Huge memory Allocation when using EPPlus Excel Library
c#, epplus, excel
Solution
Modern Excel files, ie, Xlsx files are zip-compressed, and often achieve compression down to 10%. I just uncompressed a 1.6MB file I generated using a similar tool and found it extracted to 18.8 MB of data.
You've got a 0.138 GB file that is using 1.370 GB of memory, which is almost exactly 10%. The uncompressed representation in memory is what is eating your memory.
If you're curious, you can use a tool like 7-Zip to extract the Xlsx files, or you can rename the file to end in .zip and browse it in Windows.
Problem
Context I have been using EPPLUS as my tool to automate excel report generation, using C# as the client language of the library. Problem: After trying to write a really big report (response of a SQL Query), with pivot tables, charts and so forth, i end up having a `Out of Memory Exception`. TroubleShooting In order to troubleshoot, i decided to open an existing report that has 138MB, and use the `GC` object to try to take a peek on what's happening with my memory, and here are the results. ``` ExcelPackage pkg = new ExcelPackage (new FileInfo (@"PATH TO THE REPORT.xlsx")); ExcelWorkbook wb = pkg.Workbook; ``` Garbage Collection Results, before the second line of code, and after. So, i have no idea what to do from now on. All i am doing is opening the report, which is consuming roughtly 10 (9.98 actually) times the report size itself, on memory. The ~138MB of the excel file, takes up 1.370.817.264 bytes of RAM. Update One: There's a fairly recent beta version of EPPlus that's out that has on it's changelog: ``` New Cell store * Less memory consumtion * Insert columns (not on the range level) * Faster row inserts ``` After updating the Nuget, i still have the same exception, that is thrown after the first line, instead of being raised on the second line.