cw_substrb.sqlx

config { hasOutput: true }
/*
 * Copyright 2022 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/** Similar to Vertica SUBSTRB function, which treats the multibyte character string as a string of octets (bytes). */
CREATE OR REPLACE FUNCTION ${self()}(str STRING, startpos INT64 /* 1-based */, extent INT64 /* 1-based */) RETURNS STRING 
OPTIONS (
    description="Similar to Vertica SUBSTRB function, which treats the multibyte character string as a string of octets (bytes)."
)
AS (
    (WITH octets AS (
        SELECT oct FROM UNNEST(TO_CODE_POINTS(CAST(str as bytes))) AS oct WITH OFFSET off WHERE (off+1) >= startpos and (off+1) < startpos+extent ORDER BY off
    )
    SELECT SAFE_CONVERT_BYTES_TO_STRING(CODE_POINTS_TO_BYTES(ARRAY_AGG(oct))) FROM octets
));