Install

TODO: make this a real python module and such

For now, I'm just using the following command to play with it in SQL form

rm tags.db && sqlite3 tags.db < schema.sql && sqlite3 tags.db < insert_sample_data.sql

Usage

No Python stuff now, I'm just trying to get some good SQL here

sqlite3 tags.db < sample_queries.sql

Rebuild the db and run the test on save with the help of the run script!

git ls-files | entr -cs 'bash run.sh'

General Ideas

Query language:

This is a standard set based query language with the following operators adapted from C's. The following are assumed to be querying items with tags (though the reverse could also be true).

A lot of this is taken from https://docs.python.org/3/library/stdtypes.html#set Note that I'm special-casing the unary "not in set" operator (~) because it's the only unary operator. TODO: add parens to this

<expr> = tag | <expr> <op> <expr> | ~ tag
<op> = & | \|   # The backslash is to escape the pipe (it's an operator)

& denotes set intersection (i.e. the item has all tags separated by it)
| denotes set union (i.e. the item has at least one tag)

TODO: work on precedence rules...

Examples (assuming, once again, that we're querying the tags on the items)

I need parens here...

Query: country & rock
Explanation: find all items with the tags country and rock
Python list expression:

[i for i in items if 'country' in i.tags and 'rock' in i.tags]

Query: country & ~ rock
Explanation: find all items with the tags country but no rock
Python list expression:

[i for i in items if 'country' in i.tags and 'rock' not in i.tags]

Query: country & (rock | blues)
Explanation: find all items with the tags country and either a rock or a blues tag (or both)
Python list expression:

[i for i in items if 'country' in i.tags and ('rock' in i.tags or 'blues' in i.tags)]

NOTE: could I get all of this just by using SQLAlchemy?

Schema

paste into https://app.quickdatabasediagrams.com

item
-
id PK int
name text

tag
-
id PK int
name text

item_tag
-
tag_id PK int FK >- tag.id
item_id PK int FK >- item.id

bbkane/tags