Examples with ClassLoaderResolver org.datanucleus.ClassLoaderResolver used on opensource projects

Example 26 with ClassLoaderResolver

use of org.datanucleus.ClassLoaderResolver in project datanucleus-rdbms by datanucleus.

the class MappingHelper method getObjectForApplicationIdentity.

/**
 * Get the persistent object instance for a class using application identity defined by the provided result set columns
 * @param ec ExecutionContext
 * @param mapping The mapping in which this is returned
 * @param rs the ResultSet
 * @param resultIndexes indexes in the result set to retrieve
 * @param cmd the AbstractClassMetaData
 * @return the persistent object instance
 */
public static Object getObjectForApplicationIdentity(final ExecutionContext ec, JavaTypeMapping mapping, final ResultSet rs, int[] resultIndexes, AbstractClassMetaData cmd) {
    ClassLoaderResolver clr = ec.getClassLoaderResolver();
    // Abstract class
    if (cmd instanceof ClassMetaData && ((ClassMetaData) cmd).isAbstract() && cmd.getObjectidClass() != null) {
        return getObjectForAbstractClass(ec, mapping, rs, resultIndexes, cmd);
    }
    // Create a ResultSetGetter with the data for the primary key column(s) of this class solely
    int totalMemberCount = cmd.getNoOfManagedMembers() + cmd.getNoOfInheritedManagedMembers();
    final StatementMappingIndex[] statementExpressionIndex = new StatementMappingIndex[totalMemberCount];
    DatastoreClass datastoreClass = mapping.getStoreManager().getDatastoreClass(cmd.getFullClassName(), clr);
    final int[] pkMemberPositions = cmd.getPKMemberPositions();
    int paramIndex = 0;
    for (int i = 0; i < pkMemberPositions.length; ++i) {
        AbstractMemberMetaData mmd = cmd.getMetaDataForManagedMemberAtAbsolutePosition(pkMemberPositions[i]);
        JavaTypeMapping m = datastoreClass.getMemberMapping(mmd);
        statementExpressionIndex[mmd.getAbsoluteFieldNumber()] = new StatementMappingIndex(m);
        int[] expressionsIndex = new int[m.getNumberOfColumnMappings()];
        for (int j = 0; j < expressionsIndex.length; j++) {
            expressionsIndex[j] = resultIndexes[paramIndex++];
        }
        statementExpressionIndex[mmd.getAbsoluteFieldNumber()].setColumnPositions(expressionsIndex);
    }
    final StatementClassMapping resultMappings = new StatementClassMapping();
    for (int i = 0; i < pkMemberPositions.length; i++) {
        resultMappings.addMappingForMember(pkMemberPositions[i], statementExpressionIndex[pkMemberPositions[i]]);
    }
    // TODO Use any other (non-PK) param values
    final FieldManager resultsFM = new ResultSetGetter(ec, rs, resultMappings, cmd);
    Object id = IdentityUtils.getApplicationIdentityForResultSetRow(ec, cmd, null, false, resultsFM);
    Class type = ec.getClassLoaderResolver().classForName(cmd.getFullClassName());
    return ec.findObject(id, new FieldValues() {

        public void fetchFields(DNStateManager sm) {
            sm.replaceFields(pkMemberPositions, resultsFM);
        }

        public void fetchNonLoadedFields(DNStateManager sm) {
            sm.replaceNonLoadedFields(pkMemberPositions, resultsFM);
        }

        public FetchPlan getFetchPlanForLoading() {
            return ec.getFetchPlan();
        }
    }, type, false, true);
}

Example 27 with ClassLoaderResolver

use of org.datanucleus.ClassLoaderResolver in project datanucleus-rdbms by datanucleus.

the class ResultSetGetter method processSubObjectFields.

private Object processSubObjectFields(JavaTypeMapping mapping, Class fieldType, StatementClassMapping relationMappings) {
    ClassLoaderResolver clr = ec.getClassLoaderResolver();
    AbstractClassMetaData relatedCmd = ec.getMetaDataManager().getMetaDataForClass(fieldType, clr);
    if (mapping instanceof ReferenceMapping) {
        // Special case where we have a ReferenceMapping and single implementation with FK
        ReferenceMapping refMapping = (ReferenceMapping) mapping;
        if (refMapping.getMappingStrategy() == ReferenceMapping.PER_IMPLEMENTATION_MAPPING) {
            JavaTypeMapping[] subMappings = refMapping.getJavaTypeMapping();
            if (subMappings != null && subMappings.length == 1) {
                relatedCmd = ec.getMetaDataManager().getMetaDataForClass(subMappings[0].getType(), clr);
                fieldType = clr.classForName(subMappings[0].getType());
            }
        }
    }
    ResultObjectFactory relationROF = new PersistentClassROF(ec, rs, false, ec.getFetchPlan(), relationMappings, relatedCmd, fieldType);
    return relationROF.getObject();
}

Example 28 with ClassLoaderResolver

use of org.datanucleus.ClassLoaderResolver in project datanucleus-rdbms by datanucleus.

the class MapContainsKeyMethod method containsAsSubquery.

/**
 * Method to return an expression for Map.containsKey using a subquery "EXISTS".
 * This is for use when there are "!contains" or "OR" operations in the filter.
 * Creates the following SQL,
 * <ul>
 * <li><b>Map using join table</b>
 * <pre>
 * SELECT 1 FROM JOIN_TBL A0_SUB
 * WHERE A0_SUB.JOIN_OWN_ID = A0.ID AND A0_SUB.JOIN_KEY_ID = {keyExpr}
 * </pre>
 * </li>
 * <li><b>Map with key stored in value</b>
 * <pre>
 * SELECT 1 FROM KEY_TABLE A0_SUB INNER JOIN VALUE_TBL B0 ON ...
 * WHERE B0.JOIN_OWN_ID = A0.ID AND A0_SUB.ID = {keyExpr}
 * </pre>
 * </li>
 * <li><b>Map of value stored in key</b>
 * <pre>
 * SELECT 1 FROM KEY_TABLE A0_SUB
 * WHERE A0_SUB.OWN_ID = A0.ID AND A0_SUB.ID = {keyExpr}
 * </pre>
 * </li>
 * </ul>
 * and returns a BooleanSubqueryExpression ("EXISTS (subquery)")
 * @param stmt SQLStatement
 * @param mapExpr Map expression
 * @param keyExpr Expression for the key
 * @return Contains expression
 */
protected SQLExpression containsAsSubquery(SQLStatement stmt, MapExpression mapExpr, SQLExpression keyExpr) {
    boolean keyIsUnbound = (keyExpr instanceof UnboundExpression);
    String varName = null;
    if (keyIsUnbound) {
        varName = ((UnboundExpression) keyExpr).getVariableName();
        NucleusLogger.QUERY.debug("map.containsKey binding unbound variable " + varName + " using SUBQUERY");
    // TODO What if the variable is declared as a subtype, handle this see CollectionContainsMethod
    }
    RDBMSStoreManager storeMgr = stmt.getRDBMSManager();
    SQLExpressionFactory exprFactory = stmt.getSQLExpressionFactory();
    ClassLoaderResolver clr = stmt.getQueryGenerator().getClassLoaderResolver();
    AbstractMemberMetaData mmd = mapExpr.getJavaTypeMapping().getMemberMetaData();
    AbstractClassMetaData keyCmd = mmd.getMap().getKeyClassMetaData(clr);
    MapTable joinTbl = (MapTable) storeMgr.getTable(mmd);
    SelectStatement subStmt = null;
    if (mmd.getMap().getMapType() == MapType.MAP_TYPE_JOIN) {
        // JoinTable Map
        if (keyCmd == null) {
            // Map<Non-PC, ?>
            subStmt = new SelectStatement(stmt, storeMgr, joinTbl, null, null);
            subStmt.setClassLoaderResolver(clr);
            JavaTypeMapping oneMapping = storeMgr.getMappingManager().getMapping(Integer.class);
            subStmt.select(exprFactory.newLiteral(subStmt, oneMapping, 1), null);
            // Restrict to map owner
            JavaTypeMapping ownerMapping = ((JoinTable) joinTbl).getOwnerMapping();
            SQLExpression ownerExpr = exprFactory.newExpression(subStmt, subStmt.getPrimaryTable(), ownerMapping);
            SQLExpression ownerIdExpr = exprFactory.newExpression(stmt, mapExpr.getSQLTable(), mapExpr.getSQLTable().getTable().getIdMapping());
            subStmt.whereAnd(ownerExpr.eq(ownerIdExpr), true);
            if (keyIsUnbound) {
                // Bind the variable in the QueryGenerator
                keyExpr = exprFactory.newExpression(subStmt, subStmt.getPrimaryTable(), joinTbl.getKeyMapping());
                stmt.getQueryGenerator().bindVariable(varName, null, keyExpr.getSQLTable(), keyExpr.getJavaTypeMapping());
            } else {
                // Add restrict to key
                SQLExpression elemIdExpr = exprFactory.newExpression(subStmt, subStmt.getPrimaryTable(), joinTbl.getKeyMapping());
                subStmt.whereAnd(elemIdExpr.eq(keyExpr), true);
            }
        } else {
            // Map<PC, ?>
            DatastoreClass keyTbl = storeMgr.getDatastoreClass(mmd.getMap().getKeyType(), clr);
            subStmt = new SelectStatement(stmt, storeMgr, keyTbl, null, null);
            subStmt.setClassLoaderResolver(clr);
            JavaTypeMapping oneMapping = storeMgr.getMappingManager().getMapping(Integer.class);
            subStmt.select(exprFactory.newLiteral(subStmt, oneMapping, 1), null);
            // Join to join table
            SQLTable joinSqlTbl = subStmt.join(JoinType.INNER_JOIN, subStmt.getPrimaryTable(), keyTbl.getIdMapping(), joinTbl, null, joinTbl.getKeyMapping(), null, null, true);
            // Restrict to map owner
            JavaTypeMapping ownerMapping = joinTbl.getOwnerMapping();
            SQLExpression ownerExpr = exprFactory.newExpression(subStmt, joinSqlTbl, ownerMapping);
            SQLExpression ownerIdExpr = exprFactory.newExpression(stmt, mapExpr.getSQLTable(), mapExpr.getSQLTable().getTable().getIdMapping());
            subStmt.whereAnd(ownerExpr.eq(ownerIdExpr), true);
            if (keyIsUnbound) {
                // Bind the variable in the QueryGenerator
                keyExpr = exprFactory.newExpression(subStmt, subStmt.getPrimaryTable(), keyTbl.getIdMapping());
                stmt.getQueryGenerator().bindVariable(varName, keyCmd, keyExpr.getSQLTable(), keyExpr.getJavaTypeMapping());
            } else {
                // Add restrict to key
                SQLExpression keyIdExpr = exprFactory.newExpression(subStmt, subStmt.getPrimaryTable(), keyTbl.getIdMapping());
                subStmt.whereAnd(keyIdExpr.eq(keyExpr), true);
            }
        }
    } else if (mmd.getMap().getMapType() == MapType.MAP_TYPE_KEY_IN_VALUE) {
        // Key stored in value table
        AbstractClassMetaData valCmd = mmd.getMap().getValueClassMetaData(clr);
        DatastoreClass valTbl = storeMgr.getDatastoreClass(mmd.getMap().getValueType(), clr);
        JavaTypeMapping ownerMapping = null;
        if (mmd.getMappedBy() != null) {
            ownerMapping = valTbl.getMemberMapping(valCmd.getMetaDataForMember(mmd.getMappedBy()));
        } else {
            ownerMapping = valTbl.getExternalMapping(mmd, MappingType.EXTERNAL_FK);
        }
        AbstractMemberMetaData valKeyMmd = valCmd.getMetaDataForMember(mmd.getKeyMetaData().getMappedBy());
        if (keyCmd == null) {
            subStmt = new SelectStatement(stmt, storeMgr, valTbl, null, null);
            subStmt.setClassLoaderResolver(clr);
            JavaTypeMapping oneMapping = storeMgr.getMappingManager().getMapping(Integer.class);
            subStmt.select(exprFactory.newLiteral(subStmt, oneMapping, 1), null);
            // Restrict to map owner (on value table)
            SQLExpression ownerExpr = exprFactory.newExpression(subStmt, subStmt.getPrimaryTable(), ownerMapping);
            SQLExpression ownerIdExpr = exprFactory.newExpression(stmt, mapExpr.getSQLTable(), mapExpr.getSQLTable().getTable().getIdMapping());
            subStmt.whereAnd(ownerExpr.eq(ownerIdExpr), true);
            if (keyIsUnbound) {
                // Bind the variable in the QueryGenerator
                keyExpr = exprFactory.newExpression(subStmt, subStmt.getPrimaryTable(), valTbl.getMemberMapping(valKeyMmd));
                stmt.getQueryGenerator().bindVariable(varName, null, keyExpr.getSQLTable(), keyExpr.getJavaTypeMapping());
            } else {
                // Add restrict to key
                JavaTypeMapping keyMapping = valTbl.getMemberMapping(valKeyMmd);
                SQLExpression elemIdExpr = exprFactory.newExpression(subStmt, subStmt.getPrimaryTable(), keyMapping);
                subStmt.whereAnd(elemIdExpr.eq(keyExpr), true);
            }
        } else {
            DatastoreClass keyTbl = storeMgr.getDatastoreClass(mmd.getMap().getKeyType(), clr);
            subStmt = new SelectStatement(stmt, storeMgr, keyTbl, null, null);
            subStmt.setClassLoaderResolver(clr);
            JavaTypeMapping oneMapping = storeMgr.getMappingManager().getMapping(Integer.class);
            subStmt.select(exprFactory.newLiteral(subStmt, oneMapping, 1), null);
            // Join to value table
            SQLTable valSqlTbl = subStmt.join(JoinType.INNER_JOIN, subStmt.getPrimaryTable(), keyTbl.getIdMapping(), valTbl, null, valTbl.getMemberMapping(valKeyMmd), null, null, true);
            // Restrict to map owner (on value table)
            SQLExpression ownerExpr = exprFactory.newExpression(subStmt, valSqlTbl, ownerMapping);
            SQLExpression ownerIdExpr = exprFactory.newExpression(stmt, mapExpr.getSQLTable(), mapExpr.getSQLTable().getTable().getIdMapping());
            subStmt.whereAnd(ownerExpr.eq(ownerIdExpr), true);
            if (keyIsUnbound) {
                // Bind the variable in the QueryGenerator
                keyExpr = exprFactory.newExpression(subStmt, subStmt.getPrimaryTable(), keyTbl.getIdMapping());
                stmt.getQueryGenerator().bindVariable(varName, keyCmd, keyExpr.getSQLTable(), keyExpr.getJavaTypeMapping());
            } else {
                // Add restrict to key
                SQLExpression keyIdExpr = exprFactory.newExpression(subStmt, subStmt.getPrimaryTable(), keyTbl.getIdMapping());
                subStmt.whereAnd(keyIdExpr.eq(keyExpr), true);
            }
        }
    } else if (mmd.getMap().getMapType() == MapType.MAP_TYPE_VALUE_IN_KEY) {
        DatastoreClass keyTbl = storeMgr.getDatastoreClass(mmd.getMap().getKeyType(), clr);
        JavaTypeMapping ownerMapping = null;
        if (mmd.getMappedBy() != null) {
            ownerMapping = keyTbl.getMemberMapping(keyCmd.getMetaDataForMember(mmd.getMappedBy()));
        } else {
            ownerMapping = keyTbl.getExternalMapping(mmd, MappingType.EXTERNAL_FK);
        }
        subStmt = new SelectStatement(stmt, storeMgr, keyTbl, null, null);
        subStmt.setClassLoaderResolver(clr);
        JavaTypeMapping oneMapping = storeMgr.getMappingManager().getMapping(Integer.class);
        subStmt.select(exprFactory.newLiteral(subStmt, oneMapping, 1), null);
        // Restrict to map owner (on key table)
        SQLExpression ownerExpr = exprFactory.newExpression(subStmt, subStmt.getPrimaryTable(), ownerMapping);
        SQLExpression ownerIdExpr = exprFactory.newExpression(stmt, mapExpr.getSQLTable(), mapExpr.getSQLTable().getTable().getIdMapping());
        subStmt.whereAnd(ownerExpr.eq(ownerIdExpr), true);
        if (keyIsUnbound) {
            // Bind the variable in the QueryGenerator
            keyExpr = exprFactory.newExpression(subStmt, subStmt.getPrimaryTable(), keyTbl.getIdMapping());
            stmt.getQueryGenerator().bindVariable(varName, keyCmd, keyExpr.getSQLTable(), keyExpr.getJavaTypeMapping());
        } else {
            // Add restrict to key
            JavaTypeMapping keyMapping = keyTbl.getIdMapping();
            SQLExpression keyIdExpr = exprFactory.newExpression(subStmt, subStmt.getPrimaryTable(), keyMapping);
            subStmt.whereAnd(keyIdExpr.eq(keyExpr), true);
        }
    }
    return new BooleanSubqueryExpression(stmt, "EXISTS", subStmt);
}

Example 29 with ClassLoaderResolver

use of org.datanucleus.ClassLoaderResolver in project datanucleus-rdbms by datanucleus.

the class MapContainsKeyMethod method getExpression.

/* (non-Javadoc)
     * @see org.datanucleus.store.rdbms.sql.method.SQLMethod#getExpression(org.datanucleus.store.rdbms.sql.expression.SQLExpression, java.util.List)
     */
public SQLExpression getExpression(SQLStatement stmt, SQLExpression expr, List<SQLExpression> args) {
    if (args == null || args.size() == 0 || args.size() > 1) {
        throw new NucleusException(Localiser.msg("060016", "containsKey", "MapExpression", 1));
    }
    MapExpression mapExpr = (MapExpression) expr;
    SQLExpression keyExpr = args.get(0);
    if (keyExpr.isParameter()) {
        // Key is a parameter so make sure its type is set
        AbstractMemberMetaData mmd = mapExpr.getJavaTypeMapping().getMemberMetaData();
        if (mmd != null && mmd.getMap() != null) {
            Class keyCls = stmt.getQueryGenerator().getClassLoaderResolver().classForName(mmd.getMap().getKeyType());
            stmt.getQueryGenerator().bindParameter(keyExpr.getParameterName(), keyCls);
        }
    }
    SQLExpressionFactory exprFactory = stmt.getSQLExpressionFactory();
    ClassLoaderResolver clr = stmt.getQueryGenerator().getClassLoaderResolver();
    if (expr instanceof MapLiteral) {
        // Literal Map
        MapLiteral lit = (MapLiteral) expr;
        Map map = (Map) lit.getValue();
        JavaTypeMapping m = exprFactory.getMappingForType(boolean.class, true);
        if (map == null || map.size() == 0) {
            return exprFactory.newLiteral(stmt, m, true).eq(exprFactory.newLiteral(stmt, m, false));
        }
        boolean useInExpression = false;
        List<SQLExpression> mapKeyExprs = lit.getKeyLiteral().getKeyExpressions();
        if (mapKeyExprs != null && !mapKeyExprs.isEmpty()) {
            // Make sure the the map key(s) are compatible with the keyExpr
            boolean incompatible = true;
            Class elemtype = clr.classForName(keyExpr.getJavaTypeMapping().getType());
            Iterator<SQLExpression> mapKeyExprIter = mapKeyExprs.iterator();
            while (mapKeyExprIter.hasNext()) {
                SQLExpression mapKeyExpr = mapKeyExprIter.next();
                Class mapKeyType = clr.classForName(mapKeyExpr.getJavaTypeMapping().getType());
                if (keyTypeCompatible(elemtype, mapKeyType)) {
                    incompatible = false;
                    break;
                }
            }
            if (incompatible) {
                // The provided element type isn't assignable to any of the input collection elements!
                return exprFactory.newLiteral(stmt, m, true).eq(exprFactory.newLiteral(stmt, m, false));
            }
            // Check if we should compare using an "IN (...)" expression
            SQLExpression mapKeyExpr = mapKeyExprs.get(0);
            if (mapKeyExpr instanceof StringExpression || mapKeyExpr instanceof NumericExpression || mapKeyExpr instanceof TemporalExpression || mapKeyExpr instanceof CharacterExpression || mapKeyExpr instanceof EnumExpression) {
                useInExpression = true;
            }
        }
        if (useInExpression) {
            // Return "key IN (val1, val2, ...)"
            SQLExpression[] exprs = (mapKeyExprs != null ? mapKeyExprs.toArray(new SQLExpression[mapKeyExprs.size()]) : null);
            return new InExpression(keyExpr, exprs);
        }
        // TODO If keyExpr is a parameter and mapExpr is derived from a parameter ?
        MapKeyLiteral mapKeyLiteral = lit.getKeyLiteral();
        BooleanExpression bExpr = null;
        List<SQLExpression> elementExprs = mapKeyLiteral.getKeyExpressions();
        for (int i = 0; i < elementExprs.size(); i++) {
            if (bExpr == null) {
                bExpr = (elementExprs.get(i)).eq(keyExpr);
            } else {
                bExpr = bExpr.ior((elementExprs.get(i)).eq(keyExpr));
            }
        }
        if (bExpr != null) {
            bExpr.encloseInParentheses();
        }
        return bExpr;
    }
    if (stmt.getQueryGenerator().getCompilationComponent() == CompilationComponent.FILTER) {
        boolean useSubquery = getNeedsSubquery(stmt);
        JoinType joinType = JoinType.INNER_JOIN;
        if (keyExpr instanceof UnboundExpression) {
            // See if the user has defined what should be used
            String varName = ((UnboundExpression) keyExpr).getVariableName();
            String extensionName = "datanucleus.query.jdoql." + varName + ".join";
            String extensionValue = (String) stmt.getQueryGenerator().getValueForExtension(extensionName);
            if (extensionValue != null) {
                if (extensionValue.equalsIgnoreCase("SUBQUERY")) {
                    useSubquery = true;
                } else if (extensionValue.equalsIgnoreCase("INNERJOIN")) {
                    useSubquery = false;
                } else if (extensionValue.equalsIgnoreCase("LEFTOUTERJOIN")) {
                    joinType = JoinType.LEFT_OUTER_JOIN;
                }
            }
        }
        // TODO Check if *this* "containsKey" is negated, not any of them (and remove above check)
        if (useSubquery) {
            return containsAsSubquery(stmt, mapExpr, keyExpr);
        }
        return containsAsJoin(stmt, mapExpr, keyExpr, joinType);
    }
    return containsAsSubquery(stmt, mapExpr, keyExpr);
}

Example 30 with ClassLoaderResolver

use of org.datanucleus.ClassLoaderResolver in project datanucleus-rdbms by datanucleus.

the class MapGetMethod method getAsInnerJoin.

/**
 * Implementation of Map.get() using an inner join to the table representing the map, adding a condition on the key and returning the value.
 * @param stmt SQLStatement
 * @param mapExpr The map expression
 * @param keyValExpr The key value expression
 * @return The value expression
 */
protected SQLExpression getAsInnerJoin(SQLStatement stmt, MapExpression mapExpr, SQLExpression keyValExpr) {
    ClassLoaderResolver clr = stmt.getQueryGenerator().getClassLoaderResolver();
    SQLExpressionFactory exprFactory = stmt.getSQLExpressionFactory();
    JavaTypeMapping m = mapExpr.getJavaTypeMapping();
    AbstractMemberMetaData mmd = m.getMemberMetaData();
    if (mmd != null) {
        MapMetaData mapmd = mmd.getMap();
        if (mapmd.getMapType() == MapType.MAP_TYPE_JOIN) {
            MapTable joinTbl = (MapTable) stmt.getRDBMSManager().getTable(mmd);
            // Add join to join table
            SQLTable joinSqlTbl = stmt.join(JoinType.INNER_JOIN, mapExpr.getSQLTable(), mapExpr.getSQLTable().getTable().getIdMapping(), joinTbl, null, joinTbl.getOwnerMapping(), null, null);
            // Add condition on key
            SQLExpression keyExpr = exprFactory.newExpression(stmt, joinSqlTbl, joinTbl.getKeyMapping());
            stmt.whereAnd(keyExpr.eq(keyValExpr), true);
            // Return value expression
            if (mapmd.getValueClassMetaData(clr) != null) {
                // Persistable value so join to its table
                DatastoreClass valTable = stmt.getRDBMSManager().getDatastoreClass(mapmd.getValueType(), clr);
                SQLTable valueSqlTbl = stmt.join(JoinType.INNER_JOIN, joinSqlTbl, joinTbl.getValueMapping(), valTable, null, valTable.getIdMapping(), null, null);
                return exprFactory.newExpression(stmt, valueSqlTbl, valTable.getIdMapping());
            }
            // Return mapping for the value in the join table
            SQLExpression valueExpr = exprFactory.newExpression(stmt, joinSqlTbl, joinTbl.getValueMapping());
            return valueExpr;
        } else if (mapmd.getMapType() == MapType.MAP_TYPE_KEY_IN_VALUE) {
            // Key stored in value table, so join to value table
            DatastoreClass valTable = stmt.getRDBMSManager().getDatastoreClass(mapmd.getValueType(), clr);
            AbstractClassMetaData valCmd = mapmd.getValueClassMetaData(clr);
            JavaTypeMapping mapTblOwnerMapping;
            if (mmd.getMappedBy() != null) {
                mapTblOwnerMapping = valTable.getMemberMapping(valCmd.getMetaDataForMember(mmd.getMappedBy()));
            } else {
                mapTblOwnerMapping = valTable.getExternalMapping(mmd, MappingType.EXTERNAL_FK);
            }
            SQLTable valSqlTbl = stmt.join(JoinType.INNER_JOIN, mapExpr.getSQLTable(), mapExpr.getSQLTable().getTable().getIdMapping(), valTable, null, mapTblOwnerMapping, null, null);
            // Add condition on key
            JavaTypeMapping keyMapping = valTable.getMemberMapping(valCmd.getMetaDataForMember(mmd.getKeyMetaData().getMappedBy()));
            SQLExpression keyExpr = exprFactory.newExpression(stmt, valSqlTbl, keyMapping);
            stmt.whereAnd(keyExpr.eq(keyValExpr), true);
            // Return value expression
            SQLExpression valueExpr = exprFactory.newExpression(stmt, valSqlTbl, valTable.getIdMapping());
            return valueExpr;
        } else if (mapmd.getMapType() == MapType.MAP_TYPE_VALUE_IN_KEY) {
            // Value stored in key table, so join to key table
            DatastoreClass keyTable = stmt.getRDBMSManager().getDatastoreClass(mapmd.getKeyType(), clr);
            AbstractClassMetaData keyCmd = mapmd.getKeyClassMetaData(clr);
            JavaTypeMapping mapTblOwnerMapping;
            if (mmd.getMappedBy() != null) {
                mapTblOwnerMapping = keyTable.getMemberMapping(keyCmd.getMetaDataForMember(mmd.getMappedBy()));
            } else {
                mapTblOwnerMapping = keyTable.getExternalMapping(mmd, MappingType.EXTERNAL_FK);
            }
            SQLTable keySqlTbl = stmt.join(JoinType.INNER_JOIN, mapExpr.getSQLTable(), mapExpr.getSQLTable().getTable().getIdMapping(), keyTable, null, mapTblOwnerMapping, null, null);
            // Add condition on key
            SQLExpression keyExpr = exprFactory.newExpression(stmt, keySqlTbl, keyTable.getIdMapping());
            stmt.whereAnd(keyExpr.eq(keyValExpr), true);
            // Return value expression
            JavaTypeMapping valueMapping = keyTable.getMemberMapping(keyCmd.getMetaDataForMember(mmd.getValueMetaData().getMappedBy()));
            SQLExpression valueExpr = exprFactory.newExpression(stmt, keySqlTbl, valueMapping);
            return valueExpr;
        }
    }
    throw new NucleusException("Map.get() for the filter is not supported for " + mapExpr + " with an argument of " + keyValExpr + ". Why not contribute support for it?");
}