid => '5026', descr => 'add',
+  oprname => '+', oprleft => 'numeric', oprright => 'pg_lsn',
+  oprresult => 'pg_lsn', oprcom => '+(pg_lsn,numeric)',
+  oprcode => 'numeric_pl_pg_lsn' },
+{ oid => '5027', descr => 'subtract',
+  oprname => '-', oprleft => 'pg_lsn', oprright => 'numeric',
+  oprresult => 'pg_lsn', oprcode => 'pg_lsn_mii' },
 
 # enum operators
 { oid => '3516', descr => 'equal',

src/include/catalog/pg_proc.dat

@@ -4398,6 +4398,9 @@
 { oid => '1783', descr => 'convert numeric to int2',
   proname => 'int2', prorettype => 'int2', proargtypes => 'numeric',
   prosrc => 'numeric_int2' },
+{ oid => '6103', descr => 'convert numeric to pg_lsn',
+  proname => 'pg_lsn', prorettype => 'pg_lsn', proargtypes => 'numeric',
+  prosrc => 'numeric_pg_lsn' },
 
 { oid => '3556', descr => 'convert jsonb to boolean',
   proname => 'bool', prorettype => 'bool', proargtypes => 'jsonb',
@@ -8576,6 +8579,15 @@
 { oid => '4188', descr => 'smaller of two',
   proname => 'pg_lsn_smaller', prorettype => 'pg_lsn',
   proargtypes => 'pg_lsn pg_lsn', prosrc => 'pg_lsn_smaller' },
+{ oid => '5022',
+  proname => 'pg_lsn_pli', prorettype => 'pg_lsn',
+  proargtypes => 'pg_lsn numeric', prosrc => 'pg_lsn_pli' },
+{ oid => '5023',
+  proname => 'numeric_pl_pg_lsn', prolang => 'sql', prorettype => 'pg_lsn',
+  proargtypes => 'numeric pg_lsn', prosrc => 'select $2 + $1' },
+{ oid => '5024',
+  proname => 'pg_lsn_mii', prorettype => 'pg_lsn',
+  proargtypes => 'pg_lsn numeric', prosrc => 'pg_lsn_mii' },
 
 # enum related procs
 { oid => '3504', descr => 'I/O',

src/test/regress/expected/numeric.out

@@ -2348,3 +2348,30 @@ SELECT -4!;
 ERROR:  factorial of a negative number is undefined
 SELECT factorial(-4);
 ERROR:  factorial of a negative number is undefined
+--
+-- Tests for pg_lsn()
+--
+SELECT pg_lsn(23783416::numeric);
+  pg_lsn   
+-----------
+ 0/16AE7F8
+(1 row)
+
+SELECT pg_lsn(0::numeric);
+ pg_lsn 
+--------
+ 0/0
+(1 row)
+
+SELECT pg_lsn(18446744073709551615::numeric);
+      pg_lsn       
+-------------------
+ FFFFFFFF/FFFFFFFF
+(1 row)
+
+SELECT pg_lsn(-1::numeric);
+ERROR:  pg_lsn out of range
+SELECT pg_lsn(18446744073709551616::numeric);
+ERROR:  pg_lsn out of range
+SELECT pg_lsn('NaN'::numeric);
+ERROR:  cannot convert NaN to pg_lsn

src/test/regress/expected/pg_lsn.out

@@ -71,6 +71,56 @@ SELECT '0/16AE7F8'::pg_lsn - '0/16AE7F7'::pg_lsn;
         1
 (1 row)
 
+SELECT '0/16AE7F7'::pg_lsn + 16::numeric;
+ ?column?  
+-----------
+ 0/16AE807
+(1 row)
+
+SELECT 16::numeric + '0/16AE7F7'::pg_lsn;
+ ?column?  
+-----------
+ 0/16AE807
+(1 row)
+
+SELECT '0/16AE7F7'::pg_lsn - 16::numeric;
+ ?column?  
+-----------
+ 0/16AE7E7
+(1 row)
+
+SELECT 'FFFFFFFF/FFFFFFFE'::pg_lsn + 1::numeric;
+     ?column?      
+-------------------
+ FFFFFFFF/FFFFFFFF
+(1 row)
+
+SELECT 'FFFFFFFF/FFFFFFFE'::pg_lsn + 2::numeric; -- out of range error
+ERROR:  pg_lsn out of range
+SELECT '0/1'::pg_lsn - 1::numeric;
+ ?column? 
+----------
+ 0/0
+(1 row)
+
+SELECT '0/1'::pg_lsn - 2::numeric; -- out of range error
+ERROR:  pg_lsn out of range
+SELECT '0/0'::pg_lsn + ('FFFFFFFF/FFFFFFFF'::pg_lsn - '0/0'::pg_lsn);
+     ?column?      
+-------------------
+ FFFFFFFF/FFFFFFFF
+(1 row)
+
+SELECT 'FFFFFFFF/FFFFFFFF'::pg_lsn - ('FFFFFFFF/FFFFFFFF'::pg_lsn - '0/0'::pg_lsn);
+ ?column? 
+----------
+ 0/0
+(1 row)
+
+SELECT '0/16AE7F7'::pg_lsn + 'NaN'::numeric;
+ERROR:  cannot add NaN to pg_lsn
+SELECT '0/16AE7F7'::pg_lsn - 'NaN'::numeric;
+ERROR:  cannot subtract NaN from pg_lsn
 -- Check btree and hash opclasses
 EXPLAIN (COSTS OFF)
 SELECT DISTINCT (i || '/' || j)::pg_lsn f

src/test/regress/sql/numeric.sql

@@ -1122,3 +1122,13 @@ SELECT 100000!;
 SELECT 0!;
 SELECT -4!;
 SELECT factorial(-4);
+
+--
+-- Tests for pg_lsn()
+--
+SELECT pg_lsn(23783416::numeric);
+SELECT pg_lsn(0::numeric);
+SELECT pg_lsn(18446744073709551615::numeric);
+SELECT pg_lsn(-1::numeric);
+SELECT pg_lsn(18446744073709551616::numeric);
+SELECT pg_lsn('NaN'::numeric);

src/test/regress/sql/pg_lsn.sql

@@ -27,6 +27,17 @@ SELECT '0/16AE7F7' < '0/16AE7F8'::pg_lsn;
 SELECT '0/16AE7F8' > pg_lsn '0/16AE7F7';
 SELECT '0/16AE7F7'::pg_lsn - '0/16AE7F8'::pg_lsn;
 SELECT '0/16AE7F8'::pg_lsn - '0/16AE7F7'::pg_lsn;
+SELECT '0/16AE7F7'::pg_lsn + 16::numeric;
+SELECT 16::numeric + '0/16AE7F7'::pg_lsn;
+SELECT '0/16AE7F7'::pg_lsn - 16::numeric;
+SELECT 'FFFFFFFF/FFFFFFFE'::pg_lsn + 1::numeric;
+SELECT 'FFFFFFFF/FFFFFFFE'::pg_lsn + 2::numeric; -- out of range error
+SELECT '0/1'::pg_lsn - 1::numeric;
+SELECT '0/1'::pg_lsn - 2::numeric; -- out of range error
+SELECT '0/0'::pg_lsn + ('FFFFFFFF/FFFFFFFF'::pg_lsn - '0/0'::pg_lsn);
+SELECT 'FFFFFFFF/FFFFFFFF'::pg_lsn - ('FFFFFFFF/FFFFFFFF'::pg_lsn - '0/0'::pg_lsn);
+SELECT '0/16AE7F7'::pg_lsn + 'NaN'::numeric;
+SELECT '0/16AE7F7'::pg_lsn - 'NaN'::numeric;
 
 -- Check btree and hash opclasses
 EXPLAIN (COSTS OFF)