SQLite用完内存而不会引发异常

Question

I have a simple C# application reading CSV files into an SQLite database.

When the data has been read (the database file is approximately 5GB at this time), I create an index on the single table that contains all the data.

CREATE INDEX index_name ON table_name(col_a, col_b ASC)

I can then see the following error message in the Visual Studio debug output window:

SQLite error (6154): os_win.c:41445: (8) winMapfile2() - Not enough storage is available to process this command.

The error message repeats itself a couple of hundred times during a few seconds while creating the index.

The SQLite documentation says the following:

(6154) SQLITE_IOERR_MMAP
The SQLITE_IOERR_MMAP error code is an extended error code for SQLITE_IOERR indicating an I/O error within the xFetch or xUnfetch methods on the sqlite3_io_methods object while trying to map or unmap part of the database file into the process address space.

My hard drive still has about 30GB left, the process is only using about 300MB of memory while running the command, and there is at least 30% available physical memory on the computer, so I'm not sure why it happens at all.

No exceptions are being thrown, it is only printed to the debug console. The index seems to be created properly in the database. Does that mean that the error message isn't harmful? Can I safely ignore it? Can I make it throw an actual exception if something goes wrong? I find it kind of scary that my databases may be corrupt.

Answer 1

MMAP is just an optimization. If it fails, SQLite falls back to using normal FileRead() calls.

That you don't have enough address space to map a 5 GB file is probably OK on your machine.