## What changes were proposed in this pull request?
AnalysisBarrier was introduced in SPARK-20392 to improve analysis speed (don't re-analyze nodes that have already been analyzed).
Before AnalysisBarrier, we already had some infrastructure in place, with analysis specific functions (resolveOperators and resolveExpressions). These functions do not recursively traverse down subplans that are already analyzed (with a mutable boolean flag _analyzed). The issue with the old system was that developers started using transformDown, which does a top-down traversal of the plan tree, because there was not top-down resolution function, and as a result analyzer performance became pretty bad.
In order to fix the issue in SPARK-20392, AnalysisBarrier was introduced as a special node and for this special node, transform/transformUp/transformDown don't traverse down. However, the introduction of this special node caused a lot more troubles than it solves. This implicit node breaks assumptions and code in a few places, and it's hard to know when analysis barrier would exist, and when it wouldn't. Just a simple search of AnalysisBarrier in PR discussions demonstrates it is a source of bugs and additional complexity.
Instead, this pull request removes AnalysisBarrier and reverts back to the old approach. We added infrastructure in tests that fail explicitly if transform methods are used in the analyzer.
## How was this patch tested?
Added a test suite AnalysisHelperSuite for testing the resolve* methods and transform* methods.
Author: Reynold Xin <rxin@databricks.com>
Author: Xiao Li <gatorsmile@gmail.com>
Closes#21822 from rxin/SPARK-24865.
e6e9031d7b