Revert [SPARK-24882][SQL] improve data source v2 API from branch 2.4

[cloud-fan]

What changes were proposed in this pull request?

As discussed in the dev list, we don't want to include #22009 in Spark 2.4, as it needs data source v2 users to change the implementation intensitively, while they need to change again in next release.

How was this patch tested?

existing tests

[cloud-fan]

cc @rxin@rdblue@jose-torres

[SparkQA]

Test build #95912 has finished for PR 22388 at commit e31ecfa.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[dongjoon-hyun]

This seems to be the complete revert of SPARK-24882 (#22009 and the followup #22245). Am I right?

[cloud-fan]

yes

[SparkQA]

Test build #95967 has finished for PR 22388 at commit 234b67a.

• This patch fails to build.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #95968 has finished for PR 22388 at commit 031ad29.

• This patch fails to build.
• This patch merges cleanly.
• This patch adds no public classes.

[kiszk]

Incorrect import still may exist there.

[error] /home/jenkins/workspace/SparkPullRequestBuilder/sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/continuous/ContinuousTextSocketSource.scala:40: object SupportsDeprecatedScanRow is not a member of package org.apache.spark.sql.sources.v2.reader
[error] import org.apache.spark.sql.sources.v2.reader.{InputPartition, InputPartitionReader, SupportsDeprecatedScanRow}
[error] ^

[jose-torres]

MicroBatchExecution.scala and ContinuousExecution.scala look right after the revert, although it would be helpful to understand what the diff is between this and a straight git revert.

[cloud-fan]

I can't recall the exact conflicts. There are only 2 commits(3106324 and 9f5c5b4) touched these 2 files after my PR, I carefully checked and these changs are still there.

[SparkQA]

Test build #95986 has finished for PR 22388 at commit be13162.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[gatorsmile]

LGTM

Thanks! Merged to 2.4.

[gatorsmile]

Unable to merge to master. @cloud-fan Could you submit another PR to the master branch?

[dongjoon-hyun]

Ur, @gatorsmile . Why do we need to revert this from master?

[cloud-fan]

As we discussed in the dev list, we only want to revert it from 2.4. I'm closing it now.

[rdblue]

Thanks for doing this, @cloud-fan! Sorry I'm late to reply, I was at Strata all last week.