NIFI-16067 - PutIcebergRecord maps fields by ordinal position instead of column name

[maltesander]

Summary

NIFI-16067 - PutIcebergRecord maps fields by ordinal position instead of column name

PutIcebergRecord (added in NIFI-15062) doesn't match columns by name. It writes each record's values into the Iceberg table columns by position, and the position it uses is the one from the incoming record schema, not the table schema. So the mapping is wrong whenever the input field order doesn't line up with the table's column order.

If the record has fewer fields than the table, the missing columns aren't set to NULL either - the values just shift left into whatever table column happens to sit at that position. Sometimes that lands on an incompatible type and you get a ClassCastException, which is the good outcome because at least it fails loudly. When the types happen to line up, the row is written with values in the wrong columns and nothing complains.

This gets worse with schema evolution: as soon as you add a column, the producer and the table no longer agree on the column set, and existing flows start silently writing data into the wrong place.

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[exceptionfactory]

Thanks for flagging and addressing this issue @maltesander. The general approach looks good, I will take a closer look at the changes and follow up soon.