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[WIP] Always consume guaranteed limit on pushDown #9056

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losipiuk wants to merge 1 commit into from
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[WIP] Always consume guaranteed limit on pushDown #9056

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2 changes: 1 addition & 1 deletion ...no-main/src/main/java/io/trino/connector/informationschema/InformationSchemaMetadata.java
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Original file line number Diff line number Diff line change
Expand Up @@ -183,7 +183,7 @@ public Optional<LimitApplicationResult<ConnectorTableHandle>> applyLimit(Connect
InformationSchemaTableHandle table = (InformationSchemaTableHandle) handle;

if (table.getLimit().isPresent() && table.getLimit().getAsLong() <= limit) {
return Optional.empty();
return Optional.of(new LimitApplicationResult<>(table, true, false));
}

return Optional.of(new LimitApplicationResult<>(
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9 changes: 7 additions & 2 deletions plugin/trino-base-jdbc/src/main/java/io/trino/plugin/jdbc/DefaultJdbcMetadata.java
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Expand Up @@ -439,8 +439,13 @@ public Optional<LimitApplicationResult<ConnectorTableHandle>> applyLimit(Connect
return Optional.empty();
}

boolean limitGuaranteed = jdbcClient.isLimitGuaranteed(session);

if (handle.getLimit().isPresent() && handle.getLimit().getAsLong() <= limit) {
return Optional.empty();
if (!limitGuaranteed) {
return Optional.empty();
}
return Optional.of(new LimitApplicationResult<>(handle, limitGuaranteed, false));
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@findepi findepi Aug 31, 2021

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connector should return non-empty only when plan changes.
per io.trino.spi.connector.ConnectorMetadata#applyLimit doc:

     * Connectors can indicate whether they don't support limit pushdown or that the action had no effect
     * by returning {@link Optional#empty()}.

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@findepi findepi Dec 1, 2022

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I think instead, we would need "redundant limit pruning rule"
i.e. a connector needs to be able to tell the engine what's the max cardinality to be returned
(just like it can return enforced predicates)

}

handle = new JdbcTableHandle(
Expand All @@ -452,7 +457,7 @@ public Optional<LimitApplicationResult<ConnectorTableHandle>> applyLimit(Connect
handle.getOtherReferencedTables(),
handle.getNextSyntheticColumnId());

return Optional.of(new LimitApplicationResult<>(handle, jdbcClient.isLimitGuaranteed(session), false));
return Optional.of(new LimitApplicationResult<>(handle, limitGuaranteed, false));
}

@Override
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2 changes: 1 addition & 1 deletion plugin/trino-memory/src/main/java/io/trino/plugin/memory/MemoryMetadata.java
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Expand Up @@ -401,7 +401,7 @@ public Optional<LimitApplicationResult<ConnectorTableHandle>> applyLimit(Connect
MemoryTableHandle table = (MemoryTableHandle) handle;

if (table.getLimit().isPresent() && table.getLimit().getAsLong() <= limit) {
return Optional.empty();
return Optional.of(new LimitApplicationResult<>(table, true, true));
}

return Optional.of(new LimitApplicationResult<>(
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8 changes: 4 additions & 4 deletions plugin/trino-mongodb/src/main/java/io/trino/plugin/mongodb/MongoMetadata.java
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Expand Up @@ -263,12 +263,12 @@ public Optional<LimitApplicationResult<ConnectorTableHandle>> applyLimit(Connect
return Optional.empty();
}

// MongoDB doesn't support limit number greater than integer max
if (limit > Integer.MAX_VALUE) {
return Optional.empty();
if (handle.getLimit().isPresent() && handle.getLimit().getAsInt() <= limit) {
return Optional.of(new LimitApplicationResult<>(handle, true, false));
}

if (handle.getLimit().isPresent() && handle.getLimit().getAsInt() <= limit) {
// MongoDB doesn't support limit number greater than integer max
if (limit > Integer.MAX_VALUE) {
return Optional.empty();
}

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6 changes: 5 additions & 1 deletion plugin/trino-pinot/src/main/java/io/trino/plugin/pinot/PinotMetadata.java
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Expand Up @@ -258,10 +258,14 @@ public ConnectorTableProperties getTableProperties(ConnectorSession session, Con
public Optional<LimitApplicationResult<ConnectorTableHandle>> applyLimit(ConnectorSession session, ConnectorTableHandle table, long limit)
{
PinotTableHandle handle = (PinotTableHandle) table;
Optional<DynamicTable> dynamicTable = handle.getQuery();
if (handle.getLimit().isPresent() && handle.getLimit().getAsLong() <= limit) {
if (dynamicTable.isPresent()) {
// single split - limit already present in handle is enforced
return Optional.of(new LimitApplicationResult<>(handle, true, false));
}
return Optional.empty();
}
Optional<DynamicTable> dynamicTable = handle.getQuery();
if (dynamicTable.isPresent() &&
(dynamicTable.get().getLimit().isEmpty() || dynamicTable.get().getLimit().getAsLong() > limit)) {
dynamicTable = Optional.of(new DynamicTable(dynamicTable.get().getTableName(),
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