alamb commented on code in PR #10582:
URL: https://github.com/apache/datafusion/pull/10582#discussion_r1607076013
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datafusion-examples/examples/plan_to_sql.rs:
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@@ -22,36 +22,45 @@ use datafusion::sql::unparser::expr_to_sql;
use datafusion_sql::unparser::dialect::CustomDialect;
use datafusion_sql::unparser::{plan_to_sql, Unparser};
-/// This example demonstrates the programmatic construction of
-/// SQL using the DataFusion Expr [`Expr`] and LogicalPlan [`LogicalPlan`] API.
+/// This example demonstrates the programmatic construction of SQL strings
using
+/// the DataFusion Expr [`Expr`] and LogicalPlan [`LogicalPlan`] API.
///
///
/// The code in this example shows how to:
-/// 1. Create SQL from a variety of Expr and LogicalPlan: [`main`]`
-/// 2. Create a simple expression [`Exprs`] with fluent API
-/// and convert to sql: [`simple_expr_to_sql_demo`]
-/// 3. Create a simple expression [`Exprs`] with fluent API
-/// and convert to sql without escaping column names:
[`simple_expr_to_sql_demo_no_escape`]
-/// 4. Create a simple expression [`Exprs`] with fluent API
-/// and convert to sql escaping column names a MySQL style:
[`simple_expr_to_sql_demo_escape_mysql_style`]
+///
+/// 1. [`simple_expr_to_sql_demo`]: Create a simple expression [`Exprs`] with
+/// fluent API and convert to sql suitable for passing to another database
+///
+/// 2. [`simple_expr_to_sql_demo_no_escape`] Create a simple expression
+/// [`Exprs`] with fluent API and convert to sql without escaping column names
+/// more suitable for displaying to humans.
+///
+/// 3. [`simple_expr_to_sql_demo_escape_mysql_style`]" Create a simple
+/// expression [`Exprs`] with fluent API and convert to sql escaping column
+/// names in MySQL style.
+///
+/// 4. [`simple_plan_to_sql_demo`]: Create a simple logical plan using the
+/// DataFrames API and convert to sql string.
+///
+/// 5. [`round_trip_plan_to_sql_demo`]: Create a logical plan from a SQL
string, modify it using the
+/// DataFrames API and convert it back to a sql string.
#[tokio::main]
async fn main() -> Result<()> {
// See how to evaluate expressions
simple_expr_to_sql_demo()?;
simple_expr_to_sql_demo_no_escape()?;
simple_expr_to_sql_demo_escape_mysql_style()?;
- simple_plan_to_sql_parquest_dataframe_demo().await?;
- round_trip_plan_to_sql_parquest_dataframe_demo().await?;
+ simple_plan_to_sql_demo().await?;
+ round_trip_plan_to_sql_demo().await?;
Ok(())
}
/// DataFusion can convert expressions to SQL, using column name escaping
/// PostgreSQL style.
fn simple_expr_to_sql_demo() -> Result<()> {
let expr = col("a").lt(lit(5)).or(col("a").eq(lit(8)));
- let ast = expr_to_sql(&expr)?;
- let sql = format!("{}", ast);
+ let sql = expr_to_sql(&expr)?.to_string();
Review Comment:
I think it makes it easier to use this example if we don't have to worry
about the intermediate `ast` as much, so I combined it into a single statement
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