Baguette/dodb.cr
3
0
Fork 1
Code Issues Pull Requests Releases Wiki Activity

README: talk a bit more about the limits of DODB.

Browse Source
This commit is contained in:
Philippe PITTOLI 2024-05-04 20:14:47 +02:00
parent 9fed7145e5
commit f2a76c288e
1 changed files with 31 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

36
README.md
View File

@ -13,16 +13,42 @@ A brief summary:
- no SQL
- objects are serialized (currently in JSON)
- indexes (simple symlinks on the FS) can be created to improve significantly searches in the db
- db is fully integrated in the language (basically a simple array with a few more functions)
Also, data can be `cached`.
The entire base will be kept in memory (if you can), enabling incredible speeds.
## Limitations
**TODO**: speed tests, elaborate on the matter.
DODB doesn't fully handle ACID properties:
DODB is not compatible with projects:
- having an absolute priority on speed,
however, DODB is efficient in most cases with the right indexes.
- having relational data
- no *atomicity*, you can't chain instructions and rollback if one of them fails ;
- no *consistency*, there is currently no mechanism to prevent adding invalid values ;
*Isolation* is partially taken into account, with a locking mechanism preventing a few race conditions.
FYI, in my projects the database is fast enough so I don't even need parallelism (like, by far).
*Durability* is taken into account.
Data is written on-disk each time it changes.
**NOTE**: what I need is mostly there.
What DODB doesn't provide, I hack it in a few lines in my app.
DODB will provide some form of atomicity and consistency at some point, but nothing fancy nor too advanced.
The whole point is to keep it simple.
## Speed
Since DODB doesn't use SQL and doesn't even try to handle stuff like atomicity or consistency, speed is great.
Reading data from disk takes about a few dozen microseconds, and not much more when searching an indexed data.
**On my more-than-decade-old, slow-as-fuck machine**, the simplest possible SQL request to Postgres takes about 100 to 900 microseconds.
To reach a data on-disk: 13 microseconds.
To reach a data that is indexed: same thing, 13 microseconds, since it's just a link.
With the `cached` version of DODB, there is not even deserialization happening, so 7 nanoseconds.
**NOTE:** of course SQL and DODB cannot be fairly compared based on performance since they don't have the same properties.
But still, this is the kind of speed you can get with the tool.
# Installation