DATABASE FIELD LAB / POSTGRESQL WASM
Настоящий PostgreSQL работает локально в Web Worker. Запросы дают реальный planner evidence, DDL откатывается после behavioral probes, а maintenance fixture удаляется после каждого запуска.
CASE / B-TREE / RANGE / COVERING READ
Support asks for the five newest pending orders of tenant 42 created since 2026-05-01. Return exactly id, UTC minute as created_utc, and total_cents.
01 / CONTRACT
Use equality keys before the range, preserve deterministic ordering and prove that the covering index serves the read.
The index begins with tenant_id and status equalities. created_at is then both a range boundary and the leading order key; id breaks timestamp ties. LIMIT is meaningful only after that deterministic order is established.
INCLUDE makes total_cents available to an index-only plan without changing search order. It can remove heap reads when visibility permits, but every included byte still increases index storage and write amplification.
orders id bigint primary key tenant_id integer not null status text not null created_at timestamptz not null total_cents integer not null payload text not null orders_tenant_status_created_idx btree (tenant_id, status, created_at desc, id desc) include (total_cents)
02 / QUERY
Запустите локальную PostgreSQL — dataset останется только в этой вкладке.