[OffgridwithJD]

Part of #1341: the medium docs-claims item "expire treats a half declaration as no retention". set_options accepts a ttl_column without a ttl_interval, or the reverse. PgColumnarReadTtl reads either alone as "no retention", so expire refuses with 55000 and drops nothing. No arm exercised either half.

Arms (both twins; a new pytest function, test_a_half_declaration_is_no_retention)

Two tables, every row ten days old, so a reader that filled in the missing half would retire them all:

• Premises: set_options stores a column-only declaration (ts|-) and an interval-only one (-|1 day).
• Column only: expire refuses with 55000, and all 3000 rows are still there.
• Interval only: the same.

The mutation

The first idea, removing !ivnull from the reader's test, dereferences a NULL interval and crashes. Instead, the mutant is the plausible defaulting bug: a missing interval is read as zero. PG17, main 8c61dff against this branch:

	main	this branch
ttl_expire.sh / pytest	70/70, 10 passed	"a retention column without an interval is no retention…: got [|0] want [55000|3000]": expire accepted the half declaration and retired every row

The interval-only arm arrives never-red. Filling in a missing column would need a column name the table has, and I found no plausible mutation that does that without also breaking the column-only case first.

Evidence

• Clean: ttl_expire 74/74 and test_ttl_expire.py 11 passed on each of PG 15–19. test: create_rollup's last refusals and rebase_rollup's, in both twins (#1341) #1359 moved main since, but changed no ttl or product file.
• Ledger: four rows, one dated: 2353 → 2357 rows, the census 1798 → 1801.
• Gate: rc=0.
• Counts: TESTS.md row; cluster_tests 533 → 534, which collides with test: expire refuses a non-owner, a non-time retention column and a dropped one, with rows it could drop (#1341) #1358's 534, so whichever lands second takes 535. Database-free set 429 passed.

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[jdatcmd]

The arm is good, but both new premise: checks go red under a change to this repository's own SQL, which #1236 rules out. Reviewed on PG18 at 9cd08b5.

The arm works. Green: shell 74/74, pytest 11 passed. With PgColumnarReadTtl reading a missing interval as zero (src/columnar_metadata.c:4050), both twins fail:
FAIL a retention column without an interval is no retention: refused (55000), every row kept: got [|0] want [55000|3000]

What to change:

1. The two premises. I added IF (ttl_column IS NULL) <> (ttl_interval IS NULL) THEN RAISE EXCEPTION … to set_options in pgcolumnar--1.0-alpha5.sql. Both premises go red:
   FAIL premise: set_options takes a retention column without an interval: got [P0001|-|-] want [|ts|-]
FAIL premise: and an interval without a column: got [P0001|-|-] want [|-|1 day]
   The checks themselves matter: under that change both expire arms stayed green, because expire refused for an unrelated reason. So keep them, drop the premise: prefix, and date them with that mutation.
2. The interval-only arm has no recorded red. You note it arrives as never. Removing the !colnull test is the obvious mutation; I didn't run it.
3. Rebase: it conflicts with main 9b3c181. Main is at 1821 never, ceiling 245, cluster_tests 538.

[OffgridwithJD]

Restated on dc6b060: now 8060a52. It's next in the queue now that #1369 has merged.

• Rebase: main's test_expire_refuses_what_it_cannot_honour (test: expire refuses a non-owner, a non-time retention column and a dropped one, with rows it could drop (#1341) #1358) had landed at the same spot in both twins and in TESTS.md, so both sections are kept, main's first. cluster_tests 542 → 543.
• Ledger: both new rows kept, in sort order. Rows 2505 + 4 = 2509; never 1928; dated 581; ceiling 242. The gate is clean against origin/main.
• The merged suite re-run, since main's arms and mine had never run together: ttl_expire 81/81 and test_ttl_expire.py 12 passed, on each of PG15–19. The half-declaration mutant (a missing interval read as zero) still reddens its arm by name in both twins: got [|0] want [55000|3000]. The guard set is 433/433.

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[jdatcmd]

@OffgridwithJD, the rebase looks right, but points 1 and 2 of my changes-requested review at 9cd08b5 are still open at 8060a52:

1. "premise: set_options takes a retention column without an interval" and "premise: and an interval without a column" still carry the prefix. Adding IF (ttl_column IS NULL) <> (ttl_interval IS NULL) THEN RAISE EXCEPTION … to set_options in pgcolumnar--1.0-alpha5.sql turns both red (got [P0001|-|-]). By test: 87 arms have survived every mutation aimed at their neighbours: vacuous, or named for something they do not measure #1236 they are checks. Drop the prefix in both twins and date them with that mutation.
2. The interval-only arm still arrives never. Removing the !colnull test is the obvious mutation to date it.

I'll approve once both are in.

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[OffgridwithJD]

@jdatcmd, sorry, I missed your 14:37 review entirely and rebased straight past it. Both points are in, now at 58fc64c:

1. The two set_options checks lose the prefix, in both twins, renamed in the ledger with their history. With your mutation (set_options refusing a half declaration), both are red in both twins: got [P0001|-|-] want [|ts|-] and … [|-|1 day]. They're dated by it. A comment by them says why they're checks: under that change the expire arms stay green.
2. The interval-only arm is dated by removing !colnull. That crashes the backend, as removing !ivnull did (test: half a retention declaration is no retention, in both twins (#1341) #1370's note), and the crash took the six checks after it down too, three premises among them. So that arm now runs last in the suite: under the mutant it's 80 passed + 1 failed, with only that arm red. In the pytest twin it already sat in its own test, so only that test fails (the extra error is its teardown on the dead connection).

Evidence: ttl_expire 81/81 and pytest 12 passed on each of PG15–19. Ledger: rows 2509; never 1928 → 1925; dated 584; ceiling 242. The gate is clean, and the guard set is 433/433.

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[jdatcmd]

Reproduced at 58fc64c on PG18:

run	result
this PR	ttl_expire 81/81
set_options refusing a half declaration	79 + 2: `set_options takes a retention column without an interval: got [P0001
!colnull removed	80 + 1, only and an interval without a column is no retention either. The backend crashed and the cluster went into recovery, so running that arm last does what you said.

Both points are in, and the comment explaining why the two are checks is a good addition. Approving.

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[OffgridwithJD]

Restated on main after #1374, so it's mergeable again: now 941082a. cluster_tests 549 → 550; the budget is rebased on 2549 / 1962. The gate is clean, and the guard set is 433/433. The test files are byte-identical to 58fc64c, which you approved, and main hasn't touched the ttl suite since.

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[jdatcmd]

Verified 941082a against my approval of 58fc64c. It sits on current main (6f2031c), the patch is identical outside the count files, and no main row changes (2553 / 1962, ceiling 241). I'll merge once CI is green.

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