Atomically Fetch And Update A Row (LCC.db.fetch_one)

Signature

row, err = LCC.db.fetch_one(name, opts, timeout?)

Parameters

• name
  String. Table name. Must be non-empty and no longer than 256 bytes.
• opts
  Table with:
  • conditions: table of equality filters (default {})
  • update: table of fields to update after the row is claimed
  • pick: string, choose "min", "max", or "random"; defaults to "min" based on id
• timeout
  Number, optional. Request timeout in seconds, default 60.

Returns

• row
  Table. The claimed row; nil when nothing matched.
• err
  String or nil. Error description; 'not found' when no row matched, 'unknown table' when the table is missing.

Notes

Atomically reads and updates a single row, ideal for task assignment under concurrency.
Fields in update are persisted immediately so the same record is not handed out twice.
Omitting update still performs an atomic selection but skips the write-back.

Example

local row, err = LCC.db.fetch_one("tasks", {
    conditions = { Status = "Idle" },
    update = { Status = "Running" },
    pick = "min"
})
if row then
    print("Claimed task", row.id, row.Name)
elseif err == "not found" then
    print("No idle tasks available")
end