fix(compare): match data compare columns case-insensitively

apps/desktop/src/components/diff/DataCompareDialog.vue

@@ -14,7 +14,7 @@ import { databaseOptionsForConnection, fetchNamespaceOptionsForConnection } from
 import { isSchemaAware } from "@/lib/database/databaseCapabilities";
 import { copyToClipboard } from "@/lib/common/clipboard";
 import type { DataCompareCellValue, DataCompareModifiedRow, DataCompareResult, DataCompareRow, DataCompareSyncPlan, DataCompareSyncPlanTableOptions } from "@/lib/dataGrid/dataCompare";
-import { inferCompareKeyColumns } from "@/lib/dataGrid/dataCompare";
+import { inferCompareKeyColumns, intersectCompareColumns, matchColumnNameIgnoreCase } from "@/lib/dataGrid/dataCompare";
 import type { ColumnInfo, DatabaseType } from "@/types/database";
 import * as api from "@/lib/backend/api";
 import { executeWithProductionSqlGuard } from "@/lib/database/productionExecutionGuard";
@@ -546,6 +546,8 @@ async function startCompare() {
         if (!targetTables.value.includes(task.targetTable)) {
           const sourceColumns = await loadColumnsWithCache(sourceColumnCache, sourceConnectionId.value, sourceDatabase.value, sourceSchema.value, task.sourceTable);
           const resolvedKeys = keyColumns.value.length > 0 ? keyColumns.value : [];
+          const sourceColumnNames = sourceColumns.map((column) => column.name);
+          const sourceKeyColumns = resolvedKeys.map((key) => matchColumnNameIgnoreCase(key, sourceColumnNames) ?? key);
           const preparation = await api.prepareDataCompareMissingTarget({
             sourceConnectionId: sourceConnectionId.value,
             sourceDatabase: sourceDatabase.value,
@@ -555,12 +557,12 @@ async function startCompare() {
             targetDatabase: targetDatabase.value,
             targetSchema: targetSchema.value,
             targetTable: task.targetTable,
-            keyColumns: resolvedKeys,
+            keyColumns: sourceKeyColumns,
           });
           results.push({
             sourceTable: task.sourceTable,
             targetTable: task.targetTable,
-            keyColumns: resolvedKeys,
+            keyColumns: sourceKeyColumns,
             columns: sourceColumns.map((column) => column.name),
             columnInfo: sourceColumns,
             status: "different",
@@ -591,9 +593,19 @@ async function startCompare() {
 
         const sourceColumns = await loadColumnsWithCache(sourceColumnCache, sourceConnectionId.value, sourceDatabase.value, sourceSchema.value, task.sourceTable);
         const targetColumns = await loadColumnsWithCache(targetColumnCache, targetConnectionId.value, targetDatabase.value, targetSchema.value, task.targetTable);
-        const columns = sourceColumns.map((column) => column.name).filter((column) => targetColumns.some((target) => target.name === column));
+        const matched = intersectCompareColumns(sourceColumns, targetColumns);
+        const columns = matched.columns;
         const columnInfo = columns.map((column) => targetColumns.find((target) => target.name === column)).filter((column): column is CompareColumn => !!column);
-        const missingKeys = resolvedKeys.filter((column) => !columns.includes(column));
+        const canonicalKeyColumns: string[] = [];
+        const missingKeys: string[] = [];
+        for (const key of resolvedKeys) {
+          const canonical = matchColumnNameIgnoreCase(key, columns);
+          if (!canonical) {
+            missingKeys.push(key);
+          } else if (!canonicalKeyColumns.includes(canonical)) {
+            canonicalKeyColumns.push(canonical);
+          }
+        }
         if (missingKeys.length > 0) {
           throw new Error(t("dataCompare.missingKeyColumns", { columns: missingKeys.join(", ") }));
         }
@@ -611,7 +623,8 @@ async function startCompare() {
           targetSchema: targetSchema.value,
           targetTable: task.targetTable,
           columns,
-          keyColumns: resolvedKeys,
+          keyColumns: canonicalKeyColumns,
+          sourceColumns: matched.sourceColumns,
         });
 
         const added = preparation.result.added.length;
@@ -622,7 +635,7 @@ async function startCompare() {
         results.push({
           sourceTable: task.sourceTable,
           targetTable: task.targetTable,
-          keyColumns: resolvedKeys,
+          keyColumns: canonicalKeyColumns,
           columns,
           columnInfo,
           status,

apps/desktop/src/lib/dataGrid/__tests__/dataCompareKeyInference.spec.ts

@@ -1,5 +1,5 @@
 import { describe, expect, it } from "vitest";
-import { inferCompareKeyColumns } from "../dataCompare";
+import { inferCompareKeyColumns, intersectCompareColumns, matchColumnNameIgnoreCase } from "../dataCompare";
 
 describe("inferCompareKeyColumns", () => {
   it("returns all primary-key columns when a primary key exists", () => {
@@ -34,3 +34,40 @@ describe("inferCompareKeyColumns", () => {
     expect(inferCompareKeyColumns([])).toEqual([]);
   });
 });
+
+describe("intersectCompareColumns", () => {
+  it("matches lower-case source columns against upper-case target columns", () => {
+    const intersection = intersectCompareColumns([{ name: "snid" }, { name: "username" }, { name: "amount" }], [{ name: "SNID" }, { name: "USERNAME" }, { name: "AMOUNT" }]);
+    expect(intersection.columns).toEqual(["SNID", "USERNAME", "AMOUNT"]);
+    expect(intersection.sourceColumns).toEqual(["snid", "username", "amount"]);
+  });
+
+  it("keeps source order and omits columns missing on either side", () => {
+    const intersection = intersectCompareColumns([{ name: "Amount" }, { name: "snid" }, { name: "extra" }], [{ name: "SNID" }, { name: "AMOUNT" }]);
+    expect(intersection.columns).toEqual(["AMOUNT", "SNID"]);
+    expect(intersection.sourceColumns).toEqual(["Amount", "snid"]);
+  });
+
+  it("returns an empty intersection when no column names match ignoring case", () => {
+    const intersection = intersectCompareColumns([{ name: "snid" }], [{ name: "id" }]);
+    expect(intersection.columns).toEqual([]);
+    expect(intersection.sourceColumns).toEqual([]);
+  });
+
+  it("deduplicates duplicated source columns", () => {
+    const intersection = intersectCompareColumns([{ name: "snid" }, { name: "SNID" }], [{ name: "SNID" }]);
+    expect(intersection.columns).toEqual(["SNID"]);
+    expect(intersection.sourceColumns).toEqual(["snid"]);
+  });
+});
+
+describe("matchColumnNameIgnoreCase", () => {
+  it("resolves a name to the canonical entry ignoring case", () => {
+    expect(matchColumnNameIgnoreCase("SNID", ["snid", "name"])).toBe("snid");
+    expect(matchColumnNameIgnoreCase("Name", ["SNID", "NAME"])).toBe("NAME");
+  });
+
+  it("returns undefined when no column matches", () => {
+    expect(matchColumnNameIgnoreCase("missing", ["snid"])).toBeUndefined();
+  });
+});

apps/desktop/src/lib/dataGrid/dataCompare.ts

@@ -65,6 +65,8 @@ export interface DataCompareFromTablesOptions {
   targetTable: string;
   columns: string[];
   keyColumns: string[];
+  /** Source-side column names aligned positionally with `columns`; needed when the two databases store identifier case differently (e.g. SQL Server vs Oracle). */
+  sourceColumns?: string[];
   fetchBatchSize?: number;
   degradationThreshold?: DegradationThreshold;
   samplingStrategy?: SamplingStrategy;
@@ -139,3 +141,48 @@ export function inferCompareKeyColumns(columns: Pick<ColumnInfo, "name" | "is_pr
   }
   return primaryKeys;
 }
+
+export interface CompareColumnIntersection {
+  /** Target-side column names, kept in source order. */
+  columns: string[];
+  /** Source-side names aligned positionally with `columns`. */
+  sourceColumns: string[];
+}
+
+/**
+ * Intersects source and target columns case-insensitively.
+ *
+ * Databases store identifier case differently (SQL Server keeps the created
+ * case, Oracle and Dameng store upper case, PostgreSQL lower case), so a
+ * migrated table's columns only match across engines when compared without
+ * case. Target names are canonical because sync SQL runs against the target.
+ */
+export function intersectCompareColumns(sourceColumns: Pick<ColumnInfo, "name">[], targetColumns: Pick<ColumnInfo, "name">[]): CompareColumnIntersection {
+  const targetNamesByLowerName = new Map<string, string>();
+  for (const column of targetColumns) {
+    const lowerName = column.name.toLowerCase();
+    if (!targetNamesByLowerName.has(lowerName)) targetNamesByLowerName.set(lowerName, column.name);
+  }
+
+  const columns: string[] = [];
+  const sourceNames: string[] = [];
+  const matched = new Set<string>();
+  for (const column of sourceColumns) {
+    const lowerName = column.name.toLowerCase();
+    const targetName = targetNamesByLowerName.get(lowerName);
+    if (targetName === undefined || matched.has(lowerName)) continue;
+    matched.add(lowerName);
+    columns.push(targetName);
+    sourceNames.push(column.name);
+  }
+  return { columns, sourceColumns: sourceNames };
+}
+
+/**
+ * Resolves a column name to the matching entry of `columns`, ignoring case.
+ * Returns undefined when no column matches.
+ */
+export function matchColumnNameIgnoreCase(name: string, columns: string[]): string | undefined {
+  const lowerName = name.toLowerCase();
+  return columns.find((column) => column.toLowerCase() === lowerName);
+}