https://github.com/fritzy/level-foreignkeys
Add foreign key indexing to levelup.
https://github.com/fritzy/level-foreignkeys
Last synced: 6 months ago
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Add foreign key indexing to levelup.
- Host: GitHub
- URL: https://github.com/fritzy/level-foreignkeys
- Owner: fritzy
- License: mit
- Created: 2014-07-23T04:53:39.000Z (about 11 years ago)
- Default Branch: master
- Last Pushed: 2014-12-31T08:51:40.000Z (almost 11 years ago)
- Last Synced: 2025-02-01T14:15:45.842Z (8 months ago)
- Language: JavaScript
- Size: 180 KB
- Stars: 1
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# level-foreignkeys
Manage relationships between keys, and stream the results.
Deleting keys automatically cleans up their relationships.
##Full Use Example
```js
var level = require('level');
var LevelForeignKeys = require('level-foreignkeys');
var ConcatStream = require('concat-stream');
var db = LevelForeignKeys(level('./some-path.db'));
function put1() {
db.put('greeting1', 'hello', put2);
}
function put2() {
db.put('greeting2', 'hi', put3);
}
function put3() {
db.put('signoff1', 'bye', link1);
}
function link1() {
db.addForeignKey('greeting1', 'response', 'signoff1', link2);
}
function link2() {
db.addForeignKey('greeting2', 'response', 'signoff1', get1);
}
function get1() {
var results = readForeignKeys('greeting1', 'response', {});
results.pipe(new ConcatStream(function (entries) {
console.log(entries);
/*
[{key: 'signoff1', value: 'bye'}]
*/
get2();
}));
}
function get2() {
var results = readReverseForeignKeys('signoff1', 'response', {});
results.pipe(new ConcatStream(function (entries) {
console.log(entries);
/*
[{key: 'greeting1', value: 'hello'}, {key: 'greeting2': value: 'hi'}]
*/
}));
}
put1();
```
##Installing
`npm install --save level-foreignkeys`
##Running Tests
```bash
cd node_modules/level-foreignkeys
npm i
npm test
```
##Wrapping LevelUp to "Mix-in" Foreign Key Methods
```javascript
var level = require('level'); //by default, uses leveldown+levelup
var LevelForeignKeys = require('level-foreignkeys');
var db = LevelForeignKeys(level('./some-path.db'));
```
##Adding Foreign Key
__addForeignKey(key, field, foreignKey, putOptions, callback)__
Arguments:
* key: The key you want the relationship to start from.
* field: The name of the relationship type. This may represent the field in your value object. It might not. It is the name that categorizes the relationship.
* foreignKey: The key you want to link the first key to.
* putOptions: In running this function, it does several puts. Pass in the options you want to pass to those put operations.
* callback: Function called when done.
```js
db.addForeignKey(key, relationship, foreignkey, {}, function(err) {
console.log("added link from %s to %s with the field %s", key, foreignkey, relationship);
});
```
##Removing a Foreign Key
In the same way you added the foreign key, you may remove it.
__delForeignKey(key, field, foreignKey, delOoptions, callback)__
Arguments:
* key: The key you want the relationship to start from.
* field: The name of the relationship type. This may represent the field in your value object. It might not. It is the name that categorizes the relationship.
* foreignKey: The key you want to link the first key to.
* delOptions: In running this function, it does several del calls. Pass in the options you want to pass to those del operations.
* callback: Function called when done.
```js
db.delForeignKey(key, relationship, foreignkey, {}, function(err) {
if (!err) {
console.log("deleted link from %s to %s with the field %s", key, foreignkey, relationship);
}
});
```
##Streaming Foreign Keys
__readForeignKeys(key, field, opts)__
Arguments:
* key: The key you want to get the foreign keys of.
* field: The relationship category that you want.
* opts: The extra options Object that you want to merge into the `createReadStream` call that this function makes.
Returns:
A node `stream` of key/value entries that have the queried relationship.
```js
var resultStream = db.readForeinKeys('somekey', 'somerelationship', {some: 'options'});
```
##Streaming Reversed Relationships
level-foreignkeys also keeps track of the relationships in reverse with separate indexes.
Retreiving them similarly involves starting at the other end of the relationship and using `readReverseForeignKey`.
__readReverseForeignKeys(key, field, opts)__
Arguments:
* key: The foreign key from which you want to get the keys related.
* field: The relationship category that you want.
* opts: The extra options Object that you want to merge into the `createReadStream` call that this function makes.
Returns:
A node `stream` of key/value entries that have the queried relationship.
```js
var resultStream = db.readReverseForeignKeys('someforeignkey', 'somerelationship', {some: 'options'});
```