Ryan Skraba created AVRO-2620:
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Summary: Max precision on decimal/fixed LogicalType is wrong
Key: AVRO-2620
URL: https://issues.apache.org/jira/browse/AVRO-2620
Project: Apache Avro
Issue Type: Bug
Components: java
Reporter: Ryan Skraba
A decimal logical type with an underlying fixed bytes type is invalid if the
precision is greater than can be contained in the fixed bytes. The calculation
for
[max
precision|https://github.com/apache/avro/blob/a2098bd88361b5ff9298c462a2dccafbb0c2c508/lang/java/avro/src/main/java/org/apache/avro/LogicalTypes.java#L262]
can return a wrong value when the fixed bytes size is greater than 128.
For a fixed size of *129*, the `Math.pow(2, 8 * size - 1)` part of this formula
will return `Double.INFINITY`, and the max precision will be considered
`Long.MAX_VALUE`. The expected value is 310 digits precision.
We can apply the log power rule to avoid overflow, or some bit-twiddling
approximation (like
[java.math.BigDecimal|https://github.com/openjdk/jdk/blob/jdk8-b120/jdk/src/share/classes/java/math/BigDecimal.java#L3779].
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