Function unloadSubset

packages/powersync-db-collection/src/powersync.ts:604–648

(options: LoadSubsetOptions)

        }

        const unloadSubset = async (options: LoadSubsetOptions) => {
          onUnloadSubset?.()

          const idx = activeWhereExpressions.indexOf(options.where)
          if (idx !== -1) {
            activeWhereExpressions.splice(idx, 1)
          }

          // Evict rows that were exclusively loaded by the departing predicate.
          // These are rows matching the departing WHERE that are no longer covered
          // by any remaining active predicate.
          const compiledDeparting = compileSQLite({ where: options.where })
          const departingWhereSQL = toInlinedWhereClause(compiledDeparting)

          let evictionSQL: string
          if (activeWhereExpressions.length === 0) {
            evictionSQL = `SELECT id FROM ${viewName} WHERE ${departingWhereSQL}`
          } else {
            const combinedRemaining =
              activeWhereExpressions.length === 1
                ? activeWhereExpressions[0]!
                : or(
                    activeWhereExpressions[0],
                    activeWhereExpressions[1],
                    ...activeWhereExpressions.slice(2),
                  )
            const compiledRemaining = compileSQLite({
              where: combinedRemaining,
            })
            const remainingWhereSQL = toInlinedWhereClause(compiledRemaining)
            evictionSQL = `SELECT id FROM ${viewName} WHERE (${departingWhereSQL}) AND NOT (${remainingWhereSQL})`
          }

          const rowsToEvict = await database.getAll<{ id: string }>(evictionSQL)
          if (rowsToEvict.length > 0) {
            begin()
            for (const { id } of rowsToEvict) {
              write({ type: `delete`, key: id })
            }
            commit()
          }

          // Recreate the diff trigger for the remaining active WHERE expressions.
          await loadSubset()
        }

        markReady()