[SPARK-51987][SQL] DSv2 expressions in column defaults on write #51002
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aokolnychyi
commented
May 23, 2025
| sealed class Metadata private[types] (private[types] val map: Map[String, Any]) | ||
| sealed class Metadata private[types] ( | ||
| private[types] val map: Map[String, Any], | ||
| @transient private[types] val runtimeMap: Map[String, Any]) |
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I am adding a runtime-only map of configs that is not serialized or exposed to the user. It will allow me to store alternative in-memory representations for certain configs. In particular, it would allow me to store SQL as well as the expression itself for default values.
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Below is an example of how it is being used:
val existsDefault = extractExistsDefault(default)
val (sql, expr) = extractCurrentDefault(default)
val newMetadata = new MetadataBuilder()
.withMetadata(f.metadata)
.putString(EXISTS_DEFAULT_COLUMN_METADATA_KEY, existsDefault)
.putExpression(CURRENT_DEFAULT_COLUMN_METADATA_KEY, sql, expr)
.build()
f.copy(metadata = newMetadata)
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This allows me to use the expression directly without generating/parsing SQL for it.
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What changes were proposed in this pull request?
This PR allows connectors to expose expression-based defaults on write.
Why are the changes needed?
These changes are needed to avoid the requirement of producing Spark SQL dialect in connectors.
Does this PR introduce any user-facing change?
No.
How was this patch tested?
This PR comes with tests.
Was this patch authored or co-authored using generative AI tooling?
No.