Fix IS DISTINCT FROM for decimals with precision > 18

[ptkool]

The current logic in method distinctBlockPositionLongLong compares the left value to itself. This PR corrects this by assigning the proper values to rightLow and rightHigh.

Fixes #13667.

[linux-foundation-easycla]

The committers are authorized under a signed CLA.

• ✅ Michael Styles (d5593acf6479ef97fd3d462af9bc7f74368996f2)

[ajaygeorge]

@ptkool , thanks for catching the bug and adding a fix.

Couple of observations

• Looking at the changes to fix this issue it is not very obvious how the issue is only for precision > 19 . Can you please help me understand that.
• Since this bug can be exposed by a failing unit test I would highly recommend adding one if there is not one present already.

[ptkool]

@ajaygeorge The issue is actually with decimal values with precision > 18, not 19.

IS DISTINCT FROM processing follows a different code path for decimal values with precision > 18.

Precision	Method Invoked
<= 18	DecimalInequalityOperators.distinctBlockPositionShortShort
> 18	DecimalInequalityOperators.distinctBlockPositionLongLong

Note that this issue only occurs when reading decimal values from a table and Presto creates instances of Int128ArrayBlock to represent these values.

[ajaygeorge]

LGTM.
you might need to update Release Notes in the PR since this is a user impacting change.
Also please update the issue description in #13667 to reflect that the issue is for precision > 18
Adding @cemcayiroglu and @mbasmanova who can help review and merge this.

[mbasmanova]

@ptkool Michael, looks good. Thanks for fixing this issue. Please squash the commits and make commit message clearer. Perhaps, Fix IS DISTINCT FROM for long decimals.

[mbasmanova]

• don't use a1, a2, etc. variables names; here, I'd just inline arr1 and arr2
• static import distinctBlockPositionLongLong

    @Test
    public void testIsDistinctFrom()
    {
        Block left = new Int128ArrayBlock(1, Optional.empty(), new long[] {112L, 0L});
        Block right = new Int128ArrayBlock(1, Optional.empty(), new long[] {185L, 0L});

        assertFalse(distinctBlockPositionLongLong(left, 0, left, 0));
        assertTrue(distinctBlockPositionLongLong(left, 0, right, 0));
    }

[mbasmanova]

@ptkool Looks good. Please remove the following from commit message

Add new test

Clean up based on feedback

[mbasmanova]

@ptkool Michael, I noticed that you updated the PR, but commit message didn't change. You need to use git commit --amend command to edit the commit message.

[ptkool]

@mbasmanova Commit message has been updated. Can you review this again?

[mbasmanova]

@ptkool Hmm... I don't see commit message updated. Here is what I see.

[ptkool]

@mbasmanova Commit message has been fixed.

[mbasmanova]

@ptkool Thank you for the contribution.