Rounding

[volodya-lombrozo]

I have faced with a problem of getting BigDecimal values from ResultSet:

resultSet.getBigDecimal("avg")

For example you can set the avg value = 1.333334 to a cloumn

`abg` Float64

And when you will try to get it you will have the next exception:

java.lang.ArithmeticException: Rounding necessary

	at java.base/java.math.BigDecimal.commonNeedIncrement(BigDecimal.java:4621)
	at java.base/java.math.BigDecimal.needIncrement(BigDecimal.java:4677)
	at java.base/java.math.BigDecimal.divideAndRound(BigDecimal.java:4585)
	at java.base/java.math.BigDecimal.setScale(BigDecimal.java:2891)
	at java.base/java.math.BigDecimal.setScale(BigDecimal.java:2951)
	at com.clickhouse.client.data.ClickHouseDoubleValue.asBigDecimal(ClickHouseDoubleValue.java:140)
	at com.clickhouse.client.ClickHouseValue.asBigDecimal(ClickHouseValue.java:234)
	at com.clickhouse.jdbc.ClickHouseResultSet.getBigDecimal(ClickHouseResultSet.java:237)

I added RoundingMode in order to handle decimal values

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[github-actions]

Benchmark                                 (client)  (connection)  (statement)  (type)   Mode  Cnt     Score     Error  Units
Basic.insertOneRandomNumber  clickhouse-http-jdbc1         reuse       normal  object  thrpt   20   219.917 ±  26.999  ops/s
Basic.insertOneRandomNumber  clickhouse-http-jdbc1         reuse     prepared  object  thrpt   20   227.671 ±  23.889  ops/s
Basic.insertOneRandomNumber  clickhouse-http-jdbc1           new       normal  object  thrpt   20   216.784 ±  26.931  ops/s
Basic.insertOneRandomNumber  clickhouse-http-jdbc1           new     prepared  object  thrpt   20   220.458 ±  25.412  ops/s
Basic.insertOneRandomNumber   clickhouse-grpc-jdbc         reuse       normal  object  thrpt   20   232.792 ±  25.948  ops/s
Basic.insertOneRandomNumber   clickhouse-grpc-jdbc           new       normal  object  thrpt   20   228.667 ±  28.628  ops/s
Basic.selectOneRandomNumber  clickhouse-http-jdbc1         reuse       normal  object  thrpt   20  1212.455 ± 138.125  ops/s
Basic.selectOneRandomNumber  clickhouse-http-jdbc1         reuse     prepared  object  thrpt   20  1262.955 ±  99.241  ops/s
Basic.selectOneRandomNumber  clickhouse-http-jdbc1           new       normal  object  thrpt   20  1209.858 ±  91.764  ops/s
Basic.selectOneRandomNumber  clickhouse-http-jdbc1           new     prepared  object  thrpt   20  1280.747 ±  70.558  ops/s
Basic.selectOneRandomNumber   clickhouse-grpc-jdbc         reuse       normal  object  thrpt   20   785.802 ±  87.088  ops/s
Basic.selectOneRandomNumber   clickhouse-grpc-jdbc         reuse     prepared  object  thrpt   20   848.482 ±  80.445  ops/s
Basic.selectOneRandomNumber   clickhouse-grpc-jdbc           new       normal  object  thrpt   20   834.440 ±  85.877  ops/s
Basic.selectOneRandomNumber   clickhouse-grpc-jdbc           new     prepared  object  thrpt   20   841.690 ±  75.414  ops/s

[zhicwu]

Thank you @volodya-lombrozo for the pull request. I changed the merge target from master to develop, and I'll merge it after double checking the rounding mode.

[zhicwu]

@volodya-lombrozo, I hope you don't mind that I changed RoundingMode to DOWN for consistency with server. Also I removed the check for NaN and Infinite because BigDecimal does not support them.

I'm going to release patch7 24 hours later - let me know if you have any concern for the changes.

[volodya-lombrozo]

Ok, thank you, @zhicwu. Everything fine, but can I ask you, why you decided to use exactly RoundingMode.DOWN?
For example in that line you use RoundingMode.HALF_UP.
Maybe it makes sense to create a global setting like DEFAULT_ROUNDING_MODE and use it everywhere?

[zhicwu]

why you decided to use exactly RoundingMode.DOWN?

Just trying to make it consistency with server side implementation - see here.

For example in that line you use RoundingMode.HALF_UP.

It's legacy driver and it will be removed in 0.4.0 so I didn't change the logic this time.

Maybe it makes sense to create a global setting like DEFAULT_ROUNDING_MODE and use it everywhere?

Yes. I thought about adding new default into ClickHouseDefaults but maybe better do that in a feature release like v0.3.3? Will create a separate PR for this.

[volodya-lombrozo]

Thank you for your answer. Now it's clear.
Yes, I think it's much better to add the new default into ClickHouseDefaults in a separate PR.