[FLINK-22586][table] Improve the precision dedivation for decimal ari…

[cshuo]

…thmetics

What is the purpose of the change

Currently the precision and scale derivation is not properly for decimal data arithmetics, e.g,

considering the following example:

select cast('10.1' as decimal(38, 19)) * cast('10.2' as decimal(38, 19)) from T
the result is null, which may confuses use a lot, because the result is actually not that big.

The root cause is the precision derivation for the above multiplication is:

(38, 19) * (38, 19) -> (38, 38)

So there is no space for integral digits, and the result may overflow easily, which leads to null result.

This pr aims to adjust precision/scale properly when the precision is out of range. (The derivation rules basically follow
https://docs.microsoft.com/en-us/sql/t-sql/data-types/precision-scale-and-length-transact-sql)

Brief change log

• Modify precision derivation rules for FlinkTypeSystem and LogicalTypeMerging.

Verifying this change

This change added tests and can be verified as follows:

• Unit test for decimal arithmetics are covered by DecimalTypeTest.
• integration testing covered by MathFunctionsITCase.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: no
• The runtime per-record code paths (performance sensitive): no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn/Mesos, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no

[flinkbot]

Thanks a lot for your contribution to the Apache Flink project. I'm the @flinkbot. I help the community
to review your pull request. We will use this comment to track the progress of the review.

Automated Checks

Last check on commit 6b61c49 (Sat Aug 28 11:20:24 UTC 2021)

Warnings:

• No documentation files were touched! Remember to keep the Flink docs up to date!

_{Mention the bot in a comment to re-run the automated checks.}

Review Progress

• ❓ 1. The [description] looks good.
• ❓ 2. There is [consensus] that the contribution should go into to Flink.
• ❓ 3. Needs [attention] from.
• ❓ 4. The change fits into the overall [architecture].
• ❓ 5. Overall code [quality] is good.

Please see the Pull Request Review Guide for a full explanation of the review process.

The Bot is tracking the review progress through labels. Labels are applied according to the order of the review items. For consensus, approval by a Flink committer of PMC member is required

Bot commands

The @flinkbot bot supports the following commands:

• @flinkbot approve description to approve one or more aspects (aspects: description, consensus, architecture and quality)
• @flinkbot approve all to approve all aspects
• @flinkbot approve-until architecture to approve everything until architecture
• @flinkbot attention @username1 [@username2 ..] to require somebody's attention
• @flinkbot disapprove architecture to remove an approval you gave earlier

[flinkbot]

CI report:

• 694aaee UNKNOWN
• a1eda92 Azure: CANCELED
• 6b61c49 Azure: PENDING

Bot commands

The @flinkbot bot supports the following commands:

• @flinkbot run travis re-run the last Travis build
• @flinkbot run azure re-run the last Azure build

[cshuo]

@JingsongLi

[cshuo]

@flinkbot run azure

[JingsongLi]

HIVE: https://issues.apache.org/jira/browse/HIVE-15331
SPARK: https://issues.apache.org/jira/browse/SPARK-22036

[JingsongLi]

@cshuo Can you take a look to test failure?

[cshuo]

@cshuo Can you take a look to test failure?

I'm checking...

[JingsongLi]

Thanks @cshuo for your update. Looks good to me.