[FLINK-17385][jdbc][postgres] Handled problem of numeric with 0 precision

[fpompermaier]

What is the purpose of the change

Fix error when handling numeric field types with precision 0, such as:

CREATE TABLE orders(
    ord_no integer PRIMARY KEY,
    ord_date date,
    item_name character(35),
    item_grade character(1),
    ord_qty numeric,
    ord_amount numeric,
    CONSTRAINT unq_ordno_itname UNIQUE(ord_qty,ord_amount)
);

This address the same problem of SPARK-26538 (apache/spark#23456), using the same fix.

Brief change log

In the PostgresCatalog.fromJDBCType, handle Decimal and Numeric types as follow:

if (precision > 0) {
	return DataTypes.DECIMAL(precision, metadata.getScale(colIndex));
}
return DataTypes.DECIMAL(DecimalType.MAX_PRECISION, 18);

Verifying this change

This change is already covered by existing tests, such as PostgresCatalogITCase.

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
• If yes, how is the feature documented? not documented

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[wuchong]

cc @bowenli86 , would you like to review this?

[bowenli86]

LGTM, except that can you also add array tests in PostgresCatalogITCase#testArrayTypes()?

[fpompermaier]

@bowenli86 I'll add it within tomorrow hopefully

[fpompermaier]

@flinkbot run travis
@flinkbot run azure

[bowenli86]

@flinkbot run travis

[bowenli86]

LGTM.

BTW, next time, please remember to write jira number and tags in the commit message, e.g. "[FLINK-17385][jdbc][postgres]"