Different results when fetching using Datamaps vs. Limitmaps

Question

Hello,
I'm currently using dbms_aw package to execute DML commands into AW's and using the OLAP_TABLE Function to access data. I'm encountering some unexepected behavior when trying to issue a "sort".
Please consider the following:
1. First I issue the command below and receive the following results:
SQL> exec dbms_aw.execute('lmt Product to first 5;rpr w 100 PA.SHORTLABELF')
PRODUCT PA.SHORTLABELF
TOTALPROD Total Product
FMGLC Gum Liq Ctr
FMGLC24 Gum Liq Ctr 24s
FMGLC24RP Gum Liq Ctr 24s RP
FMMXS Mints X-S
2. Next I sort the dimension values in status in ascending order by their shortlabel (simply a text variable dimensioned by my product dim.
SQL> exec dbms_aw.execute('sort PRODUCT a PA.SHORTLABELF')
PL/SQL procedure successfully completed.
3. I looked at the results of the sort I get (as expected)
SQL> exec dbms_aw.execute('rpr w 100 PA.SHORTLABELF')
PRODUCT PA.SHORTLABELF
FMGLC Gum Liq Ctr
FMGLC24 Gum Liq Ctr 24s
FMGLC24RP Gum Liq Ctr 24s RP
FMMXS Mints X-S
TOTALPROD Total Product
4. Then I enter the following commmand using the OLAP_TABLE function and LimitMaps I receive the correct set of returned values however my sort has not been applied:
SQL> SELECT * FROM TABLE(OLAP_TABLE('fmcalc DURATION SESSION','','',
2 'MEASURE Time1 FROM PA.SHORTLABELF '))
TIME1
Total Product
Gum Liq Ctr
Gum Liq Ctr 24s
Gum Liq Ctr 24s RP
Mints X-S
5. Finally, if I decide to go back and use datamaps in conjunction with the OLAP_TABLE function my sorting has "stuck"
SQL> SELECT Text1 FROM TABLE(OLAP_TABLE('fmcalc DURATION SESSION','TempTable','fetch PA.SHORTLABELF', ''))
Text1
Gum Liq Ctr
Gum Liq Ctr 24s
Gum Liq Ctr 24s RP
Mints X-S
Total Product
So, I guess the workaround to the using limitmaps is to use datamaps. My question is why does this behavior occur when using limitmaps and are there other scenrios where similiar behaviour might occur? My main reason is that during my development as a rule I have tried to use limitmaps.
thanks
brad

Answer 1

Hi Brad,
The short answer here is that SQL does not guarantee the order of rows unless it is explicitly sorted (at the SQL level). From that point of view, you could do something like
exec dbms_aw.execute('lmt Product to first 5;rpr w 100 PA.SHORTLABELF')
SELECT * FROM TABLE(OLAP_TABLE('fmcalc DURATION SESSION','','',
2 'MEASURE Time1 FROM PA.SHORTLABELF ')) order by TIME1 ascending;
(The reason this is happening is the code responsible for returning rows in the OLAP_TABLE limit map implementation is tuned to return data in the most efficient order.)
I hope this helps,
Ekrem