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https://issues.apache.org/jira/browse/FLINK-39757?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Mao Jiayi closed FLINK-39757.
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Resolution: Duplicate
> Fix unable to coerce complex types (ARRAY/MAP/ROW) to STRING
> ------------------------------------------------------------
>
> Key: FLINK-39757
> URL: https://issues.apache.org/jira/browse/FLINK-39757
> Project: Flink
> Issue Type: Bug
> Components: Flink CDC
> Reporter: Mao Jiayi
> Priority: Major
> Labels: pull-request-available
>
> When using CDC pipelines with schema merging operations that involve *complex
> types (ARRAY, MAP, ROW)* being coerced to {*}STRING type{*}, the job may fail
> due to missing type conversion logic in {*}SchemaMergingUtils{*}.
> The failure happens in {*}SchemaMergingUtils.coerceObject(){*}. When
> attempting to coerce complex types to STRING during schema merging, the
> utility only handles primitive types and binary data conversions. If the
> original field is a MapData, ArrayData, or RecordData, the coercion logic
> falls through to the default toString() conversion, which either produces
> incorrect string representations or fails entirely because these complex
> types don't have proper toString() implementations for string coercion.
> This issue is usually not exposed in simple type scenarios because primitive
> types (INTEGER, VARCHAR, BOOLEAN, TIMESTAMP, etc.) have direct coercion paths
> to STRING through existing conversion rules. The schema merging logic works
> correctly for these basic type conversions, as they can be directly
> transformed without special handling.
> However, when CDC pipelines involve schema evolution or field type changes
> where complex types need to be merged into STRING columns, the missing
> conversion logic becomes critical. For example, when merging a table with
> *ARRAY<INT>* column into a target table with *STRING* column at the same
> position, *SchemaMergingUtils* cannot properly serialize the array data
> structure into its string representation, causing the merge operation to fail
> or produce incorrect results.
> This issue is not specific to any particular source connector. It can affect
> any CDC pipeline with schema merging scenarios involving complex-to-STRING
> type coercion, regardless of whether the source is MySQL, PostgreSQL, Kafka,
> or any other distributed pipeline source with schema evolution capabilities.
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