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Merged
arhimondr merged 2 commits into from
Mar 11, 2020
Merged

Add cast bingtile to/from bigint #14125

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9a3758c
Add BingTile cast to/from bigint
jagill Feb 20, 2020
cae98f9
Improve entropy for bing tile bigint encoding
jagill Feb 20, 2020
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10 changes: 9 additions & 1 deletion presto-docs/src/main/sphinx/functions/geospatial.rst
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Expand Up @@ -456,7 +456,15 @@ Bing Tiles

These functions convert between geometries and
`Bing tiles <https://msdn.microsoft.com/en-us/library/bb259689.aspx>`_. For
Bing tiles, ``x`` and ``y`` refer to ``tile_x`` and ``tile_y``.
Bing tiles, ``x`` and ``y`` refer to ``tile_x`` and ``tile_y``. Bing Tiles
can be cast to and from BigInts, using an internal representation that encodes
the ``zoom``, ``x``, and ``y`` efficiently::

cast(cast(tile AS BIGINT) AS BINGTILE)

While every tile can be cast to a bigint, casting from a bigint that does not
represent a valid tile will raise an exception.


.. function:: bing_tile(x, y, zoom_level) -> BingTile

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39 changes: 33 additions & 6 deletions presto-geospatial/src/main/java/com/facebook/presto/plugin/geospatial/BingTile.java
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Expand Up @@ -16,16 +16,24 @@
import com.facebook.presto.spi.PrestoException;
import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.google.common.annotations.VisibleForTesting;

import java.util.Objects;

import static com.facebook.presto.spi.StandardErrorCode.INVALID_FUNCTION_ARGUMENT;
import static com.google.common.base.MoreObjects.toStringHelper;
import static com.google.common.base.Preconditions.checkArgument;
import static java.lang.String.format;

public final class BingTile
{
public static final int MAX_ZOOM_LEVEL = 23;
@VisibleForTesting
static final int VERSION_OFFSET = 63 - 5;
private static final int VERSION = 0;
private static final int BITS_23 = (1 << 24) - 1;
private static final int BITS_5 = (1 << 6) - 1;
private static final int ZOOM_OFFSET = 31 - 5;

private final int x;
private final int y;
Expand Down Expand Up @@ -148,19 +156,38 @@ public String toQuadKey()
}

/**
* Encodes Bing tile as a 64-bit long: 23 bits for X, followed by 23 bits for Y,
* followed by 5 bits for zoomLevel
* Encodes Bing tile as a 64-bit long:
* Version (5 bits), 0 (4 bits), x (23 bits), Zoom (5 bits), 0 (4 bits), y (23 bits)
* (high bits left, low bits right).
*
* This arrangement maximizes low-bit entropy for the Java long hash function.
*/
public long encode()
{
return (((long) x) << 28) + (y << 5) + zoomLevel;
// Java's long hash function just XORs itself right shifted 32.
// This is used for bucketing, so if you have 2^k buckets, this only
// keeps the k lowest bits. This puts the highest entropy bits
// (finest resolution x and y bits) in places that contribute to the
// low bits of the hash.
return (((long) VERSION << VERSION_OFFSET) | y | ((long) x << 32) | ((long) zoomLevel << ZOOM_OFFSET));
}

public static BingTile decode(long tile)
{
int tileX = (int) (tile >> 28);
int tileY = (int) ((tile % (1 << 28)) >> 5);
int zoomLevel = (int) (tile % (1 << 5));
int version = (int) (tile >>> VERSION_OFFSET) & BITS_5;
if (version == 0) {
return decodeV0(tile);
}
else {
throw new IllegalArgumentException(format("Unknown Bing Tile encoding version: %s", version));
}
}

private static BingTile decodeV0(long tile)
{
int tileX = (int) (tile >>> 32) & BITS_23;
int tileY = (int) tile & BITS_23;
int zoomLevel = (int) (tile >>> ZOOM_OFFSET) & BITS_5;

return new BingTile(tileX, tileY, zoomLevel);
}
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26 changes: 26 additions & 0 deletions presto-geospatial/src/main/java/com/facebook/presto/plugin/geospatial/BingTileFunctions.java
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Expand Up @@ -22,6 +22,7 @@
import com.facebook.presto.spi.block.BlockBuilder;
import com.facebook.presto.spi.function.Description;
import com.facebook.presto.spi.function.ScalarFunction;
import com.facebook.presto.spi.function.ScalarOperator;
import com.facebook.presto.spi.function.SqlType;
import com.facebook.presto.spi.type.RowType;
import com.facebook.presto.spi.type.StandardTypes;
Expand All @@ -38,7 +39,9 @@
import static com.facebook.presto.geospatial.serde.EsriGeometrySerde.serialize;
import static com.facebook.presto.plugin.geospatial.BingTile.MAX_ZOOM_LEVEL;
import static com.facebook.presto.plugin.geospatial.GeometryType.GEOMETRY_TYPE_NAME;
import static com.facebook.presto.spi.StandardErrorCode.INVALID_CAST_ARGUMENT;
import static com.facebook.presto.spi.StandardErrorCode.INVALID_FUNCTION_ARGUMENT;
import static com.facebook.presto.spi.function.OperatorType.CAST;
import static com.facebook.presto.spi.type.BigintType.BIGINT;
import static com.facebook.presto.spi.type.IntegerType.INTEGER;
import static com.google.common.base.Preconditions.checkArgument;
Expand Down Expand Up @@ -85,6 +88,29 @@ public class BingTileFunctions

private BingTileFunctions() {}

@Description("Encodes a Bing tile into a bigint")
@ScalarOperator(CAST)
@SqlType(StandardTypes.BIGINT)
public static long castToBigint(@SqlType(BingTileType.NAME) long tile)
{
return tile;
}

@Description("Decodes a Bing tile from a bigint")
@ScalarOperator(CAST)
@SqlType(BingTileType.NAME)
public static long castFromBigint(@SqlType(StandardTypes.BIGINT) long tile)
{
try {
BingTile.decode(tile);
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@arhimondr arhimondr Mar 10, 2020

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follow up: Currently BingTile.decode must create an object of BingTile. The main reason for calling BingTile.decode is to validate the tile stored in a long. For efficiency I would recommend to have a dedicated method, e.g.: BingTile.validate or smthng.

}
catch (IllegalArgumentException e) {
throw new PrestoException(INVALID_CAST_ARGUMENT,
format("Invalid bigint tile encoding: %s", tile));
}
return tile;
}

@Description("Creates a Bing tile from XY coordinates and zoom level")
@ScalarFunction("bing_tile")
@SqlType(BingTileType.NAME)
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50 changes: 50 additions & 0 deletions ...geospatial/src/test/java/com/facebook/presto/plugin/geospatial/TestBingTileFunctions.java
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Expand Up @@ -35,6 +35,7 @@
import static com.facebook.presto.metadata.FunctionExtractor.extractFunctions;
import static com.facebook.presto.operator.aggregation.AggregationTestUtils.assertAggregation;
import static com.facebook.presto.operator.scalar.ApplyFunction.APPLY_FUNCTION;
import static com.facebook.presto.plugin.geospatial.BingTile.MAX_ZOOM_LEVEL;
import static com.facebook.presto.plugin.geospatial.BingTile.fromCoordinates;
import static com.facebook.presto.plugin.geospatial.BingTileFunctions.MAX_LATITUDE;
import static com.facebook.presto.plugin.geospatial.BingTileFunctions.MIN_LONGITUDE;
Expand Down Expand Up @@ -80,6 +81,55 @@ public void testSerialization()
assertEquals(tile, objectMapper.readerFor(BingTile.class).readValue(json));
}

@Test
public void testBingTileEncoding()
{
for (int zoom = 0; zoom <= MAX_ZOOM_LEVEL; zoom++) {
int maxValue = (1 << zoom) - 1;
testEncodingRoundTrip(0, 0, zoom);
testEncodingRoundTrip(0, maxValue, zoom);
testEncodingRoundTrip(maxValue, 0, zoom);
testEncodingRoundTrip(maxValue, maxValue, zoom);
}
}

private void testEncodingRoundTrip(int x, int y, int zoom)
{
BingTile expected = BingTile.fromCoordinates(x, y, zoom);
BingTile actual = BingTile.decode(expected.encode());
assertEquals(actual, expected);
}

@Test
public void testBingTileCast()
{
assertBingTileCast(0, 0, 0);
assertBingTileCast(0, 0, 1);
assertBingTileCast(0, 0, 10);
assertBingTileCast(125, 900, 10);
assertBingTileCast(0, 0, 23);
assertBingTileCast((1 << 23) - 1, (1 << 23) - 1, 23);

// X/Y too big
assertBingTileCastInvalid(256L | (256L << 32) | (4L << 27));

// Wrong version
assertBingTileCastInvalid(1L << BingTile.VERSION_OFFSET);
}

private void assertBingTileCast(int x, int y, int zoom)
{
BingTile tile = BingTile.fromCoordinates(x, y, zoom);
assertFunction(format("cast(cast(%s as bigint) as bingtile)", tile.encode()), BING_TILE, tile);
assertFunction(format("cast(bing_tile('%s') as bigint)", tile.toQuadKey()), BIGINT, tile.encode());
}

private void assertBingTileCastInvalid(long encoding)
{
assertInvalidCast(format("cast(cast(%s as bigint) as bingtile)", encoding),
format("Invalid bigint tile encoding: %s", encoding));
}

@Test
public void testArrayOfBingTiles()
throws Exception
Expand Down