Getting a DataReader by stored procedure vs. SQL statment (Performance)

Question

Hallo DB-Experts,
I have encountered a performance problem regarding getting a DataReader by stored procedure versus a SQL statment
and I want to know if this is an known issue and how to tune it.
Getting a DataReader through a SQL statment is faster than with a stored procedure,
if the number of data rows are less than about 8000 datarows, although we are using an index.
The stored procedure ist only faster about 8000 datarows.
For the first 20 rows the different is between 50 abd 20 percent and between and 20 and 2000 rows it fall down to 10 percent.
Over 8000 rows the stored procedure is faster!
The time series table looks like:
CREATE TABLE TimeSeries
OBJECT_ID NUMBER(8) NOT NULL,
UNIVERSAL_TIME NUMBER(10) NOT NULL,
LOCAL_TIME DATE NOT NULL,
MOD_TIME NUMBER(10),
USERID NUMBER(10),
VALUE NUMBER NOT NULL,
FLAG NUMBER(2) DEFAULT 0 NOT NULL
The foreinkey is object_id and another index is for universal_time and mod_time
The stored procedure looks like:
PROCEDURE SELECTDATA_UT_MOD (pObjectID IN NUMBER,
pType IN VARCHAR2,
pTable IN VARCHAR2,
pFrom IN NUMBER,
pTo IN NUMBER,
IO_CURSOR OUT T_CURSOR)
IS
SQLString VARCHAR2(1024);
BEGIN
IF pOBJECTID <> 0 THEN
CASE
WHEN UPPER(pTYPE)='A' THEN
SQLString := 'SELECT UNIVERSAL_TIME, VALUE, FLAG, MOD_TIME FROM ' || pTABLE || ' WHERE OBJECT_ID = :t1 AND UNIVERSAL_TIME >= :t2 and UNIVERSAL_TIME < :t3 Order By UNIVERSAL_TIME, MOD_TIME DESC';
OPEN IO_CURSOR FOR
SQLString USING pOBJECTID,pFROM,pTO;
END IF;
END;
The SQL statment for the data reader looks like:
SELECT d.universal_time, d.VALUE, d.flag, 0 AS mod_time
FROM daten d
WHERE object_id = 18465
AND d.universal_time >= 3600
AND d.universal_time < 28803600
ORDER BY d.universal_time, mod_time DESC
Do you have any idea or tip why the sql statment for the first 8000 rows is faster than the stored procedure?
Many thanks in advance and
Best regards
George
Edited by: hakomdba on 09.01.2009 06:39

Answer 1

Hallo DB-Experts,
I have encountered a performance problem regarding getting a DataReader by stored procedure versus a SQL statment
and I want to know if this is an known issue and how to tune it.
Getting a DataReader through a SQL statment is faster than with a stored procedure,
if the number of data rows are less than about 8000 datarows, although we are using an index.
The stored procedure ist only faster about 8000 datarows.
For the first 20 rows the different is between 50 abd 20 percent and between and 20 and 2000 rows it fall down to 10 percent.
Over 8000 rows the stored procedure is faster!
The time series table looks like:
CREATE TABLE TimeSeries
OBJECT_ID NUMBER(8) NOT NULL,
UNIVERSAL_TIME NUMBER(10) NOT NULL,
LOCAL_TIME DATE NOT NULL,
MOD_TIME NUMBER(10),
USERID NUMBER(10),
VALUE NUMBER NOT NULL,
FLAG NUMBER(2) DEFAULT 0 NOT NULL
The foreinkey is object_id and another index is for universal_time and mod_time
The stored procedure looks like:
PROCEDURE SELECTDATA_UT_MOD (pObjectID IN NUMBER,
pType IN VARCHAR2,
pTable IN VARCHAR2,
pFrom IN NUMBER,
pTo IN NUMBER,
IO_CURSOR OUT T_CURSOR)
IS
SQLString VARCHAR2(1024);
BEGIN
IF pOBJECTID <> 0 THEN
CASE
WHEN UPPER(pTYPE)='A' THEN
SQLString := 'SELECT UNIVERSAL_TIME, VALUE, FLAG, MOD_TIME FROM ' || pTABLE || ' WHERE OBJECT_ID = :t1 AND UNIVERSAL_TIME >= :t2 and UNIVERSAL_TIME < :t3 Order By UNIVERSAL_TIME, MOD_TIME DESC';
OPEN IO_CURSOR FOR
SQLString USING pOBJECTID,pFROM,pTO;
END IF;
END;
The SQL statment for the data reader looks like:
SELECT d.universal_time, d.VALUE, d.flag, 0 AS mod_time
FROM daten d
WHERE object_id = 18465
AND d.universal_time >= 3600
AND d.universal_time < 28803600
ORDER BY d.universal_time, mod_time DESC
Do you have any idea or tip why the sql statment for the first 8000 rows is faster than the stored procedure?
Many thanks in advance and
Best regards
George
Edited by: hakomdba on 09.01.2009 06:39