implement pg_get_keywords

Signed-off-by: Runji Wang <[email protected]>

proto/expr.proto

@@ -330,6 +330,7 @@ message TableFunction {
     GENERATE_SUBSCRIPTS = 5;
     // buf:lint:ignore ENUM_VALUE_UPPER_SNAKE_CASE
     _PG_EXPANDARRAY = 6;
+    PG_GET_KEYWORDS = 18;
     // Jsonb functions
     JSONB_ARRAY_ELEMENTS = 10;
     JSONB_ARRAY_ELEMENTS_TEXT = 11;

src/expr/impl/Cargo.toml

@@ -57,6 +57,7 @@ regex = "1"
 risingwave_common = { workspace = true }
 risingwave_common_estimate_size = { workspace = true }
 risingwave_expr = { workspace = true }
+risingwave_sqlparser = { workspace = true }
 risingwave_pb = { workspace = true }
 rust_decimal = { version = "1", features = ["db-postgres", "maths"] }
 self_cell = "1.0.1"

src/expr/impl/src/table_function/mod.rs

@@ -16,5 +16,6 @@ mod generate_series;
 mod generate_subscripts;
 mod jsonb;
 mod pg_expandarray;
+mod pg_get_keywords;
 mod regexp_matches;
 mod unnest;

src/expr/impl/src/table_function/pg_get_keywords.rs

@@ -0,0 +1,58 @@
+// Copyright 2024 RisingWave Labs
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use risingwave_expr::function;
+use risingwave_sqlparser::keywords::{
+    ALL_KEYWORDS_INDEX, RESERVED_FOR_COLUMN_ALIAS, RESERVED_FOR_COLUMN_OR_TABLE_NAME,
+};
+
+/// Returns a set of records describing the SQL keywords recognized by the server.
+///
+/// The word column contains the keyword.
+///
+/// The catcode column contains a category code:
+/// - U for an unreserved keyword
+/// - C for a keyword that can be a column name
+/// - T for a keyword that can be a type or function name
+/// - R for a fully reserved keyword.
+///
+/// The catdesc column contains a possibly-localized string describing the keyword's category.
+///
+/// ```slt
+/// query TTT
+/// select * from pg_get_keywords() where word = 'add';
+/// ----
+/// add U unreserved
+/// ```
+#[function("pg_get_keywords() -> setof struct<word varchar, catcode varchar, catdesc varchar>")]
+fn pg_get_keywords() -> impl Iterator<Item = (Box<str>, &'static str, &'static str)> {
+    ALL_KEYWORDS_INDEX.iter().map(|keyword| {
+        // FIXME: The current category is not correct. Many are different from the PostgreSQL.
+        let catcode = if !RESERVED_FOR_COLUMN_OR_TABLE_NAME.contains(keyword) {
+            "U"
+        } else if !RESERVED_FOR_COLUMN_ALIAS.contains(keyword) {
+            "C"
+        } else {
+            "R"
+        };
+        let catdesc = match catcode {
+            "U" => "unreserved",
+            "C" => "unreserved (cannot be function or type name)",
+            "T" => "reserved (can be function or type name)",
+            "R" => "reserved",
+            _ => unreachable!(),
+        };
+        (keyword.to_string().to_lowercase().into(), catcode, catdesc)
+    })
+}

src/sqlparser/src/keywords.rs

@@ -59,7 +59,7 @@ macro_rules! define_keywords {
         ];
 
         $(kw_def!($ident $(= $string_keyword)?);)*
-        pub const ALL_KEYWORDS: &[&str] = &[
+        pub const ALL_KEYWORDS: &[&'static str] = &[
             $($ident),*
         ];
     };
@@ -651,7 +651,7 @@ pub const RESERVED_FOR_COLUMN_ALIAS: &[Keyword] = &[
 /// Can't be used as a column or table name in PostgreSQL.
 ///
 /// This list is taken from the following table, for all "reserved" words in the PostgreSQL column,
-/// includinhg "can be function or type" and "requires AS". <https://www.postgresql.org/docs/14/sql-keywords-appendix.html#KEYWORDS-TABLE>
+/// including "can be function or type" and "requires AS". <https://www.postgresql.org/docs/14/sql-keywords-appendix.html#KEYWORDS-TABLE>
 ///
 /// `SELECT` and `WITH` were commented out because the following won't parse:
 /// `SELECT (SELECT 1)` or `SELECT (WITH a AS (SELECT 1) SELECT 1)`