Updating multiple columns using forall dating sites for 50 and over
There is an overhead associated with each context switch between the two engines.If PL/SQL code loops through a collection performing the same DML operation for each item in the collection it is possible to reduce context switches by bulk binding the whole collection to the DML statement in one operation.In Oracle8i a collection must be defined for every column bound to the DML which can make the code rather long winded.Oracle9i allows us to use Record structures during bulk operations so long as we don't reference individual columns of the collection. etc I have a mapping table where "ALL" old account number and new account numbers are present.
This keyword was introduced in Oracle9i Release 2 to allow updates using record definitions without needing to reference individual elements of the record, making bulk operations significantly simpler.
tablespace_name, s.extent_management FROM user_tables t, user_tablespaces s WHERE t.tablespace_name = s.
The forall_test table is used to compare the performance of individual updates against bulk updates using the update_script listed below.
For a 126.96.36.199 database, I have been asked to add few columns and update them with new values from another table. To accomplish this, we researched 3 solutions: update via insert, merge statement and pl/sql with bulk collect. LAST SAVE EXCEPTIONS update (select col1, col2 from base_table ) set row = update_cols_tab(i) where rowid = row_id_tab(i); commit; exit when base_tab.count < 5000; end loop; commit; close base_table_cur; close new_data_cur; EXCEPTION WHEN dml_errors THEN FOR i IN 1 ..
With this method, you don’t execute any updates, instead you create a new table with the old and new data. LAST LOOP row_id_tab(i) := new_data_tab(i).row_id; update_cols_tab(i).col1 := new_data_tab(i).new_col1; update_cols_tab(i).col2 := new_data_tab(i).new_col2; end loop; FORALL i IN base_tab.
l_start := DBMS_UTILITY.get_time; SELECT * BULK COLLECT INTO l_tab FROM bulk_collect_test; DBMS_OUTPUT.put_line('Bulk (' || l_tab.count || ' rows): ' || (DBMS_UTILITY.get_time - l_start)); END; / Regular (42578 rows): 66 Bulk (42578 rows): 4 PL/SQL procedure successfully completed.