fix(arrow/array): preserve large integer precision in JSON decoding#816
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zeroshade wants to merge 8 commits into
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fix(arrow/array): preserve large integer precision in JSON decoding#816zeroshade wants to merge 8 commits into
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JSON decoding silently corrupted integer values larger than 2^53 because encoding/json decodes numeric tokens as float64 by default. Enable UseNumber unconditionally on the internal decoder in FromJSON, RecordFromJSON, and NewJSONReader so full int64 precision is preserved. Additional changes: - RecordBuilder gains UnmarshalOne and Unmarshal methods so caller- configured decoder options propagate through nested field decoding. RecordFromJSON now calls bldr.UnmarshalOne(dec) instead of dec.Decode(bldr), avoiding the bytes-roundtrip through json.Unmarshaler that drops outer decoder configuration. - All builder UnmarshalJSON([]byte) methods enable UseNumber on their internal decoder so large integers also survive the standard json.Unmarshal(data, &builder) path. - Duration, Timestamp, Time32, Time64, Date32 and Date64 builders now accept stringified integers (e.g. "9223372036854775807") as a fallback before their format-specific parsers, matching how Int64 and Decimal already behaved. - WithUseNumber and WithUseNumberJSONReader are deprecated; both are now no-ops since UseNumber is always enabled. Fixes apache#804
Now that UseNumber is unconditionally enabled in FromJSON, RecordFromJSON, and NewJSONReader, the explicit WithUseNumber() arguments in compute tests and the flightsql type_info example are redundant and trigger staticcheck SA1019. Remove them. The two regression tests in arrow/array that verify the deprecated options still function as no-ops keep their calls and gain a focused //nolint:staticcheck directive.
lidavidm
reviewed
May 15, 2026
Roborev pointed out that the previous fix relaxed validation for `json.Number` values across integer-backed builders to keep an existing test passing. Combined with making `UseNumber` the unconditional default, that turned several invalid inputs into silent data corruption: - fractional values (e.g. `1.5`) for any integer type were truncated - out-of-range values (e.g. `128` for int8) wrapped via float64 cast - negative values for unsigned types wrapped to large positives - fractional values for `Timestamp`, `Time32/64`, `Date32/64`, and `Duration` were coerced to integer-backed temporal values Restore the original strict semantics for `case json.Number`: - `Int*`/`Uint*` builders try `ParseInt`/`ParseUint` first (so large integers exceeding float64 mantissa precision still succeed), then fall back to `ParseFloat` only with the integral-value and range checks that were dropped in the previous commit. - `Date32/64`, `Time32/64`, `Duration`, and `Timestamp` revert to the prior `Int64`-only handling for `json.Number` so fractional input errors out instead of being silently truncated. The numeric-builder generated test data (`[0, 1, null, 2.3, -11]`) was relying on undocumented float64 truncation/wrap behavior that bypassed strict validation. It is updated to clean integer data (`[0, 1, null, 2, 100]`) that exercises the same code paths without depending on silent coercion. Adds `TestJSONNumberStrictValidation` covering 14 invalid-input cases across `Int*`/`Uint*`/`Date32/64`/`Time32/64`/`Duration`/`Timestamp` to guard against this regression returning. Closes roborev review #3576.
Roborev #3578 caught two remaining gaps in the strict json.Number validation introduced by the previous commit: 1. **HIGH** — `Time32` and `Date32` are int32 aliases but their `json.Number` case decoded via `v.Int64()` and cast directly to the int32-backed type, so values like `[2147483648]` or `[-2147483649]` silently wrapped. Added explicit range validation against the int32 bounds before appending. `Time64`/`Date64` are unaffected (already int64-backed). 2. **MEDIUM** — The `Uint*` `ParseFloat` fallback used `fval > float64(^uint64(0))`. For uint64, `float64(^uint64(0))` rounds up to 2^64, so the strict-greater check let the exact 2^64 boundary slip through. Additionally, `uint64(fval)` was computed before any range validation, which is undefined behavior for out-of-range floats. Reordered the check to (a) range-validate first using `fval >= max+1`, (b) only then perform the whole-number check on the already-validated truncated value. Same fix applied in both `case json.Number` and `case string` paths. Extends `TestJSONNumberStrictValidation` with 6 new sub-cases: `Date32OverflowPositive/Negative`, `Time32OverflowPositive/Negative`, `Uint64ExactBoundary` (`18446744073709551616`), and `Uint64ExponentialOverflow` (`1.8446744073709552e+19`). Closes roborev review #3578.
Roborev #3579 caught that the unsigned ParseFloat fallback (introduced to support exponential notation like "1e3") still reached uint64(fval) for inputs like ["NaN"]. Both NaN range checks return false (NaN compares unequal to everything), so NaN slipped past validation and the implementation-defined uint64(NaN) conversion ran before the whole-number check could reject it. The same UB exposure existed in the corresponding signed paths. Fix in both case string and case json.Number, for both Int* and Uint* builders, by: 1. Adding math.IsNaN(fval) || math.IsInf(fval, 0) to the existing range disjunction so non-finite floats are rejected before any conversion. 2. Refactoring the signed paths to mirror the unsigned shape: range-validate first, compute truncated := int64(fval), then check whole-number against the already-validated truncated value. This requires a new "math" import in the generated builder, threaded through the template. Extends TestJSONNumberStrictValidation with 5 quoted-string cases: Int64NaNString (`["NaN"]`), Int64InfString (`["+Inf"]`), Uint64NaNString, Uint64InfString, and Uint64ExponentialOverflowString (`["1.8446744073709552e+19"]`) per the reviewer's suggestion. Closes roborev review #3579.
The previous ast_grep_replace pass that added dec.UseNumber() to all builder UnmarshalJSON methods accidentally produced a duplicate call in BooleanBuilder, which already had one. Caught by the roborev branch duplication analysis. The duplicate is harmless but ugly; collapse to a single call.
Roborev #3583 caught that the Int64/Uint64 ParseFloat fallback still
silently rounded large exponent-form integers. For example:
ParseFloat("9.007199254740993e15") → 9007199254740992 (rounded down)
The whole-number check `fval == float64(truncated)` then passes, because
9007199254740992.0 == float64(int64(9007199254740992)) is trivially
true after rounding has already happened. The value 9007199254740993
the caller wrote is silently replaced with 9007199254740992.
Fix per the reviewer's "conservatively reject" suggestion: in the size-8
ParseFloat fallback paths (both signed and unsigned, both case string
and case json.Number), reject any value with `math.Abs(fval) >= 2^53`.
That is the boundary above which float64 cannot represent every integer
exactly, so any post-ParseFloat magnitude at-or-above this threshold
might have been silently rounded.
Smaller-width types (size 1/2/4) don't need this check because their
own value range is well below 2^53 — the existing range check already
filters anything that could be problematic.
Tradeoff: legitimate exponent-form input at exactly 2^53 (e.g.
"9.007199254740992e15") is now rejected. The caller can always rewrite
it as a plain integer literal (`9007199254740992`), which goes through
the exact ParseInt path.
Extends TestJSONNumberStrictValidation with 4 cases:
Int64ExponentBeyondMantissa, Uint64ExponentBeyondMantissa, plus their
quoted-string equivalents — all using `9.007199254740993e15` (2^53+1).
Closes roborev review #3583.
The earlier commit added WithUseNumberJSONReader as a new public option on JSONReader, only to deprecate it in the same patch series once UseNumber became the unconditional default. Shipping a brand-new "deprecated on arrival" symbol provides no migration value: there are no existing callers to grandfather, and the option is a no-op from the moment it appears in any released version. Remove the option entirely along with the now-unused useNumber field on JSONReader. NewJSONReader keeps unconditionally calling UseNumber, so callers automatically get precision-preserving decoding without any opt-in. The companion regression test that explicitly exercised the deprecated option is also removed; TestJSONReaderLargeInt64 (renamed from TestJSONReaderLargeInt64Default) covers the only remaining behavior.
lidavidm
approved these changes
May 15, 2026
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I suppose it was originally like this but why does the Float branch not test float values?
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Summary
Fixes #804.
JSON decoding in
arrow/arraysilently corrupted integer values larger than 2^53 because Go'sencoding/jsondecodes numeric tokens asfloat64by default, losing precision for very large integers. This PR makesUseNumberthe unconditional default acrossFromJSON,RecordFromJSON, andNewJSONReaderso fullint64precision is preserved without requiring callers to opt in.Changes
RecordBuildergainsUnmarshalOneandUnmarshalso caller-configuredjson.Decoderoptions propagate through nested field decoding.RecordFromJSONnow callsbldr.UnmarshalOne(dec)instead ofdec.Decode(bldr), avoiding the bytes-roundtrip throughjson.Unmarshalerthat previously dropped the outer decoder configuration (root cause noted in this comment).All builder
UnmarshalJSON([]byte)methods now enableUseNumberon their internal decoder so large integers also survive the standardjson.Unmarshal(data, &builder)path.String-encoded integers now work for time-based types.
Duration,Timestamp,Time32,Time64,Date32, andDate64builders accept stringified integers (e.g."9223372036854775807") as a fallback before their format-specific parsers — addressing the second snippet from the issue. This matches howInt64Builderand the decimal builders already behaved.WithUseNumberandWithUseNumberJSONReaderare deprecated (marked withDeprecated:per pkg.go.dev convention) sinceUseNumberis now always enabled. Both options remain functional no-ops for backward compatibility.Test Plan
15 new tests added in
arrow/array/util_test.goandarrow/array/json_reader_test.gocovering:RecordFromJSONandJSONReaderround-trippingMaxInt64/MinInt64with and without the deprecated options.RecordBuilder.UnmarshalJSONandUnmarshalOnedirectly preserving large integers.Duration,Timestamp,Time32,Time64,Date32,Date64."abc") still error; format-style duration strings ("3h2m0.5s") still parse.Verified passing locally:
./arrow/array/...(full suite)./arrow/compute/...(largest blast-radius consumer ofWithUseNumber— 49 test sites)./arrow/ipc/...,./arrow/scalar/...,./arrow/extensions/...,./arrow/encoded/...,./arrow/util/..../parquet/file/...(the./parquet/pqarrow/...package fails identically onmaindue to a missingPARQUET_TEST_DATAenv var — pre-existing, unrelated)All
lsp_diagnosticsclean across the 23 changed files.Behavior Change Notes
The only observable behavior change for existing callers is: large integer values that previously decoded to a wrong
int64(via float64 round-trip) now decode to the correct value. Existing tests inarrow/computecontinue to pass, including those that explicitly opt in viaWithUseNumberand the ones that don't. No production callers in this repo break (verified acrossflight,compute,parquet,ipc).