feat(core): release disk space faster on table drop

[ideoma]

This change closes WAL writers faster that helps deleting them from disk.

Before the change when table is dropped, there are a lot of logging like this:

2025-12-17T15:05:03.179283Z I i.q.c.w.WalPurgeJob table is dropped, but has WALs containing segments with pending tasks [table=dbRoot/price_1h~12]

Now when idle WAL writers are closed at the time of the drop, the WAL and table files are deleted faster.

[coderabbitai]

Important

Review skipped

Auto reviews are disabled on this repository.

Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Walkthrough

When a table is dropped, CairoEngine now notifies the reader pool and WAL writer pool through new notifyDropped() calls. Pools clean up allocated resources for the dropped table via a new notification method that iterates through allocations, performs compare-and-swap operations, closes tenants, and marks slots as unallocated. A new close reason constant CR_DROPPED is added to track these cleanup operations.

Changes

Cohort / File(s)	Summary
Pool notification dispatch core/src/main/java/io/questdb/cairo/CairoEngine.java	Invokes readerPool.notifyDropped(tableToken) and walWriterPool.notifyDropped(tableToken) during table drop before existing post-drop processing
Pool resource cleanup core/src/main/java/io/questdb/cairo/pool/AbstractMultiTenantPool.java	Adds public notifyDropped(TableToken token) method that iterates pool entries, performs CAS operations to move allocations from allocated to thread state, closes tenants with EV_EXPIRE event and idle close reason, and marks slots as UNALLOCATED
Pool constants and close reason handling core/src/main/java/io/questdb/cairo/pool/PoolConstants.java	Adds CR_DROPPED = 6 constant; refactors closeReasonText(int) from traditional switch to switch expression with case for CR_DROPPED returning "DROPPED" and default handling for "UNKNOWN"

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

• AbstractMultiTenantPool.notifyDropped: Pay close attention to CAS operations and thread-safety semantics when moving allocations between states during concurrent table drops
• CairoEngine integration: Verify the order and timing of pool notifications relative to existing MatViewRefreshTask and state-update logic
• CR_DROPPED constant usage: Confirm the new close reason is properly utilized in the pool cleanup path

Possibly related PRs

• fix(sql): fix internal error when concurrent threads try to drop a non-wal table #6462: Reorders dropTableOrMatView cleanup to fix concurrent-drop race condition; modifies the same CairoEngine table-drop flow

Suggested labels

storage

Suggested reviewers

• bluestreak01

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately summarizes the main change: faster disk space release when tables are dropped by closing WAL writers faster.
Description check	✅ Passed	The description is directly related to the changeset, explaining the motivation and benefit of closing WAL writers faster during table drops.

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[ideoma]

@coderabbitai review

[coderabbitai]

✅ Actions performed

Review triggered.

Note: CodeRabbit is an incremental review system and does not re-review already reviewed commits. This command is applicable only when automatic reviews are paused.

[coderabbitai]

Actionable comments posted: 2

📜 Review details

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between a800ac5 and 7cd6f0b.

📒 Files selected for processing (3)

• core/src/main/java/io/questdb/cairo/CairoEngine.java (1 hunks)
• core/src/main/java/io/questdb/cairo/pool/AbstractMultiTenantPool.java (1 hunks)
• core/src/main/java/io/questdb/cairo/pool/PoolConstants.java (1 hunks)

🧰 Additional context used

🧬 Code graph analysis (1)

core/src/main/java/io/questdb/cairo/pool/AbstractMultiTenantPool.java (2)

core/src/main/java/io/questdb/std/Unsafe.java (1)

• Unsafe (40-542)

core/src/main/java/io/questdb/cairo/pool/PoolConstants.java (1)

• PoolConstants (27-46)

⏰ Context from checks skipped due to timeout of 90000ms. You can increase the timeout in your CodeRabbit configuration to a maximum of 15 minutes (900000ms). (36)

• GitHub Check: New pull request (SelfHosted Running tests with cover on linux-other)
• GitHub Check: New pull request (SelfHosted Running tests with cover on linux-pgwire)
• GitHub Check: New pull request (SelfHosted Running tests with cover on linux-cairo-sub)
• GitHub Check: New pull request (SelfHosted Running tests with cover on linux-cairo-root)
• GitHub Check: New pull request (SelfHosted Running tests with cover on linux-fuzz2)
• GitHub Check: New pull request (SelfHosted Running tests with cover on linux-fuzz1)
• GitHub Check: New pull request (SelfHosted Running tests with cover on linux-griffin-sub)
• GitHub Check: New pull request (SelfHosted Running tests with cover on linux-griffin-root)
• GitHub Check: New pull request (Hosted Running tests on windows-other-2)
• GitHub Check: New pull request (Hosted Running tests on windows-other-1)
• GitHub Check: New pull request (Hosted Running tests on windows-pgwire)
• GitHub Check: New pull request (Hosted Running tests on windows-cairo-2)
• GitHub Check: New pull request (Hosted Running tests on windows-cairo-1)
• GitHub Check: New pull request (Hosted Running tests on windows-fuzz2)
• GitHub Check: New pull request (Hosted Running tests on windows-fuzz1)
• GitHub Check: New pull request (Hosted Running tests on windows-griffin-sub)
• GitHub Check: New pull request (Hosted Running tests on windows-griffin-base)
• GitHub Check: New pull request (Hosted Running tests on mac-other)
• GitHub Check: New pull request (Hosted Running tests on mac-pgwire)
• GitHub Check: New pull request (Hosted Running tests on mac-cairo-fuzz)
• GitHub Check: New pull request (Hosted Running tests on mac-cairo)
• GitHub Check: New pull request (Trigger Enterprise CI Trigger Enterprise Pipeline)
• GitHub Check: New pull request (SelfHosted Other tests on linux-x64-zfs)
• GitHub Check: New pull request (SelfHosted Other tests on linux-x86-graal)
• GitHub Check: New pull request (Rust Test and Lint on linux-jdk17)
• GitHub Check: New pull request (Hosted Running tests on mac-griffin)
• GitHub Check: New pull request (SelfHosted Griffin tests on linux-x64-zfs)
• GitHub Check: New pull request (SelfHosted Other tests on linux-arm64)
• GitHub Check: New pull request (SelfHosted Griffin tests on linux-x86-graal)
• GitHub Check: New pull request (SelfHosted Cairo tests on linux-x86-graal)
• GitHub Check: New pull request (SelfHosted Griffin tests on linux-arm64)
• GitHub Check: New pull request (SelfHosted Cairo tests on linux-arm64)
• GitHub Check: New pull request (SelfHosted Cairo tests on linux-x64-zfs)
• GitHub Check: New pull request (Check Changes Check changes)
• GitHub Check: build
• GitHub Check: build

🔇 Additional comments (3)

core/src/main/java/io/questdb/cairo/CairoEngine.java (1)

1197-1198: LGTM! Pool notifications correctly trigger cleanup on table drop.

The calls to notifyDropped() on both pools appropriately notify them to release idle resources when a table is dropped, which aligns with the PR objective of freeing disk space faster.

core/src/main/java/io/questdb/cairo/pool/PoolConstants.java (2)

29-29: New constant CR_DROPPED added for table drop operations.

The addition of CR_DROPPED provides a distinct close reason for dropped tables, improving observability and logging clarity. Ensure this constant is used consistently where tables are dropped (see review comment in AbstractMultiTenantPool.java).

---

36-44: LGTM! Switch expression refactoring is clean and complete.

The refactoring to a switch expression is idiomatic Java and correctly maps all close reason constants, including the new CR_DROPPED, to their text representations.

[bluestreak01]

can we have a test also?

[glasstiger]

[PR Coverage check]

😍 pass : 100 / 113 (88.50%)

file detail

	path	covered line	new line	coverage
🔵	io/questdb/cairo/wal/WalWriter.java	0	1	00.00%
🔵	io/questdb/cairo/pool/PoolConstants.java	6	8	75.00%
🔵	io/questdb/cairo/pool/AbstractMultiTenantPool.java	53	62	85.48%
🔵	io/questdb/cairo/CairoEngine.java	12	13	92.31%
🔵	io/questdb/griffin/engine/table/ReaderPoolRecordCursorFactory.java	3	3	100.00%
🔵	io/questdb/cairo/pool/TableReaderMetadataTenantImpl.java	2	2	100.00%
🔵	io/questdb/cairo/DefaultCairoConfiguration.java	1	1	100.00%
🔵	io/questdb/PropertyKey.java	2	2	100.00%
🔵	io/questdb/cairo/TxnScoreboardPoolV2.java	1	1	100.00%
🔵	io/questdb/cairo/pool/WalWriterPool.java	3	3	100.00%
🔵	io/questdb/cairo/pool/SqlCompilerPool.java	3	3	100.00%
🔵	io/questdb/cairo/CairoConfigurationWrapper.java	1	1	100.00%
🔵	io/questdb/cairo/pool/TableMetadataPool.java	1	1	100.00%
🔵	io/questdb/PropServerConfiguration.java	2	2	100.00%
🔵	io/questdb/cairo/pool/SequencerMetadataPool.java	3	3	100.00%
🔵	io/questdb/cairo/pool/ReaderPool.java	7	7	100.00%

[questdb-butler]

⚠️ Enterprise CI Failed

The enterprise test suite failed for this PR.

Build: View Details
Tested Commit: d888de941f67949ff7e559b9360d6bbe128ff22d

Please investigate the failure before merging.