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Core: Fix Metadata table's UUID #9310

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merged 2 commits into from
Dec 16, 2023
Merged

Core: Fix Metadata table's UUID #9310

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Core: Fix Metadata table's UUID
ajantha-bhat Dec 16, 2023
180a3cc
Address nits
ajantha-bhat Dec 16, 2023
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4 changes: 3 additions & 1 deletion core/src/main/java/org/apache/iceberg/BaseMetadataTable.java
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Original file line number Diff line number Diff line change
Expand Up @@ -44,13 +44,15 @@ public abstract class BaseMetadataTable extends BaseReadOnlyTable
private final SortOrder sortOrder = SortOrder.unsorted();
private final BaseTable table;
private final String name;
private final UUID uuid;

protected BaseMetadataTable(Table table, String name) {
super("metadata");
Preconditions.checkArgument(
table instanceof BaseTable, "Cannot create metadata table for non-data table: %s", table);
this.table = (BaseTable) table;
this.name = name;
this.uuid = UUID.randomUUID();
}

/**
Expand Down Expand Up @@ -202,7 +204,7 @@ public Map<String, SnapshotRef> refs() {

@Override
public UUID uuid() {
return UUID.randomUUID();
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@amogh-jahagirdar amogh-jahagirdar Dec 16, 2023 •
edited
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Wow, I can't believe I wrote it like this originally :). Good fix, yes we do want a random UUID but it should be consistent across the same Metadata Table.

The only thing is if we extend this logic further is that the same base metadata table across different references won't return the same UUID. So for example "all manifests" for t1 may have a different UUID than "all manifests" for t1 in a different query.

I don't really see a way around that without persisting the UUID somewhere (like for normal tables that's in the metadata) but considering metadata tables are really more logical tables, I think that's OK. If we wanted that strict definition for metadata tables, then we would have to throw an unsupported until we persisted those details somewhere.

For now though, I think this change is good as is. It looks like in the next change you have the UUID is used as part of caching, in which case this fix should solve that.

return uuid;
}

@Override
Expand Down
13 changes: 13 additions & 0 deletions core/src/test/java/org/apache/iceberg/TestMetadataTableScans.java
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Expand Up @@ -43,6 +43,7 @@
import org.apache.iceberg.relocated.com.google.common.collect.Streams;
import org.apache.iceberg.types.Types;
import org.apache.iceberg.util.StructLikeWrapper;
import org.assertj.core.api.Assertions;
import org.junit.Assert;
import org.junit.Assume;
import org.junit.Test;
Expand Down Expand Up @@ -138,6 +139,18 @@ public void testManifestsTableAlwaysIgnoresResiduals() throws IOException {
}
}

@Test
public void testManifestsTableUUID() {
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Table manifestsTable = new ManifestsTable(table);

Assertions.assertThat(manifestsTable.uuid())
.as("UUID should be consistent on multiple calls")
.isEqualTo(manifestsTable.uuid());
Assertions.assertThat(manifestsTable.uuid())
.as("Metadata table UUID should be different from main table UUID")
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Nit: "should be different from the base table's UUID"

.isNotEqualTo(table.uuid());
}

@Test
public void testDataFilesTableWithDroppedPartition() throws IOException {
table.newFastAppend().appendFile(FILE_A).appendFile(FILE_B).commit();
Expand Down