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dw
csvmonkey
C++2017–2020
dw / csvmonkey

csvmonkey

Header-only vectorized, lazy-decoding, zero-copy CSV file parser

3Distinct people
6Mentions
1Explicit recommenders
102GitHub stars
REPOSITORY AT A GLANCE

What to know before exploring

What it is

Header-only vectorized, lazy-decoding, zero-copy CSV file parser

GitHub

Where it is used

No documented product use has been verified yet.

What people are saying

As much as I love SQLite, and while it is open source, it is a single implementation that AFAIK has no published open specification. The only way to read an SQLite file is…

_wmd used a recommendation phrase. One indexed comment matches. This is a phrase match, not a verdict.

No classified warning is attached to this page. Read the discussions before treating silence as approval.

Also in these discussions

No other repository is repeatedly linked in the same discussions.

This week on Hacker News

Nov 7–Nov 14 UTC · Direct repository links and separately labeled related project stories. Indexed through 11/14/2026, 12:54:37 PM UTC.

No direct repository links were found in the indexed HN discussions over the past seven days. Older discussions are available below.

Mentions over time

HN mentions by year6 dated mentions

Observed mentions: 2017-06-12 17:46:52 UTC to 2020-10-10 13:18:24 UTC.

01232017-01-01 00:00:00 UTC to 2018-01-01 00:00:00 UTC (exclusive): 1 mentions; 0 submissions, 1 comments20172018-01-01 00:00:00 UTC to 2019-01-01 00:00:00 UTC (exclusive): 3 mentions; 0 submissions, 3 comments20182019-01-01 00:00:00 UTC to 2020-01-01 00:00:00 UTC (exclusive): 1 mentions; 0 submissions, 1 comments2020-01-01 00:00:00 UTC to 2021-01-01 00:00:00 UTC (exclusive): 1 mentions; 0 submissions, 1 comments2020

Counts come from the repository’s dated source evidence. Index cutoff: 2026-11-02 08:16:59 UTC.

View mention counts and date ranges
UTC ranges include their start and exclude their end. Select a period to filter the source evidence.
PeriodStart (UTC)End (exclusive, UTC)MentionsSubmissionsComments
20172017-01-01 00:00:00 UTC2018-01-01 00:00:00 UTC101
20182018-01-01 00:00:00 UTC2019-01-01 00:00:00 UTC303
20192019-01-01 00:00:00 UTC2020-01-01 00:00:00 UTC101
20202020-01-01 00:00:00 UTC2021-01-01 00:00:00 UTC101

What Hacker News says

6 sources
The parser from the article's performance is closer to 360mb/sec, the 2gb/sec is only achieved by over-allocating an incredible amount of hardware. CSV parsing is such a simple problem there is no reason to waste a whole machine on it, and in many contemporary scenarios (AWS Lambda), it's simply not possible to waste a whole machine on it. I never finished packaging and writing tests, but https://github.com/dw/csvmonkey hits 1.9gb/sec on certain data sets with one thread, and that implementation is not even representative of the limits of single thread performance. https://github.com/geofflangdale/simdcsv follows a similar approach to simdjson, where multiple passes over the input are used, but with lower latency vector instructions (csvmonkey used one of the slowest). Character set decoding is also fused into the parser. There are no ben
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chmarks published in that repo, but I expect the approach trounces my effort even if the current implementation doesn't. Why be satisfied saturating one NVMe drive when a few threads could saturate the PCIe bus instead?
In Loading CSV File at the Speed Limit of the NVMe Storage
I can't speak for this project, but my own for CSV files ( https://github.com/dw/csvmonkey ) provides a high level interface that allows the tokenized data to be manipulated in-place without full decoding. The interface exported in Python is that of a plain old dictionary with one added magical semantic (lazy decode on element access). The internal representation of the parse result is a simple fixed array of (ptr, size) pairs Methods like this are used for batch search / summation where only a fraction of the parsed data is actually relevant during any particular run. You'll find similar approaches used in e.g. the row format parser of a database like MongoDB or Postgres
In Simdjson – Parsing Gigabytes of JSON per Second
_wmd·Dec 25, 2018Recommendation phrase
As much as I love SQLite, and while it is open source, it is a single implementation that AFAIK has no published open specification. The only way to read an SQLite file is using SQLite, and in that respect, it is for many users just as closed as wrapping something in a word document. CSV isn't perfect, but it provides a ton of flexibility, for example, CSVs can be streamed or support parallel segmented download across a network with useful work possible during the transfer. The format is so simple that it can approach almost free to parse (see e.g. my own https://github.com/dw/csvmonkey ). CSV is also distinguished in that regular home users with spreadsheet programs can usually do most things a developer can do with the same file. For me user empowerment trumps all other goals in software, including warts. Things like JSON, XML or SQLite
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definitely don't fit in that category, although I guess SQLite is at least better due to the wide availability of decent GUIs for it. Finally as a data transfer format, SQLite has the potential to be massively inefficient. Done incorrectly it can ship useless indexes that can inflate size >100%, and even in the absence of those, depending on how amenable the data is to being stored in a btree and the access patterns used to insert it, can leave tons of wasted space inside the file, or AFAIK even chunks of previously deleted data.
In SQLite as an Application File Format (2014)
I'm not "making a claim" or inventing a heuristic, you can test this trivially: $ git clone https://....:x-oauth-basic@github.com/dw/csvmonkey.git Cloning into 'csvmonkey'... remote: Counting objects: 340, done. remote: Compressing objects: 100% (27/27), done. remote: Total 340 (delta 19), reused 27 (delta 10), pack-reused 303 Receiving objects: 100% (340/340), 138.93 KiB | 0 bytes/s, done. Resolving deltas: 100% (212/212), done. $ cat csvmonkey/.git/logs/HEAD 0000000000000000000000000000000000000000 c9d566bf167dcf3556008df58be37c4a27ff5062 David Wilson <dw@botanicus.net> 1497289486 +0100 clone: from https://....:x-oauth-basic@github.com/dw/csvmonkey.git If you perform a Git checkout on a web server e.g. as part of an Ansible script, and you embedded secrets in the repo URL (common enough, believe me)
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, then that secret is readable per above. FWIW this isn't some unbelievable theory or hypothetical scenario, I've seen plenty of Ansible setups like this and found domains with this exact problem in the process of writing http://pythonsweetness.tumblr.com/post/52587443706/devs-plea... a few years back
In Don't publicly expose .git (2015)

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