diff --git a/knowledgebase/importing-geojason-with-nested-object-array.md b/knowledgebase/importing-geojason-with-nested-object-array.md new file mode 100644 index 00000000000..0ec0479d475 --- /dev/null +++ b/knowledgebase/importing-geojason-with-nested-object-array.md @@ -0,0 +1,222 @@ +--- +title: Importing GeoJSON with a deeply nested object array +description: “Importing GeoJSON with a deeply nested object array“ +date: 2024-12-18 +--- + +# Importing GeoJSON with a deeply nested object array + +### Question +How do I import GeoJSON with a nested object array? + +### Answer +For this tutorial, we will use open data publicly available [here](https://opendata.esri.es/datasets/ComunidadSIG::municipios-ign/explore?location=39.536006%2C-0.303882%2C6.57). + +1. Download the data in GeoJSON format and rename the file to `geojson.json`. +2. Understand the structure. + +```sql +DESCRIBE TABLE file('geojson.json', 'JSON') +┌─name─────┬─type─────────────────────────────────────────────────────────────────────────────────────────┐ +│ type │ Nullable(String) │ +│ name │ Nullable(String) │ +│ crs │ Tuple( properties Tuple(name Nullable(String)),type Nullable(String)) │ +│ features │ Array(Tuple( │ +│ │ geometry Tuple(coordinates Array(Array(Array(Array(Nullable(Float64))))), │ +│ │ type Nullable(String)), │ +│ │ properties Tuple( CODIGOINE Nullable(String), │ +│ │ CODNUT1 Nullable(String), │ +│ │ CODNUT2 Nullable(String), │ +│ │ CODNUT3 Nullable(String), │ +│ │ FID Nullable(Int64), │ +│ │ INSPIREID Nullable(String), │ +│ │ NAMEUNIT Nullable(String), │ +│ │ NATCODE Nullable(String), │ +│ │ SHAPE_Area Nullable(Float64), │ +│ │ SHAPE_Length Nullable(Float64) │ +│ │ ), │ +│ │ type Nullable(String) │ +│ │ ) │ +│ │ ) │ +└──────────┴──────────────────────────────────────────────────────────────────────────────────────────────┘ +``` +3. Create a table to store the GeoJSON rows. + +The requirement here is to generate a row for each `object` in the `features array`. +The data type inferred for the field `geometry` suggests that it translates to ClickHouse's **MultiPolygon** [data type](https://clickhouse.com/docs/en/sql-reference/data-types/geo#multipolygon). + +```sql +create table geojson +( + type String, + name String, + crsType String, + crsName String, + featureType String, + id Int64, + inspiredId String, + natCode String, + nameUnit String, + codNut1 String, + codNut2 String, + codNut3 String, + codigoIne String, + shapeLength Float64, + shapeArea Float64, + geometryType String, + geometry MultiPolygon +) +engine = MergeTree +order by id; +``` + +4. Prepare the data. +The main purpose of the query is to verify that we obtain one row for each **object** in the **features array**. + +>The field `features.geometry.coordinates` is commented to make the result set more readable. + +```sql +SELECT + type AS type, + name AS name, + crs.type AS crsType, + crs.properties.name AS crsName, + features.type AS featureType, + features.properties.FID AS id, + features.properties.INSPIREID AS inspiredId, + features.properties.NATCODE AS natCode, + features.properties.NAMEUNIT AS nameUnit, + features.properties.CODNUT1 AS codNut1, + features.properties.CODNUT2 AS codNut2, + features.properties.CODNUT3 AS codNut3, + features.properties.CODIGOINE AS codigoIne, + features.properties.SHAPE_Length AS shapeLength, + features.properties.SHAPE_Area AS shapeArea, + features.geometry.type AS geometryType + --,features.geometry.coordinates +FROM file('municipios_ign.geojson', 'JSON') +ARRAY JOIN features +LIMIT 5 + +┌─type──────────────┬─name───────────┬─crsType─┬─crsName───────────────────────┬─featureType─┬─id─┬─inspiredId───────────────┬─natCode─────┬─nameUnit──────────────┬─codNut1─┬─codNut2─┬─codNut3─┬─codigoIne─┬────────shapeLength─┬─────────────shapeArea─┬─geometryType─┐ +│ FeatureCollection │ Municipios_IGN │ name │ urn:ogc:def:crs:OGC:1.3:CRS84 │ Feature │ 1 │ ES.IGN.SIGLIM34081616266 │ 34081616266 │ Villarejo-Periesteban │ ES4 │ ES42 │ ES423 │ 16266 │ 0.2697476997304121 │ 0.0035198414406406673 │ MultiPolygon │ +│ FeatureCollection │ Municipios_IGN │ name │ urn:ogc:def:crs:OGC:1.3:CRS84 │ Feature │ 2 │ ES.IGN.SIGLIM34081616269 │ 34081616269 │ Villares del Saz │ ES4 │ ES42 │ ES423 │ 16269 │ 0.4476083901269905 │ 0.00738179315030249 │ MultiPolygon │ +│ FeatureCollection │ Municipios_IGN │ name │ urn:ogc:def:crs:OGC:1.3:CRS84 │ Feature │ 3 │ ES.IGN.SIGLIM34081616270 │ 34081616270 │ Villarrubio │ ES4 │ ES42 │ ES423 │ 16270 │ 0.3053942273994179 │ 0.0029777582813496337 │ MultiPolygon │ +│ FeatureCollection │ Municipios_IGN │ name │ urn:ogc:def:crs:OGC:1.3:CRS84 │ Feature │ 4 │ ES.IGN.SIGLIM34081616271 │ 34081616271 │ Villarta │ ES4 │ ES42 │ ES423 │ 16271 │ 0.2831226979821184 │ 0.002680273189024594 │ MultiPolygon │ +│ FeatureCollection │ Municipios_IGN │ name │ urn:ogc:def:crs:OGC:1.3:CRS84 │ Feature │ 5 │ ES.IGN.SIGLIM34081616272 │ 34081616272 │ Villas de la Ventosa │ ES4 │ ES42 │ ES423 │ 16272 │ 0.5958276749246777 │ 0.015354885085133583 │ MultiPolygon │ +└───────────────────┴────────────────┴─────────┴───────────────────────────────┴─────────────┴────┴──────────────────────────┴─────────────┴───────────────────────┴─────────┴─────────┴─────────┴───────────┴────────────────────┴───────────────────────┴──────────────┘ +``` + +5. Insert the data. + +```sql +INSERT INTO geojson +SELECT + type AS type, + name AS name, + crs.type AS crsType, + crs.properties.name AS crsName, + features.type AS featureType, + features.properties.FID AS id, + features.properties.INSPIREID AS inspiredId, + features.properties.NATCODE AS natCode, + features.properties.NAMEUNIT AS nameUnit, + features.properties.CODNUT1 AS codNut1, + features.properties.CODNUT2 AS codNut2, + features.properties.CODNUT3 AS codNut3, + features.properties.CODIGOINE AS codigoIne, + features.properties.SHAPE_Length AS shapeLength, + features.properties.SHAPE_Area AS shapeArea, + features.geometry.type AS geometryType, + features.geometry.coordinates as geometry +FROM file('municipios_ign.geojson', 'JSON') +ARRAY JOIN features +``` +Here, we get the following error: +>Received exception from server (version 24.1.2): +Code: 53. DB::Exception: Received from localhost:9000. DB::Exception: ARRAY JOIN requires array or map argument. (TYPE_MISMATCH) + +This is caused by the parsing of `features.geometry.coordinates`. + +6. Let's check its data type. + +``` sql +SELECT DISTINCT toTypeName(features.geometry.coordinates) AS geometry +FROM file('municipios_ign.geojson', 'JSON') +ARRAY JOIN features + +┌─geometry──────────────────────────────────────┐ +│ Array(Array(Array(Array(Nullable(Float64))))) │ +└───────────────────────────────────────────────┘ +``` + +It can be fixed by casting `multipolygon.properties.coordinates` to `Array(Array(Array(Tuple(Float64,Float64))))`. +To do so, we can use the function [arrayMap(func,arr1,...)](https://clickhouse.com/docs/en/sql-reference/functions/array-functions#arraymapfunc-arr1-). + +```sql +SELECT distinct + toTypeName( + arrayMap(features.geometry.coordinates-> + arrayMap(features.geometry.coordinates-> + arrayMap(features.geometry.coordinates-> (features.geometry.coordinates[1],features.geometry.coordinates[2]) + ,features.geometry.coordinates), + features.geometry.coordinates), + features.geometry.coordinates) + ) as toTypeName +FROM file('municipios_ign.geojson', 'JSON') +ARRAY JOIN features; + +┌─toTypeName───────────────────────────────────────────────────────┐ +│ Array(Array(Array(Tuple(Nullable(Float64), Nullable(Float64))))) │ +└──────────────────────────────────────────────────────────────────┘ +``` + +7. Insert the data. + +```sql +INSERT INTO geojson +SELECT + type as type, + name as name, + crs.type as crsType, + crs.properties.name as crsName, + features.type as featureType, + features.properties.FID id, + features.properties.INSPIREID inspiredId, + features.properties.NATCODE natCode, + features.properties.NAMEUNIT nameUnit, + features.properties.CODNUT1 codNut1, + features.properties.CODNUT2 codNut2, + features.properties.CODNUT3 codNut3, + features.properties.CODIGOINE codigoIne, + features.properties.SHAPE_Length shapeLength, + features.properties.SHAPE_Area shapeArea, + features.geometry.type geometryType, + arrayMap(features.geometry.coordinates-> + arrayMap(features.geometry.coordinates-> + arrayMap(features.geometry.coordinates-> (features.geometry.coordinates[1],features.geometry.coordinates[2]),features.geometry.coordinates) + ,features.geometry.coordinates) + ,features.geometry.coordinates) geometry +FROM file('municipios_ign.geojson', 'JSON') +ARRAY JOIN features; +``` + +```sql +SELECT count() +FROM geojson + +┌─count()─┐ +│ 8205 │ +└─────────┘ + +SELECT DISTINCT toTypeName(geometry) +FROM geojson + +┌─toTypeName(geometry)─┐ +│ MultiPolygon │ +└──────────────────────┘ +``` + +### Conclusion +Handling JSON can result in a complex task. This tutorial addressed a scenario where a nested object array could make this task even more difficult. +For any other JSON-related requirements, please refer to our [documentation](https://clickhouse.com/docs/en/integrations/data-formats/json). \ No newline at end of file