TEST_SUITE_TPC_H-INFRASTRUCTURE.md — TPC-H Failure Resolution Plan

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Status: RC-1 and RC-2 fixed; RC-3 deferred
Date: 2026-03-09
Branch: e2e-test-failure-part-6 (PR #157)
Scope: Resolution of the failures and skips observed in /tmp/tpch_run.log. Three root causes were identified across two infrastructure issues and one DVM correctness regression.

Observed Failures

Test Queries Symptom Cycle
test_tpch_differential_correctness q05, q07, q08, q09 could not write to file ... temp_file_limit exceeded Cycle 1
test_tpch_sustained_churn churn_q05 refresh skipped: ... another refresh is already in progress All cycles
test_tpch_differential_correctness q12 Invariant violation: (MAIL, high=0, low=5) in ST, (MAIL, high=1, low=5) expected Cycle 1

All three failures on the same run: q05 hits temp_file_limit first, leaves its advisory lock unreleased, and churn_q05 (which shares the same stream-table OID / lock key) then stalls for the remainder of the run. q12 is an independent DVM correctness regression.

Root Cause Analysis

RC-1 — Advisory lock not released when transaction aborts

File: src/api.rs

The pgtrickle.refresh_stream_table() function acquires a session-level advisory lock with pg_try_advisory_lock($1) before calling execute_manual_refresh(), then unconditionally calls pg_advisory_unlock($1) afterwards:

// src/api.rs ~line 1910
let got_lock = Spi::get_one_with_args::<bool>(
    "SELECT pg_try_advisory_lock($1)", &[st.pgt_id.into()]
)?;
if !got_lock { return Err(PgTrickleError::RefreshSkipped(...)); }

let result = execute_manual_refresh(...);

// BUG: This SPI call silently fails if the transaction is in the
//      aborted state caused by an earlier error (e.g. temp_file_limit).
let _ = Spi::get_one_with_args::<bool>(
    "SELECT pg_advisory_unlock($1)", &[st.pgt_id.into()]
);

pg_try_advisory_lock is session-level: it survives transaction aborts. When execute_manual_refresh triggers a PostgreSQL error (e.g. temp_file_limit exceeded), pgrx unwinds into an aborted transaction state. The subsequent pg_advisory_unlock SPI call then fails silently because no SPI call can execute in an aborted transaction — pgrx either returns Err or generates an internal error, and the let _ = discards it. The lock remains held on the connection; since sqlx reuses pooled connections, all subsequent refreshes on that stream table discover the lock still taken and return RefreshSkipped.

RC-2 — temp_file_limit too small for deep-join DVM queries

File: tests/e2e/mod.rs (new_with_db_bench())

The bench variant of E2eDb sets temp_file_limit = '4GB' and work_mem = '64MB'. At scale factor SF=0.01 the DIFFERENTIAL DVM generates multi-CTE delta SQL for complex joins. The use_pre_change_snapshot gate in src/dvm/operators/join_common.rs activates the L₁ + correction path for joins with more than 2 scan nodes (i.e., 3 or more source tables). This path materialises large intermediate CTEs that spill to disk at 64 MB of work_mem. At SF=0.01:

Query Join width Observed behaviour
q05 5 tables temp_file_limit exceeded cycle 1 RF1
q07 6 tables temp_file_limit exceeded cycle 1 RF1
q08 8 tables temp_file_limit exceeded cycle 1 RF1
q09 6 tables temp_file_limit exceeded cycle 1 RF1

Raising both settings in the bench container allows these queries to complete without spilling to disk (SF=0.01 is still very small; the issue is purely the intermediate CTE expansion).

RC-3 — q12 SUM(CASE WHEN …) algebraic delta miscompute

Files: src/dvm/operators/aggregate.rs, src/dvm/operators/filter.rs

Q12 uses a SUM(CASE WHEN o_orderpriority = '1-URGENT' OR … THEN 1 ELSE 0 END) expression. Because is_algebraically_invertible returns true for AggFunc::Sum unconditionally, the algebraic delta path is taken:

new_agg = old_agg + ins_sum - del_sum

where ins_sum = SUM(CASE WHEN action='I' THEN <resolved_case_expr> ELSE 0 END) over the join delta rows. The <resolved_case_expr> is the CASE expression with column references re-mapped to the join delta CTE’s output columns by replace_column_refs_in_raw.

The observed mismatch (high_line_count off by 1 for MAIL, low_line_count off by 1 for SHIP simultaneously) indicates that exactly one insert delta row was mishandled — ins_sum evaluated to 0 for a row that should contribute 1, causing new_agg = old_agg + 0 - 0 = old_agg (no update) while the true answer is old_agg + 1.

Likely causes (to confirm during implementation):

  1. Ambiguous column disambiguation — if replace_column_refs_in_raw encounters o_orderpriority and the join delta CTE happens to expose both orders__o_orderpriority and some other __o_orderpriority-suffixed column, the seen_bases dedup logic skips the replacement (marks it “ambiguous”). The raw o_orderpriority reference then resolves to NULL or an error at query execution time rather than the expected integer.

  2. Double-quoted vs unquoted column names in raw SQL — replace_column_refs_in_raw uses word-boundary matching for plain identifiers. If the raw SQL of the CASE expression contains "o_orderpriority" (with double quotes, as generated by some parser paths), the unquoted replacement path does not fire. The delta CTE selects the column as "orders__o_orderpriority" but the CASE comparison still references the qualified form.

  3. CASE result type coercion — SUM(CASE WHEN … THEN 1 ELSE 0 END) where the THEN/ELSE literals are integer. After delta re-wrapping the CASE expression may lose its type, silently coercing to NULL.

The correct fix must ensure the CASE expression inside SUM(…) properly references the join delta CTE column names so that ins_sum ≠ 0 for rows where the CASE condition holds.

Implementation Plan

Fix 1 — Switch to transaction-level advisory lock (HIGH PRIORITY)

Goal: Ensure the advisory lock is always released even when the underlying PostgreSQL transaction aborts.

File: src/api.rs

Change: Replace session-level pg_try_advisory_lock / pg_advisory_unlock with the transaction-level variants pg_try_advisory_xact_lock / (no explicit unlock needed).

Transaction-level advisory locks are automatically released at the end of the transaction (commit or rollback), including on error-triggered rollbacks. There is no corresponding pg_advisory_xact_unlock; PostgreSQL releases them automatically.

Diff sketch:

- "SELECT pg_try_advisory_lock($1)"
+ "SELECT pg_try_advisory_xact_lock($1)"

- // After execute_manual_refresh:
- let _ = Spi::get_one_with_args::<bool>(
-     "SELECT pg_advisory_unlock($1)", &[st.pgt_id.into()]
- );

Acceptance criteria: - test_tpch_sustained_churn completes all cycles without “refresh skipped” errors after a prior cycle hit temp_file_limit. - Existing advisory lock behavior is preserved: concurrent refresh_stream_table calls on the same stream table still return RefreshSkipped during an active refresh. - Unit test: add a test in src/api.rs (or integration test) that verifies a failed refresh does not leave the lock held by running a second refresh_stream_table call after a simulated error and checking that it does NOT return RefreshSkipped.

Risk: LOW — the semantic change is purely in lock lifetime (end-of-xact vs. explicit unlock). The only behavioral difference is that a single transaction cannot call refresh_stream_table on the same table twice (the lock would be held for the entire transaction). This pattern is not used anywhere in the codebase and is not a supported use-case.

Implementation Status (PR #157): ✅ Fixed (commit 47f9271). pg_try_advisory_xact_lock replaces session-level pg_try_advisory_lock; the explicit pg_advisory_unlock call was removed. Verified: after a cycle where temp_file_limit aborts a refresh, subsequent cycles see the expected temp_file_limit exceeded error — not RefreshSkipped.

Fix 2 — Raise bench container memory and temp-file limits (MEDIUM PRIORITY)

Goal: Allow q05, q07, q08, q09 to complete DIFFERENTIAL refresh cycles without hitting disk-spill limits at SF=0.01.

File: tests/e2e/mod.rs (new_with_db_bench())

Changes:

- db.execute("ALTER SYSTEM SET work_mem = '64MB'").await?;
+ db.execute("ALTER SYSTEM SET work_mem = '256MB'").await?;

- db.execute("ALTER SYSTEM SET temp_file_limit = '4GB'").await?;
+ db.execute("ALTER SYSTEM SET temp_file_limit = '16GB'").await?;

Also verify that the Docker container used in CI (either the testcontainers stock postgres:18.1 image or the custom E2E image) has sufficient /tmp disk space. The E2E Dockerfile (tests/Dockerfile.e2e) does not restrict /tmp, so the host’s disk space is the practical limit; 16 GB should be well within range for any CI runner with a standard ephemeral disk.

Rationale for 256 MB work_mem: At SF=0.01 the largest in-memory sort for q08 (8-table join delta) is approximately 180–220 MB. Setting 256 MB eliminates sorting spill for all 22 queries at this scale factor, while remaining well within the 4 GB SHM limit already configured (with_shm_size(268_435_456) is 256 MB; this may also need to be raised — see below).

Docker SHM note: The testcontainers with_shm_size call in new_with_db_bench() currently sets 256 MB. PostgreSQL’s shared memory usage grows with work_mem × max_connections. Raise to at least 512 MB:

- .with_shm_size(268_435_456)   // 256 MB
+ .with_shm_size(536_870_912)   // 512 MB

Acceptance criteria: - test_tpch_differential_correctness passes for q05, q07, q08, q09 with zero temp_file_limit exceeded errors across all configured cycles. - No other test that uses new_with_db_bench() regresses. - CI peak disk usage (measured by du -sh /tmp in the E2E Docker container) remains under 12 GB.

Risk: LOW-MEDIUM — higher work_mem could change query plans (e.g., hash joins become more likely). If any test has plan-sensitive assertions, they may need updating. In practice all TPC-H invariant checks are multiset-equality assertions against the live query, so plan changes are fine.

Implementation Status (PR #157): ✅ Partially fixed (commit 47f9271). work_mem raised 64 MB → 256 MB; SHM raised 256 MB → 512 MB. temp_file_limit was intentionally left at 4 GB (not raised to 16 GB as originally planned): raising it to 16 GB caused q05 to write 16 GB before aborting, slowing each affected cycle by ~4×. At SF=0.01 the fast-fail at 4 GB is preferable for known-DVM-limited queries (q05 and other 5+ table joins). Additionally, pg_trickle.scheduler_interval_ms is now set to 60 000 ms in new_bench() and lock_timeout = '60s' is set in try_refresh_st() as defence-in-depth against scheduler lock contention (separate root cause — see scheduler 'calculated' schedule fix below).

Fix 3 — Repair SUM(CASE WHEN …) column resolution in join delta (MEDIUM PRIORITY)

Goal: Ensure SUM(CASE WHEN col = … THEN 1 ELSE 0 END) inside an aggregate delta correctly resolves column references from the join delta CTE so that ins_sum ≠ 0 for rows where the CASE condition holds.

Investigation steps (do first):

  1. Add a pgrx::warning!() or pgrx::log!() in agg_delta_exprs that prints the resolved col string for each AggFunc::Sum with a Expr::Raw argument. Run test_tpch_differential_correctness in isolation on q12 to capture the generated delta SQL and compare against the join delta CTE column list.

  2. Examine replace_column_refs_in_raw for q12:

    • child_cols will contain (approximately): ["orders__o_orderkey", "orders__o_orderstatus", "orders__o_orderpriority", …, "lineitem__l_shipmode", …]
    • The raw CASE expression from the parser will be something like: CASE WHEN o_orderpriority = '1-URGENT' OR o_orderpriority = '2-HIGH' THEN 1 ELSE 0 END or possibly the qualified form: CASE WHEN "orders"."o_orderpriority" = '1-URGENT' OR "orders"."o_orderpriority" = '2-HIGH' THEN 1 ELSE 0 END
    • In the first form, replace_column_refs_in_raw maps o_orderpriority → "orders__o_orderpriority" (unambiguous suffix match). If this mapping fires correctly, the CASE should work.
    • In the second form, replace_qualified_column_refs must handle the "table"."column" pattern and substitute the disambiguated name. Verify that this path handles double-quoted identifiers inside CASE expressions when they are wrapped in the aggregate delta instrumentation.

  3. Capture the full generated delta SQL for q12 by adding a temporary pgrx::warning!("delta SQL: {}", delta_sql) and running the test against a Docker container. Confirm whether orders__o_orderpriority appears in the emitted SQL.

Fix options:

Option A (conservative) — disable algebraic path for Raw arguments:

// src/dvm/operators/aggregate.rs
fn is_algebraically_invertible(agg: &AggExpr) -> bool {
    if agg.is_distinct { return false; }
    // Do not use the algebraic path when the argument is an opaque Raw
    // expression. Column references inside Raw SQL are resolved by text
    // substitution which may silently produce wrong results if the
    // substitution pattern mismatches the join delta CTE's output columns.
    if matches!(&agg.argument, Some(Expr::Raw(_))) { return false; }
    matches!(agg.function, AggFunc::CountStar | AggFunc::Count | AggFunc::Sum)
}

This forces the group-rescan path for SUM(CASE WHEN …), which is correct at the cost of a full group re-evaluation on every delta batch. For queries like q12 (simple aggregation over a 2-table join), the rescan cost is small.

Option B (preferred) — fix replace_column_refs_in_raw for Raw CASE in join context:

Confirm whether replace_qualified_column_refs correctly handles: CASE WHEN "orders"."o_orderpriority" = '1-URGENT' THEN 1 ELSE 0 END mapping "orders"."o_orderpriority" → "orders__o_orderpriority". If this does not fire, add handling in replace_qualified_column_refs for the double-quote qualified form to produce the disambiguated CTE column name. Add a unit test directly in filter.rs:

#[test]
fn test_replace_qualified_refs_case_expression() {
    let sql = r#"CASE WHEN "orders"."o_orderpriority" = '1-URGENT' THEN 1 ELSE 0 END"#;
    let child_cols = vec!["orders__o_orderpriority".to_string()];
    let result = replace_column_refs_in_raw(sql, &child_cols);
    assert!(
        result.contains("orders__o_orderpriority"),
        "CASE expression column not resolved: {result}"
    );
}

If the unit test reveals the substitution correctly fires, the bug lies elsewhere (possibly in the double-wrapping of the CASE inside the delta-action guard: ... THEN (CASE WHEN … END) ELSE 0 END). In that case, debug the generated SQL string directly.

Recommendation: Implement Option A first as a safe regression guard, then pursue Option B to restore the algebraic optimisation. Both can land in the same PR.

Acceptance criteria: - test_tpch_differential_correctness passes q12 for all configured cycles with 0 invariant violations. - No existing TPC-H query that previously used the algebraic path regresses (verify by checking that queries q01, q13 — which use SUM(col) and COUNT(*) with plain column arguments — still pass and do not switch to the group-rescan path). - New unit test test_replace_qualified_refs_case_expression passes.

Risk: LOW (Option A) — the group-rescan path is the well-tested fallback. MEDIUM (Option B) — textual SQL manipulation is fragile; changes must be covered by unit tests.

Implementation Status (PR #157): ⏳ Deferred. Root-cause investigation for SUM(CASE WHEN …) has not been performed. Option A (disable algebraic path for Raw arguments) and Option B (fix replace_qualified_column_refs for double-quoted identifiers) are both tracked separately. This item should be addressed in a follow-up PR once the scheduler and advisory lock fixes from this PR are merged.

Sequencing

Fix 1 (api.rs advisory lock)    — independent, do first
Fix 2 (bench memory limits)     — independent, do in parallel with Fix 1
Fix 3 (q12 CASE column resolve) — investigate first, then fix

Suggested branch order: 1. fix-advisory-lock-xact — Fix 1 only; one-line change + test 2. fix-bench-memory-limits — Fix 2 only; two-line change in mod.rs 3. fix-sum-case-algebraic — Fix 3; investigation + unit test + code change

Each branch can be PR’d independently.

Implementation note (PR #157): All three fixes (and the additional scheduler root cause below) were implemented together in branch e2e-test-failure-part-6 rather than in separate branches.

Additional Root Cause (discovered during PR #157)

RC-4 — Scheduler 'calculated' schedule causes test lock contention

Files: tests/e2e_tpch_tests.rs, tests/e2e/mod.rs

The 'calculated' schedule string stores NULL in the catalog and maps to ScheduleMode::Calculated in the background worker. In this mode the scheduler calls check_upstream_changes() and auto-refreshes all 22 stream tables whenever any CDC changes are pending — in a single background transaction that can run for 5+ minutes. During test_tpch_cross_query_consistency and test_tpch_sustained_churn, the RF mutation phase fills the CDC change buffers for all 22 tables. The scheduler fires, acquires refresh locks on all 22 STs, and blocks the test’s explicit try_refresh_st() calls, causing the test to appear hung.

Fix (PR #157): - Changed 'calculated' → '24h' for the two long-running tests. A 24-hour time-based schedule never fires within the test window. - Added pg_trickle.scheduler_interval_ms = 60000 (1 minute) to new_bench() as defence-in-depth. - Added lock_timeout = '60s' in try_refresh_st() so a lock-blocked refresh surfaces a clear timeout error rather than hanging indefinitely.

Result: test_tpch_cross_query_consistency now completes in ~152 s (was 5+ minutes / effectively hung).

Validation

After all three fixes land, run the full TPC-H suite:

just build-e2e-image
cargo test --test e2e_tpch_tests -- --ignored --test-threads=1 --nocapture 2>&1 | tee /tmp/tpch_validation.log

Expected outcome: - 0 queries skipped due to advisory lock cascade - 0 temp_file_limit exceeded errors - q12 invariant check passes every cycle - All 6 test functions pass (≥ 22/22 queries per function where applicable)

References

  • src/api.rs — advisory lock acquisition/release pattern (~line 1905–1930)
  • src/dvm/operators/aggregate.rs — is_algebraically_invertible, agg_delta_exprs
  • src/dvm/operators/filter.rs — replace_column_refs_in_raw, replace_qualified_column_refs
  • src/dvm/operators/join_common.rs — use_pre_change_snapshot, join_scan_count
  • tests/e2e/mod.rs — new_with_db_bench() container configuration
  • plans/testing/PLAN_TEST_SUITE_TPC_H.md — original fix log with root causes
  • plans/testing/TEST_SUITE_TPC_H-PART_2.md — second-wave improvements (T1–T6)
  • PostgreSQL docs — pg_advisory_xact_lock