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PODatabase connections and OutOfMemoryError: Java Heap Space
 

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  1. PODatabase connections and OutOfMemoryError: Java Heap Space
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    <p>Last summer, I made a Java application that would parse some PDF files and get the information they contain to store them in a SQLite database.</p> <p>Everything was fine and I kept adding new files to the database every week or so without any problems.</p> <p>Now, I'm trying to improve my application's speed and I wanted to see how it would fare if I parsed all the files I have from the last two years in a new database. That's when I started getting this error: <em>OutOfMemoryError: Java Heap Space</em>. I didn't get it before because I was only parsing about 25 new files per week, but it seems like parsing 1000+ files one after the other is a lot more demanding.</p> <p>I partially solved the problem: I made sure to close my connection after every call to the database and the error went away, but at a huge cost. Parsing the files is now unbearably slow. As for my ResultSets and Statements / PreparedStatements, I'm already closing them after every call.</p> <p>I guess there's something I don't understand about when I should close my connection and when I should keep re-using the same one. I thought that since auto-commit is on, it commits after every transaction (select, update, insert, etc.) and the connection releases the extra memory it was using. I'm probably wrong since when I parse too many files, I end up getting the error I'm mentioning.</p> <p>An easy solution would be to close it after every x calls, but then again I won't understand why and I'm probably going to get the same error later on. Can anyone explain when I should be closing my connections (if at all except when I'm done)? If I'm only supposed to do it when I'm done, then can someone explain how I'm supposed to avoid this error?</p> <p>By the way, I didn't tag this as SQLite because I got the same error when I tried running my program on my online MySQL database.</p> <p><strong>Edit</strong> As it has been pointed out by Deco and Mavrav, maybe the problem isn't my Connection. Maybe it's the files, so I'm going to post the code I use to call the function to parse the files one by one:</p> <pre><code>public static void visitAllDirsAndFiles(File dir){ if (dir.isDirectory()){ String[] children = dir.list(); for (int i = 0; i &lt; children.length; i++){ visitAllDirsAndFiles(new File(dir, children[i])); } } else{ try{ // System.out.println("File: " + dir); BowlingFilesReader.readFile(dir, playersDatabase); } catch (Exception exc){ System.out.println("Other exception in file: " + dir); } } } </code></pre> <p>So if I call the method using a directory, it recursively calls the function again using the File object I just created. My method then detects that it's a file and calls <em>BowlingFilesReader.readFile(dir, playersDatabase);</em></p> <p>The memory should be released when the method is done I think?</p>
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    1. COCOnnection may not be exact reason for the error. What is the average size of the PDF file? Are you loading all the 1000 files into memory at a single shot? Try loading them one by one.
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    2. COEnsure that you are releasing the reference to the PDF file each time you have stored it in your new database. You might be loading the 1000 files into memory all at once which is causing your OOME. Have you used a profiler to check it out too?
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    3. CO@mavrav See edited question for details about how I'm loading the files. And the average is maybe 300kb (from 175kb to about 1.2mb)
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