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[fix](planner) Fix sample partition table (#25912)

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In the past, two conditions needed to be met when sampling a partitioned table: 1. Data is evenly distributed between partitions; 2. Data is evenly distributed between buckets. Finally, the number of sampled rows in each partition and each bucket is the same.

Now, sampling will be proportional to the number of partitioned and bucketed rows.
This commit is contained in:
Xinyi Zou
2023-11-02 15:52:48 +08:00
committed by GitHub
parent 3e9e8becc6
commit f1362e0d1e
3 changed files with 82 additions and 58 deletions
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2
fe/fe-core/src/main/java/org/apache/doris/nereids/glue/translator/PhysicalPlanTranslator.java
View File

@ -624,7 +624,7 @@ public class PhysicalPlanTranslator extends DefaultPlanVisitor<PlanFragment, Pla
BaseTableRef tableRef = new BaseTableRef(ref, olapTable, tableName);
tupleDescriptor.setRef(tableRef);
olapScanNode.setSelectedPartitionIds(olapScan.getSelectedPartitionIds());
olapScanNode.setSampleTabletIds(olapScan.getSelectedTabletIds());
olapScanNode.setSampleTabletIds(olapScan.getSelectedTabletIds()); // TODO
if (olapScan.getTableSample().isPresent()) {
olapScanNode.setTableSample(new TableSample(olapScan.getTableSample().get().isPercent,
olapScan.getTableSample().get().sampleValue, olapScan.getTableSample().get().seek));

129
fe/fe-core/src/main/java/org/apache/doris/planner/OlapScanNode.java
View File

@ -59,6 +59,7 @@ import org.apache.doris.common.AnalysisException;
import org.apache.doris.common.Config;
import org.apache.doris.common.ErrorCode;
import org.apache.doris.common.ErrorReport;
import org.apache.doris.common.FeConstants;
import org.apache.doris.common.UserException;
import org.apache.doris.common.util.Util;
import org.apache.doris.nereids.glue.translator.PlanTranslatorContext;
@ -98,6 +99,7 @@ import java.security.SecureRandom;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
@ -220,7 +222,7 @@ public class OlapScanNode extends ScanNode {
public void setIsPreAggregation(boolean isPreAggregation, String reason) {
this.isPreAggregation = isPreAggregation;
this.reasonOfPreAggregation = this.reasonOfPreAggregation == null ? reason :
this.reasonOfPreAggregation + " " + reason;
this.reasonOfPreAggregation + " " + reason;
}
@ -402,7 +404,8 @@ public class OlapScanNode extends ScanNode {
String scanRangeInfo = stringBuilder.toString();
String situation;
boolean update;
CHECK: { // CHECKSTYLE IGNORE THIS LINE
CHECK:
{ // CHECKSTYLE IGNORE THIS LINE
if (olapTable.getKeysType() == KeysType.DUP_KEYS || (olapTable.getKeysType() == KeysType.UNIQUE_KEYS
&& olapTable.getEnableUniqueKeyMergeOnWrite())) {
situation = "The key type of table is duplicate, or unique key with merge-on-write.";
@ -778,7 +781,7 @@ public class OlapScanNode extends ScanNode {
// but it means we will do 3 S3 IO to get the data which will bring 3 slow query
if (-1L != coolDownReplicaId) {
final Optional<Replica> replicaOptional = replicas.stream()
.filter(r -> r.getId() == coolDownReplicaId).findAny();
.filter(r -> r.getId() == coolDownReplicaId).findAny();
replicaOptional.ifPresent(
r -> {
Backend backend = Env.getCurrentSystemInfo()
@ -930,75 +933,91 @@ public class OlapScanNode extends ScanNode {
}
/**
* First, determine how many rows to sample from each partition according to the number of partitions.
* Then determine the number of Tablets to be selected for each partition according to the average number
* of rows of Tablet,
* If seek is not specified, the specified number of Tablets are pseudo-randomly selected from each partition.
* If seek is specified, it will be selected sequentially from the seek tablet of the partition.
* And add the manually specified Tablet id to the selected Tablet.
* simpleTabletNums = simpleRows / partitionNums / (partitionRows / partitionTabletNums)
* Sample some tablets in the selected partition.
* If Seek is specified, the tablets sampled each time are the same.
*/
public void computeSampleTabletIds() {
if (tableSample == null) {
return;
}
OlapTable olapTable = (OlapTable) desc.getTable();
long sampleRows; // The total number of sample rows
long hitRows = 1; // The total number of rows hit by the tablet
long totalRows = 0; // The total number of partition rows hit
long totalTablet = 0; // The total number of tablets in the hit partition
// 1. Calculate the total number of rows in the selected partition, and sort partition list.
long selectedRows = 0;
long totalSampleRows = 0;
List<Long> selectedPartitionList = new ArrayList<>();
if (FeConstants.runningUnitTest && selectedIndexId == -1) {
selectedIndexId = olapTable.getBaseIndexId();
}
for (Long partitionId : selectedPartitionIds) {
final Partition partition = olapTable.getPartition(partitionId);
final MaterializedIndex selectedTable = partition.getIndex(selectedIndexId);
selectedRows += selectedTable.getRowCount();
selectedPartitionList.add(partitionId);
}
selectedPartitionList.sort(Comparator.naturalOrder());
// 2.Sampling is not required in some cases, will not take effect after clear sampleTabletIds.
if (tableSample.isPercent()) {
sampleRows = (long) Math.max(olapTable.getRowCount() * (tableSample.getSampleValue() / 100.0), 1);
if (tableSample.getSampleValue() >= 100) {
return;
}
totalSampleRows = (long) Math.max(selectedRows * (tableSample.getSampleValue() / 100.0), 1);
} else {
sampleRows = Math.max(tableSample.getSampleValue(), 1);
if (tableSample.getSampleValue() > selectedRows) {
return;
}
totalSampleRows = tableSample.getSampleValue();
}
// calculate the number of tablets by each partition
long avgRowsPerPartition = sampleRows / Math.max(olapTable.getPartitions().size(), 1);
for (Partition p : olapTable.getPartitions()) {
List<Long> ids = p.getBaseIndex().getTabletIdsInOrder();
if (ids.isEmpty()) {
// 3. Sampling partition. If Seek is specified, the partition will be the same for each sampling.
long hitRows = 0; // The number of rows hit by the tablet
long partitionSeek = tableSample.getSeek() != -1
? tableSample.getSeek() : (long) (new SecureRandom().nextDouble() * selectedPartitionIds.size());
for (int i = 0; i < selectedPartitionList.size(); i++) {
int seekPid = (int) ((i + partitionSeek) % selectedPartitionList.size());
final Partition partition = olapTable.getPartition(selectedPartitionList.get(seekPid));
final MaterializedIndex selectedTable = partition.getIndex(selectedIndexId);
List<Tablet> tablets = selectedTable.getTablets();
if (tablets.isEmpty()) {
continue;
}
// Skip partitions with row count < row count / 2 expected to be sampled per partition.
// It can be expected to sample a smaller number of partitions to avoid uneven distribution
// of sampling results.
if (p.getBaseIndex().getRowCount() < (avgRowsPerPartition / 2)) {
continue;
// 4. Calculate the number of rows that need to be sampled in the current partition.
long sampleRows = 0; // The number of sample rows in partition
if (tableSample.isPercent()) {
sampleRows = (long) Math.max(selectedTable.getRowCount() * (tableSample.getSampleValue() / 100.0), 1);
} else {
sampleRows = (long) Math.max(
tableSample.getSampleValue() * (selectedTable.getRowCount() / selectedRows), 1);
}
// It is assumed here that all tablets row count is uniformly distributed
// TODO Use `p.getBaseIndex().getTablet(n).getRowCount()` to get each tablet row count to compute sample.
long avgRowsPerTablet = Math.max(p.getBaseIndex().getRowCount() / ids.size(), 1);
long tabletCounts = Math.max(
avgRowsPerPartition / avgRowsPerTablet + (avgRowsPerPartition % avgRowsPerTablet != 0 ? 1 : 0), 1);
tabletCounts = Math.min(tabletCounts, ids.size());
long seek = tableSample.getSeek() != -1
? tableSample.getSeek() : (long) (new SecureRandom().nextDouble() * ids.size());
for (int i = 0; i < tabletCounts; i++) {
int seekTid = (int) ((i + seek) % ids.size());
sampleTabletIds.add(ids.get(seekTid));
// 5. Sampling tablets. If Seek is specified, the same tablet will be sampled each time.
long tabletSeek = tableSample.getSeek() != -1
? tableSample.getSeek() : (long) (new SecureRandom().nextDouble() * tablets.size());
for (int j = 0; j < tablets.size(); j++) {
int seekTid = (int) ((j + tabletSeek) % tablets.size());
long tabletRowCount;
if (!FeConstants.runningUnitTest) {
tabletRowCount = tablets.get(seekTid).getRowCount(true);
} else {
tabletRowCount = selectedTable.getRowCount() / tablets.size();
}
if (tabletRowCount == 0) {
continue;
}
sampleTabletIds.add(tablets.get(seekTid).getId());
sampleRows -= tabletRowCount;
hitRows += tabletRowCount;
if (sampleRows <= 0) {
break;
}
}
if (hitRows > totalSampleRows) {
break;
}
hitRows += avgRowsPerTablet * tabletCounts;
totalRows += p.getBaseIndex().getRowCount();
totalTablet += ids.size();
}
// all hit, direct full
if (totalRows < sampleRows) {
// can't fill full sample rows
sampleTabletIds.clear();
} else if (sampleTabletIds.size() == totalTablet) {
// TODO add limit
sampleTabletIds.clear();
} else if (!sampleTabletIds.isEmpty()) {
// TODO add limit
}
LOG.debug("after computeSampleTabletIds, hitRows {}, selectedRows {}", hitRows, selectedRows);
}
public boolean isFromPrepareStmt() {