/**
*
* Gives the display size for this column.
* @see java.sql.ResultSetMetaData#getColumnDisplaySize
*
*/
public int getColumnDisplaySize(int column)
{//throws SQLException {
// get a column object. Remember, tinySQL uses a column
// offset of zero, but JDBC columns start numbering at one.
// That's why there's a -1 in the columnAtIndex invocation.
//
TsColumn col = tsql.columnAtIndex(column - 1);
return(col.size);
}
/*
* Support function for restartable queries. Continue to
* read the query result. The current state is taken from
* tsResultSet. Proceed until maxFetchSize has reached.
*/
protected internal virtual void contSelectStatement(TsResultSet jrs)
//throws TinySQLException
{
/*
* The table scan here is an iterative tree expansion, similar to
* the algorithm shown in the outline example in Chapter 5.
*/
String columnName, columnString, whereStatus, tableAndAlias;
bool addOK;
int i;
int level = jrs.getLevel();
TinySQLTable jtbl;
TsColumn updateColumn;
java.util.Hashtable <Object, Object> tables = jrs.getTableState();
TinySQLWhere wc = jrs.getWhereClause();
/*
* Create a hashtable to enumerate the tables to be scanned and initialize
* with the first table name.
*/
java.util.Hashtable <Object, Object> tbl_list = new java.util.Hashtable <Object, Object>();
java.util.Vector <Object> t = (java.util.Vector <Object>)tables.get("TABLE_SELECT_ORDER");
String current = (String)t.elementAt(0);
tbl_list.put(current, new java.lang.Integer(1));
/*
* Create a row object; this is added to the ResultSet.
*/
TsRow record = new TsRow();
java.util.Vector <Object> resultSet = new java.util.Vector <Object>();
/*
* Keep retrieving rows until we run out of rows to process.
*/
while (level > 0)
{
bool levelFound = false;
/*
* Find an item within the tbl_list which has the same level as the
* one we're on.
*/
java.util.Enumeration <Object> keys = tbl_list.keys();
while (keys.hasMoreElements())
{
/*
* Get the next element in the "to be processed"
* Hashtable, and find out its level, storing this
* value in currLevel.
*/
String hashkey = (String)keys.nextElement();
int currLevel = ((java.lang.Integer)tbl_list.get(hashkey)).intValue();
/*
* As soon as an element is found whose level is equal to the
* one currently being processed, grab it's primary key (the hashkey),
* flag levelfound, and break!
*/
if (currLevel == level)
{
current = hashkey; levelFound = true; break;
}
}
bool haveRecord = false; // did we get a record or not?
/*
* If a table was found at the current level, then we should
* try to get another row from it.
*/
if (levelFound)
{
/*
* Get the current table
*/
jtbl = (TinySQLTable)tables.get(current);
tableAndAlias = jtbl.table + "->" + jtbl.tableAlias;
if (TinySQLGlobals.WHERE_DEBUG)
{
java.lang.SystemJ.outJ.println("Processing level " + level
+ " table " + tableAndAlias + "\n");
}
/*
* The following code is the start of setting up simple indexes
* for tinySQL. The concept involves creating a new tinySQLCondition
* class, instances of which will be created by tinySQLWhere. At least
* initially only conditions that are equal to a constant will be
* considered. One of these conditions will be stored inside the
* dbfFileTable object. Calls to NextRecord would then have to add
* logic to check to see if an index exists. The presence of a
* complete index would be indicated by a counter that was equal
* to the number of rows in the table. In that case a single get
* would deliver the record numbers required for the where condition.
* The NextRecord function would return these record numbers in
* sequence. If the index did not exist then new values in the
* index Hashtable would be created. None of this code has been
* developed or implemented, let alone tested.
*
*
* if ( wc != (tinySQLWhere)null )
* jtbl.setIndexCondition(wc.getIndexCondition(tableAndAlias));
*/
if (performDebug)
{
java.lang.SystemJ.outJ.println("Selecting records from "
+ jtbl.table);
}
/*
* Skip to the next undeleted record; at some point,
* this will run out of records, and found will be false.
*/
bool found = false;
while (jtbl.NextRecord())
{
/*
* Clear the column values for this table before starting
* to process the next row.
*/
for (i = 0; i < jrs.numcols(); i++)
{
updateColumn = jrs.columnAtIndex(i, true);
updateColumn.clear(tableAndAlias);
}
if (wc != (TinySQLWhere)null)
{
wc.clearValues(tableAndAlias);
}
if (!jtbl.isDeleted())
{
/*
* Evaluate the where clause for each column in the table. If
* it is false, skip to the next row. Otherwise, add the
* column value to the output record.
*/
java.util.Enumeration <Object> cols = jtbl.column_info.keys();
found = true;
whereStatus = "TRUE";
while (cols.hasMoreElements())
{
columnName = tableAndAlias + "."
+ (String)cols.nextElement();
columnString = jtbl.GetCol(columnName);
if (wc != (TinySQLWhere)null)
{
whereStatus = wc.evaluate(columnName, columnString);
if (whereStatus.equals("FALSE"))
{
/*
* This column value caused the where clause to
* be FALSE. Go to the next row in the table.
*/
found = false;
break;
}
}
/*
* Update the ResultSet tsColumn values
*/
jrs.updateColumns(columnName, columnString);
}
/*
* If no where condition has evaluated to false then this
* record is a candidate for output. Break to the next table
* in this case for further WHERE processing.
*/
if (found)
{
break;
}
}
}
if (found)
{
if (TinySQLGlobals.DEBUG)
{
java.lang.SystemJ.outJ.println("Build candidate record.");
}
for (i = 0; i < jrs.numcols(); i++)
{
updateColumn = jrs.columnAtIndex(i, true);
/*
* Evaluate all functions before adding the
* column to the output record.
*/
updateColumn.updateFunctions();
columnString = updateColumn.getString();
if (updateColumn.isNotNull())
{
record.put(updateColumn.name, columnString);
}
else
{
record.remove(updateColumn.name);
}
}
if (performDebug)
{
java.lang.SystemJ.outJ.println("Record is " + record.toString());
}
/*
* If the table we are processing is not the last in
* the list, then we should increment level and loop to the top.
*/
if (level < t.size())
{
/*
* Increment level
*/
level++;
/*
* Add the next table in the list of tables to
* the tbl_list, the Hashtable of "to be processed" tables.
*/
String next_tbl = (String)t.elementAt(level - 1);
tbl_list.put(next_tbl, new java.lang.Integer(level));
}
else
{
/*
* If the table that was just processed is the last in
* the list, then we have drilled down to the bottom;
* all columns have values, and we can add it to the
* result set. The next time through, the program
* will try to read another row at this level; if it's
* found, only columns for the table being read will
* be overwritten in the tsRow.
*
* Columns for the other table will be left alone, and
* another row will be added to the result set. Here
* is the essence of the Cartesian Product which is
* being built here.
*/
haveRecord = true;
}
}
else
{
/*
* We didn't find any more records at this level.
* Reset the record pointer to the top of the table,
* and decrement level. We have hit end of file here.
*/
if (wc != (TinySQLWhere)null)
{
wc.clearValues(tableAndAlias);
}
level--;
jtbl.GoTop();
}
}
else
{
/*
* No tables were found at this level; back up a level
* and see if there's any up there.
*/
level--;
}
/*
* If we got a record, then add it to the result set.
*/
if (haveRecord)
{
/*
* If group functions are involved, add records only after a break,
* which is defined as a change in all of the group columns.
* Otherwise, update the current record.
*/
if (jrs.isGrouped())
{
if (groupBreak)
{
addOK = jrs.addRow((TsRow)record.clone());
if (addOK == false)
{
jrs.setLevel(level);
return;
}
groupBreak = false;
}
else
{
jrs.updateRow((TsRow)record.clone());
}
}
else
{
/*
* No group functions are involved. Just add the record.
*/
addOK = jrs.addRow((TsRow)record.clone());
if (addOK == false)
{
jrs.setLevel(level);
return;
}
}
}
}
/*
* Close all the tables
*/
for (i = 0; i < t.size(); i++)
{
jtbl = (TinySQLTable)tables.get((String)t.elementAt(i));
jtbl.close();
}
/*
* return a result set
*/
jrs.setLevel(0);
}