tpcc: add PL/pgSQL stored-procedure mode (--stored-procs)#205
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akorotkov wants to merge 2 commits into
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tpcc: add PL/pgSQL stored-procedure mode (--stored-procs)#205akorotkov wants to merge 2 commits into
akorotkov wants to merge 2 commits into
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When --stored-procs is set on `go-tpc tpcc run` (postgres driver only), each of the five TPC-C transactions is dispatched as a single server-side CALL: tpcc_new_order / tpcc_payment / tpcc_order_status / tpcc_delivery / tpcc_stock_level. Procedures are installed via CREATE OR REPLACE on the first Run() invocation (sync.Once), so the same dataset can be benched in either mode — no separate prepare step. NEW_ORDER's 1%-rollback path (sentinel item id of -1) is handled server-side via an in-band ROLLBACK inside the procedure: the engine pays for the district/orders/new_order writes and then undoes them, matching the original Go transaction's behaviour exactly. Other procedures run their work and return; the autocommit transaction commits implicitly.
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…caches The district-specific stock distribution column (s_dist_01..s_dist_10) was selected via EXECUTE format(...), which forced PL/pgSQL to parse and plan the SELECT from scratch on every iteration — measurable cost on the hot NEW_ORDER path (10 stock rows per call). Switch to a single static SELECT that picks the right column via CASE p_d_id WHEN N THEN s_dist_NN END. PL/pgSQL caches its plan after a few executions and pg_stat_statements collapses the 10 district variants into one entry. Reading all 10 s_dist columns is essentially free — the stock row is already in cache and locked FOR UPDATE.
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While benchmarking PostgreSQL with TPC-C, one may note that backends might spend most of the time in the ClientRead wait event. That is, PostgreSQL protocol communication spends most of the time preventing us from reaching the core bottlenecks. This PR implements --stored-procs mode (similar to HammerDB's pg_storedprocs), in which a single transaction is appended to a single stored procedure on the PostgreSQL side. This allow us to reach higher performance level and explore PostgreSQL core/storage bottlenecks with TPC-C benchmark.