cloud-fan opened a new pull request #31440:
URL: https://github.com/apache/spark/pull/31440
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### What changes were proposed in this pull request?
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This is a follow-up of https://github.com/apache/spark/pull/28027
https://github.com/apache/spark/pull/28027 added a DS v2 API that allows
data sources to produce metadata/hidden columns that can only be seen when it's
explicitly selected. The way we integrate this API into Spark is:
1. The v2 relation gets normal output and metadata output from the data
source, and the metadata output is excluded from the plan output by default.
2. An analyzer rule searches the query plan, trying to find a node that has
missing inputs. If such node is found, transform the sub-plan of this node, and
update the v2 relation to include the metadata output.
The analyzer rule in step 2 brings a perf regression, for queries that do
not read v2 tables at all. This rule will calculate `QueryPlan.inputSet` (which
builds an `AttributeSet` from outputs of all children) and
`QueryPlan.missingInput` (which does a set exclusion and creates a new
`AttributeSet`) for every plan node in the query plan. In our benchmark, the
TPCDS query compilation time gets increased by more than 10%
This PR proposes a different way to integrate the DS v2 metadata col API
into Spark:
1. The v2 relation gets normal output and metadata output from the data
source, and the metadata output is **included** in the plan output by default.
2. For star expansion, do not include the metadata column in the project
list.
3. Add an analyzer rule to do:
3.1 For table insertion, exclude metadata columns from v2 relation's output.
3.2 For a single v2 table scan (e.g. `spark.table(...)`), exclude metadata
columns from v2 relation's output.
The new approach does not have overhead if the query doesn't use the
metadata col feature.
### Why are the changes needed?
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Fix perf regression in SQL query compilation
### Does this PR introduce _any_ user-facing change?
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No
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Run `org.apache.spark.sql.TPCDSQuerySuite`, and `AddMetadataColumns` is the
top 4 rule ranked by running time
```
=== Metrics of Analyzer/Optimizer Rules ===
Total number of runs: 407641
Total time: 47.257239779 seconds
Rule Effective Time / Total Time
Effective Runs / Total Runs
OptimizeSubqueries 4157690003 / 8485444626
49 / 2778
Analyzer$ResolveAggregateFunctions 1238968711 / 3369351761
49 / 2141
ColumnPruning 660038236 / 2924755292
338 / 6391
Analyzer$AddMetadataColumns 0 / 2918352992
0 / 2151
```
Now, this rule is removed.
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