The table in question has ~30mio records. Using Entity Framework I write a LINQ Query like this:
dbContext.MyTable.FirstOrDefault(t => t.Col3 == "BQJCRHHNABKAKU-KBQPJGBKSA-N");
Devart DotConnect for Oracle generates this:
SELECT
Extent1.COL1,
Extent1.COL2,
Extent1.COL3
FROM MY_TABLE Extent1
WHERE (Extent1.COL3 = :p__linq__0) OR ((Extent1.COL3 IS NULL) AND (:p__linq__0 IS NULL))
FETCH FIRST 1 ROWS ONLY
The query takes about four minutes, obviously a full table scan.
However, handcrafting this SQL:
SELECT
Extent1.COL1,
Extent1.COL2,
Extent1.COL3
FROM MY_TABLE Extent1
WHERE Extent1.COL3 = :p__linq__0
FETCH FIRST 1 ROWS ONLY
returns the expected match in 200ms.
Question: Why is it so? I would expect the query optimizer to note that the right part is false if the parameter is not null, so why doesn't the first query hit the index?
Please set UseCSharpNullComparisonBehavior=false explicitly:
var config = Devart.Data.Oracle.Entity.Configuration.OracleEntityProviderConfig.Instance;
config.QueryOptions.UseCSharpNullComparisonBehavior = false;
If this doesn't help, send us a small test project with the corresponding DDL script so that we can investigate the issue.
I tried looking for a similar example to my problem but could not reproduce the solution to my success.
I have 2 tables, Controller and Actions.
The Actions table has the columns Step, Script, Description, Wait_Until and Ref_Code.
The Controller table can only be joined on the Action table by the Ref_Code.
The Action table cannot have a PK because for each Ref_Code there is a Step to be taken.
Im getting an error when trying to update the Controller table using a merge statement:
ORA-30926: unable to get a stable set of rows in the source tables
My merge statement is as follows:
MERGE INTO DSTETL.SHB_FTPS_CONTROLLER ftpsc
USING (SELECT DISTINCT FTPSC.SESSION_ID,
FTPSC.ORDER_DATE,
sa.step,
sa.next_step,
LAST_ACTION_TMSTMP,
SA.ACTION_SCRIPT,
sa.ref_code,
SA.WAIT_UNTIL
FROM DSTETL.SHB_FTPS_CONTROLLER ftpsc, DSTETL.SHB_ACTIONS sa
WHERE SA.REF_CODE = FTPSC.REF_CODE
AND SA.STEP > ftpsc.curr_step
AND sa.step = ftpsc.next_step) v1
ON (v1.REF_CODE = FTPSC.REF_CODE)
WHEN MATCHED
THEN
UPDATE SET FTPSC.LAST_ACTION_TMSTMP = CURRENT_TIMESTAMP,
ftpsc.next_step = v1.next_step,
ftpsc.curr_step = v1.STEP,
ftpsc.action_script = v1.action_script
WHERE CURRENT_TIMESTAMP >= v1.LAST_ACTION_TMSTMP + v1.WAIT_UNTIL;
COMMIT;
I tried doing this using a normal update as well but Im getting ORA-01732: data manipulation operation not legal on this view.
UPDATE (SELECT FTPSC.SESSION_ID,
FTPSC.ORDER_DATE,
FTPSC.CURR_STEP,
FTPSC.NEXT_STEP,
FTPSC.ACTION_SCRIPT,
sa.step, --New Step
sa.next_step AS "NNS", --New Next Step
FTPSC.LAST_ACTION_TMSTMP,
SA.ACTION_SCRIPT AS "NAS", --New action script
sa.ref_code,
SA.WAIT_UNTIL
FROM DSTETL.SHB_FTPS_CONTROLLER ftpsc
LEFT JOIN
DSTETL.SHB_ACTIONS sa
ON SA.REF_CODE = FTPSC.REF_CODE
AND SA.STEP > ftpsc.curr_step
AND sa.step = ftpsc.next_step) t
SET t.curr_step = t.step,
t.LAST_ACTION_TMSTMP = CURRENT_TIMESTAMP,
t.next_step = t."NNS",
t.action_script = t."NAS";
COMMIT;
Any advice would be appreciated, I already understand this is because the Action table has multiple Ref_Codes but REF_CODE||STEP is unique. And the output of:
SELECT DISTINCT FTPSC.SESSION_ID,
FTPSC.ORDER_DATE,
sa.step,
sa.next_step,
LAST_ACTION_TMSTMP,
SA.ACTION_SCRIPT,
sa.ref_code,
SA.WAIT_UNTIL
FROM DSTETL.SHB_FTPS_CONTROLLER ftpsc, DSTETL.SHB_ACTIONS sa
WHERE SA.REF_CODE = FTPSC.REF_CODE
AND SA.STEP > ftpsc.curr_step
AND sa.step = ftpsc.next_step;
Is how I want the Controller table to be updated like.
Thanks in advance.
It sounds like what you want to do is: update each row in the Controller table with the matching "next step" details from the Actions table. But your Merge statement is querying the Controller table twice, which confuses things.
Is this what you're trying to do?
MERGE INTO DSTETL.SHB_FTPS_CONTROLLER ftpsc
USING (SELECT
step,
next_step,
ACTION_SCRIPT,
ref_code,
WAIT_UNTIL
FROM DSTETL.SHB_ACTIONS
) sa
ON (sa.REF_CODE = FTPSC.REF_CODE)
WHEN MATCHED
THEN
UPDATE SET FTPSC.LAST_ACTION_TMSTMP = CURRENT_TIMESTAMP,
ftpsc.next_step = sa.next_step,
ftpsc.curr_step = sa.STEP,
ftpsc.action_script = sa.action_script
WHERE CURRENT_TIMESTAMP >= ftpsc.LAST_ACTION_TMSTMP + sa.WAIT_UNTIL
AND SA.STEP > ftpsc.curr_step
AND sa.step = ftpsc.next_step;
EDIT: updated query
EDIT2: So, in your original query, in the USING section you were selecting the rows in the Controller table that you wanted to update... but you never joined those rows to the Controller table from the MERGE INTO section to match them up. Having the same alias "ftpsc" just made it less clear that they're two separate objects in the query, and which one you wanted to update.
Honestly I don't really understand why Oracle won't let you update columns that appear in the USING..ON clause. It apparently works fine in SQL Server.
I need to update a column in one table with the results from a select sub-query (and they should ultimately be different). But When I do this, I get the 'ORA-01427: single row sub-query returns more than one row query' error.
Can you please take a look and see what it is that I am overlooking? (I could just be overlooking something simple for all I know)
UPDATE AIRMODEL_NETWORK_SUMMARY ans
SET ANS.NBR_RETURNS = (
SELECT SUM(RQ.RETURN_QTY)
FROM RETURN_QTY RQ JOIN AIRMODEL_NETWORK_SUMMARY ANS ON RQ.LOC_ID = ANS.LOC_ID
WHERE RQ.FSCL_YR_NUM = ans.FSCL_YR_NUM
AND RQ.FSCL_WK_IN_YR_NUM =
ans.FSCL_WK_IN_YR_NUM
GROUP BY ANS.LOC_ID,
ans.FSCL_WK_IN_YR_NUM,
ANS.FSCL_YR_NUM
);
I think that your inner query is not well correlated to the table that you're trying to update. Please look here Oracle SQL: Update a table with data from another table. You should add some kind of a where condition that ties the rows you're trying to update with the values calculated by the inner statement.
I have created a view in oracle. Now i would like to fetch data from that view. So i have written a SQL Query. But the query is not working for not having a specific condition. But if I give that condition the query executes. But the problem is not occurring if i joined the same number of tables (that were used to create view) instead of using view. In the following I am giving the oracle query.
SELECT *
FROM "920_search_report"
WHERE lm_culture = '7aacb509-271d-4aca-e040-e00adea40aae'
AND hand_person_info_guid = 'eebd4257-7856-4c6e-b6b8-9b886e89e397'
AND ( Lower(handicap_type) LIKE Lower('%DQ871J%')
OR Lower(skskodenr) LIKE Lower('%DQ871J%') );
The above query executes and returns one record but if I omit or comment the third line then the query does not return any records, but it should return one or two. the query is given below:
SELECT *
FROM "920_search_report"
WHERE lm_culture = '7aacb509-271d-4aca-e040-e00adea40aae'
--AND HAND_PERSON_INFO_GUID='eebd4257-7856-4c6e-b6b8-9b886e89e397'
AND ( Lower(handicap_type) LIKE Lower('%DQ871J%')
OR Lower(skskodenr) LIKE Lower('%DQ871J%') );
Can anyone help me to solve the problem.
I have one complex SQL queries. One of the simple part of the queries looks like:
Query 1:
SELECT *
FROM table1 t1, table2 t2
WHERE t1.number = t2.number
AND UPPER(t1.name) = UPPER(t2.name)
AND t1.prefix = p_in_prefix;
Query 2:
SELECT *
FROM table1 t1, table2 t2
WHERE t1.number = t2.number
AND UPPER(t1.name) = UPPER(p_in_prefix || t2.name)
AND t1.prefix = p_in_prefix;
I have function based index on table1 as (number, UPPER(name)). I have function based index on my table2 as (number, UPPER(NAME)). p_in_prefix is a input parameter (basically a number).
Because of these indexes my Query 1 runs efficiently. But Query 2 has a performance issue, as in Query 2, 't2.name' is prefixed with p_in_prefix.
I can not create function based index for Query 2 because p_in_prefix is a input parameter and I don't know while creating index, what values it might hold. How to resolve performace issue in this scenario? Any hint/idea would be appreciated. If you require more information, please let me know.
Thanks.
Use AND UPPER(t1.name) = UPPER(p_in_prefix) || UPPER(t2.name).
As you have a function based index as UPPER(NAME) of table2, you should have an operand with the same expression in the query in order to make use of the function based index.
Using UPPER(p_in_prefix || t2.name) will not use the function based index as this does not match the function expression UPPER(NAME). Note here that using UPPER(t2.name) does not cause any problems as t2 is just a column alias.
Along with this, you can also pass an optimizer hint in your query in order to instruct the optimizer to use the index.
For more information read "Oracle Database 11g SQL" by Jason Price.
Also read Oracle Docs here and here and for optimizer hints here.