Supporting Data
INSERT...SELECT
This test is by far going to
be the fastest and simplest way to get the 1 million rows into our GAS_LOG
table. We will do a straight insert into and selecting from our source table
with the following DML.
insert into GAS_LOG
(select * from GAS_LOG_SOURCE);
The only overhead that we will
incur in this approach will be the balancing of the b-tree index. As you can
see by the following lines of output, it took just 2.41 minutes from start to
finish.
Major Events
EVENT TOTAL_WAITS TOTAL_TIMEOUTS TIME_WAITED
------------------------------ ----------- -------------- -----------
control file parallel write 53 0 260
db file sequential read 777 0 554
log file parallel write 760 743 1383
db file parallel write 402 194 1608
db file scattered read 31620 0 10537
CPU used by this session 1749
===========
16091 = 2:41 minutes
CPU Statistics
CPU used by this session 1749
parse time cpu 2
recursive cpu usage 7
PL/SQL Cursor on Regular Table
This scenario proved to be just as fast for inserting as the
straight inserts except for the procedural code. This is good to know since
most all applications have code and we do not want to have our database be
loaded down just because we are inserting through an application. Obviously,
the trick is to reduce the amount of overhead that is required to execute the
code and the DML is not really a concern.
Major Events
EVENT TOTAL_WAITS TOTAL_TIMEOUTS TIME_WAITED
------------------------------ ----------- -------------- -----------
control file sequential read 157 0 639
log buffer space 67 0 1125
log file parallel write 2584 2493 2252
db file parallel write 976 476 4532
db file scattered read 31888 0 11189
CPU used by this session 22933
===========
42670 = 7:06 minutes
CPU Statistics
CPU used by this session 22933
parse time cpu 2797
recursive cpu usage 20364
PL/SQL Cursor on Table with VARRAY
I am very disappointed in this method. I had great hopes
before I started running these tests but really have to suggest not using this
method unless you are not concerned with performance or you are not handling
massive amounts of data. It just takes way too long and is too resource
intensive to read an array into memory, manage the array for new data, and then
update that VARRAY row back into the table.
Major Events
EVENT TOTAL_WAITS TOTAL_TIMEOUTS TIME_WAITED
------------------------------ ----------- -------------- -----------
control file sequential read 487 0 964
log file parallel write 6450 6351 2599
db file scattered read 33040 0 10705
db file parallel write 4656 2321 15593
db file sequential read 243481 0 48065
CPU used by this session 141384
===========
219310 = 36:33 minutes
CPU Statistics
CPU used by this session 141384
parse time cpu 10312
recursive cpu usage 137015
Conslusion
I do not think there is much else to say here and I am
certain that you have reached the same conclusion I have. Maybe in the next
release we might have a few easier methods to manipulate VARRAYs. I can only
hope that we could manipulate individual elements without having to message the
full VARRAY in latter versions of the engine.
Listing 1
Procedure for Inserts
CREATE OR REPLACE PACKAGE Gas_Driver AS
PROCEDURE cycle (cycle IN NUMBER, message IN VARCHAR2);
PROCEDURE select_insert;
END Gas_Driver;
/
CREATE OR REPLACE PACKAGE BODY Gas_Driver AS
cycle_times NUMBER;
PROCEDURE cycle (cycle IN NUMBER, message IN VARCHAR2) AS
BEGIN
FOR cycle_times IN 1..cycle LOOP
select_insert;
END LOOP;
END cycle;
PROCEDURE select_insert AS
CURSOR cur0 IS SELECT a.* FROM gas_log_source a;
BEGIN
FOR r0 IN cur0 LOOP
EXECUTE IMMEDIATE
'INSERT INTO gas_log '||
'( VIN,GALLONS,FILLUP_DATE,GAS_STATION) '||
' VALUES (:1,:2,:3,:4)'
USING r0.vin,r0.gallons,r0.fillup_date,r0.gas_station;
END LOOP;
COMMIT;
END select_insert;
BEGIN
DBMS_OUTPUT.ENABLE(1000000);
END Gas_Driver;
/
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