Automatically detect Spanner database dialect instead of manual specification

Prerequisites

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What are you trying to do that currently feels hard or impossible?

Users must explicitly set the dialect in their source configuration:

sources:  
  my-spanner-source:  
    kind: "spanner"  
    project: "my-project"  
    instance: "my-instance"  
    database: "my_db"  
    dialect: "postgresql"  # Manual specification required

The dialect defaults to "googlesql" if not specified, but this may not match the actual database dialect. There is configuration overhead when this could be fetch from metadata.

Suggested Solution(s)

Implement automatic dialect detection by querying the Spanner database metadata during source initialization. The system should:

Connect to the database using a dialect-agnostic approach Query the database dialect from Spanner's system tables or API Set the dialect automatically based on the detected value

Alternatives Considered

No response

Additional Details

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