Looking at Dolphin with Baloo specifically, it seems to look up the metadata of every file in its search domain, even if you're doing a simple file name search. When I trace the
file.so process, I see calls to
getxattr again for every file, and even for
.. entries. These system calls retrieve metadata about the file which is stored in a different location from the file name (the file name is stored in the directory contents, but the metadata are in the inode). Querying the metadata of a file multiple times is cheap since the data would be in the disk cache, but there can be a significant difference between querying the metadata and not querying the metadata.
find is much more clever. It tries to avoid unnecessary system calls. It won't call
getxattr because it doesn't search based on extended attributes. When it's traversing a directory, it may need to call
lstat on non-matching file names because that may be a subdirectory to search recursively (
lstat is the system call that returns file metadata including the file type such as regular/directory/symlink/…). However
find has an optimization: it knows how many subdirectories a directory has from its link count, and it stops calling
lstat once it knows that it's traversed all the subdirectories. In particular, in a leaf directory (a directory with no subdirectories),
find only checks the names, not the metadata. Furthermore some filesystems keep a copy of the file type in the directory entry so that
find doesn't even need to call
lstat if that's the only information it needs.
If you run
find with options that require checking the metadata, it'll make more
lstat calls, but it still won't make an
lstat call on a file if it doesn't need the information (for example because the file is excluded by a previous condition matching on the name).
I suspect that other GUI search tools that reinvent the
find wheel are similarly less clever than the command line utility which has undergone decades of optimization. Dolphin, at least, is clever enough to use the locate database if you search “everywhere” (with the limitation which isn't clear in the UI that the results may be out of date).