Refine CREATE TABLE and CREATE INDEX

src/main.rs

@@ -90,7 +90,7 @@ impl DbValue {
 // table-metadata and data
 
 type TableName = String;
-type TablePosition = u32;
+type TablePosition = usize;
 
 struct Table {
     schema: TableSchema,
@@ -117,10 +117,6 @@ struct TableSchema {
     types: Vec<DbType>,
 }
 
-// TODO
-fn column_position(table_meta: TableSchema, column_name: ColumnName) -> Option<ColumnPosition> {
-    todo!()
-}
 // Use `TablePosition` as index
 type Tables = Vec<Table>;
 
@@ -146,17 +142,35 @@ fn select_columns(row: &Row, columns: &Vec<ColumnPosition>) -> Row {
 
 // ==============Interpreter================
 struct State {
-    table_positions: HashMap<TableName, TablePosition>,
+    table_name_position_mapping: BiMap<TableName, TablePosition>,
     tables: Vec<Table>,
 }
 
 impl State {
-    fn table_from_name<'b: 'a, 'a>(&'b self, table_name: TableName) -> Option<&'a Table> {
+    fn table_from_name<'b: 'a, 'a>(&'b self, table_name: &TableName) -> DbResult<&'a Table> {
-        todo!()
+        match self.table_name_position_mapping.get_by_left(table_name) {
+            Some(table_position) => {
+                let table = &self.tables[*table_position];
+                Ok(table)
+            },
+            None => Err(Error::TableDoesNotExist(table_name.clone()))
+        }
+    }
+
+    fn table_from_name_mut<'b: 'a, 'a>(&'b mut self, table_name: &TableName) -> DbResult<&'a mut Table> {
+        match self.table_name_position_mapping.get_by_left(table_name) {
+            Some(table_position) => {
+                let table = &mut self.tables[*table_position];
+                Ok(table)
+            },
+            None => Err(Error::TableDoesNotExist(table_name.clone()))
+        }
     }
 
     fn attach_table(&mut self, table_name: TableName, table: Table) {
-        todo!()
+        let new_table_position: TablePosition = self.tables.len();
+        self.table_name_position_mapping.insert(table_name, new_table_position);
+        self.tables.push(table);
     }
 }
 
@@ -165,13 +179,6 @@ trait SqlConsumer {
     // TODO: 
 }
 
-// TODO: This should return a reference to the table
-// 'tables_life contains 'table_life
-fn get_table<'tables_life: 'table_life, 'table_life>(tables: &'tables_life Tables, table_name: &TableName) -> &'table_life Table {
-    // let table_position: 
-    todo!()
-}
-
 // TODO: Decide if we want for this to return a response (but then you have to deal with lifetimes,
 //       because you'll be forced to put an iterator/slice into the Response data-structure.
 //       Alternative is to pass a row-consumer to the functionas that knows how to communicate with
@@ -182,17 +189,17 @@ fn interpret(table_name: TableName, operation: Operation, state: &mut State, con
 
     match operation {
         Select(table_name, column_selection, maybe_condition) => {
-            let table: &Table = todo!();
+            let table: &Table = state.table_from_name(&table_name)?;
             Ok(Response::Selected(table.select_where(column_selection, maybe_condition)?))
         },
         Insert(table_name, values) => {
-            let table: &mut Table = todo!();
+            let table: &mut Table = state.table_from_name_mut(&table_name)?;
 
             let _ = table.insert(values)?;
-            Ok(Response::Inserted())
+            Ok(Response::Inserted)
         },
         Delete(table_name, maybe_condition) => {
-            let table: &mut Table = todo!();
+            let table: &mut Table = state.table_from_name_mut(&table_name)?;
 
             let rows_affected = table.delete_where(maybe_condition)?;
             Ok(Response::Deleted(rows_affected))
@@ -200,22 +207,28 @@ fn interpret(table_name: TableName, operation: Operation, state: &mut State, con
         CreateTable(table_name, table_schema) => {
             let table = Table::new(table_schema);
             state.attach_table(table_name, table);
-            todo!()
+            Ok(Response::TableCreated)
         },
         CreateIndex(table_name, column_name) => {
-            let table: &mut Table = todo!();
+            // TODO: This is incomplete. It can happen that an index is created
-            let column_position: ColumnPosition = todo!();
+            //       after the table has some rows for a while.
+            //       In such a case the index needs to be built over all those existing rows.
+            let table: &mut Table = state.table_from_name_mut(&table_name)?;
+            let column_position: ColumnPosition = table.schema.column_position_from_column_name(&column_name)?;
 
-            let index: ColumnIndex = ColumnIndex::new();
+            let index: ColumnIndex = ColumnIndex::new(&table.rows);
             table.attach_index(column_position, index); 
-            todo!()
+            Ok(Response::IndexCreated)
         },
     }
 }
 
 impl ColumnIndex {
-    fn new() -> Self {
+    fn new(rows: &Rows) -> Self {
-        Self { index: BTreeMap::new() }
+        let index = BTreeMap::new();
+        // TODO: Take into account already existing rows
+        todo!();
+        Self { index }
     }
 }
 
@@ -236,6 +249,10 @@ impl TableSchema {
         }
     }
 
+    fn column_position_from_column_name(&self, column_name: &ColumnName) -> DbResult<ColumnPosition> {
+        self.get_column(column_name).map(|(_, column_position)| column_position)
+    }
+
     fn is_primary(&self, column_position: ColumnPosition) -> bool {
         self.primary_key == column_position
     }
@@ -243,7 +260,7 @@ impl TableSchema {
     fn column_positions_from_column_names(&self, column_names: &[ColumnName]) -> DbResult<Vec<ColumnPosition>> {
         let mut positions: Vec<ColumnPosition> = Vec::with_capacity(column_names.len());
         for column_name in column_names {
-            let (_, column_position) = self.get_column(column_name)?;
+            let column_position = self.column_position_from_column_name(column_name)?;
             positions.push(column_position)
         }
         Ok(positions)
@@ -512,14 +529,17 @@ impl ColumnIndex {
 
 enum Response {
     Selected(Vec<Row>),
-    Inserted(),
+    Inserted,
     Deleted(usize), // how many were deleted
+    TableCreated,
+    IndexCreated,
 } 
 
 type DbResult<A> = Result<A, Error>;
 
 // #[derive(Debug)]
 enum Error {
+    TableDoesNotExist(TableName),
     ColumnDoesNotExist(TableName, ColumnName),
     ColumnPositionDoesNotExist(TableName, ColumnPosition),
     ValueDoesNotMatchExpectedType(TableName, ColumnName, DbType, DbValue),