Hi,
I use the latest stable version of H2 (1.3.176).
During Index creation for very wide tables with nearly unique data in
every column/row, OutOfMemory Errors can occur.
I tracked down the reason for this within the H2 source. The reason is the
buffering of rows in the addIndex method (source added below).
The size of the buffer is limited to Constants.DEFAULT_MAX_MEMORY_ROWSand
not to the amount specified by a "SET MAX_MEMORY_ROWS <n>" statement
(which should be available through database.getMaxMemoryRows())
@Override
public Index addIndex(Session session, String indexName, int indexId,
IndexColumn[] cols, IndexType indexType, boolean create,
String indexComment) {
if (indexType.isPrimaryKey()) {
for (IndexColumn c : cols) {
Column column = c.column;
if (column.isNullable()) {
throw DbException.get(
ErrorCode.COLUMN_MUST_NOT_BE_NULLABLE_1,
column.getName());
}
column.setPrimaryKey(true);
}
}
boolean isSessionTemporary = isTemporary() &&
!isGlobalTemporary();
if (!isSessionTemporary) {
database.lockMeta(session);
}
Index index;
if (isPersistIndexes() && indexType.isPersistent()) {
int mainIndexColumn;
if (database.isStarting() &&
database.getPageStore().getRootPageId(indexId) != 0) {
mainIndexColumn = -1;
} else if (!database.isStarting() && mainIndex
.getRowCount(session) != 0) {
mainIndexColumn = -1;
} else {
mainIndexColumn = getMainIndexColumn(indexType, cols);
}
if (mainIndexColumn != -1) {
mainIndex.setMainIndexColumn(mainIndexColumn);
index = new PageDelegateIndex(this, indexId, indexName,
indexType, mainIndex, create, session);
} else if (indexType.isSpatial()) {
index = new SpatialTreeIndex(this, indexId, indexName,
cols,
indexType, true, create, session);
} else {
index = new PageBtreeIndex(this, indexId, indexName, cols,
indexType, create, session);
}
} else {
if (indexType.isHash()) {
if (cols.length != 1) {
throw DbException.getUnsupportedException(
"hash indexes may index only one column");
}
if (indexType.isUnique()) {
index = new HashIndex(this, indexId, indexName, cols,
indexType);
} else {
index = new NonUniqueHashIndex(this, indexId,
indexName,
cols, indexType);
}
} else if (indexType.isSpatial()) {
index = new SpatialTreeIndex(this, indexId, indexName,
cols,
indexType, false, true, session);
} else {
index = new TreeIndex(this, indexId, indexName, cols,
indexType);
}
}
if (database.isMultiVersion()) {
index = new MultiVersionIndex(index, this);
}
if (index.needRebuild() && rowCount > 0) {
try {
Index scan = getScanIndex(session);
long remaining = scan.getRowCount(session);
long total = remaining;
Cursor cursor = scan.find(session, null, null);
long i = 0;
int bufferSize = (int) Math.min(rowCount, Constants.
DEFAULT_MAX_MEMORY_ROWS);
ArrayList<Row> buffer = New.arrayList(bufferSize);
String n = getName() + ":" + index.getName();
int t = MathUtils.convertLongToInt(total);
while (cursor.next()) {
database.setProgress(DatabaseEventListener.
STATE_CREATE_INDEX, n,
MathUtils.convertLongToInt(i++), t);
Row row = cursor.get();
buffer.add(row);
if (buffer.size() >= bufferSize) {
addRowsToIndex(session, buffer, index);
}
remaining--;
}
addRowsToIndex(session, buffer, index);
if (SysProperties.CHECK && remaining != 0) {
DbException.throwInternalError("rowcount remaining=" +
remaining + " " + getName());
}
} catch (DbException e) {
getSchema().freeUniqueName(indexName);
try {
index.remove(session);
} catch (DbException e2) {
// this could happen, for example on failure in the
storage
// but if that is not the case it means
// there is something wrong with the database
trace.error(e2, "could not remove index");
throw e2;
}
throw e;
}
}
index.setTemporary(isTemporary());
if (index.getCreateSQL() != null) {
index.setComment(indexComment);
if (isSessionTemporary) {
session.addLocalTempTableIndex(index);
} else {
database.addSchemaObject(session, index);
}
}
indexes.add(index);
setModified();
return index;
}
Kind regards
Christoff Schmitz
F I N A R I S
Financial Software Partner GmbH
Sömmerringstrasse 23
60322 Frankfurt am Main
Fon: +49 (0)69 / 254 98 - 24
Mobile: +49 (0)176 / 206 34 186
Fax: +49 (0)69 / 254 98 - 50
eMail: mailto:christoff.schm...@finaris.de
www: http://www.finaris.de und http://www.rapidrep.com
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