Merge branch 'interpreter' into 'main'

Interpreter

See merge request x433485/minisql!2

Cargo.lock

@@ -55,6 +55,12 @@ dependencies = [
  "rustc-demangle",
 ]
 
+[[package]]
+name = "bimap"
+version = "0.6.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "230c5f1ca6a325a32553f8640d31ac9b49f2411e901e427570154868b46da4f7"
+
 [[package]]
 name = "bincode"
 version = "2.0.0-rc.3"
@@ -147,6 +153,9 @@ checksum = "f665ee40bc4a3c5590afb1e9677db74a508659dfd71e126420da8274909a0167"
 [[package]]
 name = "minisql"
 version = "0.1.0"
+dependencies = [
+ "bimap",
+]
 
 [[package]]
 name = "miniz_oxide"

minisql/Cargo.toml

@@ -6,3 +6,4 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+bimap = "0.6.3"

minisql/src/error.rs

@@ -0,0 +1,17 @@
+use crate::internals::row::ColumnPosition;
+use crate::internals::schema::{ColumnName, TableName};
+use crate::operation::InsertionValues;
+use crate::type_system::{DbType, Uuid, Value};
+
+#[derive(Debug)]
+pub enum Error {
+    TableDoesNotExist(TableName),
+    ColumnDoesNotExist(TableName, ColumnName),
+    ColumnPositionDoesNotExist(TableName, ColumnPosition),
+    ValueDoesNotMatchExpectedType(TableName, ColumnName, DbType, Value),
+    AttemptingToInsertAlreadyPresentId(TableName, Uuid),
+    MissingTypeAnnotationOfColumn(TableName, ColumnPosition),
+    MissingColumnInInsertValues(TableName, ColumnName, InsertionValues),
+    MismatchBetweenInsertValuesAndColumns(TableName, InsertionValues),
+    AttemptToIndexNonIndexableColumn(TableName, ColumnName),
+}

minisql/src/internals/column_index.rs

@@ -0,0 +1,38 @@
+use crate::type_system::{IndexableValue, Uuid};
+use std::collections::{BTreeMap, HashSet};
+
+#[derive(Debug)]
+pub struct ColumnIndex {
+    index: BTreeMap<IndexableValue, HashSet<Uuid>>,
+}
+
+impl ColumnIndex {
+    pub fn new() -> Self {
+        let index = BTreeMap::new();
+        Self { index }
+    }
+
+    pub fn get(&self, value: &IndexableValue) -> Option<&HashSet<Uuid>> {
+        self.index.get(value)
+    }
+
+    pub fn add(&mut self, value: IndexableValue, id: Uuid) {
+        match self.index.get_mut(&value) {
+            Some(ids) => {
+                ids.insert(id);
+            }
+            None => {
+                self.index.insert(value, HashSet::from([id]));
+            }
+        }
+    }
+
+    pub fn remove(&mut self, value: &IndexableValue, id_to_be_removed: Uuid) -> bool {
+        match self.index.get_mut(value) {
+            Some(ids) => {
+                ids.remove(&id_to_be_removed) // true if was present
+            }
+            None => false,
+        }
+    }
+}

minisql/src/internals/mod.rs

@@ -0,0 +1,4 @@
+pub mod column_index;
+pub mod row;
+pub mod schema;
+pub mod table;

minisql/src/internals/row.rs

@@ -0,0 +1,71 @@
+use crate::type_system::Value;
+use std::ops::{Index, IndexMut};
+use std::slice::SliceIndex;
+
+pub type ColumnPosition = usize;
+
+#[derive(Debug, Clone)]
+pub struct Row(Vec<Value>);
+
+impl<Idx> Index<Idx> for Row
+where
+    Idx: SliceIndex<[Value]>,
+{
+    type Output = Idx::Output;
+
+    fn index(&self, index: Idx) -> &Self::Output {
+        &self.0[index]
+    }
+}
+
+impl<Idx> IndexMut<Idx> for Row
+where
+    Idx: SliceIndex<[Value]>,
+{
+    fn index_mut(&mut self, index: Idx) -> &mut Self::Output {
+        &mut self.0[index]
+    }
+}
+
+impl FromIterator<Value> for Row {
+    fn from_iter<I: IntoIterator<Item = Value>>(iter: I) -> Self {
+        let mut v = vec![];
+        for x in iter {
+            v.push(x)
+        }
+        Row(v)
+    }
+}
+
+impl Row {
+    pub fn new() -> Self {
+        Row(vec![])
+    }
+
+    pub fn with_number_of_columns(number_of_columns: usize) -> Self {
+        Row(Vec::with_capacity(number_of_columns))
+    }
+
+    pub fn push(&mut self, value: Value) {
+        self.0.push(value)
+    }
+
+    pub fn len(&self) -> usize {
+        self.0.len()
+    }
+
+    pub fn get(&self, column_position: ColumnPosition) -> Option<&Value> {
+        self.0.get(column_position)
+    }
+
+    pub fn restrict_columns(&self, columns: &Vec<ColumnPosition>) -> Row {
+        // If the index from `columns` is non-existant in `row`, it will just ignore it.
+        let mut subrow: Row = Row::new();
+        for column_position in columns {
+            if let Some(value) = self.get(*column_position) {
+                subrow.0.push(value.clone())
+            }
+        }
+        subrow
+    }
+}

minisql/src/internals/schema.rs

@@ -0,0 +1,162 @@
+use crate::error::Error;
+use crate::internals::row::{ColumnPosition, Row};
+use crate::operation::{ColumnSelection, InsertionValues};
+use crate::result::DbResult;
+use crate::type_system::{DbType, IndexableValue, Uuid, Value};
+use bimap::BiMap;
+use std::collections::HashMap;
+
+// 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.
+#[derive(Debug)]
+pub struct TableSchema {
+    table_name: TableName, // used for descriptive errors
+    pub primary_key: ColumnPosition,
+    pub column_name_position_mapping: BiMap<ColumnName, ColumnPosition>,
+    pub types: Vec<DbType>,
+}
+
+pub type TableName = String;
+pub type ColumnName = String;
+
+impl TableSchema {
+    pub fn new(table_name: TableName, primary_key: ColumnPosition, column_name_position_map: Vec<(ColumnName, ColumnPosition)>, types: Vec<DbType>) -> Self {
+        let mut column_name_position_mapping: BiMap<ColumnName, ColumnPosition> = BiMap::new();
+        for (column_name, column_position) in column_name_position_map {
+            column_name_position_mapping.insert(column_name, column_position);
+        }
+        Self { table_name, primary_key, column_name_position_mapping, types }
+    }
+
+    pub fn table_name(&self) -> &TableName {
+        &self.table_name
+    }
+
+    fn get_column(&self, column_name: &ColumnName) -> DbResult<(DbType, ColumnPosition)> {
+        match self.column_name_position_mapping.get_by_left(column_name) {
+            Some(column_position) => match self.types.get(*column_position) {
+                Some(type_) => Ok((*type_, *column_position)),
+                None => Err(Error::MissingTypeAnnotationOfColumn(
+                    self.table_name.clone(),
+                    *column_position,
+                )),
+            },
+            None => Err(Error::ColumnDoesNotExist(
+                self.table_name.clone(),
+                column_name.clone(),
+            )),
+        }
+    }
+
+    pub fn column_position_from_column_name(
+        &self,
+        column_name: &ColumnName,
+    ) -> DbResult<ColumnPosition> {
+        self.get_column(column_name)
+            .map(|(_, column_position)| column_position)
+    }
+
+    pub fn is_primary(&self, column_position: ColumnPosition) -> bool {
+        self.primary_key == column_position
+    }
+
+    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.column_position_from_column_name(column_name)?;
+            positions.push(column_position)
+        }
+        Ok(positions)
+    }
+
+    pub fn column_name_from_column_position(
+        &self,
+        column_position: ColumnPosition,
+    ) -> DbResult<ColumnName> {
+        match self
+            .column_name_position_mapping
+            .get_by_right(&column_position)
+        {
+            Some(column_name) => Ok(column_name.clone()),
+            None => Err(Error::ColumnPositionDoesNotExist(
+                self.table_name.clone(),
+                column_position,
+            )),
+        }
+    }
+
+    pub fn column_positions_from_column_selection(
+        &self,
+        column_selection: &ColumnSelection,
+    ) -> DbResult<Vec<ColumnPosition>> {
+        match column_selection {
+            ColumnSelection::All => {
+                let mut column_positions: Vec<ColumnPosition> = self
+                    .column_name_position_mapping
+                    .iter()
+                    .map(|(_, column_position)| *column_position)
+                    .collect();
+                column_positions.sort();
+                Ok(column_positions)
+            }
+
+            ColumnSelection::Columns(column_names) => {
+                self.column_positions_from_column_names(column_names)
+            }
+        }
+    }
+
+    fn number_of_columns(&self) -> usize {
+        self.column_name_position_mapping.len()
+    }
+
+    pub fn row_from_insertion_values(
+        &self,
+        insertion_values: InsertionValues,
+    ) -> DbResult<(Uuid, Row)> {
+        // TODO: There should be proper validation of the insertion_values.
+        //       And it shouldn't really be done here.
+        //
+        //       In the below we don't check for duplicate column names
+        //
+        let number_of_columns = self.number_of_columns();
+        if number_of_columns != insertion_values.len() {
+            return Err(Error::MismatchBetweenInsertValuesAndColumns(
+                self.table_name.clone(),
+                insertion_values,
+            ));
+        }
+
+        let mut row: Row = Row::with_number_of_columns(number_of_columns);
+
+        let mut values: HashMap<ColumnName, Value> = HashMap::new();
+        for (column_name, db_value) in &insertion_values {
+            values.insert(column_name.clone(), db_value.clone());
+        }
+
+        for column_position in 0..number_of_columns {
+            let column_name: ColumnName = self.column_name_from_column_position(column_position)?;
+            match values.get(&column_name) {
+                Some(db_value) => row.push(db_value.clone()),
+                None => {
+                    return Err(Error::MissingColumnInInsertValues(
+                        self.table_name.clone(),
+                        column_name,
+                        insertion_values,
+                    ))
+                }
+            }
+        }
+
+        let id: Uuid = match row.get(self.primary_key) {
+            Some(Value::Indexable(IndexableValue::Uuid(id))) => *id,
+            Some(_) => unreachable!(),
+            None => unreachable!(),
+        };
+
+        Ok((id, row))
+    }
+}

minisql/src/internals/table.rs

@@ -0,0 +1,262 @@
+use std::collections::{BTreeMap, HashMap, HashSet};
+
+use crate::error::Error;
+use crate::internals::column_index::ColumnIndex;
+use crate::internals::row::{ColumnPosition, Row};
+use crate::internals::schema::{ColumnName, TableSchema, TableName};
+use crate::result::DbResult;
+use crate::type_system::{IndexableValue, Uuid, Value};
+
+#[derive(Debug)]
+pub struct Table {
+    schema: TableSchema,
+    rows: Rows, // TODO: Consider wrapping this in a lock. Also consider if we need to have the
+    // same lock for both rows and indexes
+    indexes: HashMap<ColumnPosition, ColumnIndex>,
+}
+
+pub type Rows = BTreeMap<Uuid, Row>;
+
+impl Table {
+    pub fn new(table_schema: TableSchema) -> Self {
+        Self {
+            schema: table_schema,
+            rows: BTreeMap::new(),
+            indexes: HashMap::new(),
+        }
+    }
+
+    pub fn schema(&self) -> &TableSchema {
+        &self.schema
+    }
+
+    pub fn rows(&self) -> &Rows {
+        &self.rows
+    }
+
+    pub fn indexes(&self) -> &HashMap<ColumnPosition, ColumnIndex> {
+        &self.indexes
+    }
+
+    pub fn table_name(&self) -> &TableName {
+        &self.schema.table_name()
+    }
+
+    // ======Selection======
+    fn get_row_by_id(&self, id: Uuid) -> Option<Row> {
+        self.rows.get(&id).cloned()
+    }
+
+    fn get_rows_by_ids(&self, ids: HashSet<Uuid>) -> Vec<Row> {
+        ids.into_iter()
+            .filter_map(|id| self.get_row_by_id(id))
+            .collect()
+    }
+
+    fn get_rows_by_value(&self, column_position: ColumnPosition, value: &Value) -> Vec<Row> {
+        // brute-force search
+        self.rows
+            .values()
+            .filter_map(|row| {
+                if row.get(column_position) == Some(value) {
+                    Some(row.clone())
+                } else {
+                    None
+                }
+            })
+            .collect()
+    }
+
+    pub fn select_all_rows(&self, selected_column_positions: &Vec<ColumnPosition>) -> Vec<Row> {
+        self.rows
+            .values()
+            .map(|row| row.restrict_columns(selected_column_positions))
+            .collect()
+    }
+
+    pub fn select_rows_where_eq(
+        &self,
+        selected_column_positions: &Vec<ColumnPosition>,
+        column_position: ColumnPosition,
+        value: Value,
+    ) -> DbResult<Vec<Row>> {
+        match value {
+            Value::Indexable(value) => match self.fetch_ids_from_index(column_position, &value)? {
+                Some(ids) => Ok(self
+                    .get_rows_by_ids(ids)
+                    .iter()
+                    .map(|row| row.restrict_columns(selected_column_positions))
+                    .collect()),
+                None => Ok(self
+                    .get_rows_by_value(column_position, &Value::Indexable(value))
+                    .iter()
+                    .map(|row| row.restrict_columns(selected_column_positions))
+                    .collect()),
+            },
+            _ => Ok(self
+                .get_rows_by_value(column_position, &value)
+                .iter()
+                .map(|row| row.restrict_columns(selected_column_positions))
+                .collect()),
+        }
+    }
+
+    // ======Insertion======
+    pub fn insert_row_at(&mut self, id: Uuid, row: Row) -> DbResult<()> {
+        if self.rows.get(&id).is_some() {
+            return Err(Error::AttemptingToInsertAlreadyPresentId(
+                self.table_name().clone(),
+                id,
+            ));
+        }
+
+        for (column_position, column_index) in &mut self.indexes {
+            match row.get(*column_position) {
+                Some(Value::Indexable(val)) => column_index.add(val.clone(), id),
+                Some(_) => {}
+                None => {
+                    return Err(Error::ColumnPositionDoesNotExist(
+                        self.schema.table_name().clone(), // Note that I can't simply use self.table_name() here because of rust borrowing rules.
+                        *column_position,
+                    ))
+                }
+            }
+        }
+
+        let _ = self.rows.insert(id, row);
+        Ok(())
+    }
+
+    // ======Deletion======
+    fn delete_row_by_id(&mut self, id: Uuid) -> usize {
+        match self.rows.remove(&id) {
+            Some(row) => {
+                for (column_position, column_index) in &mut self.indexes {
+                    if let Value::Indexable(value) = &row[*column_position] {
+                        let _ = column_index.remove(value, id);
+                    };
+                }
+                1
+            }
+            None => 0,
+        }
+    }
+
+    fn delete_rows_by_ids(&mut self, ids: HashSet<Uuid>) -> usize {
+        let mut total_count = 0;
+        for id in ids {
+            total_count += self.delete_row_by_id(id)
+        }
+        total_count
+    }
+
+    fn delete_rows_by_value(&mut self, column_position: ColumnPosition, value: &Value) -> usize {
+        let matched_ids: HashSet<Uuid> = self
+            .rows
+            .iter()
+            .filter_map(|(id, row)| {
+                if row.get(column_position) == Some(value) {
+                    Some(*id)
+                } else {
+                    None
+                }
+            })
+            .collect();
+        self.delete_rows_by_ids(matched_ids)
+    }
+
+    pub fn delete_all_rows(&mut self) -> usize {
+        let number_of_rows = self.rows.len();
+        self.rows = BTreeMap::new();
+        self.indexes = HashMap::new();
+        number_of_rows
+    }
+
+    pub fn delete_rows_where_eq(
+        &mut self,
+        column_position: ColumnPosition,
+        value: Value,
+    ) -> DbResult<usize> {
+        match value {
+            Value::Indexable(value) => match self.fetch_ids_from_index(column_position, &value)? {
+                Some(ids) => Ok(self.delete_rows_by_ids(ids)),
+                None => Ok(self.delete_rows_by_value(column_position, &Value::Indexable(value))),
+            },
+            _ => Ok(self.delete_rows_by_value(column_position, &value)),
+        }
+    }
+
+    // ======Indexing======
+    pub fn attach_index(&mut self, column_position: ColumnPosition) -> DbResult<()> {
+        let mut column_index: ColumnIndex = ColumnIndex::new();
+        update_index_from_table(&mut column_index, self, column_position)?;
+        self.indexes.insert(column_position, column_index);
+        Ok(())
+    }
+
+    fn fetch_ids_from_index(
+        &self,
+        column_position: ColumnPosition,
+        value: &IndexableValue,
+    ) -> DbResult<Option<HashSet<Uuid>>> {
+        if self.schema.is_primary(column_position) {
+            match value {
+                IndexableValue::Uuid(id) => Ok(Some(HashSet::from([*id]))),
+                _ => {
+                    let column_name: ColumnName = self
+                        .schema
+                        .column_name_from_column_position(column_position)?;
+                    let type_ = self.schema.types[column_position];
+                    Err(Error::ValueDoesNotMatchExpectedType(
+                        self.table_name().clone(),
+                        column_name,
+                        type_,
+                        Value::Indexable(value.clone()),
+                    ))
+                }
+            }
+        } else {
+            match self.indexes.get(&column_position) {
+                Some(index) => {
+                    // Note that we are cloning the ids here! This can be very wasteful in some cases.
+                    // It would be possible to just return a reference,
+                    // but this seems fairly non-trivial.
+                    let ids = index.get(value).cloned();
+                    Ok(ids)
+                }
+                None => Ok(None),
+            }
+        }
+    }
+}
+
+// Should be used in the case when an index is created after the table has existed for a
+// while. In such a case you need to build the index from the already existing rows.
+fn update_index_from_table(
+    column_index: &mut ColumnIndex,
+    table: &Table,
+    column_position: ColumnPosition,
+) -> DbResult<()> {
+    for (id, row) in &table.rows {
+        let value = match row.get(column_position) {
+            Some(Value::Indexable(value)) => value.clone(),
+            Some(_) => {
+                let column_name: ColumnName = table
+                    .schema
+                    .column_name_from_column_position(column_position)?;
+                return Err(Error::AttemptToIndexNonIndexableColumn(
+                    table.table_name().to_string(),
+                    column_name,
+                ));
+            }
+            None => {
+                return Err(Error::ColumnPositionDoesNotExist(
+                    table.table_name().to_string(),
+                    column_position,
+                ))
+            }
+        };
+        column_index.add(value, *id)
+    }
+    Ok(())
+}

minisql/src/interpreter.rs

@@ -0,0 +1,621 @@
+use crate::error::Error;
+use crate::internals::row::{ColumnPosition, Row};
+use crate::internals::schema::{TableName, TableSchema};
+use crate::internals::table::Table;
+use crate::operation::{ColumnSelection, Condition, Operation};
+use crate::result::DbResult;
+use crate::type_system::{DbType, IndexableValue, Value};
+use bimap::BiMap;
+
+// Use `TablePosition` as index
+pub type Tables = Vec<Table>;
+pub type TablePosition = usize;
+
+// ==============Interpreter================
+#[derive(Debug)]
+pub struct State {
+    table_name_position_mapping: BiMap<TableName, TablePosition>,
+    tables: Tables,
+}
+
+#[derive(Debug)]
+pub enum Response {
+    Selected(Vec<Row>),
+    Inserted,
+    Deleted(usize), // how many were deleted
+    TableCreated,
+    IndexCreated,
+}
+
+impl State {
+    fn new() -> Self {
+        Self {
+            table_name_position_mapping: BiMap::new(),
+            tables: vec![],
+        }
+    }
+
+    fn table_from_name<'b: 'a, 'a>(&'b self, table_name: &TableName) -> DbResult<&'a Table> {
+        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) {
+        let new_table_position: TablePosition = self.tables.len();
+        self.table_name_position_mapping
+            .insert(table_name, new_table_position);
+        self.tables.push(table);
+    }
+
+    // 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
+    //
+    //  writer: impl SqlResponseConsumer
+    pub fn interpret(&mut self, operation: Operation) -> DbResult<Response> {
+        // TODO: lock stuff
+        use Operation::*;
+
+        match operation {
+            Select(table_name, column_selection, maybe_condition) => {
+                let table: &Table = self.table_from_name(&table_name)?;
+
+                let selected_column_positions: Vec<ColumnPosition> = table
+                    .schema()
+                    .column_positions_from_column_selection(&column_selection)?;
+                let selected_rows = match maybe_condition {
+                    None => table.select_all_rows(&selected_column_positions),
+
+                    Some(Condition::Eq(eq_column_name, value)) => {
+                        let eq_column_position = table
+                            .schema()
+                            .column_position_from_column_name(&eq_column_name)?;
+                        table.select_rows_where_eq(
+                            &selected_column_positions,
+                            eq_column_position,
+                            value,
+                        )?
+                    }
+                };
+
+                Ok(Response::Selected(selected_rows))
+            }
+            Insert(table_name, values) => {
+                let table: &mut Table = self.table_from_name_mut(&table_name)?;
+
+                let (id, row) = table.schema().row_from_insertion_values(values)?;
+                table.insert_row_at(id, row)?;
+                Ok(Response::Inserted)
+            }
+            Delete(table_name, maybe_condition) => {
+                let table: &mut Table = self.table_from_name_mut(&table_name)?;
+
+                let rows_affected = match maybe_condition {
+                    None => table.delete_all_rows(),
+                    Some(Condition::Eq(eq_column_name, value)) => {
+                        let eq_column_position = table
+                            .schema()
+                            .column_position_from_column_name(&eq_column_name)?;
+                        table.delete_rows_where_eq(eq_column_position, value)?
+                    }
+                };
+
+                Ok(Response::Deleted(rows_affected))
+            }
+            CreateTable(table_name, table_schema) => {
+                let table = Table::new(table_schema);
+                self.attach_table(table_name, table);
+
+                Ok(Response::TableCreated)
+            }
+            CreateIndex(table_name, column_name) => {
+                let table: &mut Table = self.table_from_name_mut(&table_name)?;
+                let column_position: ColumnPosition = table
+                    .schema()
+                    .column_position_from_column_name(&column_name)?;
+
+                table.attach_index(column_position)?;
+                Ok(Response::IndexCreated)
+            }
+        }
+    }
+}
+
+// TODO: Give a better name to something that you can respond to with rows
+trait SqlResponseConsumer {
+    // TODO:
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::collections::HashSet;
+
+    fn users_schema() -> TableSchema {
+        let id: ColumnPosition = 0;
+        let name: ColumnPosition = 1;
+        let age: ColumnPosition = 2;
+
+        TableSchema::new(
+            "users".to_string(),
+            id,
+            vec!(
+                ("id".to_string(), id),
+                ("name".to_string(), name),
+                ("age".to_string(), age),
+            ),
+            vec![DbType::Uuid, DbType::String, DbType::Int],
+        )
+    }
+
+    #[test]
+    fn test_table_creation() {
+        let mut state = State::new();
+        let users_schema = users_schema();
+        let users = users_schema.table_name().clone();
+
+        state
+            .interpret(Operation::CreateTable(users.clone(), users_schema))
+            .unwrap();
+
+        assert!(state.tables.len() == 1);
+        let table = &state.tables[0];
+        assert!(table.rows().len() == 0);
+
+        assert!(table.table_name() == &users);
+    }
+
+    #[test]
+    fn test_select_empty() {
+        let mut state = State::new();
+        let users_schema = users_schema();
+        let users = users_schema.table_name().clone();
+
+        state
+            .interpret(Operation::CreateTable(users.clone(), users_schema))
+            .unwrap();
+        let response: Response = state
+            .interpret(Operation::Select(users.clone(), ColumnSelection::All, None))
+            .unwrap();
+        assert!(matches!(response, Response::Selected(_)));
+        let Response::Selected(rows) = response else {
+            todo!()
+        };
+        assert!(rows.len() == 0);
+    }
+
+    #[test]
+    fn test_select_nonexistant_table() {
+        let mut state = State::new();
+
+        let response: DbResult<Response> = state.interpret(Operation::Select(
+            "table_that_doesnt_exist".to_string(),
+            ColumnSelection::All,
+            None,
+        ));
+        assert!(matches!(response, Err(Error::TableDoesNotExist(_))));
+    }
+
+    #[test]
+    fn test_insert_select_basic1() {
+        use IndexableValue::*;
+        use Value::*;
+
+        let mut state = State::new();
+        let users_schema = users_schema();
+        let users = users_schema.table_name().clone();
+
+        state
+            .interpret(Operation::CreateTable(users.clone(), users_schema))
+            .unwrap();
+
+        let (id, name, age) = (
+            Indexable(Uuid(0)),
+            Indexable(String("Plato".to_string())),
+            Indexable(Int(64)),
+        );
+        state
+            .interpret(Operation::Insert(
+                users.clone(),
+                vec![
+                    ("id".to_string(), id.clone()),
+                    ("name".to_string(), name.clone()),
+                    ("age".to_string(), age.clone()),
+                ],
+            ))
+            .unwrap();
+
+        let response: Response = state
+            .interpret(Operation::Select(users.clone(), ColumnSelection::All, None))
+            .unwrap();
+
+        assert!(matches!(response, Response::Selected(_)));
+        let Response::Selected(rows) = response else {
+            todo!()
+        };
+        assert!(rows.len() == 1);
+        let row = &rows[0];
+
+        assert!(row.len() == 3);
+        assert!(row[0] == id);
+        assert!(row[1] == name);
+        assert!(row[2] == age);
+    }
+
+    #[test]
+    fn test_insert_select_basic2() {
+        use ColumnSelection::*;
+        use Condition::*;
+        use IndexableValue::*;
+        use Operation::*;
+        use Value::*;
+
+        let mut state = State::new();
+        let users_schema = users_schema();
+        let users = users_schema.table_name().clone();
+
+        state
+            .interpret(CreateTable(users.clone(), users_schema))
+            .unwrap();
+
+        let (id0, name0, age0) = (
+            Indexable(Uuid(0)),
+            Indexable(String("Plato".to_string())),
+            Indexable(Int(64)),
+        );
+        state
+            .interpret(Insert(
+                users.clone(),
+                vec![
+                    ("id".to_string(), id0.clone()),
+                    ("name".to_string(), name0.clone()),
+                    ("age".to_string(), age0.clone()),
+                ],
+            ))
+            .unwrap();
+
+        let (id1, name1, age1) = (
+            Indexable(Uuid(1)),
+            Indexable(String("Aristotle".to_string())),
+            Indexable(Int(20)),
+        );
+        state
+            .interpret(Insert(
+                users.clone(),
+                vec![
+                    ("id".to_string(), id1.clone()),
+                    ("name".to_string(), name1.clone()),
+                    ("age".to_string(), age1.clone()),
+                ],
+            ))
+            .unwrap();
+
+        {
+            let response: Response = state.interpret(Select(users.clone(), All, None)).unwrap();
+
+            assert!(matches!(response, Response::Selected(_)));
+            let Response::Selected(rows) = response else {
+                todo!()
+            };
+            assert!(rows.len() == 2);
+            let row0 = &rows[0];
+            let row1 = &rows[1];
+
+            assert!(row0.len() == 3);
+            assert!(row0[0] == id0);
+            assert!(row0[1] == name0);
+            assert!(row0[2] == age0);
+
+            assert!(row1.len() == 3);
+            assert!(row1[0] == id1);
+            assert!(row1[1] == name1);
+            assert!(row1[2] == age1);
+        }
+
+        {
+            let response: Response = state
+                .interpret(Select(
+                    users.clone(),
+                    All,
+                    Some(Eq("id".to_string(), id0.clone())),
+                ))
+                .unwrap();
+            assert!(matches!(response, Response::Selected(_)));
+            let Response::Selected(rows) = response else {
+                todo!()
+            };
+            assert!(rows.len() == 1);
+            let row0 = &rows[0];
+
+            assert!(row0.len() == 3);
+            assert!(row0[0] == id0);
+            assert!(row0[1] == name0);
+            assert!(row0[2] == age0);
+        }
+
+        {
+            let response: Response = state
+                .interpret(Select(
+                    users.clone(),
+                    Columns(vec!["name".to_string(), "id".to_string()]),
+                    Some(Eq("id".to_string(), id0.clone())),
+                ))
+                .unwrap();
+            assert!(matches!(response, Response::Selected(_)));
+            let Response::Selected(rows) = response else {
+                todo!()
+            };
+            assert!(rows.len() == 1);
+            let row0 = &rows[0];
+
+            assert!(row0.len() == 2);
+            assert!(row0[0] == name0);
+            assert!(row0[1] == id0);
+        }
+    }
+
+    #[test]
+    fn test_delete() {
+        use ColumnSelection::*;
+        use Condition::*;
+        use IndexableValue::*;
+        use Operation::*;
+        use Value::*;
+
+        let mut state = State::new();
+        let users_schema = users_schema();
+        let users = users_schema.table_name().clone();
+
+        state
+            .interpret(CreateTable(users.clone(), users_schema))
+            .unwrap();
+
+        let (id0, name0, age0) = (
+            Indexable(Uuid(0)),
+            Indexable(String("Plato".to_string())),
+            Indexable(Int(64)),
+        );
+        state
+            .interpret(Insert(
+                users.clone(),
+                vec![
+                    ("id".to_string(), id0.clone()),
+                    ("name".to_string(), name0.clone()),
+                    ("age".to_string(), age0.clone()),
+                ],
+            ))
+            .unwrap();
+
+        let (id1, name1, age1) = (
+            Indexable(Uuid(1)),
+            Indexable(String("Aristotle".to_string())),
+            Indexable(Int(20)),
+        );
+        state
+            .interpret(Insert(
+                users.clone(),
+                vec![
+                    ("id".to_string(), id1.clone()),
+                    ("name".to_string(), name1.clone()),
+                    ("age".to_string(), age1.clone()),
+                ],
+            ))
+            .unwrap();
+
+        let delete_response: Response = state
+            .interpret(Delete(
+                users.clone(),
+                Some(Eq("id".to_string(), id0.clone())),
+            ))
+            .unwrap();
+        assert!(matches!(delete_response, Response::Deleted(1)));
+
+        let response: Response = state.interpret(Select(users.clone(), All, None)).unwrap();
+
+        assert!(matches!(response, Response::Selected(_)));
+        let Response::Selected(rows) = response else {
+            todo!()
+        };
+        assert!(rows.len() == 1);
+        let row = &rows[0];
+
+        assert!(row.len() == 3);
+        assert!(row[0] == id1);
+        assert!(row[1] == name1);
+        assert!(row[2] == age1);
+    }
+
+    #[test]
+    fn test_index() {
+        use IndexableValue::*;
+        use Operation::*;
+        use Value::*;
+
+        let mut state = State::new();
+        let users_schema = users_schema();
+        let users = users_schema.table_name().clone();
+
+        state
+            .interpret(CreateTable(users.clone(), users_schema))
+            .unwrap();
+
+        state
+            .interpret(CreateIndex(users.clone(), "name".to_string()))
+            .unwrap();
+
+        let (id0, name0, age0) = (
+            Indexable(Uuid(0)),
+            Indexable(String("Plato".to_string())),
+            Indexable(Int(64)),
+        );
+        state
+            .interpret(Insert(
+                users.clone(),
+                vec![
+                    ("id".to_string(), id0.clone()),
+                    ("name".to_string(), name0.clone()),
+                    ("age".to_string(), age0.clone()),
+                ],
+            ))
+            .unwrap();
+
+        let (id1, name1, age1) = (
+            Indexable(Uuid(1)),
+            Indexable(String("Aristotle".to_string())),
+            Indexable(Int(20)),
+        );
+        state
+            .interpret(Insert(
+                users.clone(),
+                vec![
+                    ("id".to_string(), id1.clone()),
+                    ("name".to_string(), name1.clone()),
+                    ("age".to_string(), age1.clone()),
+                ],
+            ))
+            .unwrap();
+
+        assert!(state.tables.len() == 1);
+        let table = &state.tables[0];
+        assert!(table.rows().len() == 2);
+
+        let user: ColumnPosition = 1;
+        assert!(table.indexes().contains_key(&user));
+
+        let index = table.indexes().get(&user).unwrap();
+
+        let plato_id = 0;
+        let aristotle_id = 1;
+
+        let plato_ids = index.get(&String("Plato".to_string())).cloned().unwrap_or(HashSet::new());
+        assert!(plato_ids.contains(&plato_id));
+        assert!(!plato_ids.contains(&aristotle_id));
+        assert!(plato_ids.len() == 1);
+    }
+}
+
+pub fn example() {
+    use ColumnSelection::*;
+    use Condition::*;
+    use IndexableValue::*;
+    use Operation::*;
+    use Value::*;
+
+    let users_schema: TableSchema = {
+        let id: ColumnPosition = 0;
+        let name: ColumnPosition = 1;
+        let age: ColumnPosition = 2;
+
+        TableSchema::new(
+            "users".to_string(),
+            id,
+            vec!(
+                ("id".to_string(), id),
+                ("name".to_string(), name),
+                ("age".to_string(), age),
+            ),
+            vec![DbType::Uuid, DbType::String, DbType::Int],
+        )
+    };
+    let users = users_schema.table_name().clone();
+
+    let mut state = State::new();
+    state
+        .interpret(Operation::CreateTable(users.clone(), users_schema))
+        .unwrap();
+
+    let (id0, name0, age0) = (
+        Indexable(Uuid(0)),
+        Indexable(String("Plato".to_string())),
+        Indexable(Int(64)),
+    );
+    println!("==INSERT Plato==");
+    state
+        .interpret(Insert(
+            users.clone(),
+            vec![
+                ("id".to_string(), id0.clone()),
+                ("name".to_string(), name0.clone()),
+                ("age".to_string(), age0.clone()),
+            ],
+        ))
+        .unwrap();
+
+    let (id1, name1, age1) = (
+        Indexable(Uuid(1)),
+        Indexable(String("Aristotle".to_string())),
+        Indexable(Int(20)),
+    );
+    println!("==INSERT Aristotle==");
+    state
+        .interpret(Insert(
+            users.clone(),
+            vec![
+                ("id".to_string(), id1.clone()),
+                ("name".to_string(), name1.clone()),
+                ("age".to_string(), age1.clone()),
+            ],
+        ))
+        .unwrap();
+    println!();
+
+    {
+        let response: Response = state
+            .interpret(Operation::Select(users.clone(), ColumnSelection::All, None))
+            .unwrap();
+        println!("==SELECT ALL==");
+        println!("{:?}", response);
+        println!();
+    }
+    {
+        let response: Response = state
+            .interpret(Select(
+                users.clone(),
+                All,
+                Some(Eq("id".to_string(), id0.clone())),
+            ))
+            .unwrap();
+        println!("==SELECT Plato==");
+        println!("{:?}", response);
+        println!();
+    }
+
+    {
+        let _delete_response: Response = state
+            .interpret(Delete(
+                users.clone(),
+                Some(Eq("id".to_string(), id0.clone())),
+            ))
+            .unwrap();
+        println!("==DELETE Plato==");
+        let response: Response = state
+            .interpret(Select(
+                users.clone(),
+                Columns(vec!["name".to_string(), "id".to_string()]),
+                None,
+            ))
+            .unwrap();
+        println!("==SELECT All==");
+        println!("{:?}", response);
+        println!();
+    }
+}

minisql/src/main.rs

@@ -1,259 +1,10 @@
-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: what bout null?
-}
-
-// 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, // TODO: Consider wrapping this in a lock. Also consider if we need to have the
-                // same lock for both rows and indexes
-    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 =
-    // TODO: This should be some sort of an interface to a dictionary
-    // s.t. in the background it may modify stuff in memory or talk to the disk
-    BTreeMap<UUID, Row>;
-
-    // interface
-    // insert(id, value)
-
-// ==============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) {
-        match maybe_condition {
-            None => {
-                // .iter() will give us an iterator over all the rows
-
-                // two choices
-                // 1.  optimized version
-                // self.iter_with_columns(column_selection).for_each(|row| {
-                //     consumer.send(row)
-                // });
-                // 2.
-                // self.iter()
-                //     .map(|row| row.select_columns(column_selection))
-                //     .for_each(|reduced_row| {
-                //         consumer.send(row)
-                //     });
-                todo!()
-            },
-            Some(Condition::Eq(column_name, value)) => {
-                // is column_name primary key? then it is easy
-                // self.get(id)
-                // is column_name indexed? Then get the index, and then it is not easy, because you
-                // may get a set of ids.
-                // what if it is not primary nor indexed? then you need to brute force your way
-                // through the whole table?
-                todo!()
-            }
-        }
-    }
-
-    fn insert(&mut self, values: InsertionValues, consumer: impl SqlConsumer) {
-        // 1. You need to update indices
-        // 2. you simply insert the data
-        todo!()
-    }
-
-    fn delete_where(&mut self, maybe_condition: Option<Condition>, consumer: impl SqlConsumer) {
-        // kinda similar to select with respect to the conditions
-        // update index
-        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
-// } 
+mod error;
+mod internals;
+mod interpreter;
+mod operation;
+mod result;
+mod type_system;
 
 fn main() {
-    println!("Hello, world!");
+    interpreter::example();
 }

minisql/src/operation.rs

@@ -0,0 +1,40 @@
+use crate::internals::schema::{ColumnName, TableName, TableSchema};
+use crate::type_system::Value;
+
+// ==============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.
+// TODO: `TableName` should be replaced by `TablePosition`
+pub enum Operation {
+    Select(TableName, ColumnSelection, Option<Condition>),
+    Insert(TableName, InsertionValues),
+    Delete(TableName, Option<Condition>),
+    // Update(...),
+    CreateTable(TableName, TableSchema),
+    CreateIndex(TableName, ColumnName),
+    // DropTable(TableName),
+}
+
+pub type InsertionValues = Vec<(ColumnName, Value)>;
+
+pub enum ColumnSelection {
+    All,
+    Columns(Vec<ColumnName>),
+}
+
+pub enum Condition {
+    // And(Box<Condition>, Box<Condition>),
+    // Or(Box<Condition>, Box<Condition>),
+    // Not(Box<Condition>),
+    Eq(ColumnName, Value),
+    // LessOrEqual(ColumnName, DbValue),
+    // Less(ColumnName, DbValue),
+
+    // StringCondition(StringCondition),
+}
+
+// enum StringCondition {
+//     Prefix(ColumnName, String),
+//     Substring(ColumnName, String),
+// }

minisql/src/result.rs

@@ -0,0 +1,3 @@
+use crate::error::Error;
+
+pub type DbResult<A> = Result<A, Error>;

minisql/src/type_system.rs

@@ -0,0 +1,42 @@
+// ==============Types================
+#[derive(Debug, Clone, Copy)]
+pub enum DbType {
+    String,
+    Int,
+    Number,
+    Uuid,
+}
+
+// ==============Values================
+pub type Uuid = u64;
+
+// TODO: What about nulls? I would rather not have that in SQL, it sucks.
+//       I would rather have non-nullable values by default,
+//       and something like an explicit Option type for nulls.
+#[derive(Debug, Clone, PartialEq)]
+pub enum Value {
+    Number(f64), // TODO: Can't put floats as keys in maps, since they don't implement Eq. What to
+    // do?
+    Indexable(IndexableValue),
+}
+
+#[derive(Debug, Ord, Eq, Clone, PartialOrd, PartialEq)]
+pub enum IndexableValue {
+    String(String),
+    Int(u64),
+    Uuid(Uuid),
+    // TODO: what about null?
+}
+
+impl Value {
+    pub fn to_type(&self) -> DbType {
+        match self {
+            Self::Number(_) => DbType::Number,
+            Self::Indexable(val) => match val {
+                IndexableValue::String(_) => DbType::String,
+                IndexableValue::Int(_) => DbType::Int,
+                IndexableValue::Uuid(_) => DbType::Uuid,
+            },
+        }
+    }
+}