wave13: 514/239 — flink/nifi/artemis + K8s/cilium/linkerd2 + ES/OpenSearch/Solr + hadoop/hbase/spark

defects/flink/patch/flink-0004-dynamicsinkutils-updatedcolumns-hashmap.md

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+# flink-0004: DynamicSinkUtils UPDATE column resolution O(C×U) → O(C+U)
+
+## Location
+`flink-table/flink-table-planner/src/main/java/org/apache/flink/table/planner/connectors/DynamicSinkUtils.java`
+
+## Severity
+MEDIUM — triggered on every row-level UPDATE query plan compilation
+
+## Description
+`getUpdatedColumns()` iterates over all schema columns and calls `updatedColumnNames.contains(column.getName())`
+where `updatedColumnNames` is a `List<String>` from `tableModify.getUpdateColumnList()`.
+For a table with C columns and U updated columns, this is O(C×U).
+
+`projectColumnsForUpdate()` iterates over `updatedIndexes` and calls both
+`updatedColumnNames.contains(colName)` (O(U)) and `updatedColumnNames.indexOf(colName)` (O(U))
+per iteration — two linear scans per index, O(2×I×U) total.
+
+## Root Cause
+```java
+// getUpdatedColumns — line 541-544
+List<String> updatedColumnNames = tableModify.getUpdateColumnList(); // List<String>
+for (Column column : resolvedSchema.getColumns()) {                  // O(C) loop
+    if (updatedColumnNames.contains(column.getName())) {             // O(U) each → O(C×U)
+        updatedColumns.add(column);
+    }
+}
+
+// projectColumnsForUpdate — line 775-781
+List<String> updatedColumnNames = tableModify.getUpdateColumnList(); // List<String>
+for (int index : updatedIndexes) {                                   // O(I) loop
+    String colName = resolvedSchema.getColumnNames().get(index);
+    if (updatedColumnNames.contains(colName)) {                      // O(U) → O(I×U)
+        int i = updatedColumnNames.indexOf(colName);                 // O(U) again!
+        ...
+    }
+}
+```
+
+## Fix
+Pre-build a `Set<String>` for O(1) contains, and a `Map<String,Integer>` for O(1) indexOf.
+
+```java
+// getUpdatedColumns fix
+Set<String> updatedColumnSet = new HashSet<>(tableModify.getUpdateColumnList());
+for (Column column : resolvedSchema.getColumns()) {
+    if (updatedColumnSet.contains(column.getName())) {   // O(1)
+        updatedColumns.add(column);
+    }
+}
+
+// projectColumnsForUpdate fix
+List<String> updatedColumnNames = tableModify.getUpdateColumnList();
+Map<String, Integer> updatedColumnIndex = new HashMap<>();
+for (int i = 0; i < updatedColumnNames.size(); i++) {
+    updatedColumnIndex.put(updatedColumnNames.get(i), i);
+}
+for (int index : updatedIndexes) {
+    String colName = resolvedSchema.getColumnNames().get(index);
+    Integer i = updatedColumnIndex.get(colName);    // O(1) replaces contains+indexOf
+    if (i != null) {
+        RexNode rexNode = oldRexNodes.get(originColsCount + i);
+        ...
+    }
+}
+```
+
+## Complexity
+| | Before | After |
+|---|---|---|
+| getUpdatedColumns | O(C×U) | O(C+U) |
+| projectColumnsForUpdate | O(2×I×U) | O(I+U) |
+
+Where C=total columns, U=updated columns, I=updated index count.
+At C=500 columns, U=50 updates: 25,000 ops → 550 ops (45x improvement).
+
+## Duplicate locations
+Both methods are in the same file. No other copies found.