refactor(expr): allow defining functions in frontend

Cargo.toml

@@ -123,6 +123,7 @@ risingwave_compute = { path = "./src/compute" }
 risingwave_ctl = { path = "./src/ctl" }
 risingwave_connector = { path = "./src/connector" }
 risingwave_expr = { path = "./src/expr" }
+risingwave_expr_macro = { path = "./src/expr/macro" }
 risingwave_frontend = { path = "./src/frontend" }
 risingwave_hummock_sdk = { path = "./src/storage/hummock_sdk" }
 risingwave_hummock_test = { path = "./src/storage/hummock_test" }

proto/expr.proto

@@ -220,6 +220,9 @@ message ExprNode {
     VNODE = 1101;
     // Non-deterministic functions
     PROCTIME = 2023;
+
+    // Adminitration functions
+    COL_DESCRIPTION = 2100;
   }
   Type function_type = 1;
   data.DataType return_type = 3;

src/expr/macro/src/gen.rs

@@ -67,7 +67,7 @@ impl FunctionAttr {
 
         let pb_type = format_ident!("{}", utils::to_camel_case(&name));
         let ctor_name = format_ident!("{}", self.ident_name());
-        let descriptor_type = quote! { crate::sig::func::FuncSign };
+        let descriptor_type = quote! { risingwave_expr::sig::func::FuncSign };
         let build_fn = if build_fn {
             let name = format_ident!("{}", user_fn.name);
             quote! { #name }
@@ -79,7 +79,7 @@ impl FunctionAttr {
             #[ctor::ctor]
             fn #ctor_name() {
                 use risingwave_common::types::{DataType, DataTypeName};
-                unsafe { crate::sig::func::_register(#descriptor_type {
+                unsafe { risingwave_expr::sig::func::_register(#descriptor_type {
                     func: risingwave_pb::expr::expr_node::Type::#pb_type,
                     inputs_type: &[#(#args),*],
                     ret_type: #ret,
@@ -199,7 +199,7 @@ impl FunctionAttr {
                     let #prebuilt_inputs = match &#prebuilt_inputs {
                         Some(s) => s.as_scalar_ref_impl().try_into()?,
                         // the function should always return null if any const argument is null
-                        None => return Ok(Box::new(crate::expr::LiteralExpression::new(
+                        None => return Ok(Box::new(risingwave_expr::expr::LiteralExpression::new(
                             return_type,
                             None,
                         ))),
@@ -358,8 +358,8 @@ impl FunctionAttr {
         };
 
         Ok(quote! {
-            |return_type: DataType, children: Vec<crate::expr::BoxedExpression>|
-                -> crate::Result<crate::expr::BoxedExpression>
+            |return_type: DataType, children: Vec<risingwave_expr::expr::BoxedExpression>|
+                -> risingwave_expr::Result<risingwave_expr::expr::BoxedExpression>
             {
                 use std::sync::Arc;
                 use risingwave_common::array::*;
@@ -369,10 +369,10 @@ impl FunctionAttr {
                 use risingwave_common::util::iter_util::ZipEqFast;
                 use itertools::multizip;
 
-                use crate::expr::{Context, BoxedExpression};
-                use crate::Result;
+                use risingwave_expr::expr::{Context, BoxedExpression};
+                use risingwave_expr::Result;
 
-                crate::ensure!(children.len() == #num_args);
+                risingwave_expr::ensure!(children.len() == #num_args);
                 let prebuilt_arg = #prebuild_const;
                 let context = Context {
                     return_type,
@@ -388,7 +388,7 @@ impl FunctionAttr {
                     prebuilt_arg: #prebuilt_arg_type,
                 }
                 #[async_trait::async_trait]
-                impl crate::expr::Expression for #struct_name {
+                impl risingwave_expr::expr::Expression for #struct_name {
                     fn return_type(&self) -> DataType {
                         self.context.return_type.clone()
                     }
@@ -436,7 +436,7 @@ impl FunctionAttr {
 
         let pb_type = format_ident!("{}", utils::to_camel_case(&name));
         let ctor_name = format_ident!("{}", self.ident_name());
-        let descriptor_type = quote! { crate::sig::agg::AggFuncSig };
+        let descriptor_type = quote! { risingwave_expr::sig::agg::AggFuncSig };
         let build_fn = if build_fn {
             let name = format_ident!("{}", user_fn.name);
             quote! { #name }
@@ -447,8 +447,8 @@ impl FunctionAttr {
             #[ctor::ctor]
             fn #ctor_name() {
                 use risingwave_common::types::{DataType, DataTypeName};
-                unsafe { crate::sig::agg::_register(#descriptor_type {
-                    func: crate::agg::AggKind::#pb_type,
+                unsafe { risingwave_expr::sig::agg::_register(#descriptor_type {
+                    func: risingwave_expr::agg::AggKind::#pb_type,
                     inputs_type: &[#(#args),*],
                     ret_type: #ret,
                     build: #build_fn,
@@ -561,16 +561,16 @@ impl FunctionAttr {
                 use risingwave_common::buffer::Bitmap;
                 use risingwave_common::estimate_size::EstimateSize;
 
-                use crate::Result;
-                use crate::agg::AggregateState;
+                use risingwave_expr::Result;
+                use risingwave_expr::agg::AggregateState;
 
                 #[derive(Clone)]
                 struct Agg {
                     return_type: DataType,
                 }
 
                 #[async_trait::async_trait]
-                impl crate::agg::AggregateFunction for Agg {
+                impl risingwave_expr::agg::AggregateFunction for Agg {
                     fn return_type(&self) -> DataType {
                         self.return_type.clone()
                     }
@@ -664,7 +664,7 @@ impl FunctionAttr {
 
         let pb_type = format_ident!("{}", utils::to_camel_case(&name));
         let ctor_name = format_ident!("{}", self.ident_name());
-        let descriptor_type = quote! { crate::sig::table_function::FuncSign };
+        let descriptor_type = quote! { risingwave_expr::sig::table_function::FuncSign };
         let build_fn = if build_fn {
             let name = format_ident!("{}", user_fn.name);
             quote! { #name }
@@ -687,7 +687,7 @@ impl FunctionAttr {
             #[ctor::ctor]
             fn #ctor_name() {
                 use risingwave_common::types::{DataType, DataTypeName};
-                unsafe { crate::sig::table_function::_register(#descriptor_type {
+                unsafe { risingwave_expr::sig::table_function::_register(#descriptor_type {
                     func: risingwave_pb::expr::table_function::Type::#pb_type,
                     inputs_type: &[#(#args),*],
                     ret_type: #ret,
@@ -794,15 +794,15 @@ impl FunctionAttr {
                 use risingwave_common::util::iter_util::ZipEqFast;
                 use itertools::multizip;
 
-                crate::ensure!(children.len() == #num_args);
+                risingwave_expr::ensure!(children.len() == #num_args);
                 let mut iter = children.into_iter();
                 #(let #all_child = iter.next().unwrap();)*
                 #(
                     let #const_child = #const_child.eval_const()?;
                     let #const_child = match &#const_child {
                         Some(s) => s.as_scalar_ref_impl().try_into()?,
                         // the function should always return empty if any const argument is null
-                        None => return Ok(crate::table_function::empty(return_type)),
+                        None => return Ok(risingwave_expr::table_function::empty(return_type)),
                     };
                 )*
 
@@ -814,7 +814,7 @@ impl FunctionAttr {
                     prebuilt_arg: #prebuilt_arg_type,
                 }
                 #[async_trait::async_trait]
-                impl crate::table_function::TableFunction for #struct_name {
+                impl risingwave_expr::table_function::TableFunction for #struct_name {
                     fn return_type(&self) -> DataType {
                         self.return_type.clone()
                     }

src/expr/src/lib.rs

@@ -24,6 +24,8 @@
 #![feature(test)]
 #![feature(arc_unwrap_or_clone)]
 
+extern crate self as risingwave_expr;
+
 pub mod agg;
 mod error;
 pub mod expr;
@@ -34,5 +36,5 @@ pub mod vector_op;
 pub mod window_function;
 
 pub use error::{ExprError, Result};
-use risingwave_common::{bail, ensure};
+pub use risingwave_common::{bail, ensure};
 pub use risingwave_expr_macro::*;

src/frontend/Cargo.toml

@@ -24,6 +24,7 @@ auto_enums = { version = "0.8", features = ["futures03"] }
 bk-tree = "0.5.0"
 bytes = "1"
 clap = { version = "4", features = ["derive"] }
+ctor = "0.2"
 downcast-rs = "1.2"
 dyn-clone = "1.0.13"
 easy-ext = "1"
@@ -54,6 +55,7 @@ risingwave_common = { workspace = true }
 risingwave_common_service = { workspace = true }
 risingwave_connector = { workspace = true }
 risingwave_expr = { workspace = true }
+risingwave_expr_macro = { workspace = true }
 risingwave_pb = { workspace = true }
 risingwave_rpc_client = { workspace = true }
 risingwave_source = { workspace = true }

src/frontend/src/binder/expr/function.rs

@@ -1127,7 +1127,7 @@ impl Binder {
                 // TODO: really implement them.
                 // https://www.postgresql.org/docs/9.5/functions-info.html#FUNCTIONS-INFO-COMMENT-TABLE
                 // WARN: Hacked in [`Binder::bind_function`]!!!
-                ("col_description", raw_literal(ExprImpl::literal_varchar("".to_string()))),
+                ("col_description", raw_call(ExprType::ColDescription)),
                 ("obj_description", raw_literal(ExprImpl::literal_varchar("".to_string()))),
                 ("shobj_description", raw_literal(ExprImpl::literal_varchar("".to_string()))),
                 ("pg_is_in_recovery", raw_literal(ExprImpl::literal_bool(false))),

src/frontend/src/expr/function/col_description.rs

@@ -0,0 +1,11 @@
+use std::fmt::Write;
+
+use risingwave_expr::ExprError;
+use risingwave_expr_macro::function;
+
+#[function("col_description(varchar, int32) -> varchar")]
+fn col_description(_name: &str, _col: i32, writer: &mut impl Write) -> Result<(), ExprError> {
+    writer.write_str("").unwrap();
+
+    Ok(())
+}

src/frontend/src/expr/function/mod.rs

@@ -0,0 +1 @@
+mod col_description;

src/frontend/src/expr/mod.rs

@@ -46,6 +46,7 @@ pub use order_by_expr::{OrderBy, OrderByExpr};
 mod expr_mutator;
 mod expr_rewriter;
 mod expr_visitor;
+mod function;
 mod session_timezone;
 mod type_inference;
 mod utils;

src/frontend/src/expr/pure.rs

@@ -207,7 +207,9 @@ impl ExprVisitor<bool> for ImpureAnalyzer {
                 x
             }
             // expression output is not deterministic
-            expr_node::Type::Vnode | expr_node::Type::Proctime => true,
+            expr_node::Type::Vnode
+            | expr_node::Type::Proctime
+            | expr_node::Type::ColDescription => true,
         }
     }
 }