[FLINK-25568] Support Elasticsearch Source Connector

[kaori-seasons]

According to FLIP-127 to achieve source read function

[boring-cyborg[bot]]

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[WenDing-Y]

Support for FilterPushDown, ProjectPushDown, and LimitPushDown to optimize query performance. Have these functions been implemented? I don't seem to have seen this part of the code

[kaori-seasons]

Support for FilterPushDown, ProjectPushDown, and LimitPushDown to optimize query performance. Have these functions been implemented? I don't seem to have seen this part of the code

Hello, I am very happy to read your comments. Currently this PR belongs to draft status. For the three push-downs you mentioned. As shown in FLIP-127, I am going to implement related implementations of FilterPushDown, ProjectPushDown, and LimitPushDown and optimize es query expressions. Currently, only the ProjectPushDown interface is implemented, please refer to Elasticsearch7DynamicSource#applyProjection.

Due to busy work, I will finish the development after a while.

[MartijnVisser]

@kaori-seasons Are you still planning to work on this PR?

[kaori-seasons]

@kaori-seasons Are you still planning to work on this PR? @MartijnVisser Hello, I just saw your reply recently. Due to work, I did not continue this Pull request. I will start to resolve the conflict this month and request a review.