io.deephaven.engine.table.MultiJoinFactory Maven / Gradle / Ivy
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//
// Copyright (c) 2016-2024 Deephaven Data Labs and Patent Pending
//
package io.deephaven.engine.table;
import io.deephaven.api.JoinMatch;
import org.jetbrains.annotations.NotNull;
import java.util.ServiceLoader;
/**
*
* Join unique rows from a set of tables onto a set of common keys.
*
*
*
* The multiJoin operation collects the set of distinct keys from the input tables, then joins at most one row per key
* from each of the input tables onto the result. Input tables need not have a matching row for each key, but they may
* not have multiple matching rows for a given key.
*
*
*
* Input tables with non-matching key column names must use the {@link JoinMatch} format to map keys to the common
* output table key column names (e.g. "OutputKey=SourceKey"). Also, individual columns to include from input tables may
* be specified and optionally renamed using {@link io.deephaven.api.JoinAddition} format (e.g. "NewCol=OldColName"). If
* no output columns are specified then every non-key column from the input table will be included in the multi-join
* output table.
*
*
*
* The multiJoin operation can be thought of as a merge of the key columns, followed by a selectDistinct and then a
* series of iterative naturalJoin operations as follows (this example has common key column names and includes all
* columns from the input tables):
*
*
* {@code
* private Table doIterativeMultiJoin(String [] keyColumns, List inputTables) {
* final List keyTables = inputTables.stream().map(t -> t.view(keyColumns)).collect(Collectors.toList());
* final Table base = TableTools.merge(keyTables).selectDistinct(keyColumns);
*
* Table result = base;
* for (int ii = 0; ii < inputTables.size(); ++ii) {
* result = result.naturalJoin(inputTables.get(ii), Arrays.asList(keyColumns));
* }
*
* return result;
* }
* }
*
*/
public class MultiJoinFactory {
/**
* Creator interface for runtime-supplied implementation.
*/
public interface Creator {
MultiJoinTable of(@NotNull final MultiJoinInput... multiJoinInputs);
}
/**
* Creator provider to supply the implementation at runtime.
*/
@FunctionalInterface
public interface CreatorProvider {
Creator get();
}
private static final class MultiJoinTableCreatorHolder {
private static final MultiJoinFactory.Creator creator =
ServiceLoader.load(MultiJoinFactory.CreatorProvider.class).iterator().next().get();
}
private static MultiJoinFactory.Creator multiJoinTableCreator() {
return MultiJoinTableCreatorHolder.creator;
}
/**
* Join tables that have common key column names; include all columns from the input tables.
*
*
* @param keys the key column pairs in the format "Result=Source" or "ColumnInBoth"
* @param inputTables the tables to join together
* @return a MultiJoinTable with one row for each key and the corresponding row in each input table
*/
public static MultiJoinTable of(@NotNull final String[] keys, @NotNull final Table... inputTables) {
return multiJoinTableCreator().of(MultiJoinInput.from(keys, inputTables));
}
/**
* Join tables that have common key column names; include all columns from the input tables.
*
*
* @param columnsToMatch A comma separated list of key columns, in string format (e.g. "ResultKey=SourceKey" or
* "KeyInBoth").
* @param inputTables the tables to join together
* @return a MultiJoinTable with one row for each key and the corresponding row in each input table
*/
public static MultiJoinTable of(@NotNull final String columnsToMatch, @NotNull final Table... inputTables) {
return multiJoinTableCreator().of(MultiJoinInput.from(columnsToMatch, inputTables));
}
/**
* Perform a multiJoin for one or more tables; allows renaming of key column names and specifying individual input
* table columns to include in the final output table.
*
* @param multiJoinInputs the description of each table that contributes to the result
* @return a MultiJoinTable with one row for each key and the corresponding row in each input table
*/
public static MultiJoinTable of(@NotNull final MultiJoinInput... multiJoinInputs) {
return multiJoinTableCreator().of(multiJoinInputs);
}
}
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