lodash-joins
Advanced tools
A library providing join algorithms for JavaScript Arrays. LoDash is the only dependency and this library appends itself as an extension to that library.
Lodash already supports some standard SQL-like features:
Limit and offset can be accomplished using Array.slice.
These functions only work on arrays of objects (comparable to database rows). Key comparisons are coercive, so Dates should work as well.
For merge-type joins, a merger function may be provided to customize the output array. By default, all joined rows are generated from
LoDash's assign function:
_.assign({}, leftRow, rightRow);
A merger function takes both the left and right record and provides a new output record. The left or right record may be
null in cases like outer joins which do not have matching row keys.
Order of the output is indeterminate.
Each join function accepts two arrays and two accessor functions for each array that will act as the pluck function for key comparison.
_.joinFunction(leftArray, leftKeyAccessor, rightArray, rightKeyAccessor, merger);
> var _ = require('index.js');
> var left = [
... {id: 'c', left: 0},
... {id: 'c', left: 1},
... {id: 'e', left: 2},
... ],
... right = [
... {id: 'a', right: 0},
... {id: 'b', right: 1},
... {id: 'c', right: 2},
... {id: 'c', right: 3},
... {id: 'd', right: 4},
... {id: 'f', right: 5},
... {id: 'g', right: 6}
... ],
... accessor = function (obj) {
... return obj['id'];
... };
>
> var a = _.hashInnerJoin(left, accessor, right, accessor);
undefined
> a
[ { id: 'c', left: 0, right: 2 },
{ id: 'c', left: 1, right: 2 },
{ id: 'c', left: 0, right: 3 },
{ id: 'c', left: 1, right: 3 } ]
>
> var b = _.nestedLoopLeftOuterJoin(left, accessor, right, accessor);
undefined
> b
[ { id: 'c', left: 0, right: 2 },
{ id: 'c', left: 0, right: 3 },
{ id: 'c', left: 1, right: 2 },
{ id: 'c', left: 1, right: 3 },
{ id: 'e', left: 2 } ]
>
> var c = _.sortedMergeFullOuterJoin(left, accessor, right, accessor);
undefined
> c
[ { id: 'a', right: 0 },
{ id: 'b', right: 1 },
{ id: 'c', left: 0, right: 2 },
{ id: 'c', left: 0, right: 3 },
{ id: 'c', left: 1, right: 2 },
{ id: 'c', left: 1, right: 3 },
{ id: 'd', right: 4 },
{ id: 'e', left: 2 },
{ id: 'f', right: 5 },
{ id: 'g', right: 6 } ]
The main file for npm point to a Webpack build that includes the necessary
babel-regenerator-runtime functions to properly execute the script.
The npm module still includes the index.js file and lib directory to require the functions independently, but you
are on your own to install babel as well and invoke the runtime beforehand.
A simple way to do this is:
$ npm install --save babel
$ node
> require('@babel/runtime');
> var hashLeftOuterJoin = require('lodash-joins/lib/hash/hashLeftOuterJoin');
It's likely better to just use the library as intended. :smile:
Tested using Jasmine and Karma. See the /spec directory. There is also a browser test invoked through
Webpack and Mocha.
Typically for the Inner & Outer joins, with larger arrays stick with the Sorted Merge, then Hash, then Nested. With the Anti & Semi joins, Nested can out perform when there is a small cardinality of keys, but Hash may be more efficient since only one of the Arrays needs to be hashed.
Tests were run using Node v5.3.0.
Each suite performs three joins on randomly generated arrays with string keys. The sizes 'Large', 'Medium' and 'Small' correlate to the size of the join arrays being used, i.e. 1000, 100, 10 respectively.
Running suite Full Outer Joins Large...
Fastest test is Sorted Merge Join at 3.2x faster than Hash Join
Running suite Full Outer Joins Medium...
Fastest test is Hash Join at 1.11x faster than Sorted Merge Join
Running suite Full Outer Joins Small...
Fastest test is Hash Join at 1.45x faster than Nested Loop Join
Running suite Inner Joins Large...
Fastest test is Sorted Merge Join at 3.4x faster than Nested Loop Join
Running suite Inner Joins Medium...
Fastest test is Hash Join at 1.12x faster than Sorted Merge Join
Running suite Inner Joins Small...
Fastest test is Hash Join at 1.54x faster than Nested Loop Join
Running suite Left Anti Joins Large...
Fastest test is Hash Join at 1.38x faster than Nested Loop Join
Running suite Left Anti Joins Medium...
Fastest test is Hash Join at 1.38x faster than Nested Loop Join
Running suite Left Anti Joins Small...
Fastest test is Nested Loop Join at 1.06x faster than Hash Join
Running suite Left Outer Joins Large...
Fastest test is Sorted Merge Join at 3.6x faster than Nested Loop Join
Running suite Left Outer Joins Medium...
Running suite Left Outer Joins Small...
Fastest test is Hash Join at 1.60x faster than Nested Loop Join
Running suite Left Semi Joins Large...
Fastest test is Hash Join at 1.41x faster than Nested Loop Join
Running suite Left Semi Joins Medium...
Fastest test is Hash Join at 1.84x faster than Nested Loop Join
Running suite Left Semi Joins Small...
Fastest test is Hash Join at 1.22x faster than Nested Loop Join
FAQs
SQL-like joins for JS
We found that lodash-joins demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 1 open source maintainer collaborating on the project.
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