Strange database toolbox behavior
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I have a simple SQL Server query--SELECT [field list] FROM [in-database view]--that, with a where clause, returns the correct results--a 252 x 17 mixed-type cellarray--without generating a java heap outofmemory error, but without a where clause, generates a java heap outof emory error. If I add code similar to that provided by "Example 3 — Import Rows Iteratively Until You Retrieve All Data" in the help doc for cursor.fetch:
function data = grabInPieces(~, curs)
% Initialize result holder and fetch size
data = {};
rowLimit = 20;
% Check for and retrieve more data
while ~strcmp(curs.Data, 'No Data')
curs = fetch(curs, rowLimit);
data(end+1:end+size(curs.Data,1),:) = curs.Data;
end
end
and have a call to this inside a catch block following the first attempt to fetch, the outofmem error is dealt with, but the result set is drastically abbreviated--down to 8 rows from an expected 320 (which is the number of rows the same query returns in SQL Server Management Studio).
Any ideas?
Thanks, OlyDLG
2 件のコメント
Oleg Komarov
2012 年 8 月 29 日
Is the code you posted, exactly what you're using? If not, post the code you're using.
Which MATLAB version do you have?
回答 (3 件)
Oleg Komarov
2012 年 8 月 29 日
The code looks correct, unless you're doing something that fetches most of the data (without storing it) before calling grabInPieces().
2 件のコメント
Oleg Komarov
2012 年 8 月 29 日
編集済み: Oleg Komarov
2012 年 8 月 29 日
The cursor usually works like a file pointer. However, I am unsure what should happen in case of a Java out of memory error.
I would try to avoid the out of memory by estimating the memory use per row.
You can try to query the meta info of the table with:
Curs = exec(Connection, Statement);
attributes = get(rsmd(resultset(Curs)));
and establish the amount of rows to import (keeping it prudent).
Then, what you just need is to do a first pre-fetch and keep fetching iteratively but inverting the order of the commands in the while loop:
while ~strcmp(curs.Data, 'No Data')
data(end+1:end+size(curs.Data,1),:) = curs.Data;
curs = fetch(curs, rowLimit);
end
Otherwise, you can use a try catch block (but keep the commands in the loop inverted, i.e. first store the results from the previous fetch). However, I am unsure whether the state of the cursor is preserved in the catch part.
David Goldsmith
2012 年 8 月 30 日
2 件のコメント
Sean de Wolski
2012 年 8 月 30 日
What else do you have open in ML? Do you have a large *.m files open in the editor, GUIs, etc? How about the current folder, are there many files in there?
I would recommend to try closing the various desktop components you are not using in an effort to minimize your Java heap footprint to see if that helps.
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