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https://issues.apache.org/jira/browse/AVRO-2592?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16950989#comment-16950989
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Ryan Skraba commented on AVRO-2592:
-----------------------------------
Hello! I'm not _sure_ this is a bug -- the Java implementation consistently
takes the current position inside ByteBuffers into account and consumes the
bytes when they're read.
I've hit this problem in the past, when logging a record containing BYTES
fields and inadvertently consuming the buffer, and we've _very_ recently seen
AVRO-2588. It isn't limited to DecimalConversion....
This *could* be a point of confusion, but at least it's consistent: ByteBuffer
datum "disappears" once you've consumed it, and you must reset/rewind the
position if you plan to use it again. Maybe we should revisit *that* decision?
In either case, I wouldn't consider this a Blocker -- a workaround exists and
is pretty simple.
> Avro decimal fails on certain conditions - ByteBuffer.position() is the root
> cause
> ----------------------------------------------------------------------------------
>
> Key: AVRO-2592
> URL: https://issues.apache.org/jira/browse/AVRO-2592
> Project: Apache Avro
> Issue Type: Bug
> Components: java
> Affects Versions: 1.9.1
> Reporter: Werner Daehn
> Priority: Blocker
>
> The Decimal Conversion from/to Bytebuffer is using the methods that consider
> the current position, e.g. remaining().
> [https://github.com/apache/avro/blob/release-1.9.1/lang/java/avro/src/main/java/org/apache/avro/Conversions.java#L82]
> At first sight that looks like a good idea. But actually it creates all sorts
> of problems.
> For example this code fails with "Zero Length BigInteger":
>
> {code:java}
> BigDecimal d = BigDecimal.valueOf(3.1415); BigDecimal d =
> BigDecimal.valueOf(3.1415);
> Decimal decimaltype = LogicalTypes.decimal(7, 4); ByteBuffer buffer =
> DECIMAL_CONVERTER.toBytes(d, null, decimaltype);
> System.out.println(DECIMAL_CONVERTER.fromBytes(buffer, null,
> decimaltype).toString());
> BigDecimal n = DECIMAL_CONVERTER.fromBytes(buffer, null, decimaltype);
> System.out.println(n.toString());{code}
>
> Reason is obvious. The first call to fromBytes() moves the position from 0 to
> the last byte. The second invocation reads from the last position, hence zero
> records.
> There are other situations this might cause issues, e.g. a user might create
> the ByteBuffer via other means and it is normal that the position is after
> the last byte. Then the serialization would not work either. And many other.
> As the ByteBuffer is used to wrap a single BigDecimal, I would suggest to
> remove all position-aware/setting methods and read/write from position zero.
>
>
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