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Add bitwise shift operations
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Allows bitwise shift operations including arithmetic shift right,
logical shift right, and shift left.
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@gastonar
gastonar committed Jun 6, 2019
1 parent 5e3ca2c commit afe74f4
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Showing 3 changed files with 124 additions and 2 deletions.
23 changes: 23 additions & 0 deletions presto-docs/src/main/sphinx/functions/bitwise.rst
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Expand Up @@ -28,4 +28,27 @@ Bitwise Functions

Returns the bitwise XOR of ``x`` and ``y`` in 2's complement representation.

.. function:: bitwise_left_shift(x, shift, bits) -> bigint

Left shift operation on ``x`` (treated as ``bits``-bit integer)
shifted by ``shift``.

SELECT bitwise_logical_left_shift(7, 2, 4); -- 12
SELECT bitwise_logical_left_shift(7, 2, 64); -- 28

.. function:: bitwise_shift_right_logical(x, shift, bits) -> bigint

Logical right shift operation on ``x`` (treated as ``bits``-bit integer)
shifted by ``shift``.

SELECT bitwise_logical_right_shift(7, 2, 4); -- 1
SELECT bitwise_logical_right_shift(-8, 2, 5); -- 6

.. function:: bitwise_shift_right_arithmetic(x, shift) -> bigint

Arithmetic right shift operation on ``x`` shifted by ``shift`` in 2's complement representation.

SELECT bitwise_arithmetic_right_shift(-8, 2); -- -2
SELECT bitwise_arithmetic_right_shift(7, 2); -- 1

See also :func:`bitwise_and_agg` and :func:`bitwise_or_agg`.
62 changes: 60 additions & 2 deletions presto-main/src/main/java/com/facebook/presto/operator/scalar/BitwiseFunctions.java
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Expand Up @@ -23,17 +23,19 @@

public final class BitwiseFunctions
{
private static final int MAX_BITS = 64;

private BitwiseFunctions() {}

@Description("count number of set bits in 2's complement representation")
@ScalarFunction
@SqlType(StandardTypes.BIGINT)
public static long bitCount(@SqlType(StandardTypes.BIGINT) long num, @SqlType(StandardTypes.BIGINT) long bits)
{
if (bits == 64) {
if (bits == MAX_BITS) {
return Long.bitCount(num);
}
if (bits <= 1 || bits > 64) {
if (bits <= 1 || bits > MAX_BITS) {
throw new PrestoException(INVALID_FUNCTION_ARGUMENT, "Bits specified in bit_count must be between 2 and 64, got " + bits);
}
long lowBitsMask = (1L << (bits - 1)) - 1; // set the least (bits - 1) bits
Expand Down Expand Up @@ -75,4 +77,60 @@ public static long bitwiseXor(@SqlType(StandardTypes.BIGINT) long left, @SqlType
{
return left ^ right;
}

@Description("shift left operation with specified bits")
@ScalarFunction
@SqlType(StandardTypes.BIGINT)
public static long bitwiseShiftLeft(@SqlType(StandardTypes.BIGINT) long number,
@SqlType(StandardTypes.BIGINT) long shift,
@SqlType(StandardTypes.BIGINT) long bits)
{
if (bits == MAX_BITS) {
return number << shift;
}

if (bits <= 1 || bits > MAX_BITS) {
throw new PrestoException(INVALID_FUNCTION_ARGUMENT, "Bits specified must be between 2 and 64, got " + bits);
}

if (shift < 0) {
throw new PrestoException(INVALID_FUNCTION_ARGUMENT, "Specified shift must be positive");
}

return number << shift & (long) (Math.pow(2, bits) - 1);
}

@Description("logical shift right operation with specified bits")
@ScalarFunction
@SqlType(StandardTypes.BIGINT)
public static long bitwiseLogicalShiftRight(@SqlType(StandardTypes.BIGINT) long number,
@SqlType(StandardTypes.BIGINT) long shift,
@SqlType(StandardTypes.BIGINT) long bits)
{
if (bits == MAX_BITS) {
return number >>> shift;
}

if (bits <= 1 || bits > MAX_BITS) {
throw new PrestoException(INVALID_FUNCTION_ARGUMENT, "Bits specified in must be between 2 and 64, got " + bits);
}

if (shift < 0) {
throw new PrestoException(INVALID_FUNCTION_ARGUMENT, "Specified shift must be positive");
}

return (number & (long) (Math.pow(2, bits) - 1)) >>> shift;
}

@Description("arithmetic shift right operation")
@ScalarFunction
@SqlType(StandardTypes.BIGINT)
public static long bitwiseArithmeticShiftRight(@SqlType(StandardTypes.BIGINT) long number, @SqlType(StandardTypes.BIGINT) long shift)
{
if (shift < 0) {
throw new PrestoException(INVALID_FUNCTION_ARGUMENT, "Specified shift must be positive");
}

return number >> shift;
}
}
41 changes: 41 additions & 0 deletions presto-main/src/test/java/com/facebook/presto/operator/scalar/TestBitwiseFunctions.java
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Expand Up @@ -15,7 +15,9 @@

import org.testng.annotations.Test;

import static com.facebook.presto.spi.StandardErrorCode.INVALID_FUNCTION_ARGUMENT;
import static com.facebook.presto.spi.type.BigintType.BIGINT;
import static java.lang.String.format;

public class TestBitwiseFunctions
extends AbstractTestFunctions
Expand All @@ -33,6 +35,7 @@ public void testBitCount()
assertFunction("bit_count(-" + Long.MAX_VALUE + "-1, 64)", BIGINT, 1L); // bit_count(MIN_VALUE, 64)

assertFunction("bit_count(0, 32)", BIGINT, 0L);
assertFunction("bit_count(CAST (-8 AS SMALLINT), 6)", BIGINT, 3L);
assertFunction("bit_count(7, 32)", BIGINT, 3L);
assertFunction("bit_count(24, 32)", BIGINT, 2L);
assertFunction("bit_count(-8, 32)", BIGINT, 29L);
Expand Down Expand Up @@ -90,4 +93,42 @@ public void testBitwiseXor()
assertFunction("bitwise_xor(-4, 12)", BIGINT, -4L ^ 12L);
assertFunction("bitwise_xor(60, 21)", BIGINT, 60L ^ 21L);
}

@Test
public void testBitwiseSll()
{
assertFunction("bitwise_shift_left(7, 2, 4)", BIGINT, 12L);
assertFunction("bitwise_shift_left(7, 2, 64)", BIGINT, 7L << 2L);
assertFunction("bitwise_shift_left(-4, 6, 64)", BIGINT, -4L << 6L);
assertFunction("bitwise_shift_left(-4, 6, 5)", BIGINT, 0L);
assertFunction("bitwise_shift_left(-4, 6, 9)", BIGINT, 256L);

assertInvalidFunction("bitwise_shift_left(7, -3, 2)", INVALID_FUNCTION_ARGUMENT);
}

@Test
public void testBitwiseSrl()
{
assertFunction("bitwise_logical_shift_right(7, 2, 4)", BIGINT, 1L);
assertFunction("bitwise_logical_shift_right(7, 2, 64)", BIGINT, 7L >>> 2L);
assertFunction("bitwise_logical_shift_right(-4, 6, 64)", BIGINT, -4L >>> 6L);
assertFunction("bitwise_logical_shift_right(-8, 2, 5)", BIGINT, 6L);
assertFunction(format("bitwise_logical_shift_right(%s, 62, 64)", 0xF0000F0000F00000L), BIGINT, 3L);
assertFunction(format("bitwise_logical_shift_right(%s, 62, 4)", 0xF0000F0000F00000L), BIGINT, 0L);
assertFunction(format("bitwise_logical_shift_right(%s, 1, 4)", 0xF0000F0000F00000L), BIGINT, 0L);

assertInvalidFunction("bitwise_logical_shift_right(7, -3, 2)", INVALID_FUNCTION_ARGUMENT);
}

@Test
public void testBitwiseSra()
{
assertFunction("bitwise_arithmetic_shift_right(7, 2)", BIGINT, 7L >> 2L);
assertFunction("bitwise_arithmetic_shift_right(-4, 6)", BIGINT, -4L >> 6L);
assertFunction("bitwise_arithmetic_shift_right(-256, 3)", BIGINT, -32L);
assertFunction("bitwise_arithmetic_shift_right(-8, 2)", BIGINT, -2L);
assertFunction(format("bitwise_arithmetic_shift_right(%s, 62)", 0xF0000F0000F00000L), BIGINT, -1L);

assertInvalidFunction("bitwise_arithmetic_shift_right(7, -3)", INVALID_FUNCTION_ARGUMENT);
}
}

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