feat(expr): allow jsonb null values to be cast to scalar types as null

e2e_test/batch/types/jsonb.slt.part

@@ -82,14 +82,78 @@ select '2.5'::jsonb::smallint, '3.5'::jsonb::smallint;
 ----
 2 4
 
-statement error cannot cast jsonb null to type boolean
+query T
 select 'null'::jsonb::bool;
+----
+NULL
 
 query T
 select null::jsonb::bool;
 ----
 NULL
 
+query R
+select 'null'::jsonb::double precision;
+----
+NULL
+
+query R
+select '1.0'::jsonb::real;
+----
+1
+
+query T
+select 'null'::jsonb::real;
+----
+NULL
+
+statement error cannot cast jsonb array to type number
+select '[1.0]'::jsonb::real;
+
+query I
+select '12345'::jsonb::smallint;
+----
+12345
+
+query T
+select 'null'::jsonb::smallint;
+----
+NULL
+
+statement error cannot cast jsonb string to type number
+select '"hello"'::jsonb::smallint;
+
+query I
+select '12345'::jsonb::int;
+----
+12345
+
+query T
+select 'null'::jsonb::int;
+----
+NULL
+
+statement error cannot cast jsonb string to type number
+select '"hello"'::jsonb::int;
+
+query I
+select '12345'::jsonb::bigint;
+----
+12345
+
+query T
+select 'null'::jsonb::bigint;
+----
+NULL
+
+statement error cannot cast jsonb string to type number
+select '"hello"'::jsonb::bigint;
+
+query T
+select 'null'::jsonb::decimal;
+----
+NULL
+
 # Example of accessing the boolean nested inside object and array
 query T
 select ('{"k2":[2,true,4]}'::jsonb -> 'k2' -> -2)::bool;

src/expr/impl/src/scalar/cast.rs

@@ -66,8 +66,14 @@ pub fn to_int256<T: TryInto<Int256>>(elem: T) -> Result<Int256> {
 }
 
 #[function("cast(jsonb) -> boolean")]
-pub fn jsonb_to_bool(v: JsonbRef<'_>) -> Result<bool> {
-    v.as_bool().map_err(|e| ExprError::Parse(e.into()))
+pub fn jsonb_to_bool(v: JsonbRef<'_>) -> Result<Option<bool>> {
+    if v.is_jsonb_null() {
+        Ok(None)
+    } else {
+        v.as_bool()
+            .map(Some)
+            .map_err(|e| ExprError::Parse(e.into()))
+    }
 }
 
 /// Note that PostgreSQL casts JSON numbers from arbitrary precision `numeric` but we use `f64`.
@@ -78,11 +84,16 @@ pub fn jsonb_to_bool(v: JsonbRef<'_>) -> Result<bool> {
 #[function("cast(jsonb) -> decimal")]
 #[function("cast(jsonb) -> float4")]
 #[function("cast(jsonb) -> float8")]
-pub fn jsonb_to_number<T: TryFrom<F64>>(v: JsonbRef<'_>) -> Result<T> {
-    v.as_number()
-        .map_err(|e| ExprError::Parse(e.into()))?
-        .try_into()
-        .map_err(|_| ExprError::NumericOutOfRange)
+pub fn jsonb_to_number<T: TryFrom<F64>>(v: JsonbRef<'_>) -> Result<Option<T>> {
+    if v.is_jsonb_null() {
+        Ok(None)
+    } else {
+        v.as_number()
+            .map_err(|e| ExprError::Parse(e.into()))?
+            .try_into()
+            .map(Some)
+            .map_err(|_| ExprError::NumericOutOfRange)
+    }
 }
 
 #[function("cast(int4) -> int2")]

src/tests/regress/data/expected/jsonb.out

@@ -5413,6 +5413,12 @@ select 'true'::jsonb::bool AS v;
  t
 (1 row)
 
+select 'null'::jsonb::bool AS v;
+ v 
+---
+
+(1 row)
+
 select '[]'::jsonb::bool AS v;
 ERROR:  cannot cast jsonb array to type boolean
 select '1.0'::jsonb::float AS v;
@@ -5421,22 +5427,82 @@ select '1.0'::jsonb::float AS v;
  1
 (1 row)
 
+select 'null'::jsonb::float AS v;
+ v 
+---
+
+(1 row)
+
 select '[1.0]'::jsonb::float AS v;
 ERROR:  cannot cast jsonb array to type double precision
+select '1.0'::jsonb::float4 AS v;
+ v 
+---
+ 1
+(1 row)
+
+select 'null'::jsonb::float4 AS v;
+ v 
+---
+
+(1 row)
+
+select '[1.0]'::jsonb::float4 AS v;
+ERROR:  cannot cast jsonb array to type real
+select '12345'::jsonb::int2 AS v;
+  v   
+------
+ 12345
+(1 row)
+
+select 'null'::jsonb::int2 AS v;
+ v 
+---
+
+(1 row)
+
+select '"hello"'::jsonb::int2 AS v;
+ERROR:  cannot cast jsonb string to type smallint
 select '12345'::jsonb::int4 AS v;
    v   
 -------
  12345
 (1 row)
 
+select 'null'::jsonb::int4 AS v;
+ v 
+---
+
+(1 row)
+
 select '"hello"'::jsonb::int4 AS v;
 ERROR:  cannot cast jsonb string to type integer
+select '12345'::jsonb::int8 AS v;
+  v   
+------
+ 12345
+(1 row)
+
+select 'null'::jsonb::int8 AS v;
+ v 
+---
+
+(1 row)
+
+select '"hello"'::jsonb::int8 AS v;
+ERROR:  cannot cast jsonb string to type bigint
 select '12345'::jsonb::numeric AS v;
    v   
 -------
  12345
 (1 row)
 
+select 'null'::jsonb::numeric AS v;
+ v 
+---
+
+(1 row)
+
 select '{}'::jsonb::numeric AS v;
 ERROR:  cannot cast jsonb object to type numeric
 select '12345.05'::jsonb::numeric AS v;

src/tests/regress/data/sql/jsonb.sql

@@ -1464,12 +1464,25 @@ select jsonb_set('{"a": {"b": [1, 2, 3]}}', '{a, b, NULL}', '"new_value"');
 
 -- casts
 select 'true'::jsonb::bool AS v;
+--@ select 'null'::jsonb::bool AS v;
 select '[]'::jsonb::bool AS v;
 select '1.0'::jsonb::float AS v;
+--@ select 'null'::jsonb::float AS v;
 select '[1.0]'::jsonb::float AS v;
+--@ select '1.0'::jsonb::float4 AS v;
+--@ select 'null'::jsonb::float4 AS v;
+--@ select '[1.0]'::jsonb::float4 AS v;
+--@ select '12345'::jsonb::int2 AS v;
+--@ select 'null'::jsonb::int2 AS v;
+--@ select '"hello"'::jsonb::int2 AS v;
 select '12345'::jsonb::int4 AS v;
+--@ select 'null'::jsonb::int4 AS v;
 select '"hello"'::jsonb::int4 AS v;
+--@ select '12345'::jsonb::int8 AS v;
+--@ select 'null'::jsonb::int8 AS v;
+--@ select '"hello"'::jsonb::int8 AS v;
 select '12345'::jsonb::numeric AS v;
+--@ select 'null'::jsonb::numeric AS v;
 select '{}'::jsonb::numeric AS v;
 select '12345.05'::jsonb::numeric AS v;
 select '12345.05'::jsonb::float4 AS v;