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Optimize TsTable with Copy-on-Write pattern for thread-safe concurrent access #17069

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Optimize TsTable with Copy-on-Write pattern for thread-safe concurrent access #17069

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Optimize TsTable with Copy-on-Write pattern for thread-safe concurren…
luoluoyuyu Jan 23, 2026
9b221b1
fix
luoluoyuyu Jan 23, 2026
7e798b1
fix
luoluoyuyu Jan 28, 2026
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122 changes: 90 additions & 32 deletions iotdb-core/node-commons/src/main/java/org/apache/iotdb/commons/schema/table/TsTable.java
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Original file line number Diff line number Diff line change
Expand Up @@ -73,9 +73,10 @@ public class TsTable {
"When there are object fields, the %s %s shall not be '.', '..' or contain './', '.\\'.";
protected String tableName;

private final Map<String, TsTableColumnSchema> columnSchemaMap = new LinkedHashMap<>();
private final Map<String, Integer> tagColumnIndexMap = new HashMap<>();
private final Map<String, Integer> idColumnIndexMap = new HashMap<>();
// Copy-on-Write maps for thread-safe access without read locks
private volatile Map<String, TsTableColumnSchema> columnSchemaMap = new LinkedHashMap<>();
private volatile Map<String, Integer> tagColumnIndexMap = new HashMap<>();
private volatile Map<String, Integer> idColumnIndexMap = new HashMap<>();

private final ReadWriteLock readWriteLock = new ReentrantReadWriteLock();

Expand Down Expand Up @@ -149,23 +150,77 @@ public TsTableColumnSchema getColumnSchema(final String columnName) {
}

/**
* Execute a write operation with optimistic lock support. This method handles the write flag and
* version increment automatically.
* Execute a write operation with Copy-on-Write support. This method creates new copies of the
* maps before modification to ensure thread-safe reads without locks.
*
* @param writeOperation the write operation to execute
* @param writeOperation the write operation to execute on the new map copies
*/
private void executeWrite(Runnable writeOperation) {
private void executeWrite(WriteOperation writeOperation) {
readWriteLock.writeLock().lock();
isNotWrite.set(false);
try {
writeOperation.run();
// Copy-on-Write: create local copies first
Map<String, TsTableColumnSchema> newColumnSchemaMap = new LinkedHashMap<>(columnSchemaMap);
Map<String, Integer> newTagColumnIndexMap = new HashMap<>(tagColumnIndexMap);
Map<String, Integer> newIdColumnIndexMap = new HashMap<>(idColumnIndexMap);

// Execute write operation on local copies
writeOperation.execute(newColumnSchemaMap, newTagColumnIndexMap, newIdColumnIndexMap);

// After write completes, atomically update the class fields
columnSchemaMap = newColumnSchemaMap;
tagColumnIndexMap = newTagColumnIndexMap;
idColumnIndexMap = newIdColumnIndexMap;
Comment on lines +170 to +173
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@jt2594838 jt2594838 Jan 26, 2026

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There may still introduce inconsistency

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@jt2594838 jt2594838 Jan 26, 2026

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And, may only retain tagColumnIndexMap since id is a deprecated name

} finally {
instanceVersion.incrementAndGet();
isNotWrite.set(true);
readWriteLock.writeLock().unlock();
}
}

/**
* Execute a write operation with a custom columnSchemaMap transformer. This allows transforming
* the map during copy (e.g., for rename operations) in a single pass.
*
* @param columnSchemaMapTransformer transforms columnSchemaMap entries during copy
*/
private void executeWriteWithTransform(ColumnSchemaMapTransformer columnSchemaMapTransformer) {
readWriteLock.writeLock().lock();
isNotWrite.set(false);
try {
// Copy-on-Write with transformation: transform columnSchemaMap in single pass
Map<String, TsTableColumnSchema> newColumnSchemaMap = new LinkedHashMap<>();
for (Map.Entry<String, TsTableColumnSchema> entry : columnSchemaMap.entrySet()) {
columnSchemaMapTransformer.transform(entry.getKey(), entry.getValue(), newColumnSchemaMap);
}
Map<String, Integer> newTagColumnIndexMap = new HashMap<>(tagColumnIndexMap);
Map<String, Integer> newIdColumnIndexMap = new HashMap<>(idColumnIndexMap);

// After write completes, atomically update the class fields
columnSchemaMap = newColumnSchemaMap;
tagColumnIndexMap = newTagColumnIndexMap;
idColumnIndexMap = newIdColumnIndexMap;
} finally {
instanceVersion.incrementAndGet();
isNotWrite.set(true);
readWriteLock.writeLock().unlock();
}
}

@FunctionalInterface
private interface WriteOperation {
void execute(
Map<String, TsTableColumnSchema> columnSchemaMap,
Map<String, Integer> tagColumnIndexMap,
Map<String, Integer> idColumnIndexMap);
}

@FunctionalInterface
private interface ColumnSchemaMapTransformer {
void transform(
String key, TsTableColumnSchema value, Map<String, TsTableColumnSchema> targetMap);
}

public int getTagColumnOrdinal(final String columnName) {
readWriteLock.readLock().lock();
try {
Expand Down Expand Up @@ -201,67 +256,70 @@ public List<TsTableColumnSchema> getTagColumnSchemaList() {

// Currently only supports device view
public void renameTable(final String newName) {
executeWrite(() -> tableName = newName);
executeWrite((colMap, tagMap, idMap) -> tableName = newName);
}

public void addColumnSchema(final TsTableColumnSchema columnSchema) {
executeWrite(
() -> {
columnSchemaMap.put(columnSchema.getColumnName(), columnSchema);
(colMap, tagMap, idMap) -> {
colMap.put(columnSchema.getColumnName(), columnSchema);
if (columnSchema.getColumnCategory().equals(TsTableColumnCategory.TAG)) {
tagNums++;
tagColumnIndexMap.put(columnSchema.getColumnName(), tagNums - 1);
tagMap.put(columnSchema.getColumnName(), tagNums - 1);
} else if (columnSchema.getColumnCategory().equals(TsTableColumnCategory.FIELD)) {
fieldNum++;
}
});
}

public void renameColumnSchema(final String oldName, final String newName) {
executeWrite(
() -> {
// Ensures idempotency
if (columnSchemaMap.containsKey(oldName)) {
final TsTableColumnSchema schema = columnSchemaMap.remove(oldName);
// Transform during copy: rename column while preserving insertion order in single pass
executeWriteWithTransform(
(key, schema, targetMap) -> {
if (key.equals(oldName)) {
// Rename this column while preserving its position
final Map<String, String> oldProps = schema.getProps();
oldProps.computeIfAbsent(TreeViewSchema.ORIGINAL_NAME, k -> schema.getColumnName());

TsTableColumnSchema renamedSchema;
switch (schema.getColumnCategory()) {
case TAG:
columnSchemaMap.put(
newName, new TagColumnSchema(newName, schema.getDataType(), oldProps));
renamedSchema = new TagColumnSchema(newName, schema.getDataType(), oldProps);
break;
case FIELD:
columnSchemaMap.put(
newName,
renamedSchema =
new FieldColumnSchema(
newName,
schema.getDataType(),
((FieldColumnSchema) schema).getEncoding(),
((FieldColumnSchema) schema).getCompressor(),
oldProps));
oldProps);
break;
case ATTRIBUTE:
columnSchemaMap.put(
newName, new AttributeColumnSchema(newName, schema.getDataType(), oldProps));
renamedSchema = new AttributeColumnSchema(newName, schema.getDataType(), oldProps);
break;
case TIME:
default:
// Do nothing
columnSchemaMap.put(oldName, schema);
// Do nothing for TIME column
targetMap.put(key, schema);
return;
}
targetMap.put(newName, renamedSchema);
} else {
targetMap.put(key, schema);
}
});
}

public void removeColumnSchema(final String columnName) {
executeWrite(
() -> {
final TsTableColumnSchema columnSchema = columnSchemaMap.get(columnName);
(colMap, tagMap, idMap) -> {
final TsTableColumnSchema columnSchema = colMap.get(columnName);
if (columnSchema != null
&& columnSchema.getColumnCategory().equals(TsTableColumnCategory.TAG)) {
throw new SchemaExecutionException("Cannot remove an tag column: " + columnName);
} else if (columnSchema != null) {
columnSchemaMap.remove(columnName);
colMap.remove(columnName);
if (columnSchema.getColumnCategory().equals(TsTableColumnCategory.FIELD)) {
fieldNum--;
}
Expand Down Expand Up @@ -354,7 +412,7 @@ public Optional<String> getPropValue(final String propKey) {

public void addProp(final String key, final String value) {
executeWrite(
() -> {
(colMap, tagMap, idMap) -> {
if (props == null) {
props = new HashMap<>();
}
Expand All @@ -364,7 +422,7 @@ public void addProp(final String key, final String value) {

public void removeProp(final String key) {
executeWrite(
() -> {
(colMap, tagMap, idMap) -> {
if (props == null) {
return;
}
Expand Down Expand Up @@ -410,7 +468,7 @@ public static TsTable deserialize(final ByteBuffer buffer) {
}

public void setProps(Map<String, String> props) {
executeWrite(() -> this.props = props);
executeWrite((colMap, tagMap, idMap) -> this.props = props);
}

public void checkTableNameAndObjectNames4Object() throws MetadataException {
Expand Down
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