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[Drift] Configurable SQL WHERE clause prefiltering for initial snapshot replication (powersync-service #502) #425

@benitav

Description

@benitav

What shipped: A new configurable SQL WHERE clause has been added to the PowerSync Service that filters rows during the initial snapshot (binlog replication) phase, enabling partial snapshots — replicating only a subset of data matching the specified criteria. This is particularly useful for large tables or scenarios where only recent data is needed.

Why this needs docs: New configuration option that changes how sync rules can be written — users need to know this feature exists and how to use it for large-table optimisations.

Likely affected pages/sections:

  • Sync rules reference — document the prefilter/WHERE clause syntax, which source databases support it, and any limitations
  • Initial replication / how sync works conceptual page — explain partial snapshots and when to use prefiltering
  • Large-table or performance best-practices page (if exists) — reference prefiltering as a strategy for managing large tables

Source PR: powersync-ja/powersync-service#502

CC: @benitav @raffidahmad

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