Fix UUID primary keys, and stop reporting a match it never established - #158
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table-diff failed on any table with a uuid primary key as soon as the two
nodes really disagreed on a row:
ERROR: invalid input syntax for type uuid: "[17 17 17 ...]" (SQLSTATE 22P02)
readRowHashes keyed its map on fmt of the scanned primary key, and the keys of
the mismatched rows were then reused as parameters of the row-fetch query. pgx
decodes a uuid into a bare [16]byte, which Go prints as "[17 17 ...]", so the
server was handed that text as a uuid.
Keep the decoded values next to the hash and use those for the fetch. The map
key stays what it always was -- a way to match rows across nodes -- but it can
no longer reach SQL. splitCompositeKey went with it: reconstructing pkey values
out of a rendering is the bug, not a feature worth preserving.
Two supporting changes: pkeyIdentity renders each value through an explicit
type switch instead of fmt, so row identity no longer depends on a driver's
formatting; and RowKeyFromStrings quotes each part before joining, so the
composite keys ("a|b","c") and ("a","b|c") stop colliding into one entry.
Verified by mutation: restoring the old behaviour makes the new integration
test fail with the original 22P02.
A worker that lost a range-comparison work item logged the error and dropped it. The run then finished with "TABLES MATCH" and exit code 0, so the uuid failure fixed in the previous commit was reported as a clean result -- which is how it survived long enough to reach a customer. Record the affected node pairs in the diff summary and let a single place decide the verdict. An empty NodeDiffs now means "the tables match" only when every pair was really compared; otherwise the summary is still written to disk (the failed pairs are worth keeping) and DiffMtree returns an error, so the exit code stops claiming success. For a consistency checker "I do not know" has to be distinguishable from "no differences". A zero count for a pair that was never compared is the one answer the tool must never give.
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📝 WalkthroughWalkthroughChangesThe Merkle diff now preserves typed primary-key values, uses collision-safe row identities, compares supported key types with database-compatible ordering, and tracks failed comparisons. Text and HTML reports mark incomplete results. Tests cover UUID, composite, binary, boolean, floating-point, and other primary-key types. Merkle diff accuracy
Poem
Merge Risk: 🔵 Low · up to Composite keys containing the separator can collide in the HTML report, causing row selection to target the wrong entry. The PR is otherwise mergeable with explicit owner follow-up to use an unambiguous DOM identity. 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
Full details: Docstring CoverageExplanation Docstring coverage is 54.35% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 46 functions across 8 files. (1 skipped: 1 unsupported.) ✨ Finishing Touches 💡 1📝 Generate docstrings 💡
🧪 Generate unit tests (beta)
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Up to standards ✅🟢 Issues
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| Category | Results |
|---|---|
| Complexity | 3 medium |
🟢 Metrics 0 complexity · -3 duplication
Metric Results Complexity 0 Duplication -3
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Inline comments:
In `@internal/consistency/mtree/merkle.go`:
- Around line 821-844: Update compareBoundaries to compare pkeyUUID and
pkeyBytes values using typed lexicographic byte ordering rather than fmt.Sprintf
text ordering, preserving native PostgreSQL ordering for these boundaries. Add a
multi-block regression test covering values beginning with 0x02 and 0x0a to
verify inserts or deletes do not merge or select incorrect ranges.
In `@pkg/common/utils.go`:
- Around line 1067-1083: Update StringifyKey and StringifyOrderedMapKey to
construct composite keys through RowKeyFromStrings instead of joining parts with
"|", and update MerkleTreeTask.buildRowKey to use the same encoding. Preserve
the existing part ordering while ensuring delimiters inside individual values
cannot cause key collisions.
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The uuid fix two commits back stopped table-diff from failing, but it did not make a uuid-keyed table report correctly. mtree cuts blocks with ORDER BY <pkey> in the database, then merges and sorts the bounds of the mismatched blocks in Go. For a uuid those bounds arrive as [16]byte and were ordered by their Go rendering -- the decimal spelling of each byte -- which puts 0x11 before 0x02. bytea had the same problem. Where the two orders disagree, some ranges come out reversed and select no rows, so those blocks are never compared and the diff under-reports. Measured on PostgreSQL 17 with 9 differing rows: the old ordering reported 6 of them. No error, no warning -- just three rows the operator never hears about. comparePkeyValues now orders each kind the way the server does: memcmp for uuid and bytea, and NaN above every number for float, since Postgres sorts it there while Go's cmp.Compare puts it below. The property test that comes with this covers the supported key types with one question: if N rows differ, the diff has to report exactly N. Its setup is deliberate -- the divergence spans the interior blocks only, because the open-ended last leaf otherwise covers up any ordering mistake, and with a single differing row a wrong comparator gets the answer right half the time by luck. Both were measured while writing it. Known gap, documented and reproduced: a text key in a collation other than C still sorts differently here than on the server (4 of 9 rows found). The real fix is to order the bounds in SQL. Its test case is present and skipped. Bounds of a type with no case here still fall back to the Go rendering; it now says so in the log instead of doing it quietly. Refusing such a key outright is a separate change.
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Inline comments:
In `@docs/design/merkle.md`:
- Line 426: Remove the duplicate Observability and Teardown heading in the
documentation, preserving a single occurrence of that section title.
In `@internal/consistency/mtree/merkle.go`:
- Around line 2906-2914: The uniqueBoundaries de-duplication must not use
fmt.Sprint(b), because composite boundary values can collide when rendered.
Update the boundary-key construction near uniqueBoundaries to encode each
component separately and combine those encodings with the existing
collision-safe row-key encoding, preserving distinct boundaries such as
differently partitioned composite values.
In `@pkg/common/html_reporter.go`:
- Around line 683-695: Update sortPKKeys so its sort comparator uses the
original identity keys as a deterministic tie-breaker whenever comparePKKey
returns equality for the displayed values, preserving the existing displayed-key
ordering otherwise.
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ibrarahmad
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CI is red on b7a954d. TestCDCDrainHandlesLargeSingleTransaction reports 201 delete counters against 200 (tests/integration/cdc_busy_table_test.go:196). 2b70984 was green, and commit 4 only touches buildRowKey, the HTML reporter and the two Stringify*Key functions, none of which the CDC drain calls, so this looks like the double count at a sub-batch flush boundary that the test exists to catch rather than something the PR introduced. It still needs a re-run and an explanation before merge.
| @@ -2652,6 +2842,23 @@ func (m *MerkleTreeTask) getPkeyBatches(pool1, pool2 *pgxpool.Pool, mismatchedPo | |||
| return batches, nil | |||
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Line 2784 in this function: uniqueBoundaries keys on fmt.Sprint(b), so the composite bounds []any{"a b","c"} and []any{"a","b c"} both key as [a b c] and one real cut point is dropped, which shifts the slice set and can leave rows uncompared. Same collision RowKeyFromStrings fixes, right above the comparator this PR rewrites. Worth using the same encoding here.
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Fixed, and one step further than the same encoding: per-component %v still isn't injective, since two distinct uuids both render through []byte formatting. Boundary keys now go through pkeyIdentity per component, joined by RowKeyFromStrings, in a new boundaryKey. Each component carries a tag (v value, n NULL, f fmt fallback) so a NULL can't be confused with a value that renders as "nil", and the fallback can't be confused with an identity that looks the same. TestBoundaryKeyDistinguishesBounds covers ("a b","c") vs ("a","b c"), 0x02 vs 0x0a uuids, and NULL vs empty string.
| // the server orders that type. ok is false for a kind pkeyKindOf does not | ||
| // know; the caller has to decide what to do about it. | ||
| func comparePkeyValues(val1, val2 any) (result int, ok bool) { | ||
| switch pkeyKindOf(val1) { |
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The switch picks the kind from val1, but every branch then touches val2 (val2.(string), val2.([16]byte), reflect.ValueOf(val2).Int()). If the two sides ever decode to different Go types this panics instead of returning ok=false. A if pkeyKindOf(val2) != pkeyKindOf(val1) { return 0, false } at the top covers it.
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Right, and it panics rather than mis-sorts, which is worse. Added exactly the guard you describe at the top of comparePkeyValues. TestComparePkeyValuesRejectsMixedKinds covers it; with the guard removed it panics with interface conversion: interface {} is int64, not string, so the test earns its keep.
| // to the Go rendering and say so. That order rarely matches the | ||
| // server's, which makes the ranges built from these bounds | ||
| // unreliable rather than merely odd. | ||
| logger.Warn("cannot sort merkle-tree block bounds of type %T for %s.%s the way "+ |
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This warns from inside the comparator. sort.Slice calls it O(n log n) times and intervalInUnion calls it again for every leaf, so one unsupported pkey type repeats the same line thousands of times. Log it once per task.
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Fixed: sync.Once on the task, via warnBoundarySortFallback. A sync.Once rather than the existing diffMutex because the call site is a sort comparator and I don't want a mutex in there. boundaryKey's fallback reuses the same helper, so a run can't emit two variants of the same warning.
| // pkeyKind classifies a primary-key value that pgx decoded into an untyped | ||
| // destination. It is the one list of what mtree can handle, and three things | ||
| // have to agree with it: comparePkeyValues sorts these kinds, pkeyIdentity | ||
| // renders them, and validateBoundaryTypes admits them. Nothing in the language |
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validateBoundaryTypes and TestPkeyKindsAreFullySupported are not in the tree. The comment names a guard and a test that nothing enforces.
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Correct, and the comment was worse than merely wrong — it claimed a test enforced the invariant. Wrote TestPkeyKindsAreFullySupported: it walks the pkeyKind range rather than the sample map, so a newly added constant fails the test instead of being silently skipped, and asserts each kind is classified, ordered the right way by comparePkeyValues, and rendered injectively by pkeyIdentity. Dropped validateBoundaryTypes from the comment instead of inventing it — there are two lists to keep in step, not three.
| parts[i] = fmt.Sprintf("%v", scan[i]) | ||
| id, ok := pkeyIdentity(scan[i]) | ||
| if !ok { | ||
| return nil, fmt.Errorf("primary-key value of type %T cannot be used "+ |
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This makes a numeric or time pkey a hard error, and with the incomplete-pairs change the run then exits non-zero as soon as a block mismatches. docs/design/merkle.md still lists those types as ordered by their Go rendering, i.e. still running and under-reporting. One of the two needs to change, and the new exit behaviour belongs in the behaviour-change section of the description.
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Kept the refusal and changed the docs: a checker that can't produce a result has to say so. Your comment exposed something the docs were flattening, though, so I split the table's tail into the two failure modes it actually has. Struct-decoded (numeric, time): no row identity, so the first mismatched block ends the comparison, the pair lands in incomplete_pairs, exit is non-zero — but a table with no mismatched block still reports a match off bounds ordered by Go rendering, which the doc now says out loud. String-like under a foreign collation (text outside C, enum, citext): identity works and only the order is wrong, so there is nothing to refuse — the run completes and can be missing rows, and the new warning does not fire there, because Go will happily compare two strings. Behaviour-change section of the description updated too.
| // RowKeyFromValues renders each value with fmt and joins them with | ||
| // RowKeyFromStrings. fmt is lossy for driver types -- a uuid prints as | ||
| // "[17 17 ...]" -- which is why the result must not leave the process. | ||
| func RowKeyFromValues(vals []any) string { |
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RowKeyFromValues has no callers, and it is the fmt based variant the rest of the PR argues against. Exporting it leaves the old bug within easy reach.
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Deleted. Agreed that exporting the fmt-based variant keeps the old bug within reach. It had acquired one caller in the meantime — the boundary dedup in your other comment — and that now goes through pkeyIdentity, so nothing wants the fmt variant any more.
| return m | ||
| } | ||
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||
| // StringifyOrderedMapKey is StringifyKey for an OrderedMap. It must stay |
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buildPKey (line 1438) still joins raw with "|", so these two are not the only encoding for this key. It is self contained inside rowsToMap today, but the comment reads as if the codebase has a single encoding now.
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Fixed rather than re-worded: buildPKey uses RowKeyFromStrings now. It is self-contained in rowsToMap as you say, but it carries the same collision, and CompareRowSets quietly losing a modified row is the same class of bug. The comment on StringifyOrderedMapKey now names all three encoders instead of implying there are two.
| // | ||
| // Like every RowKeyFromStrings result, this is a matching key and not a pkey | ||
| // value: it must not reach SQL, a report or repair. | ||
| func StringifyKey(row map[string]any, pkeyCols []string) (string, error) { |
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These keys are user visible: executor.go interpolates pkStr into "row missing on %s (pk %s)" and table_repair.go into the pkey not found errors. Operators will now read pk "123" instead of pk 123. An unquoted display form for those messages would keep them readable.
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Good catch, and I went a different way than a separate display form. Threading one through means ~20 sites in executor.go alone, and the key can't be reliably parsed back for display — a quoted part may hold an unescaped |. So RowKeyFromStrings now quotes a part only when it must: empty, or containing | or ". pk 123 is pk 123 again, pk 123|abc is unchanged, and only genuinely ambiguous values pick up quotes. Still injective — reading left to right each element says where it ends, because a bare element holds neither a quote nor the delimiter. TestRowKeyFromStringsQuotesOnlyWhenNeeded pins the readable cases and TestRowKeyFromStringsIsInjective brute-forces pairs over |, ", , empties and pre-quoted lookalikes. The HTML report keeps its own display key regardless: data-pk feeds a CSS attribute selector, so a quote there breaks querySelector even in the rare case.
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Inline comments:
In `@pkg/common/html_reporter.go`:
- Line 492: Update the row-key generation near strings.Join and its data-pk
usage so the DOM selector identity is unambiguous when parts contain the
separator. Keep the readable joined value for display, but encode or otherwise
uniquely serialize the key components for the dedicated JavaScript selector
attribute, preserving distinct identities for different part arrays.
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| } | ||
| parts[i] = fmt.Sprintf("%v", val) | ||
| } | ||
| return strings.Join(parts, "|") |
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🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win
Keep a unique DOM selector key.
strings.Join(parts, "|") maps ["a|b", "c"] and ["a", "b|c"] to the same value. Lines 193-198 store this value in data-pk for JavaScript selectors. The report cannot select one specific row when these keys collide.
Keep the readable display value separate from an encoded row identity. Use the identity in a dedicated DOM attribute for JavaScript selection.
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In `@pkg/common/html_reporter.go` at line 492, Update the row-key generation near
strings.Join and its data-pk usage so the DOM selector identity is unambiguous
when parts contain the separator. Keep the readable joined value for display,
but encode or otherwise uniquely serialize the key components for the dedicated
JavaScript selector attribute, preserving distinct identities for different part
arrays.
Block bound de-duplication keyed each bound on fmt.Sprint of the whole slice,
so the composite bounds ("a b","c") and ("a","b c") both keyed as "[a b c]" and
one real cut point was dropped -- which shifts the whole slice set and can leave
rows uncompared. A per-component %v is no better: it renders two distinct uuids
through the same []byte formatting. The new boundaryKey sends each component
through pkeyIdentity, tags it so a NULL cannot pass for a value that renders as
"nil", and joins with RowKeyFromStrings. RowKeyFromValues is gone with it --
keeping the fmt-based helper exported left the old bug in easy reach.
buildPKey was a fourth encoder still joining raw with "|", carrying the same
collision inside CompareRowSets, where it can lose a modified row. It shares the
encoding now.
RowKeyFromStrings quoted every part. That fixed the collision but made these
keys unreadable where they are user-visible: repair interpolates them into "row
missing on %s (pk %s)", so operators read pk "123" instead of pk 123. A part is
now quoted only when it is empty or holds the delimiter or a quote. The encoding
stays injective, because reading left to right every element says where it ends:
a bare element holds neither a quote nor the delimiter, so it cannot be mistaken
for a quoted one and ends at the next delimiter.
comparePkeyValues switched on the kind of val1 and then asserted on val2 in
every branch, so two values that decoded to different Go types panicked rather
than returning ok=false -- inside a sort comparator, which takes down the run.
It rejects mixed kinds up front now.
The "cannot sort these bounds" warning was raised from that same comparator,
which runs O(n log n) times per block set and again for every leaf in
intervalInUnion, so one unsupported key type repeated the line thousands of
times. Once per task now.
pkeyKind's comment claimed a guard and a test that were never written.
TestPkeyKindsAreFullySupported now exists and walks the kind range through a
pkeyKindEnd sentinel, so a kind added without teaching comparePkeyValues and
pkeyIdentity fails the test instead of slipping through. The mention of
validateBoundaryTypes is dropped rather than invented: there are two lists to
keep in step, not three.
Finally, the design doc still described an unsupported primary key as running
and under-reporting, which stopped being true once row identity became a hard
error. It now separates the two failure modes. A struct-decoded key (numeric,
time) stops the comparison with an error on the first mismatched block, though a
run that finds no mismatched block still reports a match off bounds ordered by
Go rendering. A string-like key under a collation Go cannot reproduce is the
worse case: identity works and only the order is wrong, so the run completes and
can be missing rows.
What was wrong
mtree table-difffailed on any table whose primary key isuuid, but only once the two nodes actually disagreed on a row.Two separate defects, both in this branch.
1. A rendered map key was used as a query parameter.
readRowHashesbuilds a map keyed onfmtof the scanned primary key so it can match rows across nodes. The keys of the mismatched rows were then reused as parameters of the row-fetch query. pgx decodes auuidinto a bare[16]byte, which Go prints as[17 17 ...], so the server was handed that text as a uuid and rejected it.2. The failure was swallowed.
The worker error was logged and dropped. The run went on to print
✔ TABLES MATCHand exit 0. That is why a hard failure on every diverged uuid-keyed table stayed invisible until a customer reported it: the tool was answering "no differences" for a comparison it had never completed.What changed
readRowHashesnow keeps the decoded values next to the hash, and the row-fetch query uses those. The map key stays what it always was — a way to match rows across nodes — but it can no longer reach SQL.splitCompositeKeyis gone with it: rebuilding primary key values out of a rendering is the defect, not a helper worth keeping.Two supporting changes:
pkeyIdentityrenders each value through an explicit type switch instead offmt, so row identity no longer depends on how a driver happens to format a value.RowKeyFromStringsquotes each part before joining, so the composite keys("a|b","c")and("a","b|c")stop collapsing into one entry — which silently dropped one of the two rows from the comparison.Node pairs that lost a range-comparison work item are recorded in the diff summary (
incomplete_pairs), and one place decides the verdict. An emptyNodeDiffsnow means "the tables match" only when every pair was reallycompared. Otherwise:
TABLES MATCHis not printed;DiffMtreereturns an error, so the exit code stops claiming success;For a consistency checker, "I do not know" has to be distinguishable from "no differences". A zero count for a pair that was never compared is the one answer the tool must never give.
Behaviour change reviewers, and QA need to know
mtree table-diffnow exits non-zero when a comparison did not finish.Previously, such a run exited with code 0 and a clean verdict. Anything that schedules this command and checks the exit code — cron, the HTTP API — will start seeing failures where it previously saw success. That is the intent, but it is visible and should be included in the release notes.
A
numericprimary key — or any type the driver decodes into a struct — now fails the run instead of under-reporting.Row identity cannot be built for such a value, so the first mismatched block ends the comparison with an error, the pair is recorded in
incomplete_pairs, and the command exits with a non-zero status. Previously, the same table produced a verdict from bounds ordered by their Go rendering. Note the limit of this: a table whose blocks all match still reports a match, because the refusal occurs where rows must be matched, not at build time.Nothing else changes for a healthy run: a clean comparison still prints
TABLES MATCHand exits 0, and a real divergence still printsTABLES DO NOT MATCHand writes the same report as before.Known limitation, unchanged by this PR
A
textprimary key under a collation other thanCstill sorts differently in Go than on the server, and the diff can under-report as a result (measured: 4 of 9 rows). It is documented and has a reproducer, skipped, in the property test that comes with patch0010. The real fix is to order the bounds in SQL.