notes.md

back-to-cid

• cid from pragma_table_info
• send cid over the wire too?
  • maybe in future update
• sentinel becomes actual -1? or empty string or some such? Neg numbers are large varints
• begin_alter needs to save off cid mappings in temp table so we can detect dropped columns
  • commit_alter would need to find where names no longer exist and remove them from clock tables based on their old cid mapping
  • commit_alter would need to re-number entries in clock tables whose name via old cid matches name via new cid but where old cid != new cid

db-version

db version as col version for tx preservation on merge.

Each col_version is currently incremented independently. We can instead set it to the current db_version to ensure that all values set in the same transaction can also all win together when merging.

This isn't guaranteed since the peer being merged into could be way ahead in db_version overall but have some records behind in db_version.

pk-lookup

• New table

CREATE TABLE foo__crsql_pks (num INTEGER PRIMARY KEY, ...pks);
CREATE UNIQUE INDEX ON foo__crsql_pks (...pks);

Merges... We still send actual PKs over the wire. Each host has its own nums.

Merge:

1. Lookup num -- num missing means we have no record can do some short-circuits here
2. Do clock table stuff with num

Pull changes:

1. Join pks via num

next db version optimization

We currently nuke this on commit.

We can keep a variable in ext data to represent it and only nuke / refresh it if the data change bit is set.

The variable needs to be set on merge

crsql_next_db_version(arg?)

// arg is optional. If present, we set the `pending next db version`
function crsql_next_db_version(arg?) {
  const ret = max(crsql_db_version() + 1, pExtData.pendingDbVersion, arg);
  pExtData.pendingDbVersion = ret;
  return ret;
}

On commit, pending becomes actual.

Trigger opt

• function to insert and save a lookaside in insert_trigger

• function to get and save a lookaside in update_trigger

  • replace these lookups: (SELECT __crsql_key FROM \"{table_name}__crsql_pks\" WHERE {pk_where_list})

• Test changing pks in update creates key lookaside correctly.

---

Assuming we re-write to use a function...

function after_update(table, cols_new, cols_old) {
  // cols_new and cols_old are _in order_ as according to table_info

  // 1. Lookup the old record with `cols_old`
  // 2. Do the pk delete stuff if there exists a record with old
  // 3. If any pk is different, record a create record (sqlite value compare)
  // 4. For each non_pk, record the clock metadata
}