imback82 opened a new pull request #30321:
URL: https://github.com/apache/spark/pull/30321
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### What changes were proposed in this pull request?
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This PR proposes to migrate `SHOW CREATE TABLE` to use
`UnresolvedTableOrView` to resolve the table identifier. This allows consistent
resolution rules (temp view first, etc.) to be applied for both v1/v2 commands.
More info about the consistent resolution rule proposal can be found in
[JIRA](https://issues.apache.org/jira/browse/SPARK-29900) or [proposal
doc](https://docs.google.com/document/d/1hvLjGA8y_W_hhilpngXVub1Ebv8RsMap986nENCFnrg/edit?usp=sharing).
Note that `SHOW CREATE TABLE` works only with a v1 table and a permanent
view, and not supported for v2 tables.
### Why are the changes needed?
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The changes allow consistent resolution behavior when resolving the table
identifier. For example, the following is the current behavior:
```scala
sql("CREATE TEMPORARY VIEW t AS SELECT 1")
sql("CREATE DATABASE db")
sql("CREATE TABLE t (key INT, value STRING) USING hive")
sql("USE db")
sql("SHOW CREATE TABLE t AS SERDE") // Succeeds
```
With this change, `SHOW CREATE TABLE ... AS SERDE` above fails with the
following:
```
org.apache.spark.sql.AnalysisException: t is a temp view not table or
permanent view.; line 1 pos 0
at
org.apache.spark.sql.catalyst.analysis.package$AnalysisErrorAt.failAnalysis(package.scala:42)
at
org.apache.spark.sql.catalyst.analysis.Analyzer$ResolveTempViews$$anonfun$apply$7.$anonfun$applyOrElse$43(Analyzer.scala:883)
at scala.Option.map(Option.scala:230)
```
, which is expected since temporary view is resolved first and `SHOW CREATE
TABLE ... AS SERDE` doesn't support a temporary view.
Note that there is no behavior change for `SHOW CREATE TABLE` without `AS
SERDE` since it was already resolving to a temporary view first. See below for
more detail.
### Does this PR introduce _any_ user-facing change?
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After this PR, `SHOW CREATE TABLE t AS SERDE` is resolved to a temp view `t`
instead of table `db.t` in the above scenario.
Note that there is no behavior change for `SHOW CREATE TABLE` without `AS
SERDE`, but the exception message changes from `SHOW CREATE TABLE is not
supported on a temporary view` to `t is a temp view not table or permanent
view`.
### How was this patch tested?
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Updated existing tests.
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