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Copyright (c) 2008-2012 Vrije Universiteit, The Netherlands All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the follo...
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/* * Copyright (c) 2008-2012 Vrije Universiteit, The Netherlands All rights * reserved./*from ww w. ja v a 2s.co m*/ * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are met: * * Redistributions of source code must retain the above copyright notice, this * list of conditions and the following disclaimer. * * Redistributions in binary form must reproduce the above copyright notice, * this list of conditions and the following disclaimer in the documentation * and/or other materials provided with the distribution. * * Neither the name of the Vrije Universiteit nor the names of its contributors * may be used to endorse or promote products derived from this software without * specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS IS'' * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. */ package interdroid.vdb.persistence.impl; import java.util.ArrayList; import java.util.Map; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; /** * Utility for assisting with a merge. * * @author nick <palmer@cs.vu.nl> * */ public class MergeHelper { /** * The name of the column with a diff result. */ static final String COL_DIFF_RESULT = "diff_result"; /** * The checkout this merge helper is working in. */ // private final VdbCheckout parentCheckout_; /** * A cache of table metadata. */ private Map<String, TableMetadata> mMetadataCache; /** * Construct a merge helper. */ public MergeHelper(/* VdbCheckout checkout */) { // parentCheckout_ = checkout; } /** * The databases we need to do a merge. * @author nick <palmer@cs.vu.nl> * */ public enum Database { /** The master database we are merging into. */ MASTER(""), /** Their database. */ THEIRS("theirs."), /** Our database. */ OURS("ours."), /** The base database. */ BASE("base."); /** * The prefix for the database. */ private final String mPrefix; /** * Construct with the given prefix. * @param prefix the prefix for this database. */ private Database(final String prefix) { mPrefix = prefix; } /** * @return the prefix for the database. */ public String toString() { return mPrefix; } } /** * The type of results our difference engine gives. * * @author nick <palmer@cs.vu.nl> * */ public enum DiffResult { /** Item was inserted. */ INSERTED, /** Item was deleted. */ DELETED, /** Item was modified. */ MODIFIED, /** No difference. */ SAME } /** * A class which represents metadata for a table. * * @author nick <palmer@cs.vu.nl> * */ static class TableMetadata { /** The name of the table. */ public final String mTableName; /** The key fields in the table. */ public ArrayList<String> mKeyFields; /** The data fields in the table. */ public ArrayList<String> mNormalFields; /** * Construct metadata for the given table. * * @param tableName the name of the table. */ public TableMetadata(final String tableName) { mTableName = tableName; mKeyFields = new ArrayList<String>(); mNormalFields = new ArrayList<String>(); } } /** * @param db the database the table lives in * @param tableName the name of the table * @return metadata for the requeted table. */ public final TableMetadata getTableMetadata( final SQLiteDatabase db, final String tableName) { // TODO: (emilian) put the primary key in order if (!mMetadataCache.containsKey(tableName)) { Cursor c = db.rawQuery( "PRAGMA table_info('" + tableName + "')", null); try { int nameIndex = c.getColumnIndexOrThrow("name"); int pkIndex = c.getColumnIndexOrThrow("pk"); TableMetadata meta = new TableMetadata(tableName); c.moveToFirst(); do { String name = c.getString(nameIndex); if (c.getInt(pkIndex) == 0) { meta.mNormalFields.add(name); } else { meta.mKeyFields.add(name); } } while(c.moveToNext()); if (meta.mKeyFields.size() == 0) { throw new IllegalStateException("The table " + tableName + " has no primary key and is not supported."); } mMetadataCache.put(tableName, meta); } finally { c.close(); } } return mMetadataCache.get(tableName); } /** * Append all strings to the string builder. * @param sb the string builder to append to * @param args the strings to append. */ private void appendAll(final StringBuilder sb, final String... args) { for (String s : args) { sb.append(s); } } /** * Builds a query that joins tableOne and tableTwo on the common primaryKey. * Returns the primary key fields from the first table and the other fields * from the second table followed by a state field with the state value. * * Depending on joinType it will be used to retrieve INSERTED, DELETED or * MODIFIED rows. Sometimes joinType will be LEFT OUTER JOIN and a * corresponding row will not be found for tableTwo, this is why we select * the primary key from tableOne. * * @param tableInfo the metadata for the table * @param tableOne the first table * @param tableTwo the second table * @param joinType the join type for the tables * @param state the state of the difference * @return a string with the primary key join query */ private StringBuilder buildPkJoinQuery(final TableMetadata tableInfo, final String tableOne, final String tableTwo, final String joinType, final DiffResult state) { // TODO: (emilian) field name escaping everywhere StringBuilder qb = new StringBuilder("SELECT "); for (int i = 0; i < tableInfo.mKeyFields.size(); ++i) { String pkColumn = tableInfo.mKeyFields.get(i); appendAll(qb, tableOne, ".", pkColumn, " AS ", pkColumn); qb.append(", "); } for (int i = 0; i < tableInfo.mNormalFields.size(); ++i) { String column = tableInfo.mNormalFields.get(i); appendAll(qb, tableTwo, ".", column, " AS ", column); qb.append(", "); } appendAll(qb, " '", state.name(), "' AS ", COL_DIFF_RESULT); appendAll(qb, " FROM ", tableOne, " ", joinType, " ", tableTwo, " ON "); for (int i = 0; i < tableInfo.mKeyFields.size(); ++i) { String pkColumn = tableInfo.mKeyFields.get(i); if (i > 0) { qb.append(" AND "); } appendAll(qb, tableOne, ".", pkColumn, " = ", tableTwo, ".", pkColumn); } return qb; } /** * Builds a query for items that have been deleted. * @param tableInfo the info on the table * @param tableOne the first table * @param tableTwo the second table * @return an SQL query */ private String buildQueryDeleted(final TableMetadata tableInfo, final String tableOne, final String tableTwo) { StringBuilder qb = buildPkJoinQuery(tableInfo, tableOne, tableTwo, "LEFT OUTER JOIN", DiffResult.DELETED); // only need to test a single column from the second table primary key, // either they will all be null or all non null appendAll(qb, " WHERE ", tableTwo, ".", tableInfo.mKeyFields.get(0), " IS NULL"); return qb.toString(); } /** * Build a query for items that have been inserted. * @param tableInfo the information on the table * @param tableOne the first table * @param tableTwo the second table * @return an SQL query */ private String buildQueryInserted(final TableMetadata tableInfo, final String tableOne, final String tableTwo) { // the inserted rows are deleted if comparing the other way round StringBuilder qb = buildPkJoinQuery(tableInfo, tableTwo, tableOne, "LEFT OUTER JOIN", DiffResult.INSERTED); appendAll(qb, " WHERE ", tableOne, ".", tableInfo.mKeyFields.get(0), " IS NULL"); return qb.toString(); } /** * Build a query for tiems that have been modified. * @param tableInfo the information on the table * @param tableOne the first table * @param tableTwo the second table * @return an SQL query */ private String buildQueryModified(final TableMetadata tableInfo, final String tableOne, final String tableTwo) { StringBuilder qb = buildPkJoinQuery(tableInfo, tableOne, tableTwo, "INNER JOIN", DiffResult.MODIFIED); // we use this to have a valid query when we have no normal fields, it // will return 0 rows but have valid metadata. appendAll(qb, " WHERE 0 == 1"); for (int i = 0; i < tableInfo.mNormalFields.size(); ++i) { String normalColumn = tableInfo.mNormalFields.get(i); appendAll(qb, " OR ", tableOne, ".", normalColumn, " != ", tableTwo, ".", normalColumn); appendAll(qb, " OR ", tableOne, ".", normalColumn, " IS NULL AND ", tableTwo, ".", normalColumn, " IS NOT NULL"); appendAll(qb, " OR ", tableOne, ".", normalColumn, " IS NOT NULL AND ", tableTwo, ".", normalColumn, " IS NULL"); } return qb.toString(); } /** * Construct a diff2 cursor. * @param db the database to work in * @param table the table to difference * @param from the from database * @param to the to database * @return a cursor with the differences. */ public final Cursor diff2(final SQLiteDatabase db, final String table, final Database from, final Database to) { TableMetadata tableInfo = getTableMetadata(db, table); String fullFrom = from.mPrefix + table; String fullTo = to.mPrefix + table; StringBuilder qb = new StringBuilder(); qb.append(buildQueryDeleted(tableInfo, fullFrom, fullTo)); qb.append(" UNION "); qb.append(buildQueryInserted(tableInfo, fullFrom, fullTo)); qb.append(" UNION "); qb.append(buildQueryModified(tableInfo, fullFrom, fullTo)); qb.append(" ORDER BY "); for (int i = 0; i < tableInfo.mKeyFields.size(); ++i) { String pkColumn = tableInfo.mKeyFields.get(i); if (i > 0) { qb.append(", "); } qb.append(pkColumn); } return db.rawQuery(qb.toString(), null); } /** * Construct a diff3 cursor. * @param db the database to work in * @param table the table to diff * @return the diff3 cursor */ public final ThreeWayDiffCursor diff3(final SQLiteDatabase db, final String table) { return new ThreeWayDiffCursor(this, db, table); } }