join and from derived tables (#5477)

crates/nu-command/src/database/commands/alias.rs

@@ -29,26 +29,15 @@ impl Command for AliasExpr {
     }
 
     fn examples(&self) -> Vec<Example> {
-        vec![
-            Example {
+        vec![Example {
             description: "Creates an alias for a column selection",
             example: "db col name_a | db as new_a",
             result: None,
-            },
-            Example {
-                description: "Creates an alias for a table",
-                example: r#"db open name 
-    | db select a 
-    | db from table_a 
-    | db as table_a_new 
-    | db describe"#,
-                result: None,
-            },
-        ]
+        }]
     }
 
     fn search_terms(&self) -> Vec<&str> {
-        vec!["database", "column", "expression"]
+        vec!["database", "alias", "column"]
     }
 
     fn run(

crates/nu-command/src/database/commands/conversions.rs

@@ -0,0 +1,66 @@
+use crate::{database::values::definitions::ConnectionDb, SQLiteDatabase};
+use nu_protocol::{ShellError, Value};
+use sqlparser::ast::{ObjectName, Statement, TableAlias, TableFactor};
+
+pub fn value_into_table_factor(
+    table: Value,
+    connection: &ConnectionDb,
+    alias: Option<TableAlias>,
+) -> Result<TableFactor, ShellError> {
+    match table {
+        Value::String { val, .. } => {
+            let ident = sqlparser::ast::Ident {
+                value: val,
+                quote_style: None,
+            };
+
+            Ok(TableFactor::Table {
+                name: ObjectName(vec![ident]),
+                alias,
+                args: Vec::new(),
+                with_hints: Vec::new(),
+            })
+        }
+        Value::CustomValue { span, .. } => {
+            let db = SQLiteDatabase::try_from_value(table)?;
+
+            if &db.connection != connection {
+                return Err(ShellError::GenericError(
+                    "Incompatible connections".into(),
+                    "trying to join on table with different connection".into(),
+                    Some(span),
+                    None,
+                    Vec::new(),
+                ));
+            }
+
+            match db.statement {
+                Some(statement) => match statement {
+                    Statement::Query(query) => Ok(TableFactor::Derived {
+                        lateral: false,
+                        subquery: query,
+                        alias,
+                    }),
+                    s => Err(ShellError::GenericError(
+                        "Connection doesnt define a query".into(),
+                        format!("Expected a connection with query. Got {}", s),
+                        Some(span),
+                        None,
+                        Vec::new(),
+                    )),
+                },
+                None => Err(ShellError::GenericError(
+                    "Error creating derived table".into(),
+                    "there is no statement defined yet".into(),
+                    Some(span),
+                    None,
+                    Vec::new(),
+                )),
+            }
+        }
+        _ => Err(ShellError::UnsupportedInput(
+            "String or connection".into(),
+            table.span()?,
+        )),
+    }
+}

crates/nu-command/src/database/commands/from.rs

@@ -1,13 +1,13 @@
-use super::super::SQLiteDatabase;
+use crate::database::values::definitions::ConnectionDb;
+
+use super::{super::SQLiteDatabase, conversions::value_into_table_factor};
 use nu_engine::CallExt;
 use nu_protocol::{
     ast::Call,
     engine::{Command, EngineState, Stack},
-    Category, Example, IntoPipelineData, PipelineData, ShellError, Signature, Span, SyntaxShape,
-};
-use sqlparser::ast::{
-    Ident, ObjectName, Query, Select, SetExpr, Statement, TableFactor, TableWithJoins,
+    Category, Example, IntoPipelineData, PipelineData, ShellError, Signature, SyntaxShape, Value,
 };
+use sqlparser::ast::{Ident, Query, Select, SetExpr, Statement, TableAlias, TableWithJoins};
 
 #[derive(Clone)]
 pub struct FromDb;
@@ -25,8 +25,14 @@ impl Command for FromDb {
         Signature::build(self.name())
             .required(
                 "select",
+                SyntaxShape::Any,
+                "table of derived table to select from",
+            )
+            .named(
+                "as",
                 SyntaxShape::String,
-                "Name of table to select from",
+                "Alias for the selected table",
+                Some('a'),
             )
             .category(Category::Custom("database".into()))
     }
@@ -50,22 +56,36 @@ impl Command for FromDb {
         call: &Call,
         input: PipelineData,
     ) -> Result<PipelineData, ShellError> {
-        let table: String = call.req(engine_state, stack, 0)?;
-
         let mut db = SQLiteDatabase::try_from_pipeline(input, call.head)?;
         db.statement = match db.statement {
-            None => Some(create_statement(table)),
-            Some(statement) => Some(modify_statement(statement, table, call.head)?),
+            None => Some(create_statement(&db.connection, engine_state, stack, call)?),
+            Some(statement) => Some(modify_statement(
+                &db.connection,
+                statement,
+                engine_state,
+                stack,
+                call,
+            )?),
         };
 
         Ok(db.into_value(call.head).into_pipeline_data())
     }
 }
 
-fn create_statement(table: String) -> Statement {
+fn create_statement(
+    connection: &ConnectionDb,
+    engine_state: &EngineState,
+    stack: &mut Stack,
+    call: &Call,
+) -> Result<Statement, ShellError> {
     let query = Query {
         with: None,
-        body: SetExpr::Select(Box::new(create_select(table))),
+        body: SetExpr::Select(Box::new(create_select(
+            connection,
+            engine_state,
+            stack,
+            call,
+        )?)),
         order_by: Vec::new(),
         limit: None,
         offset: None,
@@ -73,42 +93,57 @@ fn create_statement(table: String) -> Statement {
         lock: None,
     };
 
-    Statement::Query(Box::new(query))
+    Ok(Statement::Query(Box::new(query)))
 }
 
 fn modify_statement(
+    connection: &ConnectionDb,
     mut statement: Statement,
-    table: String,
-    span: Span,
+    engine_state: &EngineState,
+    stack: &mut Stack,
+    call: &Call,
 ) -> Result<Statement, ShellError> {
     match statement {
         Statement::Query(ref mut query) => {
             match query.body {
-                SetExpr::Select(ref mut select) => select.as_mut().from = create_from(table),
+                SetExpr::Select(ref mut select) => {
+                    let table = create_table(connection, engine_state, stack, call)?;
+                    select.from.push(table);
+                }
                 _ => {
-                    query.as_mut().body = SetExpr::Select(Box::new(create_select(table)));
+                    query.as_mut().body = SetExpr::Select(Box::new(create_select(
+                        connection,
+                        engine_state,
+                        stack,
+                        call,
+                    )?));
                 }
             };
 
             Ok(statement)
         }
         s => Err(ShellError::GenericError(
-            "Connection doesnt define a statement".into(),
+            "Connection doesnt define a query".into(),
             format!("Expected a connection with query. Got {}", s),
-            Some(span),
+            Some(call.head),
             None,
             Vec::new(),
         )),
     }
 }
 
-fn create_select(table: String) -> Select {
-    Select {
+fn create_select(
+    connection: &ConnectionDb,
+    engine_state: &EngineState,
+    stack: &mut Stack,
+    call: &Call,
+) -> Result<Select, ShellError> {
+    Ok(Select {
         distinct: false,
         top: None,
         projection: Vec::new(),
         into: None,
-        from: create_from(table),
+        from: vec![create_table(connection, engine_state, stack, call)?],
         lateral_views: Vec::new(),
         selection: None,
         group_by: Vec::new(),
@@ -116,29 +151,32 @@ fn create_select(table: String) -> Select {
         distribute_by: Vec::new(),
         sort_by: Vec::new(),
         having: None,
-    }
+    })
 }
 
-// This function needs more work
-// It needs to define multi tables and joins
-// I assume we will need to define expressions for the columns instead of strings
-fn create_from(table: String) -> Vec<TableWithJoins> {
-    let ident = Ident {
-        value: table,
+fn create_table(
+    connection: &ConnectionDb,
+    engine_state: &EngineState,
+    stack: &mut Stack,
+    call: &Call,
+) -> Result<TableWithJoins, ShellError> {
+    let alias = call
+        .get_flag::<String>(engine_state, stack, "as")?
+        .map(|alias| TableAlias {
+            name: Ident {
+                value: alias,
                 quote_style: None,
-    };
+            },
+            columns: Vec::new(),
+        });
 
-    let table_factor = TableFactor::Table {
-        name: ObjectName(vec![ident]),
-        alias: None,
-        args: Vec::new(),
-        with_hints: Vec::new(),
-    };
+    let select_table: Value = call.req(engine_state, stack, 0)?;
+    let table_factor = value_into_table_factor(select_table, connection, alias)?;
 
     let table = TableWithJoins {
         relation: table_factor,
         joins: Vec::new(),
     };
 
-    vec![table]
+    Ok(table)
 }

crates/nu-command/src/database/commands/join.rs

@@ -0,0 +1,178 @@
+use super::{super::SQLiteDatabase, conversions::value_into_table_factor};
+use crate::database::values::{definitions::ConnectionDb, dsl::ExprDb};
+use nu_engine::CallExt;
+use nu_protocol::{
+    ast::Call,
+    engine::{Command, EngineState, Stack},
+    Category, Example, IntoPipelineData, PipelineData, ShellError, Signature, SyntaxShape, Value,
+};
+use sqlparser::ast::{
+    Ident, Join, JoinConstraint, JoinOperator, Select, SetExpr, Statement, TableAlias,
+};
+
+#[derive(Clone)]
+pub struct JoinDb;
+
+impl Command for JoinDb {
+    fn name(&self) -> &str {
+        "db join"
+    }
+
+    fn usage(&self) -> &str {
+        "Joins with another table or derived table. Default join type is inner"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build(self.name())
+            .required(
+                "table",
+                SyntaxShape::Any,
+                "table or derived table to join on",
+            )
+            .required("on", SyntaxShape::Any, "expression to join tables")
+            .named(
+                "as",
+                SyntaxShape::String,
+                "Alias for the selected join",
+                Some('a'),
+            )
+            .switch("left", "left outer join", Some('l'))
+            .switch("right", "right outer join", Some('r'))
+            .switch("outer", "full outer join", Some('o'))
+            .switch("cross", "cross join", Some('c'))
+            .category(Category::Custom("database".into()))
+    }
+
+    fn search_terms(&self) -> Vec<&str> {
+        vec!["database", "join"]
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "",
+            example: "",
+            result: None,
+        }]
+    }
+
+    fn run(
+        &self,
+        engine_state: &EngineState,
+        stack: &mut Stack,
+        call: &Call,
+        input: PipelineData,
+    ) -> Result<PipelineData, ShellError> {
+        let mut db = SQLiteDatabase::try_from_pipeline(input, call.head)?;
+
+        db.statement = match db.statement {
+            Some(statement) => Some(modify_statement(
+                &db.connection,
+                statement,
+                engine_state,
+                stack,
+                call,
+            )?),
+            None => {
+                return Err(ShellError::GenericError(
+                    "Error creating join".into(),
+                    "there is no statement defined yet".into(),
+                    Some(call.head),
+                    None,
+                    Vec::new(),
+                ))
+            }
+        };
+
+        Ok(db.into_value(call.head).into_pipeline_data())
+    }
+}
+
+fn modify_statement(
+    connection: &ConnectionDb,
+    mut statement: Statement,
+    engine_state: &EngineState,
+    stack: &mut Stack,
+    call: &Call,
+) -> Result<Statement, ShellError> {
+    match statement {
+        Statement::Query(ref mut query) => {
+            match &mut query.body {
+                SetExpr::Select(ref mut select) => {
+                    modify_from(connection, select, engine_state, stack, call)?
+                }
+                s => {
+                    return Err(ShellError::GenericError(
+                        "Connection doesnt define a select".into(),
+                        format!("Expected a connection with select. Got {}", s),
+                        Some(call.head),
+                        None,
+                        Vec::new(),
+                    ))
+                }
+            };
+
+            Ok(statement)
+        }
+        s => Err(ShellError::GenericError(
+            "Connection doesnt define a query".into(),
+            format!("Expected a connection with query. Got {}", s),
+            Some(call.head),
+            None,
+            Vec::new(),
+        )),
+    }
+}
+
+fn modify_from(
+    connection: &ConnectionDb,
+    select: &mut Select,
+    engine_state: &EngineState,
+    stack: &mut Stack,
+    call: &Call,
+) -> Result<(), ShellError> {
+    match select.from.last_mut() {
+        Some(table) => {
+            let alias = call
+                .get_flag::<String>(engine_state, stack, "as")?
+                .map(|alias| TableAlias {
+                    name: Ident {
+                        value: alias,
+                        quote_style: None,
+                    },
+                    columns: Vec::new(),
+                });
+
+            let join_table: Value = call.req(engine_state, stack, 0)?;
+            let table_factor = value_into_table_factor(join_table, connection, alias)?;
+
+            let on_expr: Value = call.req(engine_state, stack, 1)?;
+            let on_expr = ExprDb::try_from_value(&on_expr)?;
+
+            let join_on = if call.has_flag("left") {
+                JoinOperator::LeftOuter(JoinConstraint::On(on_expr.into_native()))
+            } else if call.has_flag("right") {
+                JoinOperator::RightOuter(JoinConstraint::On(on_expr.into_native()))
+            } else if call.has_flag("outer") {
+                JoinOperator::FullOuter(JoinConstraint::On(on_expr.into_native()))
+            } else {
+                JoinOperator::Inner(JoinConstraint::On(on_expr.into_native()))
+            };
+
+            let join = Join {
+                relation: table_factor,
+                join_operator: join_on,
+            };
+
+            table.joins.push(join);
+
+            Ok(())
+        }
+        None => Err(ShellError::GenericError(
+            "Connection without table defined".into(),
+            "Expected a table defined".into(),
+            Some(call.head),
+            None,
+            Vec::new(),
+        )),
+    }
+}

crates/nu-command/src/database/commands/mod.rs

@@ -1,3 +1,6 @@
+// Conversions between value and sqlparser objects
+pub mod conversions;
+
 mod alias;
 mod and;
 mod col;
@@ -7,6 +10,7 @@ mod describe;
 mod from;
 mod function;
 mod group_by;
+mod join;
 mod limit;
 mod open;
 mod or;
@@ -32,6 +36,7 @@ use describe::DescribeDb;
 use from::FromDb;
 use function::FunctionExpr;
 use group_by::GroupByDb;
+use join::JoinDb;
 use limit::LimitDb;
 use open::OpenDb;
 use or::OrDb;
@@ -56,20 +61,21 @@ pub fn add_database_decls(working_set: &mut StateWorkingSet) {
     bind_command!(
         AliasExpr,
         AndDb,
-        CollectDb,
         ColExpr,
+        CollectDb,
         Database,
         DescribeDb,
         FromDb,
         FunctionExpr,
         GroupByDb,
-        QueryDb,
+        JoinDb,
         LimitDb,
-        ProjectionDb,
         OpenDb,
         OrderByDb,
         OrDb,
         OverExpr,
+        QueryDb,
+        ProjectionDb,
         SchemaDb,
         TestingDb,
         WhereDb

crates/nu-command/src/database/commands/schema.rs

@@ -68,7 +68,7 @@ impl Command for SchemaDb {
 
         cols.push("db_filename".into());
         vals.push(Value::String {
-            val: sqlite_db.path.to_string_lossy().to_string(),
+            val: sqlite_db.connection.to_string(),
             span,
         });
 

crates/nu-command/src/database/values/definitions/mod.rs

@@ -1,3 +1,7 @@
+use nu_protocol::{ShellError, Span};
+use serde::{Deserialize, Serialize};
+use std::{fmt::Display, path::PathBuf};
+
 pub mod db;
 pub mod db_column;
 pub mod db_constraint;
@@ -6,3 +10,24 @@ pub mod db_index;
 pub mod db_row;
 pub mod db_schema;
 pub mod db_table;
+
+#[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
+pub enum ConnectionDb {
+    Path(PathBuf),
+}
+
+impl Display for ConnectionDb {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Self::Path(path) => write!(f, "{}", path.to_str().unwrap_or("")),
+        }
+    }
+}
+
+impl ConnectionDb {
+    pub fn as_path(&self, _span: Span) -> Result<&PathBuf, ShellError> {
+        match self {
+            Self::Path(path) => Ok(path),
+        }
+    }
+}

crates/nu-command/src/database/values/sqlite.rs

@@ -1,3 +1,4 @@
+use super::definitions::ConnectionDb;
 use crate::database::values::definitions::{
     db::Db, db_column::DbColumn, db_constraint::DbConstraint, db_foreignkey::DbForeignKey,
     db_index::DbIndex, db_table::DbTable,
@@ -19,14 +20,14 @@ pub struct SQLiteDatabase {
     // I considered storing a SQLite connection here, but decided against it because
     // 1) YAGNI, 2) it's not obvious how cloning a connection could work, 3) state
     // management gets tricky quick. Revisit this approach if we find a compelling use case.
-    pub path: PathBuf,
+    pub connection: ConnectionDb,
     pub statement: Option<Statement>,
 }
 
 impl SQLiteDatabase {
     pub fn new(path: &Path) -> Self {
         Self {
-            path: PathBuf::from(path),
+            connection: ConnectionDb::Path(PathBuf::from(path)),
             statement: None,
         }
     }
@@ -51,7 +52,7 @@ impl SQLiteDatabase {
         match value {
             Value::CustomValue { val, span } => match val.as_any().downcast_ref::<Self>() {
                 Some(db) => Ok(Self {
-                    path: db.path.clone(),
+                    connection: db.connection.clone(),
                     statement: db.statement.clone(),
                 }),
                 None => Err(ShellError::CantConvert(
@@ -83,7 +84,7 @@ impl SQLiteDatabase {
     }
 
     pub fn query(&self, sql: &Spanned<String>, call_span: Span) -> Result<Value, ShellError> {
-        let db = open_sqlite_db(&self.path, call_span)?;
+        let db = open_sqlite_db(self.connection.as_path(call_span)?, call_span)?;
         run_sql_query(db, sql).map_err(|e| {
             ShellError::GenericError(
                 "Failed to query SQLite database".into(),
@@ -112,7 +113,7 @@ impl SQLiteDatabase {
             span: call_span,
         };
 
-        let db = open_sqlite_db(&self.path, call_span)?;
+        let db = open_sqlite_db(self.connection.as_path(call_span)?, call_span)?;
         run_sql_query(db, &sql).map_err(|e| {
             ShellError::GenericError(
                 "Failed to query SQLite database".into(),
@@ -127,7 +128,7 @@ impl SQLiteDatabase {
     pub fn describe(&self, span: Span) -> Value {
         let cols = vec!["connection".to_string(), "query".to_string()];
         let connection = Value::String {
-            val: self.path.to_str().unwrap_or("").to_string(),
+            val: self.connection.to_string(),
             span,
         };
 
@@ -146,7 +147,7 @@ impl SQLiteDatabase {
     }
 
     pub fn open_connection(&self) -> Result<Connection, rusqlite::Error> {
-        let conn = match Connection::open(self.path.to_string_lossy().to_string()) {
+        let conn = match Connection::open(self.connection.to_string()) {
             Ok(conn) => conn,
             Err(err) => return Err(err),
         };
@@ -350,7 +351,7 @@ impl SQLiteDatabase {
 impl CustomValue for SQLiteDatabase {
     fn clone_value(&self, span: Span) -> Value {
         let cloned = SQLiteDatabase {
-            path: self.path.clone(),
+            connection: self.connection.clone(),
             statement: self.statement.clone(),
         };
 
@@ -365,7 +366,7 @@ impl CustomValue for SQLiteDatabase {
     }
 
     fn to_base_value(&self, span: Span) -> Result<Value, ShellError> {
-        let db = open_sqlite_db(&self.path, span)?;
+        let db = open_sqlite_db(self.connection.as_path(span)?, span)?;
         read_entire_sqlite_db(db, span).map_err(|e| {
             ShellError::GenericError(
                 "Failed to read from SQLite database".into(),
@@ -387,7 +388,7 @@ impl CustomValue for SQLiteDatabase {
     }
 
     fn follow_path_string(&self, _column_name: String, span: Span) -> Result<Value, ShellError> {
-        let db = open_sqlite_db(&self.path, span)?;
+        let db = open_sqlite_db(self.connection.as_path(span)?, span)?;
 
         read_single_table(db, _column_name, span).map_err(|e| {
             ShellError::GenericError(