findepi opened a new pull request, #13489:
URL: https://github.com/apache/datafusion/pull/13489

   ## Which issue does this PR close?
   
   - fixes https://github.com/apache/datafusion/issues/13476
   - fixes https://github.com/apache/datafusion/issues/13487
   - fixes https://github.com/apache/datafusion/issues/6543 
   
   
   ## Rationale for this change
   
   In SQL, selecting single column multiple times is legal and most modern
   databases support this. This commit adds such support to DataFusion too.
   
   ## What changes are included in this PR?
   
   - allow creation of schemas for duplicated names. DFSchema is used in 
logical plan to describe output of a relational operator, and In SQL, this is 
totally valid to have duplicated names
     - a better long term fix would be to limit Schema use for field resolution 
during initial query plan building and use unambiguous "symbols" or "variables" 
in the logical plan. This would fall under 
https://github.com/apache/datafusion/issues/12723
   - add checks for CREATE TABLE and CREATE VIEW to disallow creation of tables 
with duplicate field names
     - previously this was taken care of by schema construction checks, but 
only partially, as witnessed by 
https://github.com/apache/datafusion/issues/13487
   
   ## Are these changes tested?
   
   yes
   
   ## Are there any user-facing changes?
   
   yes, more valid queries are supported
   


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