ClickHouse/src/Functions/FunctionsStringSearch.h

#pragma once

#include <Columns/ColumnConst.h>
#include <Columns/ColumnNullable.h>
#include <Columns/ColumnString.h>
#include <Columns/ColumnFixedString.h>
#include <Columns/ColumnVector.h>
#include <DataTypes/DataTypeArray.h>
#include <DataTypes/DataTypeNullable.h>
#include <DataTypes/DataTypeString.h>
#include <DataTypes/DataTypesNumber.h>
#include <Functions/FunctionHelpers.h>
#include <Functions/IFunction.h>
#include <Interpreters/Context.h>
#include <IO/WriteHelpers.h>

namespace DB
{
/** Search and replace functions in strings:
  * position(haystack, needle)     - the normal search for a substring in a string, returns the position (in bytes) of the found substring starting with 1, or 0 if no substring is found.
  * positionUTF8(haystack, needle) - the same, but the position is calculated at code points, provided that the string is encoded in UTF-8.
  * positionCaseInsensitive(haystack, needle)
  * positionCaseInsensitiveUTF8(haystack, needle)
  *
  * like(haystack, pattern)        - search by the regular expression LIKE; Returns 0 or 1. Case-insensitive, but only for Latin.
  * notLike(haystack, pattern)
  *
  * ilike(haystack, pattern) - like 'like' but case-insensitive
  * notIlike(haystack, pattern)
  *
  * match(haystack, pattern)       - search by regular expression re2; Returns 0 or 1.
  *
  * countSubstrings(haystack, needle) -- count number of occurrences of needle in haystack.
  * countSubstringsCaseInsensitive(haystack, needle)
  * countSubstringsCaseInsensitiveUTF8(haystack, needle)
  *
  * hasToken()
  * hasTokenCaseInsensitive()
  *
  * JSON stuff:
  * visitParamExtractBool()
  * simpleJSONExtractBool()
  * visitParamExtractFloat()
  * simpleJSONExtractFloat()
  * visitParamExtractInt()
  * simpleJSONExtractInt()
  * visitParamExtractUInt()
  * simpleJSONExtractUInt()
  * visitParamHas()
  * simpleJSONHas()
  *
  * Applies regexp re2 and pulls:
  * - the first subpattern, if the regexp has a subpattern;
  * - the zero subpattern (the match part, otherwise);
  * - if not match - an empty string.
  * extract(haystack, pattern)
  */

namespace ErrorCodes
{
    extern const int ILLEGAL_COLUMN;
    extern const int ILLEGAL_TYPE_OF_ARGUMENT;
    extern const int NUMBER_OF_ARGUMENTS_DOESNT_MATCH;
}

enum class ExecutionErrorPolicy
{
    Null,
    Throw
};

template <typename Impl, ExecutionErrorPolicy execution_error_policy = ExecutionErrorPolicy::Throw>
class FunctionsStringSearch : public IFunction
{
public:
    static constexpr auto name = Impl::name;

    static FunctionPtr create(ContextPtr) { return std::make_shared<FunctionsStringSearch>(); }

    String getName() const override { return name; }

    bool isVariadic() const override { return Impl::supports_start_pos; }

    bool isSuitableForShortCircuitArgumentsExecution(const DataTypesWithConstInfo & /*arguments*/) const override { return true; }

    size_t getNumberOfArguments() const override
    {
        if (Impl::supports_start_pos)
            return 0;
        return 2;
    }

    bool useDefaultImplementationForConstants() const override { return Impl::use_default_implementation_for_constants; }

    ColumnNumbers getArgumentsThatAreAlwaysConstant() const override
    {
        return Impl::getArgumentsThatAreAlwaysConstant();
    }

    DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
    {
        if (arguments.size() < 2 || 3 < arguments.size())
            throw Exception(
                ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH,
                "Number of arguments for function {} doesn't match: passed {}, should be 2 or 3",
                getName(), arguments.size());

        if (!isStringOrFixedString(arguments[0]))
            throw Exception(
                ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT,
                "Illegal type {} of argument of function {}",
                arguments[0]->getName(), getName());

        if (!isString(arguments[1]))
            throw Exception(
                ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT,
                "Illegal type {} of argument of function {}",
                arguments[1]->getName(), getName());

        if (arguments.size() >= 3)
        {
            if (!isUnsignedInteger(arguments[2]))
                throw Exception(
                    ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT,
                    "Illegal type {} of argument of function {}",
                    arguments[2]->getName(), getName());
        }

        auto return_type = std::make_shared<DataTypeNumber<typename Impl::ResultType>>();
        if constexpr (execution_error_policy == ExecutionErrorPolicy::Null)
            return makeNullable(return_type);

        return return_type;
    }

    ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr & result_type, size_t /*input_rows_count*/) const override
    {
        const ColumnPtr & column_haystack = arguments[0].column;
        const ColumnPtr & column_needle = arguments[1].column;

        ColumnPtr column_start_pos = nullptr;
        if (arguments.size() >= 3)
            column_start_pos = arguments[2].column;

        const ColumnConst * col_haystack_const = typeid_cast<const ColumnConst *>(&*column_haystack);
        const ColumnConst * col_needle_const = typeid_cast<const ColumnConst *>(&*column_needle);

        using ResultType = typename Impl::ResultType;
        auto col_res = ColumnVector<ResultType>::create();
        auto & vec_res = col_res->getData();

        const auto create_null_map = [&]() -> ColumnUInt8::MutablePtr
        {
            if constexpr (execution_error_policy == ExecutionErrorPolicy::Null)
                return ColumnUInt8::create(vec_res.size());

            return {};
        };

        if constexpr (!Impl::use_default_implementation_for_constants)
        {
            if (col_haystack_const && col_needle_const)
            {
                const auto is_col_start_pos_const = !column_start_pos || isColumnConst(*column_start_pos);
                vec_res.resize(is_col_start_pos_const ? 1 : column_start_pos->size());
                const auto null_map = create_null_map();

                Impl::constantConstant(
                    col_haystack_const->getValue<String>(),
                    col_needle_const->getValue<String>(),
                    column_start_pos,
                    vec_res,
                    null_map.get());

                if (is_col_start_pos_const)
                    return result_type->createColumnConst(col_haystack_const->size(), toField(vec_res[0]));
                else
                    return col_res;
            }
        }

        vec_res.resize(column_haystack->size());
        auto null_map = create_null_map();

        const ColumnString * col_haystack_vector = checkAndGetColumn<ColumnString>(&*column_haystack);
        const ColumnFixedString * col_haystack_vector_fixed = checkAndGetColumn<ColumnFixedString>(&*column_haystack);
        const ColumnString * col_needle_vector = checkAndGetColumn<ColumnString>(&*column_needle);

        if (col_haystack_vector && col_needle_vector)
            Impl::vectorVector(
                col_haystack_vector->getChars(),
                col_haystack_vector->getOffsets(),
                col_needle_vector->getChars(),
                col_needle_vector->getOffsets(),
                column_start_pos,
                vec_res,
                null_map.get());
        else if (col_haystack_vector && col_needle_const)
            Impl::vectorConstant(
                col_haystack_vector->getChars(),
                col_haystack_vector->getOffsets(),
                col_needle_const->getValue<String>(),
                column_start_pos,
                vec_res,
                null_map.get());
        else if (col_haystack_vector_fixed && col_needle_vector)
            Impl::vectorFixedVector(
                col_haystack_vector_fixed->getChars(),
                col_haystack_vector_fixed->getN(),
                col_needle_vector->getChars(),
                col_needle_vector->getOffsets(),
                column_start_pos,
                vec_res,
                null_map.get());
        else if (col_haystack_vector_fixed && col_needle_const)
            Impl::vectorFixedConstant(
                col_haystack_vector_fixed->getChars(),
                col_haystack_vector_fixed->getN(),
                col_needle_const->getValue<String>(),
                vec_res,
                null_map.get());
        else if (col_haystack_const && col_needle_vector)
            Impl::constantVector(
                col_haystack_const->getValue<String>(),
                col_needle_vector->getChars(),
                col_needle_vector->getOffsets(),
                column_start_pos,
                vec_res,
                null_map.get());
        else
            throw Exception(
                ErrorCodes::ILLEGAL_COLUMN,
                "Illegal columns {} and {} of arguments of function {}",
                arguments[0].column->getName(),
                arguments[1].column->getName(),
                getName());

        if constexpr (execution_error_policy == ExecutionErrorPolicy::Null)
            return ColumnNullable::create(std::move(col_res), std::move(null_map));

        return col_res;
    }
};

}