pg_size_pretty(numeric)

The output of the new pg_xlog_location_diff function is of type numeric,
since it could theoretically overflow an int8 due to signedness; this
provides a convenient way to format such values.

Fujii Masao, with some beautification by me.

Author: robertmhaas

doc/src/sgml/func.sgml

@@ -14981,7 +14981,20 @@ postgres=# SELECT * FROM pg_xlogfile_name_offset(pg_stop_backup());
         <literal><function>pg_size_pretty(<type>bigint</type>)</function></literal>
         </entry>
        <entry><type>text</type></entry>
-       <entry>Converts a size in bytes into a human-readable format with size units</entry>
+       <entry>
+         Converts a size in bytes expressed as a 64-bit integer into a
+         human-readable format with size units
+       </entry>
+      </row>
+      <row>
+       <entry>
+        <literal><function>pg_size_pretty(<type>numeric</type>)</function></literal>
+        </entry>
+       <entry><type>text</type></entry>
+       <entry>
+         Converts a size in bytes expressed as a numeric value into a
+         human-readable format with size units
+       </entry>
       </row>
       <row>
        <entry>

src/backend/utils/adt/dbsize.c

@@ -24,6 +24,7 @@
 #include "storage/fd.h"
 #include "utils/acl.h"
 #include "utils/builtins.h"
+#include "utils/numeric.h"
 #include "utils/rel.h"
 #include "utils/relmapper.h"
 #include "utils/syscache.h"
@@ -550,6 +551,137 @@ pg_size_pretty(PG_FUNCTION_ARGS)
 	PG_RETURN_TEXT_P(cstring_to_text(buf));
 }
 
+static char *
+numeric_to_cstring(Numeric n)
+{
+	Datum		d = NumericGetDatum(n);
+	return DatumGetCString(DirectFunctionCall1(numeric_out, d));
+}
+
+static Numeric
+int64_to_numeric(int64 v)
+{
+	Datum		d = Int64GetDatum(v);
+	return DatumGetNumeric(DirectFunctionCall1(int8_numeric, d));
+}
+
+static bool
+numeric_is_less(Numeric a, Numeric b)
+{
+	Datum		da = NumericGetDatum(a);
+	Datum		db = NumericGetDatum(b);
+
+	return DatumGetBool(DirectFunctionCall2(numeric_lt, da, db));
+}
+
+static Numeric
+numeric_plus_one_over_two(Numeric n)
+{
+	Datum		d = NumericGetDatum(n);
+	Datum		one;
+	Datum		two;
+	Datum		result;
+
+	one = DirectFunctionCall1(int8_numeric, Int64GetDatum(1));
+	two = DirectFunctionCall1(int8_numeric, Int64GetDatum(2));
+	result = DirectFunctionCall2(numeric_add, d, one);
+	result = DirectFunctionCall2(numeric_div_trunc, result, two);
+	return DatumGetNumeric(result);
+}
+
+static Numeric
+numeric_shift_right(Numeric n, unsigned count)
+{
+	Datum		d = NumericGetDatum(n);
+	Datum		divisor_int64;
+	Datum		divisor_numeric;
+	Datum		result;
+
+	divisor_int64 = Int64GetDatum((int64) (1 << count));
+	divisor_numeric = DirectFunctionCall1(int8_numeric, divisor_int64);
+	result = DirectFunctionCall2(numeric_div_trunc, d, divisor_numeric);
+	return DatumGetNumeric(result);
+}
+
+Datum
+pg_size_pretty_numeric(PG_FUNCTION_ARGS)
+{
+	Numeric		size = PG_GETARG_NUMERIC(0);
+	Numeric		limit,
+				limit2;
+	char	   *buf,
+			   *result;
+
+	limit = int64_to_numeric(10 * 1024);
+	limit2 = int64_to_numeric(10 * 1024 * 2 - 1);
+
+	if (numeric_is_less(size, limit))
+	{
+		buf = numeric_to_cstring(size);
+		result = palloc(strlen(buf) + 7);
+		strcpy(result, buf);
+		strcat(result, " bytes");
+	}
+	else
+	{
+		/* keep one extra bit for rounding */
+		/* size >>= 9 */
+		size = numeric_shift_right(size, 9);
+
+		if (numeric_is_less(size, limit2))
+		{
+			/* size = (size + 1) / 2 */
+			size = numeric_plus_one_over_two(size);
+			buf = numeric_to_cstring(size);
+			result = palloc(strlen(buf) + 4);
+			strcpy(result, buf);
+			strcat(result, " kB");
+		}
+		else
+		{
+			/* size >>= 10 */
+			size = numeric_shift_right(size, 10);
+			if (numeric_is_less(size, limit2))
+			{
+				/* size = (size + 1) / 2 */
+				size = numeric_plus_one_over_two(size);
+				buf = numeric_to_cstring(size);
+				result = palloc(strlen(buf) + 4);
+				strcpy(result, buf);
+				strcat(result, " MB");
+			}
+			else
+			{
+				/* size >>= 10 */
+				size = numeric_shift_right(size, 10);
+
+				if (numeric_is_less(size, limit2))
+				{
+					/* size = (size + 1) / 2 */
+					size = numeric_plus_one_over_two(size);
+					buf = numeric_to_cstring(size);
+					result = palloc(strlen(buf) + 4);
+					strcpy(result, buf);
+					strcat(result, " GB");
+				}
+				else
+				{
+					/* size >>= 10 */
+					size = numeric_shift_right(size, 10);
+					/* size = (size + 1) / 2 */
+					size = numeric_plus_one_over_two(size);
+					buf = numeric_to_cstring(size);
+					result = palloc(strlen(buf) + 4);
+					strcpy(result, buf);
+					strcat(result, " TB");
+				}
+			}
+		}
+	}
+
+	PG_RETURN_TEXT_P(cstring_to_text(result));
+}
+
 /*
  * Get the filenode of a relation
  *

src/include/catalog/catversion.h

@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201204131
+#define CATALOG_VERSION_NO	201204141
 
 #endif

src/include/catalog/pg_proc.h

@@ -3410,6 +3410,8 @@ DATA(insert OID = 2286 ( pg_total_relation_size PGNSP PGUID 12 1 0 0 0 f f f f t
 DESCR("total disk space usage for the specified table and associated indexes");
 DATA(insert OID = 2288 ( pg_size_pretty			PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 25 "20" _null_ _null_ _null_ _null_ pg_size_pretty _null_ _null_ _null_ ));
 DESCR("convert a long int to a human readable text using size units");
+DATA(insert OID = 3166 ( pg_size_pretty			PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 25 "1700" _null_ _null_ _null_ _null_ pg_size_pretty_numeric _null_ _null_ _null_ ));
+DESCR("convert a numeric to a human readable text using size units");
 DATA(insert OID = 2997 ( pg_table_size			PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 20 "2205" _null_ _null_ _null_ _null_ pg_table_size _null_ _null_ _null_ ));
 DESCR("disk space usage for the specified table, including TOAST, free space and visibility map");
 DATA(insert OID = 2998 ( pg_indexes_size		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 20 "2205" _null_ _null_ _null_ _null_ pg_indexes_size _null_ _null_ _null_ ));

src/include/utils/builtins.h

@@ -453,6 +453,7 @@ extern Datum pg_database_size_name(PG_FUNCTION_ARGS);
 extern Datum pg_relation_size(PG_FUNCTION_ARGS);
 extern Datum pg_total_relation_size(PG_FUNCTION_ARGS);
 extern Datum pg_size_pretty(PG_FUNCTION_ARGS);
+extern Datum pg_size_pretty_numeric(PG_FUNCTION_ARGS);
 extern Datum pg_table_size(PG_FUNCTION_ARGS);
 extern Datum pg_indexes_size(PG_FUNCTION_ARGS);
 extern Datum pg_relation_filenode(PG_FUNCTION_ARGS);