Re: [tarantool-patches] [PATCH v2 2/2] Track wal vclock changes instead of copying

[Vladimir Davydov <vdavydov.dev@gmail.com>]

On Wed, Feb 13, 2019 at 11:35:17AM +0300, Georgy Kirichenko wrote:
> +/*
> + * Assign lsn and replica identifier for local writes and track
> + * row into vclock_diff.
> + */
>  static void
> -wal_assign_lsn(struct vclock *vclock, struct xrow_header **row,
> +wal_assign_lsn(struct vclock *vclock_diff, struct vclock *base,
> +	       struct xrow_header **row,
>  	       struct xrow_header **end)
>  {
>  	/** Assign LSN to all local rows. */
>  	for ( ; row < end; row++) {
>  		if ((*row)->replica_id == 0) {
> -			(*row)->lsn = vclock_inc(vclock, instance_id);
> +			(*row)->lsn = vclock_inc(vclock_diff, instance_id) +
> +				      vclock_get(base, instance_id);
>  			(*row)->replica_id = instance_id;
>  		} else {
> -			vclock_follow_xrow(vclock, *row);
> +			vclock_follow(vclock_diff, (*row)->replica_id,
> +				      (*row)->lsn - vclock_get(base,
> +							       (*row)->replica_id));

vclock_follow_xrow() checks that LSN doesn't go backwards and panics if
it does.

vclock_follow() doesn't have such check.