Using multiple Collections in Report queries

Question

I am using many collections in my Report Queries (where conditions) to create the XML needed for running reports (see where condition below). I name each one with a different collection name. I am seeing some performance issues and it looks like it has to do with the amount of collections I am using. It looks like after around 6 collections used in the query, the sql slows down tremendously. It doesn't matter which ones I use, so it doesn't seem to be a specific one.
Are there issues with using many collections? Should I try using 1 collection and add an identifier to one of the collection columns instead?
where ...
and C.FK_SCHOOL IN (SELECT c001
FROM apex_collections AC1
WHERE AC1.collection_name = 'SIS_REPORTS_SCHOOLS')
and nvl(C.ACTIVE,'NONE') IN (SELECT decode(c001,'NONE',nvl(C.ACTIVE,'NONE'),C001)
FROM apex_collections AC2
WHERE AC2.collection_name = 'SIS_REPORTS_ACTIVES')
and nvl(C5.CALENDAR_NO,'NONE') IN (SELECT decode(c001,'NONE',nvl(C5.CALENDAR_NO,'NONE'),C001)
FROM apex_collections AC3
WHERE AC3.collection_name = 'SIS_REPORTS_SCHOOL_CALENDAR_NOS')
and nvl(C10.CLUSTER_CODE,'NONE') IN (SELECT decode(c001,'NONE',nvl(C10.CLUSTER_CODE,'NONE'),C001)
FROM apex_collections AC4
WHERE AC4.collection_name = 'SIS_REPORTS_CLUSTER_CODES')
and nvl(C4.EMPLOYEE_NUMBER,'NONE') IN (SELECT decode(c001,'NONE',nvl(C4.EMPLOYEE_NUMBER,'NONE'),C001)
FROM apex_collections AC5
WHERE AC5.collection_name = 'SIS_REPORTS_COUNSELORS')
and nvl(I3.DISTRICT,'NONE') IN (SELECT decode(c001,'NONE',nvl(I3.DISTRICT,'NONE'),C001)
FROM apex_collections AC6
WHERE AC6.collection_name = 'SIS_REPORTS_DISTRICTS')
and nvl(A1.ETHNIC,'NONE') IN (SELECT decode(c001,'NONE',nvl(A1.ETHNIC,'NONE'),C001)
FROM apex_collections AC7
WHERE AC7.collection_name = 'SIS_REPORTS_ETHNICS')
and nvl(C2.GRADE_LEVEL,'NONE') IN (SELECT decode(c001,'NONE',nvl(C2.GRADE_LEVEL,'NONE'),C001)
FROM apex_collections AC8
WHERE AC8.collection_name = 'SIS_REPORTS_GRADE_LEVELS')
and nvl(C3.HOMEROOM,'NONE') IN (SELECT decode(c001,'NONE',nvl(C3.HOMEROOM,'NONE'),C001)
FROM apex_collections AC9
WHERE AC9.collection_name = 'SIS_REPORTS_HOMEROOMS')
and nvl(C9.PROGRAM_CODE,'NONE') IN (SELECT decode(c001,'NONE',nvl(C9.PROGRAM_CODE,'NONE'),C001)
FROM apex_collections AC10
WHERE AC10.collection_name = 'SIS_REPORTS_PROGRAM_CODES')
and nvl(E2.S_TYPE,'NONE') IN (SELECT decode(c001,'NONE',nvl(E2.S_TYPE,'NONE'),C001)
FROM apex_collections AC11
WHERE AC11.collection_name = 'SIS_REPORTS_SCH_TYPES')
and nvl(A.SEX,'NONE') IN (SELECT decode(c001,'NONE',nvl(A.SEX,'NONE'),C001)
FROM apex_collections AC12
WHERE AC12.collection_name = 'SIS_REPORTS_SEXS')
and nvl(C7.SPECIAL_ED,'NONE') IN (SELECT decode(c001,'NONE',nvl(C7.SPECIAL_ED,'NONE'),C001)
FROM apex_collections AC13
WHERE AC13.collection_name = 'SIS_REPORTS_SPECIAL_EDS')
and nvl(A.STUDENT_ID,'NONE') IN (SELECT decode(c001,'NONE',nvl(A.STUDENT_ID,'NONE'),C001)
FROM apex_collections AC14
WHERE AC14.collection_name = 'SIS_REPORTS_STUDENTS')
and A.PK_ID IN (SELECT decode(c001,'NONE',A.PK_ID,AC16.FK_STU_BASE)
FROM student_list_det AC16, apex_collections AC15
WHERE AC15.collection_name = 'SIS_REPORTS_STUDENT_LISTS' and
AC16.fk_student_list (+) = AC15.c001)

Answer 1

Hi,
APEX_COLLECTIONS are special structures that do not have indexes, expect for the one on SEQ_ID. The result is that as the number of collections used in a query increases the number of full table scans on underlying tables kill speed. They are not intended for such heavy use as has been discussed in some of the threads in this forum.
They are extremely useful , but no good for very large data sets or large number of joins. Global temporary tables are also not an option with Apex.
You may have to resort to Materialized Views or intermediate/temp tables to get speed.
Regards,