org.h2.command.dml.AllColumnsForPlan Maven / Gradle / Ivy
/*
* Copyright 2004-2019 H2 Group. Multiple-Licensed under the MPL 2.0,
* and the EPL 1.0 (https://h2database.com/html/license.html).
* Initial Developer: H2 Group
*/
package org.h2.command.dml;
import java.util.ArrayList;
import java.util.HashMap;
import org.h2.expression.ExpressionVisitor;
import org.h2.table.Column;
import org.h2.table.Table;
import org.h2.table.TableFilter;
/**
* This information is expensive to compute for large queries, so do so
* on-demand. Also store the information pre-mapped by table to avoid expensive
* traversal.
*/
public class AllColumnsForPlan {
private final TableFilter[] filters;
private HashMap> map;
public AllColumnsForPlan(TableFilter[] filters) {
this.filters = filters;
}
/**
* Called by ExpressionVisitor.
*
* @param newCol new column to be added.
*/
public void add(Column newCol) {
ArrayList cols = map.get(newCol.getTable());
if (cols == null) {
cols = new ArrayList<>();
map.put(newCol.getTable(), cols);
}
if (!cols.contains(newCol))
cols.add(newCol);
}
/**
* Used by index to calculate the cost of a scan.
*
* @param table the table.
* @return all table's referenced columns.
*/
public ArrayList get(Table table) {
if (map == null) {
map = new HashMap<>();
ExpressionVisitor.allColumnsForTableFilters(filters, this);
}
return map.get(table);
}
}