Sql Postgres函数-显示复制命令错误

我的函数定义是这样的，它抛出了一个错误

CREATE OR REPLACE FUNCTION traffic.addcsv (
      filename text
    )
    RETURNS void AS
    $body$
    BEGIN
    DROP TABLE IF EXISTS traffic.tsdata;

    create table if not EXISTS traffic.tsdata
    (
        ldir text,
        dtime timestamp,
        epoch integer,
        ln_m integer,
        freeflow real,
        spdlimit integer,
        cnt integer,
        mean_spd real,
        stddev real,
        mn integer,
        mx integer,
        conf integer
    );

    COPY traffic.tsdata FROM '$1' DELIMITER ',' CSV HEADER;

    CREATE TABLE IF NOT EXISTS traffic.psdata
    (
         l_id BIGINT,
         direction char(1),
         dtime timestamp,
         day_number SMALLINT,
         epoch smallint,
         length_m integer,
         freeflow smallint,
         spdlimit smallint,
         cnt integer,
         mean_speed smallint,
         stddev double precision ,
         mn smallint,
         mx SMALLINT,
         confidence smallint
    ); 

    INSERT INTO traffic.psdata (
    l_id,
    direction,
    dtime,
    day_number,
    epoch,
    length_m,
    freeflow,
    spdlimit,
    cnt,
    mean_speed,
    stddev,
    mn,
    mx,
    confidence
    )
    SELECT
            (replace ( (replace(ldir,'F','')) ,'T',''  )::integer,
        RIGHT(tsdata.ldir,1)::char(1) ,
            dtime,
        EXTRACT(ISODOW FROM traffic.tsdata.dtime)::smallint ,
            epoch,
            ln_m,
            freeflow,
        spdlimit,
            cnt,
            mean_spd,
            stddev,
            mn,
            mx,
            conf)
    FROM traffic.tsdata;

    END;
    $body$
    LANGUAGE 'plpgsql'
    VOLATILE
    CALLED ON NULL INPUT
    SECURITY INVOKER
    PARALLEL UNSAFE
    COST 100;

错误：无法打开文件$1进行读取：没有这样的文件或目录 提示：复制自指示PostgreSQL server进程读取文件。您可能需要一个客户端工具，如psql的\copy。 上下文：SQL语句从“$1”分隔符、“CSV头”复制traffic.tsdata

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PL/pgSQL函数traffic.addcsvtext第21行的SQL语句

我认为PL/pgSQL不允许在COPY语句中使用变量

您可以使用动态SQL执行此操作：

EXECUTE format('COPY traffic.tsdata FROM %L DELIMITER '','' CSV HEADER', $1);