Table defination in datatype size can effect on query execution time.

Hello Oracle Guru,
I have one question , suppose I have create one table with more than 100 column
and i tacke every column datatype varchar2(4000).
Actual data are in every column not more than 300 character so in this case
if i execute only select query
so oracle cursor internaly read up to 4000 character one by one
or it read character one by one and in last character ex. 300 it will stop there.
If i reduce varchar2 size 300 instend of 4000 in table defination,
so is it effect on select query execution time ?
Thanks in advance.

When you declare VARCHAR2 column you specify maximum size that can be stored in that column. Database stores actual number of bytes (plus 2 bytes for length). So if yiou insert 300 character string, only 302 bytes will be used (assuming database character set is single byte character set).
SY.

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Below query is resulting in a wrong total amount and seems to be cartesian.
SELECT    SUM(F.DOLLARS)
FROM       SALES_FACTS         F
,               DIM_TIME                A
,               DIM_CUSTOMER      B
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,               DIM_SALESTYPE     D
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FROM       SALES_FACTS         F
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,               DIM_SALESAGENT C
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AND         F.CUST_ID     =    B.CUST_ID
AND         F.SA_ID         =    C.SA_ID
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Db:11.2.0.3
We have a 3rd party app and the web app runs very slow. We want to make the 3rd party to fix the issue. for the
app login process, I did an AWR , found the problem query it runs 10 mins. Then I did the sqltrace
here is it:
select clndr_id , count(*)
from
task where (clndr_id = :"SYS_B_0") group by clndr_id union select clndr_id ,
count(*) from project where (clndr_id = :"SYS_B_1") group by clndr_id
call     count       cpu    elapsed       disk      query    current        rows
Parse        1      0.01       0.00          0          0          0           0
Execute      1      0.01       0.00          0          0          0           0
Fetch        2     53.32     612.03      81650      58920          0           2
total        4     53.34     612.04      81650      58920          0           2
Misses in library cache during parse: 1
Optimizer mode: ALL_ROWS
Parsing user id: 34 (PX)
Number of plan statistics captured: 1
Rows (1st) Rows (avg) Rows (max) Row Source Operation
         2          2          2 SORT UNIQUE (cr=58923 pr=81650 pw=22868 time=113329109 us cost=58277 size=24 card=2)
         2          2          2   UNION-ALL (cr=58923 pr=81650 pw=22868 time=113329001 us)
         1          1          1    SORT GROUP BY NOSORT (cr=58330 pr=81070 pw=22868 time=104312437 us cost=58128 size=7 card=1)
   5589739    5589739    5589739     VIEW index$_join$_003 (cr=58330 pr=81070 pw=22868 time=619784236 us cost=57240 size=38875249 card=5553607)
   5589739    5589739    5589739      HASH JOIN (cr=58330 pr=81070 pw=22868 time=617373467 us)
   5590158    5590158    5590158       INDEX RANGE SCAN NDX_TASK_CALENDAR (cr=21676 pr=21676 pw=0 time=113637058 us cost=11057 size=38875249 card=5553607)(object id 24749)
   6673774    6673774    6673774       INDEX FAST FULL SCAN NDX_TASK_PROJ_RSRC (cr=36651 pr=36526 pw=0 time=213370625 us cost=21921 size=38875249 card=5553607)(object id 217274)
         1          1          1    SORT GROUP BY NOSORT (cr=593 pr=580 pw=0 time=9016527 us cost=149 size=17 card=1)
    136390     136390     136390     INDEX FAST FULL SCAN NDX_PROJECT_CALENDAR (cr=593 pr=580 pw=0 time=165434 us cost=132 size=2315876 card=136228)(object id 154409)
Rows     Execution Plan
      0 SELECT STATEMENT   MODE: ALL_ROWS
      2   SORT (UNIQUE)
      2    UNION-ALL
      1     SORT (GROUP BY NOSORT)
5589739      TABLE ACCESS   MODE: ANALYZED (BY INDEX ROWID) OF 'TASK'
                 (TABLE)
5589739       INDEX   MODE: ANALYZED (RANGE SCAN) OF
                  'NDX_TASK_CALENDAR' (INDEX)
5590158     SORT (GROUP BY NOSORT)
6673774      INDEX   MODE: ANALYZED (RANGE SCAN) OF
                 'NDX_PROJECT_CALENDAR' (INDEX)
Elapsed times include waiting on following events:
Event waited on                             Times   Max. Wait Total Waited
----------------------------------------   Waited ---------- ------------
SQL*Net message to client                       2        0.00          0.00
Disk file operations I/O                        2        0.00          0.00
db file sequential read                     22235        1.61        138.66
direct path write                            1620        3.25        177.42
db file scattered read                       2313        1.89        238.98
direct path read                              385        1.72         19.52
SQL*Net message from client                     2        0.11          0.21Please make your comments.
Thanks in Advance.

Salman Qureshi wrote:
Hi,
It looks to me that end result will give you distinct values because of distinct clndr_id. If my thinking is correct, can you use UNION ALL istead of UNION? This will reduce your query execution time by not spending time on removing duplication of results (UNION removes duplication).
Do you have fresh statistics on the tables/indexes involved in this query?
SalmanIt is a 3rd party app, not sure the query is exactly doing for, a good input though,
I have given a try as comparison.
Found
$$$$$$$$$$$$$$$$$$$$$$$$$$$$$
UNION
select clndr_id , count(*)
from
task where (clndr_id = :"SYS_B_0") group by clndr_id union select clndr_id ,
count(*) from project where (clndr_id = :"SYS_B_1") group by clndr_id
call     count       cpu    elapsed       disk      query    current        rows
Parse        1      0.00       0.00          0          0          0           0
Execute      1      0.00       0.00          0          0          0           0
Fetch        2     31.18      70.39      25288      58920          0           2
total        4     31.18      70.39      25288      58920          0           2
Misses in library cache during parse: 0
Optimizer mode: ALL_ROWS
Parsing user id: 34 (PX)
Number of plan statistics captured: 1
Rows (1st) Rows (avg) Rows (max) Row Source Operation
         2          2          2 SORT UNIQUE (cr=58923 pr=25288 pw=25284 time=70390927 us cost=58277 size=24 card=2)
         2          2          2   UNION-ALL (cr=58923 pr=25288 pw=25284 time=70390652 us)
         1          1          1    SORT GROUP BY NOSORT (cr=58330 pr=25288 pw=25284 time=70309151 us cost=58128 size=7 card=1)
   5589739    5589739    5589739     VIEW index$_join$_003 (cr=58330 pr=25288 pw=25284 time=70027453 us cost=57240 size=38875249 card=5553607)
   5589739    5589739    5589739      HASH JOIN (cr=58330 pr=25288 pw=25284 time=68083254 us)
   5590158    5590158    5590158       INDEX RANGE SCAN NDX_TASK_CALENDAR (cr=21676 pr=0 pw=0 time=2449897 us cost=11057 size=38875249 card=5553607)(object id 24749)
   6673774    6673774    6673774       INDEX FAST FULL SCAN NDX_TASK_PROJ_RSRC (cr=36651 pr=0 pw=0 time=3097204 us cost=21921 size=38875249 card=5553607)(object id 217274)
         1          1          1    SORT GROUP BY NOSORT (cr=593 pr=0 pw=0 time=81462 us cost=149 size=17 card=1)
    136390     136390     136390     INDEX FAST FULL SCAN NDX_PROJECT_CALENDAR (cr=593 pr=0 pw=0 time=68732 us cost=132 size=2315876 card=136228)(object id 154409)
Rows     Execution Plan
      0 SELECT STATEMENT   MODE: ALL_ROWS
      2   SORT (UNIQUE)
      2    UNION-ALL
      1     SORT (GROUP BY NOSORT)
5589739      TABLE ACCESS   MODE: ANALYZED (BY INDEX ROWID) OF 'TASK'
                 (TABLE)
5589739       INDEX   MODE: ANALYZED (RANGE SCAN) OF
                  'NDX_TASK_CALENDAR' (INDEX)
5590158     SORT (GROUP BY NOSORT)
6673774      INDEX   MODE: ANALYZED (RANGE SCAN) OF
                 'NDX_PROJECT_CALENDAR' (INDEX)
Elapsed times include waiting on following events:
Event waited on                             Times   Max. Wait Total Waited
----------------------------------------   Waited ---------- ------------
SQL*Net message to client                       2        0.00          0.00
direct path write                            3347        1.59         43.26
direct path read                              130        0.20          0.32
SQL*Net message from client                     2        0.23          0.27
********************************************************************************$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$
UNION ALL
SQL ID: d6z3ag876m67h Plan Hash: 4277397671
select clndr_id , count(*)
from
task where (clndr_id = :"SYS_B_0") group by clndr_id union all select
clndr_id , count(*) from project where (clndr_id = :"SYS_B_1") group by
clndr_id
call     count       cpu    elapsed       disk      query    current        rows
Parse        1      0.00       0.00          0          0          0           0
Execute      1      0.01       0.00          0          0          0           0
Fetch        2     31.77      89.93      22886      58920          0           2
total        4     31.78      89.94      22886      58920          0           2
Misses in library cache during parse: 1
Optimizer mode: ALL_ROWS
Parsing user id: 34 (PX)
Number of plan statistics captured: 1
Rows (1st) Rows (avg) Rows (max) Row Source Operation
         2          2          2 UNION-ALL (cr=58932 pr=22887 pw=22868 time=89865448 us)
         1          1          1   SORT GROUP BY NOSORT (cr=58339 pr=22887 pw=22868 time=89865428 us cost=57240 size=7 card=1)
   5589739    5589739    5589739    VIEW index$_join$_003 (cr=58339 pr=22887 pw=22868 time=302390812 us cost=57240 size=38875249 card=5553607)
   5589739    5589739    5589739     HASH JOIN (cr=58339 pr=22887 pw=22868 time=300505731 us)
   5590158    5590158    5590158      INDEX RANGE SCAN NDX_TASK_CALENDAR (cr=21676 pr=0 pw=0 time=2275780 us cost=11057 size=38875249 card=5553607)(object id 24749)
   6673774    6673774    6673774      INDEX FAST FULL SCAN NDX_TASK_PROJ_RSRC (cr=36651 pr=18 pw=0 time=3233656 us cost=21921 size=38875249 card=5553607)(object id 217274)
         1          1          1   SORT GROUP BY NOSORT (cr=593 pr=0 pw=0 time=77989 us cost=132 size=17 card=1)
    136390     136390     136390    INDEX FAST FULL SCAN NDX_PROJECT_CALENDAR (cr=593 pr=0 pw=0 time=55006 us cost=132 size=2315876 card=136228)(object id 154409)
Rows     Execution Plan
      0 SELECT STATEMENT   MODE: ALL_ROWS
      2   UNION-ALL
      1    SORT (GROUP BY NOSORT)
5589739     TABLE ACCESS   MODE: ANALYZED (BY INDEX ROWID) OF 'TASK'
                (TABLE)
5589739      INDEX   MODE: ANALYZED (RANGE SCAN) OF 'NDX_TASK_CALENDAR'
                 (INDEX)
5590158    SORT (GROUP BY NOSORT)
6673774     INDEX   MODE: ANALYZED (RANGE SCAN) OF
                'NDX_PROJECT_CALENDAR' (INDEX)
Elapsed times include waiting on following events:
Event waited on                             Times   Max. Wait Total Waited
----------------------------------------   Waited ---------- ------------
SQL*Net message to client                       2        0.00          0.00
Disk file operations I/O                        2        0.00          0.00
direct path write                            2069        3.12         58.90
db file sequential read                        18        0.78          4.35
direct path read                               22        0.12          0.15
SQL*Net message from client                     2        0.46          0.71
********************************************************************************found union all used 90s vs union 70s, and the logic and the physical reads are about the same.
Notice that we now have it ran less that 2 mins for the query vs 10 mins before.
The before was at the peak hrs and now it is off the peak. the disk read from peak's 81650 reduced to 22886.
that was the cause of slow -- I/O contentions at peak hrs.
How can we improve the query performance by increasing disk throughput?
SQL> show parameter mem
NAME                                 TYPE        VALUE
hi_shared_memory_address             integer     0
memory_max_target                    big integer 4000M
memory_target                        big integer 3600M
shared_memory_address                integer     0
SQL> show parameter db_b
NAME                                 TYPE        VALUE
db_block_buffers                     integer     0
db_block_checking                    string      FALSE
db_block_checksum                    string      TYPICAL
db_block_size                        integer     8192
SQL>

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There are no i's to dot and t's to cross when it comes to space planning. Byte counting for space planning is, IMO, irrelevant today.

30EA3 - Edit Table/Create Table(Advanced) - Table Name, Text Box Size

I am not sure if its the same on non-Linux versions, but in the edit table dialog, the table name text box size is tiny. Its only wide enough that you can see approx 7 chars.
Is it possible to increase this? The size of the text box in the simple create table dialog seems like a good size. As far as I can tell, it is not tiny to conserve space for other items.
Anyway, it's just a minor issue that wont prevent me from doing work - just think it'd be better a bit bigger. I am sure it didn't used to be this small.
Ta,
Trent

oh interesting.
are you using openJDK?
$ /usr/lib/jvm/java-6-sun-1.6.0.22/bin/java -version
java version "1.6.0_22"
Java(TM) SE Runtime Environment (build 1.6.0_22-b04)
Java HotSpot(TM) 64-Bit Server VM (build 17.1-b03, mixed mode)
Ta,
Trent

How to select all the colomns_names from a table, with their datatypes ..

hi :)
i would like to know, how to select in SQL all the columns names from a table with their datatypes so that i get something like this :
Table 1 : table_name
the column ID has the Datatype NUMBER
the column name has the Datatype Varchar2
Table 2 : table_name
the column check has the Datatype NUMBER
the column air has the Datatype Varchar2
and that has to be for all the tables that i own ! ..
P. S : i m trying to do this with java, so it s would be enough if you just tell me how to select all the tables_names with all their colums_names and with all their datatypes ! ..
thank you :)
i ve heard it can be done with USER_TABLES .. but i have no idea how :( ..
Edited by: user8865125 on 17.05.2011 12:22

Hi,
The data dictionary view USER_TAB_COLUMNS has one row for every column in every table in your schema. The columns TABLE_NAME, COLUMN_NAME and DATA_TYPE have all the information you need.
Another data dictionary view, USER_TABLES, may be useful, too. It has one row pre table.

Table defination in datatype size can effect on query execution time.

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