mz_expr/scalar/func/impls/

array.rs

// Copyright Materialize, Inc. and contributors. All rights reserved.
//
// Use of this software is governed by the Business Source License
// included in the LICENSE file.
//
// As of the Change Date specified in that file, in accordance with
// the Business Source License, use of this software will be governed
// by the Apache License, Version 2.0.

use std::fmt;

use mz_expr_derive::sqlfunc;
use mz_repr::adt::array::{Array, ArrayDimension};
use mz_repr::{Datum, DatumList, Row, RowArena, RowPacker, SqlColumnType, SqlScalarType};
use serde::{Deserialize, Serialize};

use crate::scalar::func::{LazyUnaryFunc, stringify_datum};
use crate::{Eval, EvalError, MirScalarExpr};

// NOTE: This cast does not preserve uniqueness: It returns only the array's elements and drops the
// dimension metadata, so arrays that differ only in their lower bounds (e.g. `[1:1]={42}` and
// `[2:2]={42}`) collapse to the same list.
#[sqlfunc(sqlname = "arraytolist", introduces_nulls = false)]
fn cast_array_to_list_one_dim<'a, T>(a: Array<'a, T>) -> Result<DatumList<'a, T>, EvalError> {
    let ndims = a.dims().ndims();
    if ndims > 1 {
        return Err(EvalError::Unsupported {
            feature: format!(
                "casting multi-dimensional array to list; got array with {} dimensions",
                ndims
            )
            .into(),
            discussion_no: None,
        });
    }
    Ok(a.elements())
}

#[derive(
    Ord,
    PartialOrd,
    Clone,
    Debug,
    Eq,
    PartialEq,
    Serialize,
    Deserialize,
    Hash
)]
pub struct CastArrayToString {
    pub ty: SqlScalarType,
}

impl LazyUnaryFunc for CastArrayToString {
    fn eval<'a>(
        &'a self,
        datums: &[Datum<'a>],
        temp_storage: &'a RowArena,
        a: &'a impl Eval,
    ) -> Result<Datum<'a>, EvalError> {
        let a = a.eval(datums, temp_storage)?;
        if a.is_null() {
            return Ok(Datum::Null);
        }
        let mut buf = String::new();
        stringify_datum(&mut buf, a, &self.ty)?;
        Ok(Datum::String(temp_storage.push_string(buf)))
    }

    fn output_sql_type(&self, input_type: SqlColumnType) -> SqlColumnType {
        SqlScalarType::String.nullable(input_type.nullable)
    }

    fn propagates_nulls(&self) -> bool {
        true
    }

    fn introduces_nulls(&self) -> bool {
        false
    }

    fn preserves_uniqueness(&self) -> bool {
        true
    }

    fn inverse(&self) -> Option<crate::UnaryFunc> {
        // TODO? If we moved typeconv into `expr` we could determine the right
        // inverse of this.
        None
    }

    fn is_monotone(&self) -> bool {
        false
    }

    fn is_eliminable_cast(&self) -> bool {
        false
    }
}

impl fmt::Display for CastArrayToString {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.write_str("arraytostr")
    }
}

#[derive(
    Ord,
    PartialOrd,
    Clone,
    Debug,
    Eq,
    PartialEq,
    Serialize,
    Deserialize,
    Hash
)]
pub struct CastArrayToJsonb {
    pub cast_element: Box<MirScalarExpr>,
}

impl LazyUnaryFunc for CastArrayToJsonb {
    fn eval<'a>(
        &'a self,
        datums: &[Datum<'a>],
        temp_storage: &'a RowArena,
        a: &'a impl Eval,
    ) -> Result<Datum<'a>, EvalError> {
        fn pack<'a>(
            temp_storage: &RowArena,
            elems: &mut impl Iterator<Item = Datum<'a>>,
            dims: &[ArrayDimension],
            cast_element: &MirScalarExpr,
            packer: &mut RowPacker,
        ) -> Result<(), EvalError> {
            packer.push_list_with(|packer| match dims {
                [] => Ok(()),
                [dim] => {
                    for _ in 0..dim.length {
                        let elem = elems.next().unwrap();
                        let elem = match cast_element.eval(&[elem], temp_storage)? {
                            Datum::Null => Datum::JsonNull,
                            d => d,
                        };
                        packer.push(elem);
                    }
                    Ok(())
                }
                [dim, rest @ ..] => {
                    for _ in 0..dim.length {
                        pack(temp_storage, elems, rest, cast_element, packer)?;
                    }
                    Ok(())
                }
            })
        }

        let a = a.eval(datums, temp_storage)?;
        if a.is_null() {
            return Ok(Datum::Null);
        }
        let a = a.unwrap_array();
        let elements = a.elements();
        let dims = a.dims().into_iter().collect::<Vec<_>>();
        let mut row = Row::default();
        pack(
            temp_storage,
            &mut elements.into_iter(),
            &dims,
            &self.cast_element,
            &mut row.packer(),
        )?;
        Ok(temp_storage.push_unary_row(row))
    }

    fn output_sql_type(&self, input_type: SqlColumnType) -> SqlColumnType {
        SqlScalarType::Jsonb.nullable(input_type.nullable)
    }

    fn propagates_nulls(&self) -> bool {
        true
    }

    fn introduces_nulls(&self) -> bool {
        false
    }

    fn preserves_uniqueness(&self) -> bool {
        // NOTE: JSONB arrays reconstruct nested arrays from dimension lengths
        // only and carry no lower bounds, so arrays that differ only in their
        // lower bounds (e.g. `[1:1]={42}` and `[2:2]={42}`) produce the same
        // JSONB value. This cast is therefore not uniqueness-preserving.
        false
    }

    fn inverse(&self) -> Option<crate::UnaryFunc> {
        // TODO? If we moved typeconv into `expr` we could determine the right
        // inverse of this.
        None
    }

    fn is_monotone(&self) -> bool {
        false
    }

    fn is_eliminable_cast(&self) -> bool {
        false
    }
}

impl fmt::Display for CastArrayToJsonb {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.write_str("arraytojsonb")
    }
}

/// Casts an array of one type to an array of another type. Does so by casting
/// each element of the first array to the desired inner type and collecting
/// the results into a new array.
#[derive(
    Ord,
    PartialOrd,
    Clone,
    Debug,
    Eq,
    PartialEq,
    Serialize,
    Deserialize,
    Hash
)]
pub struct CastArrayToArray {
    pub return_ty: SqlScalarType,
    pub cast_expr: Box<MirScalarExpr>,
}

impl LazyUnaryFunc for CastArrayToArray {
    fn eval<'a>(
        &'a self,
        datums: &[Datum<'a>],
        temp_storage: &'a RowArena,
        a: &'a impl Eval,
    ) -> Result<Datum<'a>, EvalError> {
        let a = a.eval(datums, temp_storage)?;
        if a.is_null() {
            return Ok(Datum::Null);
        }

        let arr = a.unwrap_array();
        let dims = arr.dims().into_iter().collect::<Vec<ArrayDimension>>();

        let casted_datums = arr
            .elements()
            .iter()
            .map(|datum| self.cast_expr.eval(&[datum], temp_storage))
            .collect::<Result<Vec<Datum<'a>>, EvalError>>()?;

        Ok(temp_storage.try_make_datum(|packer| packer.try_push_array(&dims, casted_datums))?)
    }

    fn output_sql_type(&self, _input_type: SqlColumnType) -> SqlColumnType {
        self.return_ty.clone().nullable(true)
    }

    fn propagates_nulls(&self) -> bool {
        true
    }

    fn introduces_nulls(&self) -> bool {
        false
    }

    fn preserves_uniqueness(&self) -> bool {
        false
    }

    fn inverse(&self) -> Option<crate::UnaryFunc> {
        None
    }

    fn is_monotone(&self) -> bool {
        false
    }

    fn is_eliminable_cast(&self) -> bool {
        false
    }
}

impl fmt::Display for CastArrayToArray {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.write_str("arraytoarray")
    }
}