groue
Joined 15 years ago
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Dec 2
[ my public key: https://keybase.io/groue; my proof: https://keybase.io/groue/sigs/knREShdojU_VyeRJ_ykxWtiYquBB3txRSZW2yAi4uAg ]
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Comment · 9 months ago
Gentium is a very beautiful font: https://software.sil.org/gentium/
Comment · 1 year ago
You are not your code.
Comment · 1 year ago
Yes. GRDB encourages Codable because the user can profit from the code generated by the compiler, and this implies that database values are accessed by column name, on top of the Codable runtime, and those layers have a high cost. When necessary it is possible to access database values by position, and in this case GRDB achieves speed of light (performance nearly identical as raw SQLite).
Comment · 1 year ago
You're welcome :)
Comment · 1 year ago
Thank you (GRDB author here).
It is not mentioned in the README of the repository, but SQLiteData wraps GRDB to access the database and get notified of database changes (the meat and butter).
GRDB is by itself a solid "toolkit for SQLite databases, with a focus on application development", with both high levels APIs for everyday coding, and expert SQLite features for the demanding developers. Many apps rely on GRDB alone.
Comment · 2 years ago
Out of curiosity, I asked on the SQLite forum how the query optimizer fits in this schema: https://sqlite.org/forum/forumpost/93f9bfcec0
Comment · 4 years ago
I do, for JSON columns. I store UTF8 strings in SQLite, so that it is easy to see JSON values with a plain `SELECT *`). And I load blobs, because I code in Swift and the standard JSON decoder eats raw UTF8 memory buffers, not strings.
This avoids two useless conversions:
- first from a C string loaded from SQLite to a Swift Unicode string (with UTF8 validation).
- next from this Swift Unicode string to a UTF8 memory buffer (so that JSONDecoder can do its job).
SQLite is smart enough to strip the trailing \0 when you load a blob from a string stored in the database :-)
Comment · 4 years ago
Yes. Now, many short writes look exactly as one very long write from the point of view of an enqueued write that is waiting for its turn :-) I don't quite remember how fair is SQLite scheduling, in practice.
Comment · 4 years ago
What's cool with WAL mode is that SQLITE_BUSY won't happen for readers (except very rare scenarios: https://www.sqlite.org/wal.html#sometimes_queries_return_sql...)
One should only expect SQLITE_BUSY for writes (if a writer is already holding the lock, and the busy timeout expires before the other writer releases the lock). So yes, prefer short writes, or adjust your timeout. Generally speaking, SQLITE_BUSY can not be 100% prevented for writes.
Comment · 4 years ago
It is always safe, and by "safe" I mean "safe for data". You won't have to deal with data corruption. Precisely, see "How To Corrupt An SQLite Database File": https://www.sqlite.org/howtocorrupt.html
Now concurrent accesses from different processes/connections can lead to runtime errors (SQLITE_BUSY), because the database happens to be locked by one connection.
Those errors are greatly reduced by the WAL mode (https://sqlite.org/wal.html) which provides ultra-robust single-writer/multiple-readers semantics:
- Writes can not happen concurrently (SQLITE_BUSY).
- One can reduce the occurrences of such SQLITE_BUSY errors by using a built-in timeout (https://www.sqlite.org/c3ref/busy_timeout.html).
- Several reads can happen concurrently, including with writers.
- A writer connection can enter the "Serializable" isolation level.
- A reader connection can enter the "Snapshot Isolation" level.
For more details, see https://www.sqlite.org/isolation.html
During all the years I've been developing the GRDB library (https://github.com/groue/GRDB.swift), I could never see SQLite fail its documented guarantees. This made it possible to build one of the most concurrency-focused SQLite toolkit for Swift, and I'm pretty happy with it (https://github.com/groue/GRDB.swift/blob/master/Documentatio...).
Comment · 4 years ago
The music is quite good! The covers of Freddie Freeloader and Flamenco Sketches are quite worth it, IMHO :-)
Comment · 4 years ago
Library author here - SQLite concurrency needs a little care: don't miss the Concurrency Guide: https://github.com/groue/GRDB.swift/blob/master/Documentatio...
Comment · 5 years ago
You can try https://github.com/groue/GRDB.swift
It's a thin wrapper around SQLite, with convenience APIs for record types, robust support for concurrency, and a focus on GUI apps.