[iamvirul]

Problem

Cross-engine data diffs (e.g. PostgreSQL → Oracle) silently reported "No data differences found", even when the target was missing rows or had drifted values.

Root cause: engines fold unquoted identifier case differently — PostgreSQL stores customers, Oracle stores CUSTOMERS. Table matching and the row hash keyed on the raw identifier, so:

• no tables matched (customers ≠ CUSTOMERS)
• zero rows were hashed/compared
• real missing and changed rows went undetected

For a migration-verification tool, that's a dangerous false negative.

Fix

Compare on a canonical (case-folded) identifier, while preserving the real identifier for SQL generation — quoted identifiers are case-sensitive in most engines (notably Oracle), so lower-casing a real Oracle table name would break the query.

• schema.CanonicalIdent — case/whitespace-normalized identifier for matching
• content.orderedColumns — order columns by canonical name so both engines produce a comparable sequence
• content.hashRow — emit canonical column names so identical row data hashes equal regardless of case
• content.BuildDataDiff — match tables by canonical name; look up hashes by each side's real name; label output with the prod-side name
• runDiff — build the shared-table set by canonical name so both sides get hashed

Scope / non-goals

• Schema drift is still reported honestly. Legitimate cross-engine type differences (integer vs number, varchar vs varchar2) remain visible — they are real differences, not masked.
• gen-pack / apply SQL generation is unchanged. Generating a cross-engine migration pack to backfill the target is a separate, larger change (type mapping, quoting) and is intentionally out of scope here.

Verification

End-to-end against live PostgreSQL 16 + Oracle XE 21 containers (Postgres = source of truth with 6 rows, Oracle = migrated target with 4 rows, one row's value changed):

Before → No data differences found (count=0 tables matched)
After →

{ "table": "customers", "removed_keys": ["5","6"], "updated_keys": ["4"] }

i.e. ids 5 & 6 missing in Oracle, id 4 drifted — correct.

Tests

• schema.TestCanonicalIdent (+ cross-engine match invariant)
• content.TestHashTable_CrossEngineCaseInsensitive — identical data hashes equal across identifier case
• content.TestBuildDataDiff_CaseInsensitiveTableMatch — customers ↔ CUSTOMERS matches; missing/changed rows detected

All existing content/schema tests continue to pass.

Summary by CodeRabbit

• Bug Fixes
  • Table and column names that differ only by capitalization or surrounding whitespace are now matched consistently across database engines.
  • Data comparisons produce consistent hashes despite differences in identifier casing, with stable diff ordering and production-side table labels.

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📥 Commits

Reviewing files that changed from the base of the PR and between 9c8b349 and 4100c6a.

📒 Files selected for processing (7)

• cmd/deepdiffdb/main.go
• internal/content/diff.go
• internal/content/hash.go
• internal/schema/identifiers.go
• internal/schema/identifiers_test.go
• tests/content/diff_test.go
• tests/content/hash_test.go

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[codecov]

Codecov Report

❌ Patch coverage is 94.73684% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
internal/content/diff.go	92.30%	0 Missing and 1 partial ⚠️

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