Add convenience functions pg_sleep_for and pg_sleep_until.

Vik Fearing, reviewed by Pavel Stehule and myself

doc/src/sgml/func.sgml

@@ -7664,20 +7664,28 @@ SELECT TIMESTAMP 'now';  -- incorrect for use with DEFAULT
    </indexterm>
 
    <para>
-    The following function is available to delay execution of the server
+    The following functions are available to delay execution of the server
     process:
 <synopsis>
 pg_sleep(<replaceable>seconds</replaceable>)
+pg_sleep_for(<type>interval</>)
+pg_sleep_until(<type>timestamp with time zone</>)
 </synopsis>
 
     <function>pg_sleep</function> makes the current session's process
     sleep until <replaceable>seconds</replaceable> seconds have
     elapsed.  <replaceable>seconds</replaceable> is a value of type
     <type>double precision</>, so fractional-second delays can be specified.
+    <function>pg_sleep_for</function> is a convenience function for larger
+    sleep times specified as an <type>interval</>.
+    <function>pg_sleep_until</function> is a convenience function for when
+    a specific wake-up time is desired.
     For example:
 
 <programlisting>
 SELECT pg_sleep(1.5);
+SELECT pg_sleep_for('5 minutes');
+SELECT pg_sleep_until('tomorrow 03:00');
 </programlisting>
    </para>
 
@@ -7686,15 +7694,17 @@ SELECT pg_sleep(1.5);
       The effective resolution of the sleep interval is platform-specific;
       0.01 seconds is a common value.  The sleep delay will be at least as long
       as specified. It might be longer depending on factors such as server load.
+      In particular, <function>pg_sleep_until</function> is not guaranteed to
+      wake up exactly at the specified time, but it will not wake up any earlier.
      </para>
    </note>
 
    <warning>
      <para>
       Make sure that your session does not hold more locks than necessary
-      when calling <function>pg_sleep</function>.  Otherwise other sessions
-      might have to wait for your sleeping process, slowing down the entire
-      system.
+      when calling <function>pg_sleep</function> or its variants.  Otherwise
+      other sessions might have to wait for your sleeping process, slowing down
+      the entire system.
      </para>
    </warning>
   </sect2>

src/include/catalog/catversion.h

@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201401291
+#define CATALOG_VERSION_NO	201401301
 
 #endif

src/include/catalog/pg_proc.h

@@ -3034,6 +3034,10 @@ DATA(insert OID = 2625 ( pg_ls_dir			PGNSP PGUID 12 1 1000 0 0 f f f f t t v 1 0
 DESCR("list all files in a directory");
 DATA(insert OID = 2626 ( pg_sleep			PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "701" _null_ _null_ _null_ _null_ pg_sleep _null_ _null_ _null_ ));
 DESCR("sleep for the specified time in seconds");
+DATA(insert OID = 3935 ( pg_sleep_for			PGNSP PGUID 14 1 0 0 0 f f f f t f v 1 0 2278 "1186" _null_ _null_ _null_ _null_ "select pg_catalog.pg_sleep(extract(epoch from pg_catalog.now() operator(pg_catalog.+) $1) operator(pg_catalog.-) extract(epoch from pg_catalog.now()))" _null_ _null_ _null_ ));
+DESCR("sleep for the specified interval");
+DATA(insert OID = 3936 ( pg_sleep_until			PGNSP PGUID 14 1 0 0 0 f f f f t f v 1 0 2278 "1184" _null_ _null_ _null_ _null_ "select pg_catalog.pg_sleep(extract(epoch from $1) operator(pg_catalog.-) extract(epoch from pg_catalog.now()))" _null_ _null_ _null_ ));
+DESCR("sleep until the specified time");
 
 DATA(insert OID = 2971 (  text				PGNSP PGUID 12 1 0 0 0 f f f f t f i 1 0 25 "16" _null_ _null_ _null_ _null_ booltext _null_ _null_ _null_ ));
 DESCR("convert boolean to text");

src/test/regress/expected/stats.out

@@ -18,9 +18,9 @@ SET enable_indexscan TO on;
 SET enable_indexonlyscan TO off;
 -- wait to let any prior tests finish dumping out stats;
 -- else our messages might get lost due to contention
-SELECT pg_sleep(2.0);
- pg_sleep 
-----------
+SELECT pg_sleep_for('2 seconds');
+ pg_sleep_for 
+--------------
  
 (1 row)
 

src/test/regress/sql/stats.sql

@@ -16,7 +16,7 @@ SET enable_indexonlyscan TO off;
 
 -- wait to let any prior tests finish dumping out stats;
 -- else our messages might get lost due to contention
-SELECT pg_sleep(2.0);
+SELECT pg_sleep_for('2 seconds');
 
 -- save counters
 CREATE TEMP TABLE prevstats AS