datafusion_issue

issue_8922

easy issue, just need to change the format of all the test

issue_8969

we need to modify the parser & ScalarFunctionDefinition to add a new function which is called PosPosition

0.change the sqlparser-rs and add the keywords in src/keywords.rs
1.change the definition of keywords src/parser/mod.rs
2.add corresponding information in arrow-datafusion/datafusion/physical-expr/src/string_expressions.rs
3./home/yanxinxiang/code/DF/arrow-datafusion/datafusion/physical-expr/src/unicode_expressions.rs

issue_8838

answer the following questions first

1.where does the order information stored?
table information stored in

1. transfer a ident into table reference
   

2. location which it stores
   

3. SessionContext created here
   

4. final store position
   
5. final creation in this function
   
6. final register
   
7. entry for doing optimization on logical plan
   
8. analyze the plan
   
9. optimize plan
   
   11.
   
   EXPLAIN
   SELECT
   CAST(c_customer_sk AS BIGINT) AS a,
   CAST(c_current_cdemo_sk AS BIGINT) AS b
   FROM delta_encoding_required_column
   ORDER BY a DESC;
   12.
   where does it build oeq_class?

EXPLAIN
SELECT
c_customer_sk AS c_customer_sk_big,
c_current_cdemo_sk
FROM delta_encoding_required_column
ORDER BY c_customer_sk_big DESC, c_current_cdemo_sk DESC;

EXPLAIN
SELECT
CAST(c_customer_sk AS BIGINT) AS c_customer_sk_big,
c_current_cdemo_sk
FROM delta_encoding_required_column
ORDER BY c_customer_sk_big DESC, c_current_cdemo_sk DESC;