parser.java

hsql是很有名的嵌入式数据库

        if (e.getType() == Expression.VALUE) {
            return resolveOrderByColumnIndex(e, vcolumn, visiblecols);
        }

        if (e.getType() != Expression.COLUMN) {
            if (union) {
                throw Trace.error(Trace.INVALID_ORDER_BY);
            }

            return e;
        }

        String ecolname   = e.getColumnName();
        String etablename = e.getTableName();

        for (int i = 0, size = visiblecols; i < size; i++) {
            Expression colexpr    = (Expression) vcolumn.get(i);
            String     colalias   = colexpr.getDefinedAlias();
            String     colname    = colexpr.getColumnName();
            String     tablename  = colexpr.getTableName();
            String     filtername = colexpr.getFilterTableName();

            if ((ecolname.equals(colalias) || ecolname.equals(colname))
                    && (etablename == null || etablename.equals(tablename)
                        || etablename.equals(filtername))) {
                colexpr.joinedTableColumnIndex = i;

                return colexpr;
            }
        }

        if (union) {
            throw Trace.error(Trace.INVALID_ORDER_BY, ecolname);
        }

        return e;
    }

    private static Expression resolveOrderByColumnIndex(Expression e,
            HsqlArrayList vcolumn, int visiblecols) throws HsqlException {

        // order by 1,2,3
        if (e.getDataType() == Types.INTEGER) {
            int i = ((Integer) e.getValue(null)).intValue();

            if (0 < i && i <= visiblecols) {
                Expression colexpr = (Expression) vcolumn.get(i - 1);

                colexpr.joinedTableColumnIndex = i - 1;

                return colexpr;
            }
        }

        throw Trace.error(Trace.INVALID_ORDER_BY);
    }

    private TableFilter parseSimpleTableFilter(int type)
    throws HsqlException {

        String alias  = null;
        String token  = tokenizer.getName();
        String schema = session.getSchemaName(tokenizer.getLongNameFirst());
        Table table = database.schemaManager.getTable(session, token, schema);

        checkTableWriteAccess(table, type);

//
        token = tokenizer.getString();

        if (token.equals(Token.T_AS)) {
            alias = tokenizer.getSimpleName();
        } else if (tokenizer.wasSimpleName()) {
            alias = token;
        } else {
            tokenizer.back();
        }

        return new TableFilter(table, alias, false);
    }

    /**
     * Retrieves a TableFilter object newly constructed from the current
     * parse context. <p>
     *
     * @param  outerjoin if the filter is to back an outer join
     * @return a newly constructed TableFilter object
     * @throws  HsqlException if a parsing error occurs
     */
    private TableFilter parseTableFilter(boolean outerjoin)
    throws HsqlException {

        Table       t = null;
        SubQuery    sq;
        TableFilter tf;
        String      sAlias = null;

        if (tokenizer.isGetThis(Token.T_OPENBRACKET)) {
            int brackets = Parser.parseOpenBrackets(tokenizer);

            tokenizer.getThis(Token.T_SELECT);

            // fredt - not correlated - a joined subquery table must resolve fully
            sq = parseSubquery(brackets, null, true, Expression.QUERY);

            tokenizer.getThis(Token.T_CLOSEBRACKET);

            t = sq.table;
        } else {
            String token = tokenizer.getName();
            String schema =
                session.getSchemaName(tokenizer.getLongNameFirst());

            t = database.schemaManager.getTable(session, token, schema);

            session.check(t.getName(), UserManager.SELECT);

            if (t.isView()) {
                sq        = getViewSubquery((View) t);
                sq.select = ((View) t).viewSelect;
                t         = sq.table;
                sAlias    = token;
            }
        }

        // fredt - we removed LEFT from the list of reserved words in Tokenizer
        // to allow LEFT() to work. Thus wasName() will return true for LEFT
        // and we check separately for this token
        String token = tokenizer.getString();

        if (tokenizer.wasLongName()) {
            tokenizer.throwUnexpected();
        }

        if (token.equals(Token.T_LEFT) &&!tokenizer.wasQuotedIdentifier()) {
            tokenizer.back();
        } else if (token.equals(Token.T_AS)
                   &&!tokenizer.wasQuotedIdentifier()) {
            sAlias = tokenizer.getSimpleName();
        } else if (tokenizer.wasSimpleName()) {
            sAlias = token;
        } else {
            tokenizer.back();
        }

        tf = new TableFilter(t, sAlias, outerjoin);

        return tf;
    }

    /**
     *  Add a condition from the WHERE clause.
     *
     * @param  e1
     * @param  e2
     * @return
     */
    private static Expression addCondition(Expression e1, Expression e2) {

        if (e1 == null) {
            return e2;
        } else if (e2 == null) {
            return e1;
        } else {
            return new Expression(Expression.AND, e1, e2);
        }
    }

    /**
     *  Conjuntively adds a condition from the JOIN table ON clause.
     *
     * @param  e1 an existing condition with which e2 is to be combined
     *      in order to form a new conjunction
     * @param  e2 the new condition
     * @param tf the table filter that should become e2's join
     *      table filter
     * @param outer true if join is outer
     * @throws HsqlException if e2 responds that it cannot participate
     *      in the join
     * @return a new Expression object; the conjunction of e1 and e2
     */
    private static Expression addJoinCondition(Expression e1, Expression e2,
            TableFilter tf, boolean outer) throws HsqlException {

        if (!e2.setForJoin(tf, outer)) {
            throw Trace.error(Trace.OUTER_JOIN_CONDITION);
        }

        return addCondition(e1, e2);
    }

    /**
     *  Method declaration
     *
     * @return the Expression resulting from the parse
     * @throws  HsqlException
     */
    Expression parseExpression() throws HsqlException {

        read();

        Expression r = readOr();

        tokenizer.back();

        return r;
    }

    private Expression readAggregate() throws HsqlException {

        boolean distinct = false;
        boolean all      = false;
        int     type     = iToken;

        read();

        String token = tokenizer.getString();

        if (token.equals(Token.T_DISTINCT)) {
            distinct = true;
        } else if (token.equals(Token.T_ALL)) {
            all = true;
        } else {
            tokenizer.back();
        }

        readThis(Expression.OPEN);

        Expression s = readOr();

        readThis(Expression.CLOSE);

        if ((all || distinct)
                && (type == Expression.STDDEV_POP
                    || type == Expression.STDDEV_SAMP
                    || type == Expression.VAR_POP
                    || type == Expression.VAR_SAMP)) {
            throw Trace.error(Trace.INVALID_FUNCTION_ARGUMENT);
        }

        Expression aggregateExp = new Expression(type, s, null);

        aggregateExp.setDistinctAggregate(distinct);

        return aggregateExp;
    }

    /**
     *  Method declaration
     *
     * @return a disjuntion, possibly degenerate
     * @throws  HsqlException
     */
    private Expression readOr() throws HsqlException {

        Expression r = readAnd();

        while (iToken == Expression.OR) {
            int        type = iToken;
            Expression a    = r;

            read();

            r = new Expression(type, a, readAnd());
        }

        return r;
    }

    /**
     *  Method declaration
     *
     * @return a conjunction, possibly degenerate
     * @throws  HsqlException
     */
    private Expression readAnd() throws HsqlException {

        Expression r = readCondition();

        while (iToken == Expression.AND) {
            int        type = iToken;
            Expression a    = r;

            read();

            r = new Expression(type, a, readCondition());
        }

        return r;
    }

    /**
     *  Method declaration
     *
     * @return a predicate, possibly composite
     * @throws  HsqlException
     */
    private Expression readCondition() throws HsqlException {

        switch (iToken) {

            case Expression.NOT : {
                int type = iToken;

                read();

                return new Expression(type, readCondition(), null);
            }
            case Expression.EXISTS : {
                int type = iToken;

                read();
                readThis(Expression.OPEN);

                int brackets = 0;

                if (iToken == Expression.OPEN) {
                    brackets += Parser.parseOpenBrackets(tokenizer) + 1;

                    read();
                }

                Trace.check(iToken == Expression.SELECT,
                            Trace.UNEXPECTED_TOKEN);

                SubQuery sq = parseSubquery(brackets, null, false,
                                            Expression.EXISTS);
                Expression s = new Expression(sq);

                read();
                readThis(Expression.CLOSE);

                return new Expression(type, s, null);
            }
            default : {
                Expression a = readConcat();

                if (iToken == Expression.IS) {
                    read();

                    boolean not;

                    if (iToken == Expression.NOT) {
                        not = true;

                        read();
                    } else {
                        not = false;
                    }

                    Trace.check(iToken == Expression.VALUE && oData == null,
                                Trace.UNEXPECTED_TOKEN);
                    read();

                    // TODO: the TableFilter needs a right hand side to avoid null pointer exceptions...
                    a = new Expression(Expression.IS_NULL, a,
                                       new Expression(Types.NULL, null));

                    if (not) {
                        a = new Expression(Expression.NOT, a, null);
                    }

                    return a;
                }

                boolean not = false;

                if (iToken == Expression.NOT) {
                    not = true;

                    read();
                }

                switch (iToken) {

                    case Expression.LIKE : {
                        a = parseLikePredicate(a);

                        break;
                    }
                    case Expression.BETWEEN : {
                        a = parseBetweenPredicate(a);

                        break;
                    }
                    case Expression.IN : {
                        a = this.parseInPredicate(a);

                        break;
                    }
                    default : {
                        Trace.check(!not, Trace.UNEXPECTED_TOKEN);

                        if (Expression.isCompare(iToken)) {
                            int type = iToken;

                            read();

                            return new Expression(type, a, readConcat());
                        }

                        return a;
                    }
                }

                if (not) {
                    a = new Expression(Expression.NOT, a, null);
                }

                return a;
            }
        }
    }

    private Expression parseLikePredicate(Expression a) throws HsqlException {

        read();

        Expression b      = readTerm();
        Character  escape = null;

        if (sToken.equals(Token.T_ESCAPE)) {
            read();

            Expression c = readTerm();

            Trace.check(c.getType() == Expression.VALUE,
                        Trace.INVALID_ESCAPE);

            String s = (String) c.getValue(session, Types.VARCHAR);

            // boucherb@users 2003-09-25
            // CHECKME:
            // Assert s.length() == 1 for xxxchar comparisons?
            // TODO:
            // SQL200n says binary escape can be 1 or more octets.
            // Maybe we need to retain s and check this in
            // Expression.resolve()?
            if (s == null || s.length() < 1) {
                throw Trace.error(Trace.INVALID_ESCAPE, s);
            }

            escape = new Character(s.charAt(0));
        }

        boolean hasCollation = database.collation.name != null;