Winnow is made for applying sql to geojson in memory. It is useful for working against geojson objects but also has built-in primitives for piping streams.
Build and apply a query to a feature collection object or an array of features
const features = Object
const options = {
where: String // A sql where statement
geometry: Object // GeoJSON or Esri geometry Object
spatialPredicate: String // ST_Within || ST_Contains || ST_Intersects
fields: Array // Set of fields to select from feature properties
aggregates: Object // Describes the set of aggregations to perform on fields
groupBy: Array // Set of fields for grouping statistics
order: Array // Set of fields or aggregates by which to order results
projection: Number || String // An EPSG code, an OGC WKT or an ESRI WKT used to convert geometry
geometryPrecision: Number // number of digits to appear after decimal point for geometry
}
winnow.query(features, options)
// Returns the set of features that match the query
A sql where statement.
'Trunk_Diameter > 10'
'Trunk_Diameter > 10 AND Genus like 'Quercus%'
(Genus like '%Quercus%' OR Common_Name like '%Live Oak%') AND Street_Type like '%AVE%'
A GeoJSON or Esri Geometry Object
// GeoJSON Polygon
{
type: 'Polygon',
coordinates: [[[-118.163, 34.162], [-118.108, 34.162], [-118.108, 34.173], [-118.163, 34.173], [-118.163, 34.162]]],
}
// Esri Envelope (aka Bounding box)
{
xmin: -13155799.066536672,
ymin: 4047806.77771083,
xmax: -13143569.142011061,
ymax: 4050673.16627152,
spatialReference: {
wkid: 102100
}
}
Specifies the relationship between the passed-in geometry and the features in the data
- ST_Within: Features in the data must be completely within the passed-in geometry
- ST_Contains: Features in the data must completely contain the passed-in geometry
- ST_Intersects: Features in the data must intersect the passed-in geometry
Can also specify the esri-style predicates esriSpatialRelWithin, esriSpatialRelContains, esriSpatialRelIntersects
An array that specifies fields should be returned from each features properties or attributes. Will also accept a comma-delimited string.
e.g. [Trunk_Diameter, Common_Name, Genus]
An array that specifies aggregations to apply across all features or properties. Must specify at least a type and a field. Providing a name for the aggregation is optional
Types: [sum, avg, count, max, min, first, last]
e.g:
[
{
type: 'sum',
field: 'Trunk_Diameter',
name: 'Total_Trunk_Diameter'
},
{
type: 'avg',
field: 'Trunk_Diameter'
}
]
An array of fields used to group the results. Must be used with aggregates. Note this will not return any geometry
The total number of results to return
An array of fields use to sort the output
Can be an epsg code, an ogc wkt or an esri wkt. This parameter controls how the geometry will be projected to another coordinate system.
If true, the object returned will be an esri feature collection.
Winnow will automatically determine field types from the first feature passed in. If a given attribute is null, Winnow will assume it is a string.
You can also pass in a metadata object that describes the fields in the feature collection. This is recommended if you know your schema ahead of time
e.g.
{
type: 'FeatureCollection',
features: [],
metadata: {
fields: [
{
name: 'SomeDateField',
type: 'Date'
},
{
name: 'SomeDoubleField',
type: 'Double'
},
{
name: 'SomeIntegerField',
type: 'Integer'
},
{
name: 'SomeStringField',
type: 'String'
}
]
}
}
Returns a function that can be applied directly to a feature collection object, an array of features, or a single feature. Useful when you want to pass a stream of features through a filter.
const options = {
where: String,
geometry: Object,
spatialPredicate: String,
fields: Array,
aggregates: Array
}
const filter = winnow.prepareQuery(options)
filter(geojson)
// returns the set of feature that match the query
Execute sql directly against the query engine.
- Replace any variables with ?
- Table name should always be replaced by ?
- Non-string values always be replaced by ?
const statement = 'Select * from ? where Genus in ?'
const data = geojson
const genus = ['Quercus']
winnow.querySql(statement, [geojson, genus])
// returns all features that match the query
Pass in a statement and return a filter than can be applied to a feature collection object, an array of features or a single feature. Variables work in the same way as winnow.sql
const statement = 'Select Trunk_Diameter from ? where Trunk_Diameter > 100'
const filter = winnow.prepareSql(statement)
filter(geojson)
// returns all the features that match the query
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