Add pg_sysconf_size, vm_free_size, drop pgsysconf

pg_sysconf_size returns 'immutable' sizes from sysconf and pg:
- postgres page size
- system page size
- total memory
vm_free_size returns the current free memory on the system

Remove pgsysconf datum which is obsolete, and add an SQL wrapper on top
of the new functions.
Users are encouraged to update their code using pgsysconf which is now
deprecated and will be removed in the future.

expected/pgfincore.out

@@ -92,3 +92,22 @@ select NULL || pgfincore_drawer(databit) from pgfincore('test','main',true);
 
 (1 row)
 
+--
+-- tests pg_sysconf_size
+--
+-- assume most systems have same defaults
+-- it's possible to add another output file
+-- to manage larger PostgreSQL and or system page size.
+select pg_page_size, sys_pages_size from pg_sysconf_size();
+ pg_page_size | sys_pages_size 
+--------------+----------------
+         8192 |           4096
+(1 row)
+
+--
+-- tests vm_free_pages
+--
+select from vm_free_pages();
+--
+(1 row)
+

pgfincore--1.3.1--2.0.0.sql

@@ -0,0 +1,47 @@
+CREATE FUNCTION
+pg_sysconf_size(
+  OUT pg_page_size    bigint
+, OUT sys_pages_size  bigint
+, OUT sys_total_pages bigint
+)
+RETURNS record
+AS '$libdir/pgfincore'
+LANGUAGE C IMMUTABLE;
+
+COMMENT ON FUNCTION pg_sysconf_size()
+IS 'Get system information:
+ - pg_page_size is PostgreSQL page size
+ - sys_pages_size is system page size
+ - sys_total_pages is total memory pages';
+
+CREATE FUNCTION
+vm_free_pages(
+  OUT sys_pages_free    bigint
+)
+RETURNS bigint
+AS '$libdir/pgfincore'
+LANGUAGE C STABLE;
+
+COMMENT ON FUNCTION vm_free_pages()
+IS 'Get system information:
+ - sys_pages_free is current number of free pages in system memory';
+
+REPLACE FUNCTION
+pgsysconf(OUT os_page_size   bigint,
+          OUT os_pages_free  bigint,
+          OUT os_total_pages bigint)
+RETURNS record
+AS $pgsysconf$
+SELECT
+  p.sys_pages_size as os_page_size
+, v.sys_pages_free as os_pages_free
+, p.sys_total_pages as os_total_pages
+FROM pg_sysconf_size() p, vm_free_pages() v
+$pgsysconf$
+LANGUAGE SQL STABLE;
+
+COMMENT ON FUNCTION pgsysconf()
+IS 'pgsysconf is DEPRECATED, use pg_sysconf_size and vm_free_pages instead.';
+
+COMMENT ON FUNCTION pgsysconf_pretty()
+IS 'pgsysconf_pretty is DEPRECATED, use pg_sysconf_size and vm_free_pages with pg_size_pretty';

pgfincore--2.0.0.sql

@@ -1,24 +1,52 @@
 --
 -- SYSCONF
 --
-CREATE OR REPLACE FUNCTION
+CREATE FUNCTION
+pg_sysconf_size(
+  OUT pg_page_size    bigint
+, OUT sys_pages_size  bigint
+, OUT sys_total_pages bigint
+)
+RETURNS record
+AS '$libdir/pgfincore'
+LANGUAGE C IMMUTABLE;
+
+COMMENT ON FUNCTION pg_sysconf_size()
+IS 'Get system information:
+ - pg_page_size is PostgreSQL page size
+ - sys_pages_size is system page size
+ - sys_total_pages is total memory pages';
+
+CREATE FUNCTION
+vm_free_pages(
+  OUT sys_pages_free    bigint
+)
+RETURNS bigint
+AS '$libdir/pgfincore'
+LANGUAGE C STABLE;
+
+COMMENT ON FUNCTION vm_free_pages()
+IS 'Get system information:
+ - sys_pages_free is current number of free pages in system memory';
+
+CREATE FUNCTION
 pgsysconf(OUT os_page_size   bigint,
           OUT os_pages_free  bigint,
           OUT os_total_pages bigint)
 RETURNS record
-AS '$libdir/pgfincore'
-LANGUAGE C;
+AS $pgsysconf$
+SELECT
+  p.sys_pages_size as os_page_size
+, v.sys_pages_free as os_pages_free
+, p.sys_total_pages as os_total_pages
+FROM pg_sysconf_size() p, vm_free_pages() v
+$pgsysconf$
+LANGUAGE SQL STABLE;
 
 COMMENT ON FUNCTION pgsysconf()
-IS 'Get system configuration information at run time:
- - os_page_size is _SC_PAGESIZE 
- - os_pages_free is _SC_AVPHYS_PAGES
- - os_total_pages is _SC_PHYS_PAGES
-
-man 3 sysconf for details';
+IS 'pgsysconf is DEPRECATED, use pg_sysconf_size and vm_free_pages instead.';
 
-
-CREATE OR REPLACE FUNCTION
+CREATE FUNCTION
 pgsysconf_pretty(OUT os_page_size   text,
                  OUT os_pages_free  text,
                  OUT os_total_pages text)
@@ -31,7 +59,7 @@ from pgsysconf()'
 LANGUAGE SQL;
 
 COMMENT ON FUNCTION pgsysconf_pretty()
-IS 'Pgsysconf() with human readable output';
+IS 'pgsysconf_pretty is DEPRECATED, use pg_sysconf_size and vm_free_pages with pg_size_pretty';
 
 --
 -- PGFADVISE

pgfincore.c

@@ -44,7 +44,16 @@
 PG_MODULE_MAGIC;
 #endif
 
-#define PGSYSCONF_COLS  		3
+#define PG_SYSCONF_SIZE_COLS	3
+static long		_sc_pagesize	= 0;
+static long		_sc_phys_pages	= 0;
+
+PG_FUNCTION_INFO_V1(pg_sysconf_size);
+Datum	pg_sysconf_size(PG_FUNCTION_ARGS);
+
+PG_FUNCTION_INFO_V1(vm_free_pages);
+Datum	vm_free_pages(PG_FUNCTION_ARGS);
+
 #define PGFADVISE_COLS			4
 #define PGFADVISE_LOADER_COLS	5
 #define PGFINCORE_COLS  		10
@@ -62,6 +71,7 @@ PG_MODULE_MAGIC;
 #else
 #define FINCORE_BITS    2
 #endif
+
 /*
  * pgfadvise_fctx structure is needed
  * to keep track of relation path, segment number, ...
@@ -127,8 +137,6 @@ typedef struct
 	VarBit	*databit;
 } pgfincoreStruct;
 
-Datum pgsysconf(PG_FUNCTION_ARGS);
-
 Datum 		pgfadvise(PG_FUNCTION_ARGS);
 static int	pgfadvise_file(char *filename, int advice, pgfadviseStruct *pgfdv);
 
@@ -151,44 +159,6 @@ Datum		pgfincore_drawer(PG_FUNCTION_ARGS);
         relpathbackend((rel)->rd_locator, (rel)->rd_backend, (forkname_to_number(text_to_cstring(forkName))))
 #endif
 
-/*
- * pgsysconf
- * just output the actual system value for
- * _SC_PAGESIZE     --> Page Size
- * _SC_AVPHYS_PAGES --> Free page in memory
- * _SC_PHYS_PAGES   --> Total memory
- *
- */
-PG_FUNCTION_INFO_V1(pgsysconf);
-Datum
-pgsysconf(PG_FUNCTION_ARGS)
-{
-	HeapTuple	tuple;
-	TupleDesc	tupdesc;
-	Datum		values[PGSYSCONF_COLS];
-	bool		nulls[PGSYSCONF_COLS];
-
-	/* initialize nulls array to build the tuple */
-	memset(nulls, 0, sizeof(nulls));
-
-	/* Build a tuple descriptor for our result type */
-	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
-		elog(ERROR, "pgsysconf: return type must be a row type");
-
-	/* Page size */
-	values[0] = Int64GetDatum(sysconf(_SC_PAGESIZE));
-
-	/* free page in memory */
-	values[1] = Int64GetDatum(sysconf(_SC_AVPHYS_PAGES));
-
-	/* total memory */
-	values[2] = Int64GetDatum(sysconf(_SC_PHYS_PAGES));
-
-	/* Build and return the result tuple. */
-	tuple = heap_form_tuple(tupdesc, values, nulls);
-	PG_RETURN_DATUM( HeapTupleGetDatum(tuple) );
-}
-
 #if defined(USE_POSIX_FADVISE)
 /*
  * pgfadvise_file
@@ -209,7 +179,9 @@ pgfadvise_file(char *filename, int advice, pgfadviseStruct *pgfdv)
 	/*
 	 * OS Page size and Free pages
 	 */
-	pgfdv->pageSize	= sysconf(_SC_PAGESIZE);
+	if (_sc_pagesize == 0)
+		_sc_pagesize = sysconf(_SC_PAGESIZE);
+	pgfdv->pageSize = _sc_pagesize;
 
 	/*
 	 * Fopen and fstat file
@@ -472,7 +444,9 @@ pgfadvise_loader_file(char *filename,
 	/*
 	 * OS things : Page size
 	 */
-	pgfloader->pageSize = sysconf(_SC_PAGESIZE);
+	if (_sc_pagesize == 0)
+		_sc_pagesize = sysconf(_SC_PAGESIZE);
+	pgfloader->pageSize = _sc_pagesize;
 
 	/*
 	 * we count the action we perform
@@ -717,7 +691,9 @@ pgfincore_file(char *filename, pgfincoreStruct *pgfncr)
 	/*
 	 * OS Page size
 	 */
-	pgfncr->pageSize  = sysconf(_SC_PAGESIZE);
+	if (_sc_pagesize == 0)
+	  _sc_pagesize = sysconf(_SC_PAGESIZE);
+	pgfncr->pageSize  = _sc_pagesize;
 
 	/*
 	 * Initialize counters
@@ -1111,3 +1087,57 @@ pgfincore_drawer(PG_FUNCTION_ARGS)
 	*r = '\0';
 	PG_RETURN_CSTRING(result);
 }
+
+/*
+ * Output the value for:
+ * - System page size:    sysconf(_SC_PAGESIZE)
+ * - Total memory:        sysconf(_SC_PHYS_PAGES)
+ * - PostgreSQL page size
+ *
+ * All of them are of interest to output size in bytes instead of blocks with
+ * other functions provided by pgfincore.
+ * We consider the values are immutable.
+ */
+Datum
+pg_sysconf_size(PG_FUNCTION_ARGS)
+{
+	TupleDesc	tupdesc;
+	Datum		values[PG_SYSCONF_SIZE_COLS];
+	bool		nulls[PG_SYSCONF_SIZE_COLS] = {0};
+	int			col = 0;
+
+	/* Build a tuple descriptor for our result type */
+	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
+		ereport(ERROR,
+				errcode(ERRCODE_DATATYPE_MISMATCH),
+				errmsg("return type must be a row type"),
+				errhint("please report a bug if you get this message: function is not correctly defined"));
+
+	if (_sc_pagesize == 0)
+		_sc_pagesize = sysconf(_SC_PAGESIZE);
+
+	if (_sc_phys_pages == 0)
+		_sc_phys_pages = sysconf(_SC_PHYS_PAGES);
+
+	/* PostgreSQL Page size */
+	values[col++] = Int64GetDatum((off_t) BLCKSZ);
+	/* System Page size */
+	values[col++] = Int64GetDatum(_sc_pagesize);
+	/* total memory */
+	values[col++] = Int64GetDatum(_sc_phys_pages);
+
+	/* Build and return the result tuple. */
+	PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
+/*
+ * vm_free_pages
+ * just output the actual system value for
+ * _SC_AVPHYS_PAGES --> Free page in memory
+ */
+Datum
+vm_free_pages(PG_FUNCTION_ARGS)
+{
+	long free_pages = sysconf(_SC_AVPHYS_PAGES);
+	PG_RETURN_INT64(free_pages);
+}

sql/pgfincore.sql

@@ -51,3 +51,17 @@ select from pgfadvise_normal('test');
 -- tests drawers
 --
 select NULL || pgfincore_drawer(databit) from pgfincore('test','main',true);
+
+
+--
+-- tests pg_sysconf_size
+--
+-- assume most systems have same defaults
+-- it's possible to add another output file
+-- to manage larger PostgreSQL and or system page size.
+select pg_page_size, sys_pages_size from pg_sysconf_size();
+
+--
+-- tests vm_free_pages
+--
+select from vm_free_pages();