wpdb replace returning 1 where delete and insert is expected

Question

If I enter a row with wpdb->replace using an ID that already exists, it's replaced and 2 is returned. If I enter a new row, the ID is auto generated, a new row is inserted and 1 is returned. Perfect.

If, however, I enter a row that exactly matches an existing row (where I would still expect a delete and insert), 1 is returned instead (even though no new rows are inserted in the database). Why is this happening?!

I am trying to insert a post when a row is inserted into my database. ie.) when replace returns 1. but I'm alse getting new posts when when I insert an exact copy of an existing row.

function xxxx_insert_entry( $post_id, $entry, $type, $entry_id = null ) {
    global $wpdb;

    $result = $wpdb->replace( 
        $wpdb->prefix . 'xxxx_entries', 
        array( 
            'ID' => $entry_id, // PRIMARY KEY
            'post_id' => $post_id,
            'entry' => $entry, 
            'type' => $type 
        ) 
    );
    if ( $result === false ) return $result;

    $insert_id = $wpdb->insert_id;

    if ( 1 == $result ){ // INSERT OCCURRED
        $args = array(
            'post_type'     => 'entry',
            'post_title'    => $entry,
            'post_status'   => 'publish',
            'meta_input'    => array( 'entry_id' => $insert_id ),
        );
        wp_insert_post( $args, true );

    } // ELSE REPLACE OCCURRED


    return $insert_id;
}

Answer 1

I have found here that;

It is possible that in the case of a duplicate-key error, a storage engine may perform the REPLACE as an update rather than a delete plus insert, but the semantics are the same.

Which would return 1 row affected on what should otherwise be a delete and insert.

I am now checking if an entry_id was provided to the function. ie. if I was expecting an insert.

    if ( 1 == result || isset( $entry_id ) )