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Add h3_cell_to_latlng #3

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merged 2 commits into from
Oct 25, 2022
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Add h3_cell_to_latlng #3

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128e0cb
Add h3_cell_to_latlng
Oct 14, 2022
43644fe
Update src/main/java/com/foursquare/presto/h3/CellToLatLngFunction.java
Oct 25, 2022
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37 changes: 37 additions & 0 deletions src/main/java/com/foursquare/presto/h3/CellToLatLngFunction.java
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Original file line number Diff line number Diff line change
@@ -0,0 +1,37 @@
package com.foursquare.presto.h3;

import static com.facebook.presto.common.type.DoubleType.DOUBLE;

import com.facebook.presto.common.block.Block;
import com.facebook.presto.common.block.BlockBuilder;
import com.facebook.presto.common.type.StandardTypes;
import com.facebook.presto.spi.function.Description;
import com.facebook.presto.spi.function.ScalarFunction;
import com.facebook.presto.spi.function.SqlNullable;
import com.facebook.presto.spi.function.SqlType;
import com.uber.h3core.util.LatLng;

/**
* Wraps {@link com.uber.h3core.H3Core#cellToLatLng(long)}. Produces a row of latitude, longitude
* degrees.
*/
public final class CellToLatLngFunction {
@ScalarFunction(value = "h3_cell_to_latlng")
@Description("Convert H3 index to degrees lat/lng")
@SqlNullable
@SqlType("ARRAY(DOUBLE)")
public static Block latLngToCell(@SqlType(StandardTypes.BIGINT) long h3) {
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try {
LatLng latLng = H3Plugin.h3.cellToLatLng(h3);
// TODO: It would be nice to return this as a ROW(lat DOUBLE, lng DOUBLE)
// but that is blocked on https://github.com/prestodb/presto/issues/18494
// (determining how to build the Block to return)
BlockBuilder blockBuilder = DOUBLE.createFixedSizeBlockBuilder(2);
DOUBLE.writeDouble(blockBuilder, latLng.lat);
DOUBLE.writeDouble(blockBuilder, latLng.lng);
return blockBuilder.build();
} catch (Exception e) {
return null;
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For my info: Is it faster to catch the exception, or faster to validate the input?

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Catching exceptions is generally very slow. uber/h3-java#107 tracks adding a no-throw API for performance.

}
}
}
2 changes: 1 addition & 1 deletion src/main/java/com/foursquare/presto/h3/H3Plugin.java
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Original file line number Diff line number Diff line change
Expand Up @@ -33,7 +33,7 @@ static int longToInt(long l) {
@Override
public Set<Class<?>> getFunctions() {
return ImmutableSet.<Class<?>>builder()
.add(LatLngToCellFunction.class, CellToParentFunction.class)
.add(LatLngToCellFunction.class, CellToLatLngFunction.class, CellToParentFunction.class)
.build();
}
}
34 changes: 34 additions & 0 deletions src/test/java/com/foursquare/presto/h3/CellToLatLngFunctionTest.java
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package com.foursquare.presto.h3;

import static com.foursquare.presto.h3.H3PluginTest.assertQueryResults;
import static com.foursquare.presto.h3.H3PluginTest.createQueryRunner;

import com.facebook.presto.testing.QueryRunner;
import com.google.common.collect.ImmutableList;
import java.util.Collections;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.TestInstance;
import org.junit.jupiter.api.TestInstance.Lifecycle;

@TestInstance(Lifecycle.PER_CLASS)
public class CellToLatLngFunctionTest {
@Test
public void testCellToLatLng() {
try (QueryRunner queryRunner = createQueryRunner()) {
assertQueryResults(
queryRunner,
"SELECT h3_cell_to_latlng(578536630256664575)",
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Nit: Does Presto support any hexidecimal syntax? In general I think we should prefer human-readable cell indexes in tests if possible (easier to debug, etc).

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@isaacbrodsky isaacbrodsky Oct 25, 2022 •
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I'm not aware of a way to embed a hex literal integer in Presto SQL. (You could use a string literal and from_base)

ImmutableList.of(
ImmutableList.of(ImmutableList.of(2.300882111626747, -5.245390296777327))));

assertQueryResults(
queryRunner,
"SELECT h3_cell_to_latlng(null)",
ImmutableList.of(Collections.singletonList(null)));
assertQueryResults(
queryRunner,
"SELECT h3_cell_to_latlng(-1)",
ImmutableList.of(Collections.singletonList(null)));
}
}
}