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Handle nullable columns #233
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Description
This PR adds handling for nullable columns of a few types for which the schema couldn't be generated. With commit e961a17, a schema can be generated for the most frequently used types (except numeric and timestamp).
SQL
NULL
s need to be represented asnil
s in Go (i.e., in a record's payload). This means that we need to use pointers for such values. For example, a SQLtimestamp
is a*time.Time
. The corresponding Avro schema needs to be a union schema where one of the types isNull
, e.g.:This union schema can only be used with a pointer type and not with a value type. Using a union schema with
Null
to marshal a value type results inavro: unknown union type int.date
.Similarly, an Avro schema that has no
Null
cannot be used to marshal a pointer type. This results in an error like:avro: *time.Time is unsupported for Avro long
.This means that a nullable SQL type needs to result in a pointer type, and a
not null
SQL type needs to result in a "normal" Avro schema. For this reason, we need to fetch information about each column to determine whether it's nullable or not. This is done through theTableInfoFetcher
.The changes have been tested in a built-in and a standalone connector.
Additional changes:
lang.Ptr()
everywhere)Quick checks: