From 0aa9f7ed7fe8af6ea19015b9d8bf271a128d4bee Mon Sep 17 00:00:00 2001
From: Noel Kwan <47273164+kwannoel@users.noreply.github.com>
Date: Mon, 16 Oct 2023 13:13:01 +0800
Subject: [PATCH] fix(sqlsmith): fix generation of decode (#12855)

---
 src/tests/sqlsmith/src/sql_gen/functions.rs | 11 +++++++++++
 src/tests/sqlsmith/src/sql_gen/types.rs     |  8 +++++++-
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/src/tests/sqlsmith/src/sql_gen/functions.rs b/src/tests/sqlsmith/src/sql_gen/functions.rs
index 3583b820f1204..01cbb0604d262 100644
--- a/src/tests/sqlsmith/src/sql_gen/functions.rs
+++ b/src/tests/sqlsmith/src/sql_gen/functions.rs
@@ -49,6 +49,7 @@ impl<'a, R: Rng> SqlGenerator<'a, R> {
                 4 => self.gen_overlay(context),
                 _ => unreachable!(),
             },
+            T::Bytea => self.gen_decode(context),
             _ => match self.rng.gen_bool(0.5) {
                 true => self.gen_case(ret, context),
                 false => self.gen_coalesce(ret, context),
@@ -121,6 +122,16 @@ impl<'a, R: Rng> SqlGenerator<'a, R> {
             .collect()
     }
 
+    fn gen_decode(&mut self, context: SqlGeneratorContext) -> Expr {
+        let input_string = self.gen_expr(&DataType::Varchar, context);
+        let encoding = &["base64", "hex", "escape"].choose(&mut self.rng).unwrap();
+        let args = vec![
+            input_string,
+            Expr::Value(Value::SingleQuotedString(encoding.to_string())),
+        ];
+        Expr::Function(make_simple_func("decode", &args))
+    }
+
     fn gen_fixed_func(&mut self, ret: &DataType, context: SqlGeneratorContext) -> Expr {
         let funcs = match FUNC_TABLE.get(ret) {
             None => return self.gen_simple_scalar(ret),
diff --git a/src/tests/sqlsmith/src/sql_gen/types.rs b/src/tests/sqlsmith/src/sql_gen/types.rs
index ea3c00e45e1da..06d170e604ace 100644
--- a/src/tests/sqlsmith/src/sql_gen/types.rs
+++ b/src/tests/sqlsmith/src/sql_gen/types.rs
@@ -109,7 +109,10 @@ impl TryFrom<RwCastSig> for CastSig {
 /// effectiveness, e.g. cause it to crash.
 static FUNC_BAN_LIST: LazyLock<HashSet<ExprType>> = LazyLock::new(|| {
     [
-        ExprType::Repeat, // FIXME: https://github.com/risingwavelabs/risingwave/issues/8003
+        // FIXME: https://github.com/risingwavelabs/risingwave/issues/8003
+        ExprType::Repeat,
+        // The format argument needs to be handled specially. It is still generated in `gen_special_func`.
+        ExprType::Decode,
     ]
     .into_iter()
     .collect()
@@ -117,6 +120,9 @@ static FUNC_BAN_LIST: LazyLock<HashSet<ExprType>> = LazyLock::new(|| {
 
 /// Table which maps functions' return types to possible function signatures.
 // ENABLE: https://github.com/risingwavelabs/risingwave/issues/5826
+// TODO: Create a `SPECIAL_FUNC` table.
+// Otherwise when we dump the function table, we won't include those functions in
+// gen_special_func.
 pub(crate) static FUNC_TABLE: LazyLock<HashMap<DataType, Vec<&'static FuncSign>>> =
     LazyLock::new(|| {
         let mut funcs = HashMap::<DataType, Vec<&'static FuncSign>>::new();