v.19.14Improvement

Split Expressionanalyzer.appendjoin()

Split ExpressionAnalyzer.appendJoin(). Prepare a place in ExpressionAnalyzer for MergeJoin. #6524 (Artem Zuikov)
Refactor of ExpressionAnalyzer.appendJoin() to prepare for the implementation of MergeJoin functionality in ClickHouse.

Why it matters

This change restructures the ExpressionAnalyzer to create a dedicated place for supporting MergeJoin, a join algorithm that can optimize join operations by leveraging sorted inputs. It sets the foundation for improved join performance and scalability.

How to use it

This is an internal refactor and preparatory step. Users will benefit from the upcoming MergeJoin feature once fully implemented and exposed, but no immediate action or configuration is needed in this update.