Field Detail

• probeValues

  protected DataValueDescriptor[] probeValues

  The values with which we will probe the table.

• origProbeValues

  protected DataValueDescriptor[] origProbeValues

  The values with which we will probe the table, as they were passed to the constructor. We need to keep them unchanged in case the result set is reused when a statement is re-executed (see DERBY-827).

• probeValIndex

  protected int probeValIndex

  0-based position of the next value to lookup w.r.t. the probe values list.

• sortRequired

  private int sortRequired

  Indicator as to which type of sort we need: ASCENDING, DESCENDING, or NONE (NONE is represented by "RowOrdering.DONTCARE" and is used for cases where all necessary sorting occurred at compilation time).

• skipNextScan

  private boolean skipNextScan

  Tells whether or not we should skip the next attempt to (re)open the scan controller. If it is true it means that the previous call to initStartAndStopKey() did not find a new probe value, which means that the probe list is exhausted and we shouldn't perform a scan.

Constructor Detail

• MultiProbeTableScanResultSet

  MultiProbeTableScanResultSet​(long conglomId,
                               StaticCompiledOpenConglomInfo scoci,
                               Activation activation,
                               int resultRowTemplate,
                               int resultSetNumber,
                               GeneratedMethod startKeyGetter,
                               int startSearchOperator,
                               GeneratedMethod stopKeyGetter,
                               int stopSearchOperator,
                               boolean sameStartStopPosition,
                               Qualifier[][] qualifiers,
                               DataValueDescriptor[] probingVals,
                               int sortRequired,
                               java.lang.String tableName,
                               java.lang.String userSuppliedOptimizerOverrides,
                               java.lang.String indexName,
                               boolean isConstraint,
                               boolean forUpdate,
                               int colRefItem,
                               int indexColItem,
                               int lockMode,
                               boolean tableLocked,
                               int isolationLevel,
                               boolean oneRowScan,
                               double optimizerEstimatedRowCount,
                               double optimizerEstimatedCost)
                        throws StandardException

  Constructor. Just save off the relevant probing state and pass everything else up to TableScanResultSet.

  Throws:

  StandardException - thrown on failure to open

  See Also:

  ResultSetFactory.getMultiProbeTableScanResultSet(org.apache.derby.iapi.sql.Activation, long, int, int, int, org.apache.derby.iapi.services.loader.GeneratedMethod, int, org.apache.derby.iapi.services.loader.GeneratedMethod, int, boolean, org.apache.derby.iapi.store.access.Qualifier[][], org.apache.derby.iapi.types.DataValueDescriptor[], int, java.lang.String, java.lang.String, java.lang.String, boolean, boolean, int, int, int, boolean, int, boolean, double, double)

Method Detail

• openCore

  public void openCore()
                throws StandardException

  Description copied from class: TableScanResultSet
  open a scan on the table. scan parameters are evaluated at each open, so there is probably some way of altering their values...

  Specified by:

  openCore in interface NoPutResultSet

  Overrides:

  openCore in class TableScanResultSet

  Throws:

  StandardException - thrown on failure to open

  See Also:

  NoPutResultSet.openCore()

• reopenCore

  public void reopenCore()
                  throws StandardException

  Description copied from class: TableScanResultSet
  Reopen a table scan. Here we take advantage of the reopenScan() interface on scanController for optimimal performance on joins where we are an inner table.

  Specified by:

  reopenCore in interface NoPutResultSet

  Overrides:

  reopenCore in class TableScanResultSet

  Throws:

  StandardException - thrown on failure to open

  See Also:

  NoPutResultSet.reopenCore()

• reopenCore

  private void reopenCore​(boolean forNextProbe)
                   throws StandardException

  There are two scenarios for which we reopen this kind of scan: A - The first is for join processing. In this case we have a(nother) row from some outer table and we want to reopen this scan to look for rows matching the new outer row. B - The second is for multi-probing. Here we want to reopen the scan on this table to look for rows matching the next value in the probe list. If we are reopening the scan for scenario A (join processing) then we need to reset our position within the probe list. If we are reopening the scan for scenario B then we do *not* want to reset our position within the probe list because that position tells us where to find the next probe value. That said, this method does the work of reopenCore() using the received boolean to determine which of the two scenarios we are in. Note that if our current position (i.e. the value of probeValIndex) is beyond the length of the probe list then we know that we are reopening the scan for scenario A. Or put another away, we should never get here for scenario B if probeValIndex is greater than or equal to the length of the probe list. The reason is that the call to reopenCore() for scenario B will only ever happen when moreInListVals() returns true--and in that case we know that probeValIndex will be less than the length of the probeValues. But the opposite is not true: i.e. it is *not* safe to say that a probeValIndex which is less than the length of probe list is always for scenario B. That's not true because it's possible that the join to which this scan belongs is a "oneRowRightSide" join, meaning that this, the "right" side scan, will be "interrupted" after we return a single row for the current outer row. If we then come back with a new outer row we need to reset our position-- even though probeValIndex will be less than probeValues.length in that case. DERBY-3603.

  Throws:

  StandardException

• reopenScanController

  protected void reopenScanController()
                               throws StandardException

  Reopen the scan controller

  Overrides:

  reopenScanController in class TableScanResultSet

  Throws:

  StandardException - thrown on failure to open

• initStartAndStopKey

  void initStartAndStopKey()
                    throws StandardException

  Initialize the start key and the stop key used in the scan. Both keys will be set to the probe value. If no new probe value was found (the probe list was exhausted), the flag skipNextScan will be true when the method returns to prevent a new scan from being reopened with a missing or incorrect probe value.

  Overrides:

  initStartAndStopKey in class TableScanResultSet

  Throws:

  StandardException

• skipScan

  protected boolean skipScan​(ExecIndexRow startPosition,
                             ExecIndexRow stopPosition)
                      throws StandardException

  Check if the scan should be skipped. It should be skipped if (1) initStartAndStopKey() exhausted the probe list, or (2) the scan should return no results because of nulls in the start key or stop key. See NoPutResultSetImpl.skipScan(ExecIndexRow,ExecIndexRow) for details about (2).

  Overrides:

  skipScan in class NoPutResultSetImpl

  Parameters:

  startPosition - the key on which to start the scan

  stopPosition - the key on which to stop the scan

  Returns:

  true if scan should be skipped, false otherwise

  Throws:

  StandardException

• getNextRowCore

  public ExecRow getNextRowCore()
                         throws StandardException

  Return the next row (if any) from the scan (if open). More specifically we do the following: 1 - See if we have a row to read from the current scan position. If so, return that row (done). 2 - If there are no more rows to read from the current scan position AND if there are more probe values to look at, then a) reposition the scan using the next probe value as the start/stop key and b) go back to step 1. Otherwise proceed to step 3. 3 - Return null (no more rows). Note that step 1 is important for cases where multiple rows in this table match a single probe value. In such a scenario we have to be sure that we do *not* move on to the next probe value until we have returned all of the rows for the _current_ probe value.

  Specified by:

  getNextRowCore in interface NoPutResultSet

  Overrides:

  getNextRowCore in class TableScanResultSet

  Returns:

  the next row in the result

  Throws:

  StandardException - thrown on failure to get next row

  See Also:

  NoPutResultSet.getNextRowCore()

• close

  public void close()
             throws StandardException

  Description copied from class: TableScanResultSet
  If the result set has been opened, close the open scan.

  Specified by:

  close in interface ResultSet

  Overrides:

  close in class TableScanResultSet

  Throws:

  StandardException - on error

  See Also:

  ResultSet.close()

• moreInListVals

  private boolean moreInListVals()

  Figure out whether or not we can (re-)position the scan controller based on the next value in probeValues. This will return false when we have exhausted the probe list (i.e. when we've gone through all of the values).

• getNextProbeValue

  private DataValueDescriptor getNextProbeValue()

  Return the next non-duplicate value from the probe list. Assumption is that the list is sorted so that duplicates appear next to each other, and that probeValIndex is the index of the next value. If we've exhausted the probe list then just return null.