Every client mutation funnels through SyncInbound, which ran O(n) DB
round-trips per call: one SELECT per client, a Save+UpdateColumn per
client, and a per-row junction INSERT. Toggling a single client on a
large inbound issued thousands of queries and timed out, badly so on
PostgreSQL where each round-trip pays TCP latency.
SyncInbound now:
- loads existing records with a single chunked SELECT ... email IN (...)
instead of one query per client
- writes only the records that actually changed (skips no-op Saves), so
toggling/editing one client writes one row, not all of them
- batch-creates new records and batch-inserts the junction rows
Merge and sticky-field semantics are unchanged. Measured on PostgreSQL
16: a single-client toggle on a 50k-client inbound drops from ~8m54s to
~0.9s, and seeding 50k clients from ~2m48s to ~1.6s; 200k clients sync
in seconds.
A skip-gated benchmark (web/service/sync_scale_postgres_test.go, run
with XUI_DB_TYPE=postgres) reproduces and verifies the scaling.
