On 1/17/07, Gints Plivna <gints.plivna@xxxxxxxxx> wrote:
Refresh method has been changed. Previously (<9i) for complete refreshes Oracle did truncate mv and insert /*+ append */. Now (10g) it does delete, normal insert. It is discussed for example here http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:15695764787749
I didn't see in the AskTom article cited where it said that the refresh mechanism changed from truncate/insert append to delete and insert when moving from 9i to 10g. It does say that the if the MV is part of a refresh group, a complete refresh will be done as delete/insert, rather than as truncate/append. The last post in that thread (from Pavel Ruzicka) implies that the default refresh mechanism did indeed change from 9i->10g, but that there is a workaround. I ran a small test to create an MV and do a complete refresh on both 9.2.0.6 and 10.2.0.1 that confirms this behavior. From the 9i trace: PARSING IN CURSOR #15 len=56 dep=1 uid=45 oct=85 lid=45 tim=1141749498683672 hv=68464594 ad='5cad9640' truncate table "JS001292"."MVTEST_MV" purge snapshot log END OF STMT ... INSERT /*+ APPEND */ INTO "JS001292"."MVTEST_MV"("OWNER","TABLE_NAME","TABLESPACE_NAME") SELECT "MVTEST"."OWNER","MVTEST"."TABLE_NAME","MVTEST"."TABL ESPACE_NAME" FROM "MVTEST" "MVTEST" END OF STMT From the 10g trace: PARSING IN CURSOR #15 len=35 dep=1 uid=56 oct=7 lid=56 tim=1141749792514219 hv=540326182 ad='733ed2d0' delete from "JS001292"."MVTEST_MV" END OF STMT ... INSERT /*+ BYPASS_RECURSIVE_CHECK */ INTO "JS001292"."MVTEST_MV"("OWNER","TABLE_NAME","TABLESPACE_NAME") SELECT "MVTEST"."OWNER","MVTEST"."TABLE_NAME ","MVTEST"."TABLESPACE_NAME" FROM "MVTEST" "MVTEST" By changing the refresh method to set atomic_refresh = false, the truncate/append behavior can be restored. begin -- dbms_mview.refresh('MVTEST_MV',method => 'C'); -- use this with 10g to return to truncate/append behavior dbms_mview.refresh('MVTEST_MV',method => 'C', atomic_refresh=>false); end; / Here's the results of doing so in 10g: PARSING IN CURSOR #24 len=57 dep=1 uid=56 oct=85 lid=56 tim=1141750173641027 hv=455978900 ad='705be890' truncate table "JS001292"."MVTEST_MV" purge snapshot log END OF STMT ... PARSING IN CURSOR #24 len=208 dep=1 uid=56 oct=2 lid=56 tim=1141750173945788 hv=896677336 ad='6d21e8f0' INSERT /*+ BYPASS_RECURSIVE_CHECK APPEND */ INTO "JS001292"."MVTEST_MV"("OWNER","TABLE_NAME","TABLESPACE_NAME") SELECT "MVTEST"."OWNER","MVTEST"."TA BLE_NAME","MVTEST"."TABLESPACE_NAME" FROM "MVTEST" "MVTEST" END OF STMT Nice to know. -- Jared Still Certifiable Oracle DBA and Part Time Perl Evangelist