Add string_to_array function

doc/user/data/sql_funcs.yml

@@ -471,7 +471,22 @@
     description: Convert `s` to uppercase.
 
   - signature: 'reverse(s: str) -> str'
-    description: Reverse the characters in `s`.
+    description: |
+      Reverse the characters in `s`.
+
+      Splits the string at occurrences of delimiter and returns a text array of
+      the split segments. 
+
+      If `delimiter` is NULL, each character in the string will become a
+      separate element in the array.
+
+      If `delimiter` is an empty string, then the string is treated as a single
+      field. 
+
+      If `null_string` is supplied and is not NULL, fields matching that string
+      are replaced by NULL.
+
+      For example: `string_to_array('xx~~yy~~zz', '~~', 'yy')` → `{xx,NULL,zz}`
 
 - type: Scalar
   description: Scalar functions take a list of scalar expressions

src/expr/src/scalar.proto

@@ -720,6 +720,7 @@ message ProtoVariadicFunc {
     google.protobuf.Empty regexp_split_to_array = 39;
     google.protobuf.Empty regexp_replace = 40;
     mz_repr.relation_and_scalar.ProtoScalarType map_build = 41;
+    google.protobuf.Empty string_to_array = 42;
   }
 }
 

src/expr/src/scalar/func.rs

@@ -2125,6 +2125,87 @@ fn parse_ident<'a>(
     })?)
 }
 
+fn string_to_array<'a>(
+    string_datum: Datum<'a>,
+    delimiter: Datum<'a>,
+    null_string: Datum<'a>,
+    temp_storage: &'a RowArena,
+) -> Result<Datum<'a>, EvalError> {
+    if string_datum.is_null() {
+        return Ok(Datum::Null);
+    }
+
+    let string = string_datum.unwrap_str();
+
+    if string.is_empty() {
+        let mut row = Row::default();
+        let mut packer = row.packer();
+        packer.try_push_array(&[], std::iter::empty::<Datum>())?;
+
+        return Ok(temp_storage.push_unary_row(row));
+    }
+
+    if delimiter.is_null() {
+        let split_all_chars_delimiter = "";
+        return string_to_array_impl(string, split_all_chars_delimiter, null_string, temp_storage);
+    }
+
+    let delimiter = delimiter.unwrap_str();
+    if delimiter.is_empty() {
+        let mut row = Row::default();
+        let mut packer = row.packer();
+        packer.try_push_array(
+            &[ArrayDimension {
+                lower_bound: 1,
+                length: 1,
+            }],
+            vec![string].into_iter().map(Datum::String),
+        )?;
+
+        Ok(temp_storage.push_unary_row(row))
+    } else {
+        string_to_array_impl(string, delimiter, null_string, temp_storage)
+    }
+}
+
+fn string_to_array_impl<'a>(
+    string: &str,
+    delimiter: &str,
+    null_string: Datum<'a>,
+    temp_storage: &'a RowArena,
+) -> Result<Datum<'a>, EvalError> {
+    let mut row = Row::default();
+    let mut packer = row.packer();
+
+    let result = string.split(delimiter);
+    let found: Vec<&str> = if delimiter.is_empty() {
+        result.filter(|s| !s.is_empty()).collect()
+    } else {
+        result.collect()
+    };
+    let array_dimensions = [ArrayDimension {
+        lower_bound: 1,
+        length: found.len(),
+    }];
+
+    if null_string.is_null() {
+        packer.try_push_array(&array_dimensions, found.into_iter().map(Datum::String))?;
+    } else {
+        let null_string = null_string.unwrap_str();
+        let found_datums = found.into_iter().map(|chunk| {
+            if chunk.eq(null_string) {
+                Datum::Null
+            } else {
+                Datum::String(chunk)
+            }
+        });
+
+        packer.try_push_array(&array_dimensions, found_datums)?;
+    }
+
+    Ok(temp_storage.push_unary_row(row))
+}
+
 fn regexp_split_to_array<'a>(
     text: Datum<'a>,
     regexp: Datum<'a>,
@@ -7845,6 +7926,7 @@ pub enum VariadicFunc {
     ArrayFill {
         elem_type: ScalarType,
     },
+    StringToArray,
     TimezoneTime,
     RegexpSplitToArray,
     RegexpReplace,
@@ -7951,6 +8033,11 @@ impl VariadicFunc {
                 regexp_split_to_array(ds[0], ds[1], flags, temp_storage)
             }
             VariadicFunc::RegexpReplace => regexp_replace_dynamic(&ds, temp_storage),
+            VariadicFunc::StringToArray => {
+                let null_string = if ds.len() == 2 { Datum::Null } else { ds[2] };
+
+                string_to_array(ds[0], ds[1], null_string, temp_storage)
+            }
         }
     }
 
@@ -7997,6 +8084,7 @@ impl VariadicFunc {
             | VariadicFunc::ArrayFill { .. }
             | VariadicFunc::TimezoneTime
             | VariadicFunc::RegexpSplitToArray
+            | VariadicFunc::StringToArray
             | VariadicFunc::RegexpReplace => false,
         }
     }
@@ -8102,6 +8190,9 @@ impl VariadicFunc {
                 ScalarType::Array(Box::new(ScalarType::String)).nullable(in_nullable)
             }
             RegexpReplace => ScalarType::String.nullable(in_nullable),
+            StringToArray => {
+                ScalarType::Array(Box::new(ScalarType::String)).nullable(input_types[0].nullable)
+            }
         }
     }
 
@@ -8129,6 +8220,7 @@ impl VariadicFunc {
                 | VariadicFunc::RangeCreate { .. }
                 | VariadicFunc::ArrayPosition
                 | VariadicFunc::ArrayFill { .. }
+                | VariadicFunc::StringToArray
         )
     }
 
@@ -8173,6 +8265,7 @@ impl VariadicFunc {
             | ArrayFill { .. }
             | TimezoneTime
             | RegexpSplitToArray
+            | StringToArray
             | RegexpReplace => false,
             Coalesce
             | Greatest
@@ -8286,6 +8379,7 @@ impl VariadicFunc {
             | VariadicFunc::DateDiffTime
             | VariadicFunc::TimezoneTime
             | VariadicFunc::RegexpSplitToArray
+            | VariadicFunc::StringToArray
             | VariadicFunc::RegexpReplace => false,
         }
     }
@@ -8344,6 +8438,7 @@ impl fmt::Display for VariadicFunc {
             VariadicFunc::TimezoneTime => f.write_str("timezonet"),
             VariadicFunc::RegexpSplitToArray => f.write_str("regexp_split_to_array"),
             VariadicFunc::RegexpReplace => f.write_str("regexp_replace"),
+            VariadicFunc::StringToArray => f.write_str("string_to_array"),
         }
     }
 }
@@ -8466,6 +8561,7 @@ impl RustType<ProtoVariadicFunc> for VariadicFunc {
             VariadicFunc::TimezoneTime => TimezoneTime(()),
             VariadicFunc::RegexpSplitToArray => RegexpSplitToArray(()),
             VariadicFunc::RegexpReplace => RegexpReplace(()),
+            VariadicFunc::StringToArray => StringToArray(()),
         };
         ProtoVariadicFunc { kind: Some(kind) }
     }
@@ -8532,6 +8628,7 @@ impl RustType<ProtoVariadicFunc> for VariadicFunc {
                 TimezoneTime(()) => Ok(VariadicFunc::TimezoneTime),
                 RegexpSplitToArray(()) => Ok(VariadicFunc::RegexpSplitToArray),
                 RegexpReplace(()) => Ok(VariadicFunc::RegexpReplace),
+                StringToArray(()) => Ok(VariadicFunc::StringToArray),
             }
         } else {
             Err(TryFromProtoError::missing_field(

src/sql/src/func.rs

@@ -3161,6 +3161,10 @@ pub static PG_CATALOG_BUILTINS: LazyLock<BTreeMap<&'static str, Func>> = LazyLoc
             }) => String, 3538;
             params!(Bytes, Bytes) => Operation::binary(|_ecx, _l, _r| bail_unsupported!("string_agg on BYTEA")) => Bytes, 3545;
         },
+        "string_to_array" => Scalar {
+            params!(String, Any) => VariadicFunc::StringToArray => ScalarType::Array(Box::new(ScalarType::String)), 376;
+            params!(String, Any, String) => VariadicFunc::StringToArray => ScalarType::Array(Box::new(ScalarType::String)), 394;
+        },
         "sum" => Aggregate {
             params!(Int16) => AggregateFunc::SumInt16 => Int64, 2109;
             params!(Int32) => AggregateFunc::SumInt32 => Int64, 2108;