Re: [I] Support parsing SQL strings to `Expr`s [datafusion]

[via GitHub]

alamb commented on issue #8736:
URL: https://github.com/apache/datafusion/issues/8736#issuecomment-2176140997

   This came up again on discord: 
https://discord.com/channels/885562378132000778/1166447479609376850/1252616019357470731
   
   Here is some code that @Omega359  shared
   
   
   ```rust
   pub(crate) fn build_expression(norm: &FieldNormalizer, df: &DataFrame, 
expression: &str) -> Result<Expr> {
       let parser = Parser::new(&AnsiDialect {});
       let tokenized = parser.try_with_sql(expression);
       if tokenized.is_err() {
           bail!("Unable to tokenize expression '{}': {:?}", &expression, 
tokenized.err())
       }
   
       let parsed = tokenized?.parse_expr();
       if parsed.is_err() {
           bail!("Unable to parse expression '{}': {:?}", &expression, 
parsed.err())
       }
   
       let expr = parsed?;
       debug!("Parsed expression was '{}'", expr);
   
       let parser_options = ParserOptions {
           enable_ident_normalization: false,
           parse_float_as_decimal: false,
       };
   
       let table_schema_provider = 
TableSchemaProvider::new(norm.table_name.clone(), norm.session_context.clone());
       let sql_to_rel = SqlToRel::new_with_options(&table_schema_provider, 
parser_options);
       let sql_to_expr = sql_to_rel.sql_to_expr(expr.clone(), df.schema(), &mut 
PlannerContext::new());
   
       if sql_to_expr.is_err() {
           bail!("Unable to transform sql expression '{}' to datafusion Expr: 
{:?}", &expression, sql_to_expr.err())
       }
   
       Ok(sql_to_expr?)
   }
   ```
   
   I think it would be great to add an API to `DataFrame` and `SessionContext` 
to do this:
   
   ```rust
   impl SessionContext {
      /// parse the provided expression as a string
     fn parse_sql(&self, sql: &str) -> Result<Expr> { ... }
   }
   ```
   
   ```rust
   impl DataFrame {
      /// parse the provided expression as a string
     fn parse_sql(&self, sql: &str) -> Result<Expr> { ... }
   }
   ```
   
   Perhaps @xinlifoobar has time to help here 🤔 


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