Functions under development for parsing RRULE directives directly within

the database.

dba/rrule_functions.sql

@@ -0,0 +1,186 @@
+/**
+* PostgreSQL Functions for RRULE handling
+*
+* @package rscds
+* @subpackage database
+* @author Andrew McMillan <andrew@catalyst.net.nz>
+* @copyright Catalyst IT Ltd
+* @license   http://gnu.org/copyleft/gpl.html GNU GPL v2
+*/
+
+-- How many days are there in a particular month?
+CREATE or REPLACE FUNCTION rrule_days_in_month( TIMESTAMP WITH TIME ZONE ) RETURNS INT AS '
+DECLARE
+  in_time ALIAS FOR $1;
+  days INT;
+BEGIN
+  RETURN date_part( ''days'', date_trunc( ''month'', in_time + interval ''1 month'') - interval ''1 day'' );
+END;
+' LANGUAGE 'plpgsql' IMMUTABLE STRICT;
+
+
+-- Return a SETOF text strings, split on the commas in the original one
+CREATE or REPLACE FUNCTION rrule_split_on_commas( TEXT ) RETURNS SETOF TEXT AS '
+DECLARE
+  in_text ALIAS FOR $1;
+  part TEXT;
+  cpos INT;
+  remainder TEXT;
+BEGIN
+  remainder := in_text;
+  LOOP
+    cpos := position( '','' in remainder );
+    IF cpos = 0 THEN
+      part := remainder;
+      EXIT;
+    ELSE
+      part := substring( remainder for cpos - 1 );
+      remainder := substring( remainder from cpos + 1);
+      RETURN NEXT part;
+    END IF;
+  END LOOP;
+  RETURN NEXT part;
+  RETURN;
+END;
+' LANGUAGE 'plpgsql' IMMUTABLE STRICT;
+
+-- Return a SETOF dates within the month of a particular date which match a single BYDAY rule specification
+CREATE or REPLACE FUNCTION rrule_month_bydayrule_set( TIMESTAMP WITH TIME ZONE, TEXT ) RETURNS SETOF TIMESTAMP WITH TIME ZONE AS '
+DECLARE
+  in_time ALIAS FOR $1;
+  bydayrule ALIAS FOR $2;
+  dow INT;
+  index INT;
+  first_dow INT;
+  each_day TIMESTAMP WITH TIME ZONE;
+  this_month INT;
+BEGIN
+  dow := position(substring( bydayrule from ''..$'') in ''SUMOTUWETHFRSA'') / 2;
+  each_day := date_trunc( ''month'', in_time ) + (in_time::time)::interval;
+  this_month := date_part( ''month'', in_time );
+  first_dow := date_part( ''dow'', each_day );
+  each_day := each_day - ( first_dow::text || ''days'')::interval
+                       + ( dow::text || ''days'')::interval
+                       + CASE WHEN dow > first_dow THEN ''1 week''::interval ELSE ''0s''::interval END;
+
+  IF length(bydayrule) > 2 THEN
+    index := (substring(bydayrule from ''^[0-9-]+''))::int;
+
+    -- Possibly we should check that (index != 0) here, which is an error
+
+    IF index = 0 THEN
+      RAISE NOTICE ''Ignored invalid BYDAY rule part "%".'', bydayrule;
+    ELSIF index > 0 THEN
+      -- The simplest case, such as 2MO for the second monday
+      each_day := each_day + ((index - 1)::text || '' weeks'')::interval;
+    ELSE
+      each_day := each_day + ''5 weeks''::interval;
+      WHILE date_part(''month'', each_day) != this_month LOOP
+        each_day := each_day - ''1 week''::interval;
+      END LOOP;
+      -- Note that since index is negative, (-2 + 1) == -1, for example
+      each_day := each_day + ( (index + 1)::text || '' weeks'')::interval ;
+    END IF;
+
+    -- Sometimes (e.g. 5TU or -5WE) there might be no such date in some months
+    IF date_part(''month'', each_day) = this_month THEN
+      RETURN NEXT each_day;
+    END IF;
+
+  ELSE
+    -- Return all such days that are within the given month
+    WHILE date_part(''month'', each_day) = this_month LOOP
+      RETURN NEXT each_day;
+      each_day := each_day + ''1 week''::interval;
+    END LOOP;
+  END IF;
+
+  RETURN;
+
+END;
+' LANGUAGE 'plpgsql' IMMUTABLE STRICT;
+
+
+-- Return a SETOF dates within the month of a particular date which match a string of BYDAY rule specifications
+CREATE or REPLACE FUNCTION rrule_month_byday_set( TIMESTAMP WITH TIME ZONE, TEXT ) RETURNS SETOF TIMESTAMP WITH TIME ZONE AS '
+DECLARE
+  in_time ALIAS FOR $1;
+  byday ALIAS FOR $2;
+  dayrule RECORD;
+  day RECORD;
+BEGIN
+
+  FOR dayrule IN SELECT * FROM rrule_split_on_commas( byday ) LOOP
+    FOR day IN SELECT * FROM rrule_month_bydayrule_set( in_time, dayrule.rrule_split_on_commas ) LOOP
+      RETURN NEXT day.rrule_month_bydayrule_set;
+    END LOOP;
+  END LOOP;
+
+  RETURN;
+
+END;
+' LANGUAGE 'plpgsql' IMMUTABLE STRICT;
+
+
+
+
+-- Return a SETOF dates within the month of a particular date which match a string of BYDAY rule specifications
+CREATE or REPLACE FUNCTION rrule_month_bymonthday_set( TIMESTAMP WITH TIME ZONE, TEXT ) RETURNS SETOF TIMESTAMP WITH TIME ZONE AS '
+DECLARE
+  in_time ALIAS FOR $1;
+  bymonthday ALIAS FOR $2;
+  dayrule RECORD;
+  daysinmonth INT;
+  month_start TIMESTAMP WITH TIME ZONE;
+  dayoffset INT;
+BEGIN
+
+  daysinmonth := rrule_days_in_month(in_time);
+  month_start := date_trunc( ''month'', in_time ) + (in_time::time)::interval;
+
+  FOR dayrule IN SELECT * FROM rrule_split_on_commas( bymonthday ) LOOP
+    dayoffset := dayrule.rrule_split_on_commas::int;
+    IF dayoffset = 0 THEN
+      RAISE NOTICE ''Ignored invalid BYMONTHDAY part "%".'', dayrule.rrule_split_on_commas;
+      dayoffset := 0;
+    ELSIF dayoffset > daysinmonth THEN
+      dayoffset := 0;
+    ELSIF dayoffset < (-1 * daysinmonth) THEN
+      dayoffset := 0;
+    ELSIF dayoffset > 0 THEN
+      RETURN NEXT month_start + ((dayoffset - 1)::text || ''days'')::interval;
+    ELSE
+      RETURN NEXT month_start + ((daysinmonth + dayoffset)::text || ''days'')::interval;
+    END IF;
+
+  END LOOP;
+
+  RETURN;
+
+END;
+' LANGUAGE 'plpgsql' IMMUTABLE STRICT;
+
+
+
+-- Return a SETOF dates within the week of a particular date which match a single BYDAY rule specification
+CREATE or REPLACE FUNCTION rrule_week_byday_set( TIMESTAMP WITH TIME ZONE, TEXT ) RETURNS SETOF TIMESTAMP WITH TIME ZONE AS '
+DECLARE
+  in_time ALIAS FOR $1;
+  byweekday ALIAS FOR $2;
+  dayrule RECORD;
+  dow INT;
+  our_day TIMESTAMP WITH TIME ZONE;
+BEGIN
+  our_day := date_trunc( ''week'', in_time ) + (in_time::time)::interval;
+
+  FOR dayrule IN SELECT * FROM rrule_split_on_commas( byweekday ) LOOP
+    dow := position(substring( dayrule.rrule_split_on_commas from ''..$'') in ''SUMOTUWETHFRSA'') / 2;
+    RETURN NEXT our_day + ((dow - 1)::text || ''days'')::interval;
+  END LOOP;
+
+  RETURN;
+
+END;
+' LANGUAGE 'plpgsql' IMMUTABLE STRICT;
+
+