Use EXCLUDED values for history-node upserts

[perfloop-agent]

What changed?

The PostgreSQL history-node upsert now takes prev_txn_id, data, and data_encoding from EXCLUDED during conflict updates instead of binding those values a second time.

Added focused PostgreSQL coverage for insert and conflict-update readback, transaction IDs, empty and nil bytea behavior, rows affected, errors, and rollback across the supported drivers.

Why?

This avoids sending duplicate history-node values on each append while preserving the stored-row and conflict-update behavior. The change does not alter the driver, schema, transaction handling, or durability settings.

Workload: RespondWorkflowTaskCompleted with one sequential 1 KiB echo activity (256 workflows)

Metric	Before	After	Change
postgresql_protocol_bytes_per_workflow	91630	80912	11.7% lower

Workload: RespondWorkflowTaskCompleted with ten sequential 1 KiB echo activities (256 workflows)

Metric	Before	After	Change
postgresql_protocol_bytes_per_workflow	451605	388873	13.9% lower
Checks: 1 passed.

How did you test it?

• built
• run locally and tested manually
• covered by existing tests
• added new unit test(s)
• added new functional test(s)

Ran the focused PostgreSQL HistoryNode and HistoryStore suites for lib/pq, pgx extended protocol, and pgx simple protocol against PostgreSQL 17.11 with durability enabled. Also ran complete SDK workflow checks and protocol-byte validation for one- and ten-activity workloads.

Potential risks

The regression coverage is limited to the supported managed PostgreSQL schema and role. Unsupported custom triggers or unusual role policies are not covered.

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Generated by Perfloop. Human sponsor: Tomás Senart. Measurements and checks. Reproduce this comparison (tenant access required).

[CLAassistant]

All committers have signed the CLA.

[tsenart]

Hi, I'm Tomás, I build Perfloop. I approved this contribution and will handle review feedback here.

We've had performance PRs merged in ClickHouse, Prometheus, Ruff/ty, parquet-go, RoaringBitmap, and more. The measurements for this one cover complete Temporal workflows, with correctness checks across all three PostgreSQL driver modes.