Source

File: wp-includes/comment.php

function wp_delete_comment( $comment_id, $force_delete = false ) {
	global $wpdb;
	$comment = get_comment( $comment_id );
	if ( ! $comment ) {
		return false;
	}

	if ( ! $force_delete && EMPTY_TRASH_DAYS && ! in_array( wp_get_comment_status( $comment ), array( 'trash', 'spam' ), true ) ) {
		return wp_trash_comment( $comment_id );
	}

	/**
	 * Fires immediately before a comment is deleted from the database.
	 *
	 * @since 1.2.0
	 * @since 4.9.0 Added the `$comment` parameter.
	 *
	 * @param int        $comment_id The comment ID.
	 * @param WP_Comment $comment    The comment to be deleted.
	 */
	do_action( 'delete_comment', $comment->comment_ID, $comment );

	// Move children up a level.
	$children = $wpdb->get_col( $wpdb->prepare( "SELECT comment_ID FROM $wpdb->comments WHERE comment_parent = %d", $comment->comment_ID ) );
	if ( ! empty( $children ) ) {
		$wpdb->update( $wpdb->comments, array( 'comment_parent' => $comment->comment_parent ), array( 'comment_parent' => $comment->comment_ID ) );
		clean_comment_cache( $children );
	}

	// Delete metadata.
	$meta_ids = $wpdb->get_col( $wpdb->prepare( "SELECT meta_id FROM $wpdb->commentmeta WHERE comment_id = %d", $comment->comment_ID ) );
	foreach ( $meta_ids as $mid ) {
		delete_metadata_by_mid( 'comment', $mid );
	}

	if ( ! $wpdb->delete( $wpdb->comments, array( 'comment_ID' => $comment->comment_ID ) ) ) {
		return false;
	}

	/**
	 * Fires immediately after a comment is deleted from the database.
	 *
	 * @since 2.9.0
	 * @since 4.9.0 Added the `$comment` parameter.
	 *
	 * @param int        $comment_id The comment ID.
	 * @param WP_Comment $comment    The deleted comment.
	 */
	do_action( 'deleted_comment', $comment->comment_ID, $comment );

	$post_id = $comment->comment_post_ID;
	if ( $post_id && 1 == $comment->comment_approved ) {
		wp_update_comment_count( $post_id );
	}

	clean_comment_cache( $comment->comment_ID );

	/** This action is documented in wp-includes/comment.php */
	do_action( 'wp_set_comment_status', $comment->comment_ID, 'delete' );

	wp_transition_comment_status( 'delete', $comment->comment_approved, $comment );

	return true;
}