README
¶
go-writer-geoparquet
GeoParquet support for the writer/go-writer/v3 Writer interface.
Example
Error handling removed for the sake of brevity.
import (
"context"
"os"
"github.com/whosonfirst/go-writer/v3"
_ "github.com/whosonfirst/go-writer-geoparquet/v3"
)
func main() {
ctx := context.Background()
geojson_r, _ := os.Open("/path/to/feature.geojson")
defer geojson_r.Close()
wr, _ := writer.NewWriter(ctx, "geoparquet:///path/to/database.geoparquet")
wr.Write(ctx, "key", geojson_r)
wr.Close(ctx)
}
Have a look at geoparquet_test.go for a complete example of how to use the package.
If you are just looking for something to create a GeoParquet file from one or more Who's On First data repositories, take a look at the whosonfirst/wof-cli emit tool.
How does it work?
First of all, this writer only works with GeoJSON Feature records.
For each Feature record passed to the Write() method the code will:
- Derive a
whosonfirst/gpq-fork/not-internal/geo.Featureinstance. - Derive a
whosonfirst/go-whosonfirst-spr/v2.StandardPlaceResponseinstance and convert it to amap[string]any. - Append any additional properties defined in the constructor URI (details below) to the SPR map.
- Assign the SPR map to the
geo.Featureinstance'sPropertiesproperty. - Write the the
geo.Featureinstance to the underlying GeoParquet database.
URIs
go-writer-geoparquet URIs take the form of:
geoparquet://{PATH}?{PARAMETERS}
Where {PATH} is a valid path on disk where the final GeoParquet database will be written to. If {PATH} is empty then data will be written to STDOUT.
Valid paramters are:
| Name | Value | Default | Notes |
|---|---|---|---|
| min | int | 10 | Minimum number of features to consider when building a (GeoParquet) schema. |
| max | int | 100 | Maximum number of features to consider when building a (GeoParquet) schema. |
| compression | string | zstd | Parquet compression to use. Possible values: uncompressed, snappy, gzip, brotli, zstd. |
| row-group-length | int | 10 | Maximum number of rows per group when writing Parquet data. |
| append-property | string | Zero or more relative properties to append to the initial SPR instance (derived from the original GeoJSON Feature) before adding it to the GeoParquet database. |
Important
This package uses a hard fork of the planetlabs/gpq package in order to expose functions for writing GeoParquet files.
See also
Documentation
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Index ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
Types ¶
type GeoParquetWriter ¶
type GeoParquetWriter struct {
writer.Writer
// contains filtered or unexported fields
}
GeoParquetWriter implements the `writer.Writer` interface for writing GeoParquet records.
func (*GeoParquetWriter) Close ¶
func (gpq *GeoParquetWriter) Close(ctx context.Context) error
Close will close the underlying GeoParquet database.
func (*GeoParquetWriter) Write ¶
func (gpq *GeoParquetWriter) Write(ctx context.Context, key string, r io.ReadSeeker) (int64, error)
Write derives a `whosonfirst/go-whosonfirst-spr/v2.StandardPlaceResponse` and `whosonfirst/gpq-fork/not-internal/geo.Feature` instances from 'r' assigning the former to the latter's `Properties` element and then writes the feature to a GeoParquet database defined in the constructor.
Source Files