CREATE OR REPLACE FUNCTION "public"."DeleteTask" (taskid integer) RETURNS bit AS
$body$
DECLARE ID1 INTEGER;
DECLARE quan INTEGER;

BEGIN

-- delete next dependency
       -- select all taskids children
CREATE TEMPORARY TABLE tmpIDs AS SELECT TA."ChildTaskID" FROM "TasksAssociations" TA
                               WHERE TA."ParentTaskID" = taskid;
       -- delete all dependencies with taskids children
DELETE FROM "TasksAssociations" WHERE "ParentTaskID" = taskid;

       -- get count of our saved taskids children from our rec
SELECT INTO quan count(*) FROM tmpIDs;
WHILE (quan !=  0 )
LOOP
 SELECT INTO ID1 tmpIDs."ChildTaskID" FROM tmpIDs;
 PERFORM * FROM public."DeleteTask"(ID1);
 DELETE FROM tmpIDs WHERE tmpIDs."ChildTaskID" = ID1;
END LOOP;

DELETE FROM "TasksAssociations" WHERE "ChildTaskID" = ID1;



DELETE FROM "Tasks"
WHERE "TaskID" = taskid;

RETURN  1 ;

END;
$body$
LANGUAGE 'plpgsql' VOLATILE CALLED ON NULL INPUT SECURITY INVOKER;

CREATE OR REPLACE FUNCTION "public"."DeleteTask" (taskid integer) RETURNS bit AS
$body$
DECLARE ID1 INTEGER;
DECLARE rec RECORD;
DECLARE quan INTEGER;

BEGIN

-- delete next dependency
       -- select all taskids children
SELECT INTO rec "ChildID" FROM "TasksAssociations" WHERE "ParentTaskID" = taskid;

       -- delete all dependencies with taskids children
DELETE FROM "TasksAssociations" WHERE "ParentTaskID" = taskid;

       -- get count of our saved taskids children from our rec
quan := rec.count;
WHILE (quan !=  0 )
LOOP
 SELECT INTO ID1 "ChildTaskID" FROM rec;
 PERFORM * FROM public."DeleteTask"(ID1);
 DELETE FROM rec WHERE "ChildTaskID" = ID1;
END LOOP;

DELETE FROM "TasksAssociations" WHERE "ChildTaskID" = ID1;



DELETE FROM "Tasks"
WHERE "TaskID" = taskid;

RETURN  1 ;

END;
$body$
LANGUAGE 'plpgsql' VOLATILE CALLED ON NULL INPUT SECURITY INVOKER;

 SELECT INTO ID1 "ChildTaskID" FROM rec;
...
 DELETE FROM rec WHERE "ChildTaskID" = ID1;

CREATE TABLE "public"."Tasks" (
  "ProjectID" INTEGER NOT NULL, 
  "TaskID" INTEGER DEFAULT nextval(('"public"."tasks_taskid_seq"'::text)::regclass) NOT NULL, 
  "Name" VARCHAR( 50 ), 
  "Custom1" VARCHAR( 50 ), 
  "Custom2" VARCHAR( 50 ), 
  "Custom3" VARCHAR( 50 ), 
  "Remarks" VARCHAR( 255 ), 
  "ActualFundingID" INTEGER, 
  CONSTRAINT "Tasks_pkey" PRIMARY KEY("TaskID"), 
) WITHOUT OIDS;


INSERT INTO "public"."Tasks" ("ProjectID", "TaskID", "Name", "Custom1", "Custom2", "Custom3", "Remarks", "ActualFundingID")
VALUES ( 1 ,  15 , 'f1', NULL, NULL, NULL, NULL,  1 );

INSERT INTO "public"."Tasks" ("ProjectID", "TaskID", "Name", "Custom1", "Custom2", "Custom3", "Remarks", "ActualFundingID")
VALUES ( 1 ,  7 , 'f2', NULL, NULL, NULL, NULL,  1 );

INSERT INTO "public"."Tasks" ("ProjectID", "TaskID", "Name", "Custom1", "Custom2", "Custom3", "Remarks", "ActualFundingID")
VALUES ( 1 ,  8 , 'f3', NULL, NULL, NULL, NULL,  1 );

INSERT INTO "public"."Tasks" ("ProjectID", "TaskID", "Name", "Custom1", "Custom2", "Custom3", "Remarks", "ActualFundingID")
VALUES ( 1 ,  9 , 'f4', NULL, NULL, NULL, NULL,  1 );

INSERT INTO "public"."Tasks" ("ProjectID", "TaskID", "Name", "Custom1", "Custom2", "Custom3", "Remarks", "ActualFundingID")
VALUES ( 1 ,  10 , 'f5', NULL, NULL, NULL, NULL,  1 );

INSERT INTO "public"."Tasks" ("ProjectID", "TaskID", "Name", "Custom1", "Custom2", "Custom3", "Remarks", "ActualFundingID")
VALUES ( 1 ,  11 , 'f6', NULL, NULL, NULL, NULL,  1 );

INSERT INTO "public"."Tasks" ("ProjectID", "TaskID", "Name", "Custom1", "Custom2", "Custom3", "Remarks", "ActualFundingID")
VALUES ( 1 ,  12 , 'f7', NULL, NULL, NULL, NULL,  1 );

INSERT INTO "public"."Tasks" ("ProjectID", "TaskID", "Name", "Custom1", "Custom2", "Custom3", "Remarks", "ActualFundingID")
VALUES ( 1 ,  13 , 'f8', NULL, NULL, NULL, NULL,  1 );

INSERT INTO "public"."Tasks" ("ProjectID", "TaskID", "Name", "Custom1", "Custom2", "Custom3", "Remarks", "ActualFundingID")
VALUES ( 1 ,  14 , 'f9', NULL, NULL, NULL, NULL,  1 );

-- ///////////////////////////////////////////////////////////////////////////////

CREATE TABLE "public"."TasksAssociations" (
  "ParentTaskID" INTEGER NOT NULL, 
  "ChildTaskID" INTEGER NOT NULL, 
  CONSTRAINT "TasksAssociations_pkey" PRIMARY KEY("ParentTaskID", "ChildTaskID"), 
  CONSTRAINT "TasksAssociations_fk" FOREIGN KEY ("ParentTaskID")
    REFERENCES "public"."Tasks"("TaskID")
    MATCH FULL
    ON DELETE RESTRICT
    ON UPDATE NO ACTION
    NOT DEFERRABLE, 
  CONSTRAINT "TasksAssociations_fk1" FOREIGN KEY ("ChildTaskID")
    REFERENCES "public"."Tasks"("TaskID")
    MATCH FULL
    ON DELETE RESTRICT
    ON UPDATE NO ACTION
    NOT DEFERRABLE
) WITHOUT OIDS;

INSERT INTO "public"."TasksAssociations" ("ParentTaskID", "ChildTaskID")
VALUES ( 7 ,  9 );

INSERT INTO "public"."TasksAssociations" ("ParentTaskID", "ChildTaskID")
VALUES ( 7 ,  10 );

INSERT INTO "public"."TasksAssociations" ("ParentTaskID", "ChildTaskID")
VALUES ( 7 ,  13 );

INSERT INTO "public"."TasksAssociations" ("ParentTaskID", "ChildTaskID")
VALUES ( 9 ,  12 );

INSERT INTO "public"."TasksAssociations" ("ParentTaskID", "ChildTaskID")
VALUES ( 15 ,  7 );

INSERT INTO "public"."TasksAssociations" ("ParentTaskID", "ChildTaskID")
VALUES ( 15 ,  8 );

INSERT INTO "public"."TasksAssociations" ("ParentTaskID", "ChildTaskID")
VALUES ( 15 ,  11 );

...
child  int references tasks(id) on delete cascade
...

create table t1 ( id serial primary key, name text, parent integer references t1(id) on delete cascade );
...

CREATE OR REPLACE FUNCTION "public"."DeleteTask" (taskid integer) RETURNS bit AS
$body$
DECLARE ID1 INTEGER;
DECLARE quan INTEGER;

BEGIN

-- узнаём кол-во детей данного таска
SELECT INTO quan count(*) FROM "TasksAssociations" WHERE "ParentTaskID" = taskid;

-- пока дети есть в таблице ассоциаций
WHILE (quan !=  0 )
LOOP
 -- выбираем одного ребёнка в переменную
 SELECT INTO ID1 "ChildTaskID" FROM "TasksAssociations" WHERE "ParentTaskID" = taskid;
 -- удаляем ребёнка (CASCADE удалит и ео связи со всеми из таблицы TasksAssosiations)
 PERFORM * FROM public."DeleteTask"(ID1);
 -- узнаём новое кол-во детей у заданного таска
 SELECT INTO quan count(*) FROM "TasksAssociations" WHERE "ParentTaskID" = taskid;

END LOOP;

-- удаляем заданный таск, который уже без детей
DELETE FROM "Tasks"
WHERE "TaskID" = taskid;

RETURN  1 ;

END;
$body$
LANGUAGE 'plpgsql' VOLATILE CALLED ON NULL INPUT SECURITY INVOKER;

FOR child IN select * from TasksAssosiations where ParentTaskID =  15  LOOP
  select DeleteTask(child.ChildTaskID);
END LOOP;

CREATE OR REPLACE FUNCTION "public"."DeleteTask" (taskid integer) RETURNS bit AS
$body$

DECLARE rec RECORD;

BEGIN


FOR rec IN select * from "TasksAssociations" where "ParentTaskID" = taskid
LOOP
  perform "public"."DeleteTask"(rec."ChildTaskID");
END LOOP;


DELETE FROM "Tasks"
WHERE "TaskID" = taskid;

RETURN  1 ;

END;
$body$
LANGUAGE 'plpgsql' VOLATILE CALLED ON NULL INPUT SECURITY INVOKER;