Merge branch 'tables' into 'main'

Refine design

See merge request x433485/minisql!1

.gitignore

@@ -0,0 +1,2 @@
+/target
+tmp_repl.txt

Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "minisql"
+version = "0.1.0"

Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "minisql"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

DESIGN.md

@@ -69,11 +69,41 @@ which will store the database as a file `path/to/db/my-db.db` and open a TCP ser
   how will the parsing output look like?
   Consider something like
 ```
+// TODO: Parser has access to all table metadata
+
 // Could also be called `SQLAbstractSyntaxTree`
-enum Operations {
-  Select(Vector<FieldName>, TableName),
-  Update(...)
+enum Operation {
+  Select(TableName, ColumnSelection, Option<Condition>),
+  Insert(TableName, Vec<(ColumnName, DbValue)>), // String because we don't yet know which type of value this is for sure
+  Delete(TableName, Option<Condition>),
+  // Update(...),
 }
+
+enum ColumnSelection {
+    All,
+    Columns(Vec<ColumnName>),
+}
+
+enum Condition = {
+    // And(Condition, Condition),
+    // Or(Condition, Condition),
+    // Not(Condition),
+
+    Eq(ColumnName, DbValue)
+    // LessOrEqual(ColumnName, DbValue)
+    // Less(ColumnName, DbValue)
+
+    // StringCondition(StringCondition)
+}
+
+enum StringCondition {
+    Prefix(ColumnName, String)
+    Substring(ColumnName, String)
+}
+
+
+
+INSERT 123
 ```
 * We also have to write an interpreter for these operations. How will the db-state be represented in memory?
   For example how can we implement a table?
@@ -82,11 +112,46 @@ enum Operations {
 enum DbValue {
   DbString(String),
   DbNumber(Float),
-  DbByte(u8),
   DbUUID(u32)
 }
 
+// We also need a type of db-types
+enum DbType {
+    TString,
+    TNumber,
+    TId,
+}
+
+value_to_type(db_val: DbValue) -> DbType
+
+
+// table-metadata and data
+
+type TableName = String
+
+// Note that it is nice to split metadata from the data because
+// then you can give the metadata to the parser without giving it the data.
+struct TableMetaData {
+    name: TableName, // TODO: Is this really necessary? probably not
+    columns: Vec<(ColumnName, DbType, ColumnPosition)>
+}
+
+fn column_position(TableMetaData, ColumnName) -> ColumnPosition
+
+struct Table {
+    meta: TableMetaData,
+    rows: Rows // defined below
+    indexes:
+        BTree<ColumnName, Index> // TODO: Consider generalizing ColumnName to semething that would also apply to a pair of ColumnNames etc
+}
+
+type Tables = HashMap<TableName, Table>
+
+// We also need a function that for a given value computes its type (for validation)
+
+
 type ColumnName = String
+type ColumnPosition = u32
 
 // The below type is a type of a table row
 type Row = HashMap<ColumnName, DbValue>
@@ -94,6 +159,9 @@ type Row = HashMap<ColumnName, DbValue>
 // Or you know... some appropriate Dictionary Type
 HashMap::make![("id", 1), ("name", "Alice"), ("salary", 20.0)] : Row
 
+type Rows =
+    BTree<Id, Row>
+
 // possible optimization: have a mapping
 // column names ~> indexes
 // so that we could represent rows as
@@ -112,6 +180,47 @@ e.g. Row ~> vec![DbUUID 1, DbSTring "Alice"]
 Vec<Vec<DbValue>>
 
 ```
+* Interpreter
+```
+trait SqlConsumer {
+    // TODO: 
+    ???
+}
+
+fn interpret<T: SqlConsumer>(operation: Operation, tables: &mut Tables, consumer: T) -> ()  {
+    // TODO: lock stuff
+    match operation {
+          Select(table_name, column_selection, maybe_condition) => {
+            let table: Table = ...
+            // TODO: Wrap this into a response
+            select(table, column_selection, maybe_condition, consumer)
+          },
+          Insert(table_name, Vec<(ColumnName, DbValue)>) => {
+             insert(table, ???)
+          }
+          Delete(table_name, maybe_condition) => {
+
+          }
+    }
+}
+
+  response = interpret(...)
+  knows_how_to_respond(response, client)
+
+
+enum Response {
+    Selected(impl Iter<???>) // TODO: How to do this? Some reference to an iterator somehow... slice..?
+    Inserted(???),
+    Deleted(usize), // how many were deleted
+} 
+
+fn select(table: Table, ColumnName
+
+
+
+```
+
+
 * TODO: Consider streaming the response to the client and not just dumping 10K rows at once.
 
 

src/main.rs

@@ -0,0 +1,223 @@
+use std::collections::{BTreeMap, HashMap};
+
+// ==============SQL operations================
+// TODO: Note that every operation has a table name.
+//       Perhaps consider factoring the table name out
+//       and think of the operations as operating on a unique table.
+enum Operation {
+    Select(TableName, ColumnSelection, Option<Condition>),
+    Insert(TableName, InsertionValues),
+    Delete(TableName, Option<Condition>),
+    // Update(...),
+    //
+    CreateTable(TableName, TableSchema),
+    CreateIndex(TableName, ColumnName), // TODO: Is this sufficient?
+    // DropTable(TableName),
+}
+
+type InsertionValues = Vec<(ColumnName, DbValue)>;
+
+enum ColumnSelection {
+    All,
+    Columns(Vec<ColumnName>),
+}
+
+enum Condition {
+    // And(Box<Condition>, Box<Condition>),
+    // Or(Box<Condition>, Box<Condition>),
+    // Not(Box<Condition>),
+
+    Eq(ColumnName, DbValue),
+    // LessOrEqual(ColumnName, DbValue),
+    // Less(ColumnName, DbValue),
+
+    // StringCondition(StringCondition),
+}
+
+// enum StringCondition {
+//     Prefix(ColumnName, String),
+//     Substring(ColumnName, String),
+// }
+
+
+// ==============Values and Types================
+type UUID = u64;
+
+// TODO: What about nulls? I would rather not have that as in SQL, it sucks.
+//       I would rather have non-nullable values by default,
+//       and something like an explicit Option type for nulls.
+enum DbValue {
+    String(String),
+    Int(u64),
+    Number(f64),
+    UUID(UUID),
+}
+
+// TODO: Can this be autogenerated from the values?
+enum DbType {
+    String,
+    Int,
+    Number,
+    UUID,
+}
+
+impl DbValue {
+    // TODO: Can this be autogenerated?
+    fn to_type(self) -> DbType {
+        match self {
+            Self::String(_) => DbType::String,
+            Self::Int(_) => DbType::Int,
+            Self::Number(_) => DbType::Number,
+            Self::UUID(_) => DbType::UUID,
+        }
+    }
+}
+
+
+// ==============Tables================
+// table-metadata and data
+
+type TableName = String;
+type TablePosition = u32;
+
+struct Table {
+    schema: TableSchema,
+    rows: Rows,
+    indexes:
+        HashMap<ColumnPosition, ColumnIndex> // TODO: Consider generalizing `ColumnPosition` to something that would also apply to a pair of `ColumnNames` etc
+}
+
+// TODO: Is this really indexed by DbValues?
+//       Maybe we should have a separate index type for each type of value we're indexing over
+struct ColumnIndex {
+    index: BTreeMap<DbValue, UUID>
+}
+
+// Note that it is nice to split metadata from the data because
+// then you can give the metadata to the parser without giving it the data.
+struct TableSchema {
+    columns: HashMap<ColumnName, (DbType, ColumnPosition)>
+}
+
+// TODO
+fn column_position(table_meta: TableSchema, column_name: ColumnName) -> Option<ColumnPosition> {
+    todo!()
+}
+
+// Use `TablePosition` as index
+type Tables = Vec<Table>;
+
+
+type ColumnName = String;
+type ColumnPosition = u32;
+
+// Use `ColumnPosition` as index
+type Row = Vec<DbValue>;
+
+type Rows =
+    BTreeMap<UUID, Row>;
+
+// ==============Interpreter================
+struct State {
+    table_positions: HashMap<TableName, TablePosition>,
+    tables: Vec<Table>,
+}
+
+impl State {
+    fn table_from_name<'b: 'a, 'a>(&'b self, table_name: TableName) -> Option<&'a Table> {
+        todo!()
+    }
+
+    fn attach_table(&mut self, table: Table) {
+        todo!()
+    }
+}
+
+// TODO: Give a better name to something that you can respond to with rows
+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
+//       the client, but the details of communication are hidden behind an interface
+fn interpret(table_name: TableName, operation: Operation, state: &mut State, consumer: impl SqlConsumer) -> ()  {
+    // TODO: lock stuff
+    use Operation::*;
+
+    match operation {
+        Select(table_name, column_selection, maybe_condition) => {
+            let table: &Table = todo!();
+            table.select_where(column_selection, maybe_condition, consumer)
+        },
+        Insert(table_name, values) => {
+            let table: &mut Table = todo!();
+
+            table.insert(values, consumer)
+        },
+        Delete(table_name, maybe_condition) => {
+            let table: &mut Table = todo!();
+
+            table.delete_where(maybe_condition, consumer)
+        },
+        CreateTable(table_name, table_schema) => {
+            let table = Table::new(table_name, table_schema);
+            state.attach_table(table);
+            todo!()
+        },
+        CreateIndex(table_name, column_name) => {
+            let table: &mut Table = todo!();
+
+            let index: ColumnIndex = ColumnIndex::new(table, column_name);
+            table.attach_index(index);
+        }, // TODO: Is this sufficient?
+                                            //
+    }
+}
+
+impl ColumnIndex {
+    fn new(table: &Table, column_name: ColumnName) -> ColumnIndex {
+        todo!()
+    }
+}
+
+
+impl Table {
+    fn new(table_name: TableName, table_schema: TableSchema) -> Table {
+        todo!()
+    }
+
+    fn attach_index(&mut self, column_index: ColumnIndex) {
+        todo!()
+    }
+
+    fn select_where(&self, column_selection: ColumnSelection, maybe_condition: Option<Condition>, consumer: impl SqlConsumer) {
+        todo!()
+    }
+
+    fn insert(&mut self, values: InsertionValues, consumer: impl SqlConsumer) {
+        todo!()
+    }
+
+    fn delete_where(&mut self, maybe_condition: Option<Condition>, consumer: impl SqlConsumer) {
+        todo!()
+    }
+}
+
+// enum Response {
+//     Selected(impl Iter<???>), // TODO: How to do this? Some reference to an iterator somehow... slice..?
+//     Inserted(???),
+//     Deleted(usize), // how many were deleted
+// } 
+
+fn main() {
+    println!("Hello, world!");
+}