From ce1af934e894ec8bc1ed103b85d0fb2d354ac19f Mon Sep 17 00:00:00 2001
From: Fedomn <fedomn.ma@gmail.com>
Date: Sat, 8 Oct 2022 18:11:48 +0800
Subject: [PATCH] feat(alias): support alias subquery

Signed-off-by: Fedomn <fedomn.ma@gmail.com>
---
 src/binder/table/mod.rs | 18 +++++++++++++++++-
 src/catalog/mod.rs      | 15 +++++++++++++++
 tests/slt/alias.slt     | 11 +++++++++++
 3 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/src/binder/table/mod.rs b/src/binder/table/mod.rs
index da626fe..8128f6f 100644
--- a/src/binder/table/mod.rs
+++ b/src/binder/table/mod.rs
@@ -4,6 +4,7 @@ pub use join::*;
 use sqlparser::ast::{TableFactor, TableWithJoins};
 
 use super::{BindError, Binder, BoundSelect};
+use crate::binder::BoundExpr::ColumnRef;
 use crate::catalog::{ColumnCatalog, ColumnId, TableCatalog, TableId};
 
 pub static DEFAULT_DATABASE_NAME: &str = "postgres";
@@ -131,9 +132,24 @@ impl Binder {
                 subquery,
                 alias,
             } => {
+                // handle subquery table
                 let table = self.bind_select(subquery)?;
                 if let Some(alias) = alias {
-                    todo!("alias for subquery {}", alias)
+                    // add subquery into context
+                    let columns = table
+                        .select_list
+                        .iter()
+                        .map(|expr| match expr {
+                            ColumnRef(col) => col.column_catalog.clone(),
+                            _ => {
+                                unreachable!("subquery select list should only contains column ref")
+                            }
+                        })
+                        .collect::<Vec<_>>();
+                    let table_alias = alias.to_string().to_lowercase();
+                    let table_catalog =
+                        TableCatalog::new_from_columns(table_alias.clone(), columns);
+                    self.context.tables.insert(table_alias, table_catalog);
                 }
                 Ok(BoundTableRef::Subquery(Box::new(table)))
             }
diff --git a/src/catalog/mod.rs b/src/catalog/mod.rs
index af3a2ed..1258a45 100644
--- a/src/catalog/mod.rs
+++ b/src/catalog/mod.rs
@@ -52,6 +52,21 @@ impl TableCatalog {
             .map(|id| self.columns.get(id).cloned().unwrap())
             .collect()
     }
+
+    pub fn new_from_columns(table_id: String, columns: Vec<ColumnCatalog>) -> Self {
+        let mut columns_tree = BTreeMap::new();
+        let mut column_ids = Vec::new();
+        for c in columns {
+            column_ids.push(c.column_id.clone());
+            columns_tree.insert(c.column_id.clone(), c);
+        }
+        TableCatalog {
+            id: table_id.to_string(),
+            name: table_id,
+            column_ids,
+            columns: columns_tree,
+        }
+    }
 }
 
 /// use column name as id for simplicity
diff --git a/tests/slt/alias.slt b/tests/slt/alias.slt
index 620044b..e087982 100644
--- a/tests/slt/alias.slt
+++ b/tests/slt/alias.slt
@@ -40,3 +40,14 @@ select t_1.a from t1 t_1 left join t2 t_2 on t_1.a=t_2.b and t_1.c > t_2.c;
 0
 1
 2
+
+# subquery alias
+query I
+select t.a from (select * from t1 where a > 1) t where t.b > 7;
+----
+2
+
+query III
+select t.* from (select * from t1 where a > 1) t where t.b > 7;
+----
+2 8 1