wuchong commented on a change in pull request #11906:
URL: https://github.com/apache/flink/pull/11906#discussion_r427835703
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File path:
flink-connectors/flink-connector-jdbc/src/main/java/org/apache/flink/connector/jdbc/catalog/AbstractJdbcCatalog.java
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@@ -126,31 +124,33 @@ public String getBaseUrl() {
// ------ retrieve PK constraint ------
- protected UniqueConstraint getPrimaryKey(DatabaseMetaData metaData,
String schema, String table) throws SQLException {
+ protected Optional<UniqueConstraint> getPrimaryKey(DatabaseMetaData
metaData, String schema, String table) throws SQLException {
// According to the Javadoc of
java.sql.DatabaseMetaData#getPrimaryKeys,
// the returned primary key columns are ordered by COLUMN_NAME,
not by KEY_SEQ.
// We need to sort them based on the KEY_SEQ value.
ResultSet rs = metaData.getPrimaryKeys(null, schema, table);
- List<Map.Entry<Integer, String>> columnsWithIndex = null;
+ Map<Integer, String> keySeqColumnName = new HashMap<>();
String pkName = null;
- while (rs.next()) {
+ while (rs.next()) {
String columnName = rs.getString("COLUMN_NAME");
- pkName = rs.getString("PK_NAME");
+ pkName = rs.getString("PK_NAME"); // all the PK_NAME
should be the same
int keySeq = rs.getInt("KEY_SEQ");
- if (columnsWithIndex == null) {
- columnsWithIndex = new ArrayList<>();
- }
- columnsWithIndex.add(new
AbstractMap.SimpleEntry<>(Integer.valueOf(keySeq), columnName));
+ keySeqColumnName.put(keySeq - 1, columnName); //
KEY_SEQ is 1-based index
}
- if (columnsWithIndex != null) {
- // sort columns by KEY_SEQ
-
columnsWithIndex.sort(Comparator.comparingInt(Map.Entry::getKey));
- List<String> cols =
columnsWithIndex.stream().map(Map.Entry::getValue).collect(Collectors.toList());
- return UniqueConstraint.primaryKey(pkName, cols);
+ List<String> pkFields = Arrays.asList(new
String[keySeqColumnName.size()]); // initialize size
+ keySeqColumnName.forEach(pkFields::set);
+ if (!pkFields.isEmpty()) {
+ if (pkName == null) {
+ // PK_NAME maybe null according to the javadoc,
+ // generate an unique name for the primary key
+ pkName = "pk_" + String.join("_", pkFields);
+ }
+ return Optional.of(UniqueConstraint.primaryKey(pkName,
pkFields));
+ } else {
Review comment:
Yes... this is a guideline to return Optional instead of null unless
there is a performance concern.
> Always use Optional to return nullable values in the API/public methods
except the case of a proven performance concern.
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