Documentation
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Overview ¶
Package migrate moves the documents in a collab store out of a snapshot format that is no longer read.
crdt v0.42.0 stopped reading text format 6, on the reasoning that nobody holds a snapshot in it. A store is exactly where one is held: every document a server has persisted is a snapshot in whatever format its crdt wrote, and collab selected a crdt that wrote format 6 until collab v0.37.0.
So a DirStore directory, a Postgres table or a git repository filled before then has documents a current build cannot open. This reads each one with a build that still can and writes it back in a format that will be read, which is the only way across: nothing converts a snapshot without understanding it.
Build this against the pinned versions ¶
The module pins crdt v0.41.0 because it reads format 6 and writes 8. Built against anything that has forgotten 6, Rewrite refuses rather than reporting that every document was already current -- which is what a silent no-op would look like from outside.
Index ¶
Constants ¶
This section is empty.
Variables ¶
var ErrCannotRead = errors.New("migrate: this build cannot read the format it exists to move")
ErrCannotRead reports a build that has itself forgotten the format it was meant to move documents out of.
Functions ¶
This section is empty.
Types ¶
type Result ¶
type Result struct {
// Moved were read in an old format and written back in a current one.
Moved []string
// Current were already in a format a current build reads, and were left
// alone rather than rewritten for the sake of it.
Current []string
// Failed could not be read at all, with the reason. A document here is not
// lost -- nothing was written over it -- but it is not moved either.
Failed map[string]error
}
A Result counts what happened, because "it worked" is not a thing a person should have to take on trust after rewriting their documents.
func Rewrite ¶
Rewrite moves each named document into a format a current build can read.
The names come from the caller because a store enumerates its documents in its own way and its own signature: DirStore.Documents takes no context, pgstore's does, MemoryStore's returns no error. Asking for the list rather than an interface keeps this from inventing a fourth shape.
A document already in a readable format is left exactly as it is. Rewriting it would change its bytes for nothing, and a migration that touches what it need not is a migration nobody can check.
Source Files