[IMPALA-2057] Improve error message for incorrect avro decimal column declaration

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: Impala 2.0
• Fix Version/s: Impala 2.8.0
• Component/s: Frontend
• Labels: ramp-up usability
• Target Version: Product Backlog
• Assignee: Anuj Phadke
• Reporter: casey
• Created: 10/Jun/15 22:03
• Updated: 24/Jan/17 04:16
• Resolved: 13/Dec/16 16:46

Description

The example in the current avro decimal documentation doesn't make it clear that the "type" needs to be a complex type. It's easy to make the mistake of including the logical type information at the wrong level.

Ex:

 create TABLE table1
STORED AS AVRO
TBLPROPERTIES (
'avro.schema.literal'='{
"type": "record",
"name": "my_record",
"fields": [
{"name": "a", "logicalType": "decimal", "precision": 4, "scale": 2, "type": "bytes"}
]}')

ERROR: AnalysisException: Error parsing Avro schema for table 'default.table1': Unsupported type 'bytes' of column 'a'

When that happens the error message saying "Unsupported type 'bytes'..." is confusing since "bytes" is in a way a supported type. It would be great to give a more accurate error message. For example, the error message could say the logicalType field was given at the wrong level.

Btw, here is a correct version of the example

create TABLE table1
STORED AS AVRO
TBLPROPERTIES (
'avro.schema.literal'='{
"type": "record",
"name": "my_record",
"fields": [
{"name": "a", "type": {"type": "bytes", "logicalType": "decimal", "precision": 4, "scale": 2}}
]}')

Fetched 0 row(s) in 0.05s

Avro docs: https://avro.apache.org/docs/1.7.7/spec.html#Decimal