Query about parasitic firefox file

[Bret Busby]

Hello.

In the last 12 hours, 1.4GB of my home directory free space
disappeared, rendering the system unusable.

After having progressively shut the system down, before it crashed,
and, rebooting the system, with the free space still having been
disappeared, in searching for unexplained things, I found in the path
/home/me/.mozilla/firefox/<mixedstring>.default-<numericstring>/
the file places.sqlite-wal with Type "unknown" and size 1.5GB and Date
Modified being a couple of hours ago.

Does anyone know what is this file, what does it contain, and, can I
safely delete it without it causing further harm?

Thank you in anticipation.

-- 
Bret Busby
Armadale
West Australia
..............

"So once you do know what the question actually is,
 you'll know what the answer means."
- Deep Thought,
 Chapter 28 of Book 1 of
 "The Hitchhiker's Guide to the Galaxy:
 A Trilogy In Four Parts",
 written by Douglas Adams,
 published by Pan Books, 1992

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