Mercurial > dive4elements > river
view artifacts/src/main/java/org/dive4elements/river/utils/BatchLoader.java @ 8587:07c9ac22f611
(issue1755) Generalise BedQuality result handling
The bedquality calculation now produces a result for each time period
which has BedQualityResultValues for each specific result type.
Formally this was split up in density, porosity and diameter classes
with some bedload diameter classes mixed in for extra fun.
The intent of this commit is to allow more shared code and generic
access patterns to the BedQuality results.
author | Andre Heinecke <andre.heinecke@intevation.de> |
---|---|
date | Wed, 18 Mar 2015 18:42:08 +0100 |
parents | b0c88ac9f63b |
children | 0a5239a1e46e |
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/* Copyright (C) 2011, 2012, 2013 by Bundesanstalt für Gewässerkunde * Software engineering by Intevation GmbH * * This file is Free Software under the GNU AGPL (>=v3) * and comes with ABSOLUTELY NO WARRANTY! Check out the * documentation coming with Dive4Elements River for details. */ package org.dive4elements.river.utils; import java.util.ArrayList; import java.util.HashMap; import java.util.Iterator; import java.util.List; import java.util.Map; import org.apache.log4j.Logger; import org.hibernate.SQLQuery; import org.hibernate.Session; /** To reduce the number of SQL queries send to the backend * (mainly by the fixings overviews) we execute them in batches of ids * and store the results in a small cache. * TODO: It currently relies on dynamic SQL. * Is there a way to use Hibernate with java.sql.Array * in cross database compatible manner? */ public abstract class BatchLoader<T> { private static Logger log = Logger.getLogger(BatchLoader.class); public static final int BATCH_SIZE = 100; private Map<Integer, T> loaded; private List<Integer> rest; private Session session; private String sqlTemplate; public BatchLoader( List<Integer> columns, Session session, String sqlTemplate ) { rest = new ArrayList<Integer>(columns.size()); loaded = new HashMap<Integer, T>(); this.session = session; this.sqlTemplate = sqlTemplate; // Insert in reverse order to minize searching. for (int i = columns.size()-1; i >= 0; --i) { rest.add(columns.get(i)); } } /** Searches for id and fill a batch to load containing the found id. */ private List<Integer> prepareBatch(int id) { List<Integer> batch = new ArrayList<Integer>(BATCH_SIZE); boolean found = false; for (int i = rest.size()-1; batch.size() < BATCH_SIZE && i >= 0; --i) { Integer cid = rest.get(i); if (cid == id) { found = true; batch.add(cid); rest.remove(i); } else if ((found && batch.size() < BATCH_SIZE) || (!found && batch.size() < BATCH_SIZE-1)) { batch.add(cid); rest.remove(i); } } return batch; } /** Converts id to a list of comma separated ints. */ private static String idsAsString(List<Integer> ids) { StringBuilder sb = new StringBuilder(); for (Iterator<Integer> i = ids.iterator(); i.hasNext();) { sb.append(i.next()); if (i.hasNext()) { sb.append(','); } } return sb.toString(); } /** Get data for id. */ public T get(int id) { T already = loaded.get(id); if (already != null) { return already; } List<Integer> batch = prepareBatch(id); if (batch.isEmpty()) { return null; } String sql = sqlTemplate.replace("$IDS", idsAsString(batch)); if (log.isDebugEnabled()) { log.debug(sql + " " + sql.length()); } fill(session.createSQLQuery(sql)); return get(id); } /** Call this from fill() to store data in the cache. */ protected void cache(int key, T data) { loaded.put(key, data); } /** Override this to fill the cache */ protected abstract void fill(SQLQuery query); }