No file system attributes or metadata on records which also means no (xattrs/fattrs) being written or updated, no checks to see if it's a physical file or a pipe/symlink, no permission checks, no block size alignment mismatches, single open command.
Makes sense when you consider you're throwing out functionality and disregarding general purpose design.
If you use a fuse mapping to SQLite, mount that directory and access it, you'd probably be very similar performance (perhaps even slower) and storage use as you'd need to add additional columns in the table to track these attributes.
I have no doubt that you could create a custom tuned file system on a dedicated mount with attributes disabled, minimized file table and correct/optimized block size and get very near to this perf.
Let's not forget the simplicity of being able to use shell commands (like rsync) to browse and manipulate those files without running the application or an SQL client to debug.
Makes sense for developers to use SQLite for this use case though for an appliance-type application or for packaged static assets (this is already commonplace in game development - a cab file is essentially the same concept)
For example, Ceph uses RocksDB as their metadata DB (and it's recommend to put it) directly on a block device, with the WAL on yet another separate raw device
(smaller block size, 100,000 inode file table entries (tuned to the number of blobs), no journal, no checksumming, no extended file attributes, use smaller integer file offset IDs, 32 bit padded vs 64 bit)
Then mount it and run the same test.
You could go even further and tune fopen BUFSIZE to be no greater than 12,000 bytes. You can even create this mount on a file inside your existing mount... which is essentially akin to having an sqlite file without needing a client library to read/write to it.
Anyway - if the purpose is to speed up reads and save disk space on small blob files, there is little need to ditch the file system and it's many many upsides.
Let's also note the 4x speed increase on windows 10, once again underlining just how slow windows filesystem calls are, when compared to direct access, and other (kernel, filesystem) combinations.
NTFS is really horrible handling many small files. When compiling/watching node modules (easily 10-100k files), we've seen a 10x size difference internally (same hardware, just different OSes). At some point that meant a compile time difference of 10-30 sec vs 6-10 min. Not fun.
Their "windows dev drive" setup addresses this. I haven't tested it myself but I saw a couple of inexpertly executed tests showing significant performance gains. I honestly have no idea if my compile times are quicker.
With the right code, NTFS is not much slower than ext4, for example. Nearly 3% for tar.gz and more than 30% for a heavily multi-threaded use like Pack.
I did some research in a database research lab, and we had a lot of colleagues working on OS research. It was always interesting to compare the constraints and assumptions across the two systems. I remember one of the big differences was the scale of individual records we expected to be working with, which in turn affected how memory and disk was managed. Most relational databases are very much optimized for small individual records and eventual consistency, which allows them to cache a lot more in memory. On the other hand, performance often drops sharply with the size of your rows.
This is precisely why I'm considering appending to a sqlite DB in WAL2 mode instead of plain text log files. Almost no performance penalty for writes but huge advantages for reading/analysis. No more Grafana needed.
Careful, some people will be along any second pointing out your approach limits your ability to use "grep" and "cat" on your log after recovering it to your pdp-11 running in your basement. Also something about the "Unix philosophy" :p
Seriously though, I think this is a great idea, and would be interested in how easy it is to write sqlite output adaptors for the various logging libraries out there.
> Careful, some people will be along any second pointing out your approach limits your ability to use "grep" and "cat" on your log after recovering it
I wish Splunk and friends would have an interface like that. Sure it does basic grep, and it is a much more powerful language, but sometimes you just needed some command line magic to find what you wanted.
I've been doing this for years. I keep SQLite log databases at varying grains depending on the solution. One for global logs, one per user/session/workflow, etc. I've also done things like in-memory SQLite trace databases that only get written to disk if an exception occurs.
SQLite doesn't look like a good fit for large logs - nothing can beat liner write at least on HDD and with plain text logs you will have it (though linear write of compressed data even better but rare software supports it out of the box). With SQLite I would expect more write requests for the same stream of logs (may be not much more). Reading analysis will be faster than using grep over plain text log only if you'll create indices which add write cost (and space overhead).
ClikcHouse works really well when you need to store and analyze large logs but compare to SQLite it would require to maintain a server(s). There is DuckDB which is embedded like SQLite and it could be a better than SQLite fit for logs but I have no experience with DuckDB.
I recently had the idea to record every note coming out of my digital piano in real-time. That way if I come up with a good idea when noodling around I don’t have to hope I can remember it later.
I was debating what storage layer to use and decided to try SQLite because of its speed claims — essentially a single table where each row is a MIDI event from the piano (note on, note off, control pedal, velocity, timestamp). No transactions, just raw inserts on every possible event. It so far has worked beautifully: it’s performant AND I can do fun analysis later on, e.g. to see what keys I hit more than others or what my average note velocity is.
If you play ten note chords — one for each finger — in quick succession, that can rack up a lot of inserts in short time period (say, medium-worst case, 100Hz, for playing a chord like that five times per second, counting both “on” and “off” events).
It’s also worth taking into consideration damper pedal velocity changes. When you go from “off” (velocity 0) to fully “on” and depressed (velocity 127), a lot of intermediate values will get fired off at high frequency.
Ultimately though you are right; it’s not enough frequency of information to overload SQLite (or a file system), probably by several orders of magnitude.
> The performance difference arises (we believe) because when working from an SQLite database, the open() and close() system calls are invoked only once, whereas open() and close() are invoked once for each blob when using blobs stored in individual files. It appears that the overhead of calling open() and close() is greater than the overhead of using the database
When something built on top of the filesystem is "faster" than the filesystem, it just means "when you use the filesystem in a less-than-optimal manner, it will be slower than an app that uses it in a sophisticated manner." An interesting point, but perhaps obvious...
To read/write blobs, you have to serialize/deserialize your objects to bytes. This process is not only tedious, but also varies for different objects and it's not a first-class citizen in other tools, so serialization kept breaking as my dependencies upgraded.
As my app matured, I found that I often wanted hierarchical folder-like functionality. Rather than recreating this mess in db relationships, it was easier to store the path and other folder-level metadata in sqlite so that I could work with it in Python. E.g. `os.listdir(my_folder)`.
Also, if you want to interact with other systems/services, then you need files. sqlite can't be read over NFS (e.g. AWS EFS) and by design it has no server for requests. so i found myself caching files to disk for export/import.
SQLite has some settings for handling parallel requests from multiple services, but when I experimented with them I always wound up with a locked db due to competing requests.
For one reason or another, you will end up with hybrid (blob/file) ways of persisting data.
> As my app matured, I found that I often wanted hierarchical folder-like functionality. Rather than recreating this mess in db relationships, it was easier to store the path and other folder-level metadata in sqlite so that I could work with it in Python. E.g. `os.listdir(my_folder)`.
This is a silly argument, there's no reason to recreate the full hierarchy. If you have something like this:
CREATE TABLE files (path TEXT UNIQUE COLLATE NOCASE);
Then you can do this:
SELECT path FROM files WHERE path LIKE "./some/path/%";
This gets you everything in that path and everything in the subpaths (if you just want from the single folder, you can always just add a `directory` column). I benchmarked it using hyperfine on the Linux kernel source tree and a random deep folder: `/bin/ls` took ~1.5 milliseconds, the SQLite query took ~3.0 milliseconds (this is on a M1 MacBook Pro).
The reason it's fast is because the table has a UNIQUE index, and LIKE uses it if you turn off case-sensitivity. No need to faff about with hierarchies.
EDIT: btw, I am using SQLite for this purpose in a production application, couldn't be happier with it.
> To read/write blobs, you have to serialize/deserialize your objects to bytes. This process is not only tedious, but also varies for different objects and it's not a first-class citizen in other tools, so things kept breaking as my dependencies upgraded.
I'm confused what you mean by this. Files also only contain bytes, so that serialization/deserialization has to happen anyway?
Also note that SQLite does have an incremental blob I/O API (sqlite3_blob_xxx), so unlike most other RDBMS there is no need to read/write blobs as a contiguous piece of memory - handling large blobs is more reasonable than in those. Though the blob API is still separate from normal querying.
Do you have or know of a clear example of how to do this? I have to ask because I spent half of yesterday trying to make it work. The blob_open command wouldn't work until I set a default value on the blob column and then the blob_write command wouldn't work because you can't resize a blob. It was very weird but I'm pretty confident it's because I'm missing something stupid.
MS SQL Server: READTEXT, WRITETEXT, substring, UPDATE.WRITE
Oracle: DBMS_LOB.READ, DBMS_LOB.WRITE
PG: Large Objects
Most of my experience is with SQL server and it can stream large objects incrementally through a web app to browser without loading the whole thing into memory at 100's Mbytes/sec on normal hardware.
> so i found myself caching files to disk for export/import
Could use a named pipe.
I’m reminded of what I often do at the shell with psub in fish. psub -f creates and returns the path to a fifo/named pipe in $TMPDIR and writes stdin to that; you’ve got a path but aren’t writing to the filesystem.
e.g. you want to feed some output to something that takes file paths as arguments. We want to compare cmd1 | grep foo and cmd2 | grep foo. We pipe each to psub in command substitutions:
> As my app matured, I found that I often wanted hierarchical folder-like functionality. Rather than recreating this mess in db relationships, it was easier to store the path in sqlite and work with it in Python. E.g. `os.listdir(my_folder)`
This makes total sense and it is also "frowned upon" by people who take a too purist view of databases
(Until it comes a time to backup, or extract files, or grow a hard drive etc and then you figure out how you shot yourself in the foot)
> As my app matured, I found that I often wanted hierarchical folder-like functionality.
In the process of prototyping some "remote" collaborating file systems, I always wonder whether it is a good idea maintaining a flat map from path concatenated with "/" like an S3 to the file content, in term of efficiency or elegancy.
All fs/drive access is managed by the OS. No DB systems have raw access to sectors or direct raw access to files.
Having a database file on the disc, offers a "cluster" of successive blocks on the hard drive (if it's not fragmented), resulting in relatively short moving distances of the drive head to seek the necessary sectors. There will still be the same sectors occupied, even after vast insert/write/del operations. Absolutely no change of DB file's position on hard drive. It's not a problem with SSDs, though.
So, the following apply:
client -> DB -> OS -> Filesystem
I think, you already can see the DB part is an extra layer. So, if one wouldn't have this, it would be "faster" in terms of execution time. Always.
If it's slower, then you use the not-optimal settings for your use case/filesystem.
My father did this once. He took H2 and made it even more faster :) incredible fast on Windows in direct comparison of H2/h2-modificated with same data.
So having a DBMS is convenient and made in decisions to serve certain domains and their problems. Having it is convenient, but that doesn't mean it's the most optimized way of doing it.
> No DB systems have raw access to sectors or direct raw access to files.
Oracle can use raw disks without having a filesystem on them, though it's more common to use ASM (Automatic Storage Management) which is Oracle's alternative to raw or OS managed disks.
SQLite can be faster than FileSystem for small files. For big files, it can do more than 1 GB/s.
On Pack [1], I benchmarked these speeds, and you can go very fast. It can be even 2X faster than tar [2].
In my opinion, SQLite can be faster in big reads and writes too, but the team didn't optimise it as much (like loading the whole content into memory) as maybe it was not the main use of the project. My hope is that we will see even faster speeds in the future.
Let's assume that filesystems are fairly optimized pieces of software. Let's assume that the people building them heard of databases and at some point along the way considered things like the costs of open/close calls.
How much more performance could you get by bypassing the filesystem and writing directly to the block device? Of course, you'd need to effectively implement your own filesystem, but you'd be able to optimise it more for the specific workload.
Because SQLite not being an FS is apparently the reason why it’s fast:
> The performance difference arises (we believe) because when working from an SQLite database, the open() and close() system calls are invoked only once, whereas open() and close() are invoked once for each blob when using blobs stored in individual files.
Additionally, it may also be that accesses to a single file allows the OS to efficiently retrieve (and IIRC in the case of Windows, predict) the working set allowing the reduction of access times; which is not the case if you open multiple files.
Proxmox puts the VM configuration information in a SQLite database and exposes it through a FUSE file system. It even gets replicated across the cluster using their replication algorithm. It’s a bespoke implementation, but it’s a SQLite-backed filesystem.
I remember reading someone's comments about how instead of databases using their own data serialisation formats for persistence and then optimizing writes and read over that they should just utilize the FS directly and let all of the optimisations built by FS authors be taken advantage of.
I wish I could find that comment, because my explanation doesn't do it justice. Very interesting idea, someone's probably going to explain how it's already been tried in some old IBM database a long time ago and failed due to whatever reason.
I still think it should be tried with newer technologies though, sounds like a very interesting idea.
> instead of databases using their own data serialisation formats for persistence and then optimizing writes and read over that they should just utilize the FS directly and let all of the optimisations built by FS authors be taken advantage of.
The original article effectively argues the opposite: if your use case matches a database, then that will be way faster. Because the filesystem is both fully general, multi-process and multi-user, it's got to be pessimistic about its concurrency.
This is why e.g. games distribute their assets as massive blobs which are effectively filesystems - better, more predictable seek performance. Starting from the Doom WAD onwards.
For an example of databases that use the file system, both the mbox and maildir systems for email probably count?
ReiserFS was built on the premise that doing a filesystem right could get us to a point where the filesystem is the database for a lot of use cases.
It's now "somewhat possible" in that modern filesystem are overall mostly less broken about handling large number of small (or at least moderately small) files than they used to be.
But databases are still far more optimized for handling small pieces of data in the ways we want to handle data we put into databases, which typically also includes a need to index etc.
As far as I can remember MongoDB did not have any dedicated block caching mechanism in its earlier releases.
They basically mmap’ed the database file and argued that OS cache should do its job. Which makes sense but I guess it did not perform as well as any fune tuned caching mechanism.
What do you expect the value proposition of something loosely described as a sqlitefs to be?
One of the main selling points of SQLite is that you can statically link it into a binary and no one needs to maintain anything between the OS and the client application. I'm talking about things like versioning.
What benefit would there be to replace a library with a full blown file system?
I don't think SQLite can run on a block device out of the box, it needs locking primitives and a second file for the journal or WAL plus a shared memory file in WAL mode
No file system attributes or metadata on records which also means no (xattrs/fattrs) being written or updated, no checks to see if it's a physical file or a pipe/symlink, no permission checks, no block size alignment mismatches, single open command.
Makes sense when you consider you're throwing out functionality and disregarding general purpose design.
If you use a fuse mapping to SQLite, mount that directory and access it, you'd probably be very similar performance (perhaps even slower) and storage use as you'd need to add additional columns in the table to track these attributes.
I have no doubt that you could create a custom tuned file system on a dedicated mount with attributes disabled, minimized file table and correct/optimized block size and get very near to this perf.
Let's not forget the simplicity of being able to use shell commands (like rsync) to browse and manipulate those files without running the application or an SQL client to debug.
Makes sense for developers to use SQLite for this use case though for an appliance-type application or for packaged static assets (this is already commonplace in game development - a cab file is essentially the same concept)
> tuned FS + dedicated mount
For example, Ceph uses RocksDB as their metadata DB (and it's recommend to put it) directly on a block device, with the WAL on yet another separate raw device
https://docs.ceph.com/en/latest/rados/configuration/bluestor...
More just this:
mke2fs -t ext4 -b 1024 -N 100000 -O ^has_journal,^uninit_bg,^ext_attr,^huge_file,^64bit [/dev/sdx]
(smaller block size, 100,000 inode file table entries (tuned to the number of blobs), no journal, no checksumming, no extended file attributes, use smaller integer file offset IDs, 32 bit padded vs 64 bit)
Then mount it and run the same test.
You could go even further and tune fopen BUFSIZE to be no greater than 12,000 bytes. You can even create this mount on a file inside your existing mount... which is essentially akin to having an sqlite file without needing a client library to read/write to it.
Anyway - if the purpose is to speed up reads and save disk space on small blob files, there is little need to ditch the file system and it's many many upsides.
> If you use a fuse mapping to SQLite, mount that directory and access it
Related ongoing discussion, if someone cares to test this:
https://news.ycombinator.com/item?id=41085856
Some nice write up on this topic, although not the resolution of all discussion. But rather hints and guesses to keep it alive :)
https://unixdigest.com/articles/battle-testing-php-fopen-sql...
Has been on HN lately..
That's a very rigorously written article.
Let's also note the 4x speed increase on windows 10, once again underlining just how slow windows filesystem calls are, when compared to direct access, and other (kernel, filesystem) combinations.
maybe the malware detection program adds to the performance as well
NTFS is really horrible handling many small files. When compiling/watching node modules (easily 10-100k files), we've seen a 10x size difference internally (same hardware, just different OSes). At some point that meant a compile time difference of 10-30 sec vs 6-10 min. Not fun.
55 replies →
Their "windows dev drive" setup addresses this. I haven't tested it myself but I saw a couple of inexpertly executed tests showing significant performance gains. I honestly have no idea if my compile times are quicker.
1 reply →
With the right code, NTFS is not much slower than ext4, for example. Nearly 3% for tar.gz and more than 30% for a heavily multi-threaded use like Pack.
https://forum.lazarus.freepascal.org/index.php/topic,66281.m...
https://news.ycombinator.com/item?id=18783525 has previous discussion on why windows filesystem is slow
But is it faster than accessing the filesystem with io_uring as well? I feel like this article should be updated
io_uring/IOCP won't change how long it takes to access a file.
2 replies →
I did some research in a database research lab, and we had a lot of colleagues working on OS research. It was always interesting to compare the constraints and assumptions across the two systems. I remember one of the big differences was the scale of individual records we expected to be working with, which in turn affected how memory and disk was managed. Most relational databases are very much optimized for small individual records and eventual consistency, which allows them to cache a lot more in memory. On the other hand, performance often drops sharply with the size of your rows.
This is precisely why I'm considering appending to a sqlite DB in WAL2 mode instead of plain text log files. Almost no performance penalty for writes but huge advantages for reading/analysis. No more Grafana needed.
Careful, some people will be along any second pointing out your approach limits your ability to use "grep" and "cat" on your log after recovering it to your pdp-11 running in your basement. Also something about the "Unix philosophy" :p
Seriously though, I think this is a great idea, and would be interested in how easy it is to write sqlite output adaptors for the various logging libraries out there.
> some people will be along any second pointing out your approach limits your ability to use "grep" and "cat" on your log
And they won’t be wrong.
4 replies →
How would you tail or watch a sqlite log? (on a pdp-11 if necessary :)
6 replies →
> Careful, some people will be along any second pointing out your approach limits your ability to use "grep" and "cat" on your log after recovering it
I wish Splunk and friends would have an interface like that. Sure it does basic grep, and it is a much more powerful language, but sometimes you just needed some command line magic to find what you wanted.
1 reply →
Is there a way to mount the sqlite tables as a filesystem?
I've been doing this for years. I keep SQLite log databases at varying grains depending on the solution. One for global logs, one per user/session/workflow, etc. I've also done things like in-memory SQLite trace databases that only get written to disk if an exception occurs.
I didn’t know what WAL/WAL2 mode was, so I looked it up. For anyone else interested: https://www.sqlite.org/wal.html
Some people have thought of this before. Here is one implementation
https://git.sr.ht/~martijnbraam/logbookd
Although I'm not sure it uses WAL2 mode, but that should be a trivial change.
There’s a tool called lnav that will parse logfiles into a temporary SQLite database and allows to analyse them using SQL features:
https://lnav.org/
It could probably work. For a peculiar application I even used sqlite to record key frame-only video. (There was a reason)
One could flip it around and store logs in a multimedia container, but then you won't have nice indices like with sqlite, just the one big time index
Are you using the wal2 branch of SQLite?
SQLite doesn't look like a good fit for large logs - nothing can beat liner write at least on HDD and with plain text logs you will have it (though linear write of compressed data even better but rare software supports it out of the box). With SQLite I would expect more write requests for the same stream of logs (may be not much more). Reading analysis will be faster than using grep over plain text log only if you'll create indices which add write cost (and space overhead).
ClikcHouse works really well when you need to store and analyze large logs but compare to SQLite it would require to maintain a server(s). There is DuckDB which is embedded like SQLite and it could be a better than SQLite fit for logs but I have no experience with DuckDB.
SQLite is meant for transactional data, DuckDB for analytical data.
I am not sure which one would be better for logs, I would need to play around with it. But i am not sure if SQLite wouldn’t be a better fit.
1 reply →
I recently had the idea to record every note coming out of my digital piano in real-time. That way if I come up with a good idea when noodling around I don’t have to hope I can remember it later.
I was debating what storage layer to use and decided to try SQLite because of its speed claims — essentially a single table where each row is a MIDI event from the piano (note on, note off, control pedal, velocity, timestamp). No transactions, just raw inserts on every possible event. It so far has worked beautifully: it’s performant AND I can do fun analysis later on, e.g. to see what keys I hit more than others or what my average note velocity is.
I wouldn't expect performance of pretty much any plausible approach to matter much. The notes just aren't going to be coming very quickly.
If you play ten note chords — one for each finger — in quick succession, that can rack up a lot of inserts in short time period (say, medium-worst case, 100Hz, for playing a chord like that five times per second, counting both “on” and “off” events).
It’s also worth taking into consideration damper pedal velocity changes. When you go from “off” (velocity 0) to fully “on” and depressed (velocity 127), a lot of intermediate values will get fired off at high frequency.
Ultimately though you are right; it’s not enough frequency of information to overload SQLite (or a file system), probably by several orders of magnitude.
1 reply →
What counts as plausible nowadays may surprise you given your grasp on true performance. Observe these professionals. https://www.primevideotech.com/video-streaming/scaling-up-th...
Insertion times are not a problem but maybe after a few years of playing you will be managing millions of records
1 reply →
> The performance difference arises (we believe) because when working from an SQLite database, the open() and close() system calls are invoked only once, whereas open() and close() are invoked once for each blob when using blobs stored in individual files. It appears that the overhead of calling open() and close() is greater than the overhead of using the database
I wonder how io_uring compares.
RecordIO would be a good choice for this use case
https://mesos.apache.org/documentation/latest/recordio/
Yeah but imagine a Beowulf cluster^H^H io_uring of SQLites
It seems like nobody has suggested putting SQLite databases inside SQLite blobs yet... you could have SQLite all the way down.
2 replies →
When something built on top of the filesystem is "faster" than the filesystem, it just means "when you use the filesystem in a less-than-optimal manner, it will be slower than an app that uses it in a sophisticated manner." An interesting point, but perhaps obvious...
TLDR; don't do it.
I've used SQLite blob fields for storing files extensively.
Note that there is a 2GB blob maximum: https://www.sqlite.org/limits.html
To read/write blobs, you have to serialize/deserialize your objects to bytes. This process is not only tedious, but also varies for different objects and it's not a first-class citizen in other tools, so serialization kept breaking as my dependencies upgraded.
As my app matured, I found that I often wanted hierarchical folder-like functionality. Rather than recreating this mess in db relationships, it was easier to store the path and other folder-level metadata in sqlite so that I could work with it in Python. E.g. `os.listdir(my_folder)`.
Also, if you want to interact with other systems/services, then you need files. sqlite can't be read over NFS (e.g. AWS EFS) and by design it has no server for requests. so i found myself caching files to disk for export/import.
SQLite has some settings for handling parallel requests from multiple services, but when I experimented with them I always wound up with a locked db due to competing requests.
For one reason or another, you will end up with hybrid (blob/file) ways of persisting data.
> As my app matured, I found that I often wanted hierarchical folder-like functionality. Rather than recreating this mess in db relationships, it was easier to store the path and other folder-level metadata in sqlite so that I could work with it in Python. E.g. `os.listdir(my_folder)`.
This is a silly argument, there's no reason to recreate the full hierarchy. If you have something like this:
Then you can do this:
This gets you everything in that path and everything in the subpaths (if you just want from the single folder, you can always just add a `directory` column). I benchmarked it using hyperfine on the Linux kernel source tree and a random deep folder: `/bin/ls` took ~1.5 milliseconds, the SQLite query took ~3.0 milliseconds (this is on a M1 MacBook Pro).
The reason it's fast is because the table has a UNIQUE index, and LIKE uses it if you turn off case-sensitivity. No need to faff about with hierarchies.
EDIT: btw, I am using SQLite for this purpose in a production application, couldn't be happier with it.
The postgres ltree extension does this beautifully. I'm not sure if similar things exist for sqlite or other rdbmses.
https://www.postgresql.org/docs/current/ltree.html
1 reply →
cool. i don't want to recreate a filesystem in my app logic
4 replies →
> To read/write blobs, you have to serialize/deserialize your objects to bytes. This process is not only tedious, but also varies for different objects and it's not a first-class citizen in other tools, so things kept breaking as my dependencies upgraded.
I'm confused what you mean by this. Files also only contain bytes, so that serialization/deserialization has to happen anyway?
The tools associated with every file type you support have to support reading/writing a buffer/bytestream or whatever it is called.
For example, `pd.read_parquet` accepts "file-like objects" as its first argument: https://pandas.pydata.org/docs/reference/api/pandas.read_par...
However, this is not the case for fringe tools
Maybe you need to encode bytes as text for sql?
1 reply →
> I've used SQLite blob fields for storing files extensively. Note that there is a 2GB blob maximum: https://www.sqlite.org/limits.html
Also note that SQLite does have an incremental blob I/O API (sqlite3_blob_xxx), so unlike most other RDBMS there is no need to read/write blobs as a contiguous piece of memory - handling large blobs is more reasonable than in those. Though the blob API is still separate from normal querying.
Do you have or know of a clear example of how to do this? I have to ask because I spent half of yesterday trying to make it work. The blob_open command wouldn't work until I set a default value on the blob column and then the blob_write command wouldn't work because you can't resize a blob. It was very weird but I'm pretty confident it's because I'm missing something stupid.
2 replies →
Most RDBMS's have streaming blob apis:
MS SQL Server: READTEXT, WRITETEXT, substring, UPDATE.WRITE
Oracle: DBMS_LOB.READ, DBMS_LOB.WRITE
PG: Large Objects
Most of my experience is with SQL server and it can stream large objects incrementally through a web app to browser without loading the whole thing into memory at 100's Mbytes/sec on normal hardware.
2 replies →
I wish the API was compatible with iovec though. As that's what all the c standard lib APIs use for non-contiguous memory
That sounds nice for chunking, but what if you need contiguous memory? E.g. viewing an image or running an AI model
1 reply →
> so i found myself caching files to disk for export/import
Could use a named pipe.
I’m reminded of what I often do at the shell with psub in fish. psub -f creates and returns the path to a fifo/named pipe in $TMPDIR and writes stdin to that; you’ve got a path but aren’t writing to the filesystem.
e.g. you want to feed some output to something that takes file paths as arguments. We want to compare cmd1 | grep foo and cmd2 | grep foo. We pipe each to psub in command substitutions:
which expands to something like
As long as the tool doesn’t seek around the file. (caveats are numerous enough that without -f, psub uses regular files.)
> I’m reminded of what I often do at the shell with psub in fish.
ksh and bash too have this as <(…) and >(…) under Process Substitution.
An example from ksh(1) man page:
bash (at least) has a built-in mechanism to do that
diff <(cmd1 | grep foo) <(cmd2 | grep foo)
1 reply →
> As my app matured, I found that I often wanted hierarchical folder-like functionality. Rather than recreating this mess in db relationships, it was easier to store the path in sqlite and work with it in Python. E.g. `os.listdir(my_folder)`
This makes total sense and it is also "frowned upon" by people who take a too purist view of databases
(Until it comes a time to backup, or extract files, or grow a hard drive etc and then you figure out how you shot yourself in the foot)
To make it more queryable, you can have different classes for dataset types with metadata like: file_format, num_files, sizes
> As my app matured, I found that I often wanted hierarchical folder-like functionality.
In the process of prototyping some "remote" collaborating file systems, I always wonder whether it is a good idea maintaining a flat map from path concatenated with "/" like an S3 to the file content, in term of efficiency or elegancy.
> As my app matured, I found that I often wanted hierarchical folder-like functionality
(1) Slim table "items"
- id / parent_id / kind (0/1 file folder) integer
- name text
- Maybe metadata.
(2) Separate table "content"
- id integer
- data blob
There you have file-system-like structure and fast access times (don't mix content in the first table)
Or, if you wish for deduplication or compression, add item_content (3)
Can you describe how you stored the paths in sqlite? I'm not entirely getting it.
just a string field that points to the file path
The idea to emulate hierarchical folder-like functionality ala filepaths is quite brilliant - I might try it out.
Storing Hierarchical Data in Relational Databases
https://medium.com/@rishabhdevmanu/from-trees-to-tables-stor...
I was looking at self hosted RSS readers recently. The application is single user. I don't expect it to be doing a lot of DB intensive stuff.
It surprised me that almost all required PostgreSQL, and most of those that didn't opted for something otherwise complex such as Mongo or MySQL.
SQLite, with no dependencies, would have simplified the process no end.
Last I checked, FreshRSS[1] can use a SQLite database.
[1] https://freshrss.org
Depends, depends.. but just of logic:
All fs/drive access is managed by the OS. No DB systems have raw access to sectors or direct raw access to files.
Having a database file on the disc, offers a "cluster" of successive blocks on the hard drive (if it's not fragmented), resulting in relatively short moving distances of the drive head to seek the necessary sectors. There will still be the same sectors occupied, even after vast insert/write/del operations. Absolutely no change of DB file's position on hard drive. It's not a problem with SSDs, though.
So, the following apply:
client -> DB -> OS -> Filesystem
I think, you already can see the DB part is an extra layer. So, if one wouldn't have this, it would be "faster" in terms of execution time. Always.
If it's slower, then you use the not-optimal settings for your use case/filesystem.
My father did this once. He took H2 and made it even more faster :) incredible fast on Windows in direct comparison of H2/h2-modificated with same data.
So having a DBMS is convenient and made in decisions to serve certain domains and their problems. Having it is convenient, but that doesn't mean it's the most optimized way of doing it.
> No DB systems have raw access to sectors or direct raw access to files.
Oracle can use raw disks without having a filesystem on them, though it's more common to use ASM (Automatic Storage Management) which is Oracle's alternative to raw or OS managed disks.
Oh nooo, I forgot, there are real databases existing in the wild, too ... :)
https://docs.oracle.com/en/database/oracle/oracle-database/1...
Indeed. Offers 10-12 percent performance writing direct on a block device. But, this block device is still attached to a running system :)
MySQL also supported this a million years ago, I'm not sure if it still does
MySQL can work off a block device without a file system.
numbers are from 2017, update would be cool
This discussion never gets old.
* https://news.ycombinator.com/item?id=34387407 2 years ago
SQLite can be faster than FileSystem for small files. For big files, it can do more than 1 GB/s. On Pack [1], I benchmarked these speeds, and you can go very fast. It can be even 2X faster than tar [2].
In my opinion, SQLite can be faster in big reads and writes too, but the team didn't optimise it as much (like loading the whole content into memory) as maybe it was not the main use of the project. My hope is that we will see even faster speeds in the future.
[1] https://pack.ac [2] https://forum.lazarus.freepascal.org/index.php/topic,66281.m...
Let's assume that filesystems are fairly optimized pieces of software. Let's assume that the people building them heard of databases and at some point along the way considered things like the costs of open/close calls.
What is SQLite not doing that filesystems are?
A discussion in the comments of the cost of opening a file on Windows: https://stackoverflow.com/questions/21309852/what-is-the-mem...
Access control is a big cost. Some AV systems (like everyone's favourite Crowdstrike) also hook every open/close.
How much more performance could you get by bypassing the filesystem and writing directly to the block device? Of course, you'd need to effectively implement your own filesystem, but you'd be able to optimise it more for the specific workload.
Oracle, some other databases did this back in a day in 00s by wrong with block devices directly.
I am not sure if this is done anymore, because the performance gains were modest compared to the hassle of a custom formatted partition.
i.e. opening and closing many files from disk is slower than opening and closing one file and using memory.
It's important. But understandable.
Why hasn’t someone made sqlitefs yet?
Because SQLite not being an FS is apparently the reason why it’s fast:
> The performance difference arises (we believe) because when working from an SQLite database, the open() and close() system calls are invoked only once, whereas open() and close() are invoked once for each blob when using blobs stored in individual files.
Additionally, it may also be that accesses to a single file allows the OS to efficiently retrieve (and IIRC in the case of Windows, predict) the working set allowing the reduction of access times; which is not the case if you open multiple files.
1 reply →
Here you go:)
https://github.com/narumatt/sqlitefs
And it seems quite interesting:
"sqlite-fs allows Linux and MacOS to mount a sqlite database file as a normal filesystem."
"If a database file name isn't specified, sqlite-fs use in-memory-db instead of a file. All data will be deleted when the filesystem is closed."
Proxmox puts the VM configuration information in a SQLite database and exposes it through a FUSE file system. It even gets replicated across the cluster using their replication algorithm. It’s a bespoke implementation, but it’s a SQLite-backed filesystem.
I remember reading someone's comments about how instead of databases using their own data serialisation formats for persistence and then optimizing writes and read over that they should just utilize the FS directly and let all of the optimisations built by FS authors be taken advantage of.
I wish I could find that comment, because my explanation doesn't do it justice. Very interesting idea, someone's probably going to explain how it's already been tried in some old IBM database a long time ago and failed due to whatever reason.
I still think it should be tried with newer technologies though, sounds like a very interesting idea.
> instead of databases using their own data serialisation formats for persistence and then optimizing writes and read over that they should just utilize the FS directly and let all of the optimisations built by FS authors be taken advantage of.
The original article effectively argues the opposite: if your use case matches a database, then that will be way faster. Because the filesystem is both fully general, multi-process and multi-user, it's got to be pessimistic about its concurrency.
This is why e.g. games distribute their assets as massive blobs which are effectively filesystems - better, more predictable seek performance. Starting from the Doom WAD onwards.
For an example of databases that use the file system, both the mbox and maildir systems for email probably count?
ReiserFS was built on the premise that doing a filesystem right could get us to a point where the filesystem is the database for a lot of use cases.
It's now "somewhat possible" in that modern filesystem are overall mostly less broken about handling large number of small (or at least moderately small) files than they used to be.
But databases are still far more optimized for handling small pieces of data in the ways we want to handle data we put into databases, which typically also includes a need to index etc.
As far as I can remember MongoDB did not have any dedicated block caching mechanism in its earlier releases.
They basically mmap’ed the database file and argued that OS cache should do its job. Which makes sense but I guess it did not perform as well as any fune tuned caching mechanism.
1 reply →
> Why hasn’t someone made sqlitefs yet?
What do you expect the value proposition of something loosely described as a sqlitefs to be?
One of the main selling points of SQLite is that you can statically link it into a binary and no one needs to maintain anything between the OS and the client application. I'm talking about things like versioning.
What benefit would there be to replace a library with a full blown file system?
There's quite a number of sqlite FUSE implementations around, if you want to head in that direction.
No mention of how it performs when you need random access (seek) into files. Perhaps it underperforms the file system at that?
Probably because you wouldn't seek into a database row?
I guess querying by PK has some similarities but it is not as unstructured and random as a seek.
Also side effects such as sparse files do not mean much from a database interface standpoint.
SQLite does have low-level C APIs for that:
https://www.sqlite.org/c3ref/blob_open.html
https://www.sqlite.org/c3ref/blob_read.html
I've not seen performance numbers for those. Could make for an interesting micro-benchmark.
POSIX interfaces (open, read, write, seek, close, etc) are very challenging to implement in an efficient/reliable way.
Using SQLite let's you tailor your data access patterns in a much more rigorous way and side step the POSIX tarpit.
There are at least two for macOS. But they run into trouble nowadays because FUSE wants kernel extensions.
Would you put sqlite in the kernel? Or using something like FUSE?
It seems to me that all the extra indirection from using FUSE would lead to more than a 35% performance hit.
Statically linking an sqlite into a kernel module and providing it with filesystem access seems like something non trivial to me.
Could we expect performance gains from Sqlite being in the kernel?
1 reply →
just point it at your block device
I don't think SQLite can run on a block device out of the box, it needs locking primitives and a second file for the journal or WAL plus a shared memory file in WAL mode
1 reply →
Slight OT: does this apply to SQLite on OpenBSD?
Because with OpenBSD introduction of pinning all syscalls to libc, doesn’t this block SQLite from making syscall direct.
https://news.ycombinator.com/item?id=38579913
Reminds me of this talk: https://www.destroyallsoftware.com/talks/the-birth-and-death...
Deleting a lot of rows from an sqlite database can be awfully slow, compared with deleting a file.
> Reading is about an order of magnitude faster than writing
not a native speaker, what does it mean?
Order of magnitude usually refers to a 10x difference. Two orders of magnitude would be 100x difference.
(Sometimes the phrase is casually used to just mean "a lot", but here I think they mean 10x).
An order of magnitude is for example from 10 to 100, or from 1,000 to 10,000, so typically an increase by 10x or similar.
(Very) approximately 10 times faster
Reading is about 10 times faster than writing
[dead]
* for certain operations.
Which is a bit d'oh, since being faster for some things is one of the main motivations for a database in the first place.