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Closed 3 years ago.
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I have a problem with a stored procedure.
The procedure gets as an argument the number of rows needed, but the following does not work in HANA:
SELECT TOP :NUM_OF_ROWS * FROM TABLE_NAME
I read that TOP in HANA only receives a number, not an expression. Is there another way to do this? My solution for the moment is to select everything and delete the unneeded records on the service, but it's not very efficient.
Instead of TOP n you can use the LIMIT n option.
That one can bind variables.
Related
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Closed 5 years ago.
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I understand that .collect(pf), where pf is a partial function, is the equivalent to .filter(pf.isDefinedAt _).map(pf). What I don't understand is what just .collect() does. Can anyone explain this?
collect without parameters fetches all data stored in a RDD to the driver.
Return an array that contains all of the elements in this RDD.
Note
This method should only be used if the resulting array is expected to be small, as all the data is loaded into the driver's memory.
There is no connection to the version with PartialFunction whatsoever. Both are used for completely different things.
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Closed 8 years ago.
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Is this a perpetually denied feature request or something specific to Postgres?
I've read that Postgre has potentially higher performance than InnoDB but also potentially larger chance of less serialization (I apologize that I don't have a source, and please give that statement a wide berth because of my noobity and memory) and wonder if it might have something to do with that.
Postgres is amazingly functional compared to MySQL, and that's why I've switched. Already I've cut down lines of code & unnecessary replication immensely.
This is just a small annoyance, but I'm curious if it's considered unnecessary because of the UPDATE then INSERT workaround, or if it's very difficult to develop (possibly vs the perceived added value) like boost::lockfree::queue's ability to pass "anything" (, or if it's something else).
PostgreSQL committers are working on a patch to introduce "INSERT ... ON DUPLICATE KEY", which is functionally equivalent to an "upsert". MySQL and Oracle already have functionality (in Oracle it is called "MERGE")
A link to the PostgreSQL archives where the functionality is discussed and a patch introduced: http://www.postgresql.org/message-id/CAM3SWZThwrKtvurf1aWAiH8qThGNMZAfyDcNw8QJu7pqHk5AGQ#mail.gmail.com
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Closed 9 years ago.
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In Postgresql, the hstore and json datatypes seem to have very similar use cases. When would you choose to use one vs. the other? Initial thoughts:
You can nest with json; you can't with hstore
Functions for parsing json won't be available until 9.3
The json type is just a string. There are no built in functions to parse it. The only thing to be gained when using it is the validity checking.
Edit for those downvoting: This was written when 9.3 still didn't exist.It is correct for 9.2. Also the question was different. Check the edit history.
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Closed 11 years ago.
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What speed optimization techniques do antiviruses use today to scan a file, provided they have to check for all the signatures + the behavioral scan?
I'm not a antivirus programmer, but I think the scan engine scans through a file searching for known pattern inside. The greater number of patterns it can identify, the longer it will take to scan.
Optimization maybe similar to database optimization, with patterns indexing.
Identification Methods
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Closed 6 years ago.
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I want to select certain amount of data from one table. Based on those data, I want to check another two tables and insert into 2 tables.
So I want to iterate the resulted data. Which way is better(faster) and reasonable using DataReader or DataTable?
Thanks in advance
RedsDevils
You end up creating a reader to fill the table. The reverse isn't true, So I would stick with the dataReader.
-Josh