[SQL] - Support cache/uncache table syntax

[francis-du]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.

Currently, DataFrame can cache tables in memory, but cannot cache DataFusion tables or views through SQL.

Describe the solution you'd like

I want to cache views and tables via CACHE TABLE <table_name> syntax like Spark SQL.At the same time, it is also necessary to support the UNCACHE TABLE <table_name> syntax to allow users to delete tables and views that do not require caching in memory.

Here are some docs aboutCACHE TABLE and UNCACHE TABLE in Spark SQL:

1.CACHE TABLE: https://docs.databricks.com/spark/latest/spark-sql/language-manual/sql-ref-syntax-aux-cache-cache-table.html

2.UNCACHE TABLE: https://docs.databricks.com/spark/latest/spark-sql/language-manual/sql-ref-syntax-aux-cache-uncache-table.html

Describe alternatives you've considered

I has been implemented the syntax in apache/datafusion-sqlparser-rs#670, I will support it in DataFusion next, if anyone is interested, welcome to discuss here.

[Dandandan]

How much different is this from CREATE TABLE AS (which currently also creates an in memory table)?

I am not necessarily against this, but I think the syntax is very spark-specific. We can do about the same currently?

[francis-du]

I looked at some code and I found CREATE TABLE is indeed possible to create an in-memory table. And also useDROP TABLE uncache in-memory table. 😢

[francis-du]

It doesn't look like it's necessary to support those syntax 😥