TDbiDBProxy.cxx

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//////////////////////////////////////////////////////////////////////////
////////////////////////////     ROOT API     ////////////////////////////
//////////////////////////////////////////////////////////////////////////


#include <memory>
#include <cassert>

#include "TCollection.h"
#include "TList.h"
#include "TSQLColumnInfo.h"
#include "TSQLStatement.h"
#include "TSQLServer.h"
#include "TSQLTableInfo.h"
#include "TString.h"

#include "DbiDetector.hxx"
#include "DbiSimFlag.hxx"
#include "TDbiDBProxy.hxx"
#include "TDbiCascader.hxx"
#include "TDbiFieldType.hxx"
#include "TDbiInRowStream.hxx"
#include "TDbiServices.hxx"
#include "TDbiString.hxx"
#include "TDbiStatement.hxx"
#include "TDbiTableMetaData.hxx"
#include "TDbiTimerManager.hxx"
#include "TDbiValidityRec.hxx"
#include <TSK_DBI_Log.hxx>
#include <MsgFormat.h>
using std::endl;
#include "TVldContext.hxx"

#include "UtilString.hxx"

ClassImp(TDbiDBProxy)

//   Typedefs
//   ********

//   Definition of static data members
//   *********************************


//    Definition of all member functions (static or otherwise)
//    *******************************************************
//
//    -  ordered: ctors, dtor, operators then in alphabetical order.


//.....................................................................

TDbiDBProxy::TDbiDBProxy(TDbiCascader& cascader,
                       const string& tableName,
                       const TDbiTableMetaData* metaData,
                       const TDbiTableMetaData* metaValid,
                       const TDbiTableProxy* tableProxy) :
fCascader(cascader),
fMetaData(metaData),
fMetaValid(metaValid),
fTableName(tableName),
fTableProxy(tableProxy)
{
//
//
//  Purpose:  Constructor
//
//  Arguments:
//  cascader   in   Reference to one and only cascader
//  tableName  in   Table name.
//  metaData   in   Meta data for main table.
//  metaValid  in   Meta data for validity.
//  tableProxy in   Owning TDbiTableProxy.
//


}

//.....................................................................

TDbiDBProxy::~TDbiDBProxy() {
//
//
//  Purpose: Destructor


  SK_DBI_Trace( "Destroying TDbiDBProxy "
                          << fTableName << " at " << this
                          << "  ");

}
//.....................................................................

void TDbiDBProxy::FindTimeBoundaries(const TVldContext& vc,
                                    const TDbi::Task& task,
                                    UInt_t dbNo,
                                    const TDbiValidityRec& lowestPriorityVrec,
                                    Bool_t resolveByCreationDate,
                                    TVldTimeStamp& start,
                                    TVldTimeStamp& end) const {
//
//
//  Purpose: Find next time boundaries beyond standard time gate.
//
//  Arguments:
//    vc                    in    The Validity Context for the query.
//    task                  in    The task of the query.
//    dbNo                  in    Database number in cascade (starting at 0).
//    lowestPriorityVrec    in    Lowest priority VLD in the time gate
//    resolveByCreationDate in  The method for resolving VLDs:
//                                 if true use CREATIONDATE (MINOS scheme)
//                                 if false use EPOCH,TIMESTART,INSERTDATE (T2K scheme)
//    start                 out   Lower time boundary or TVldTimeStamp(0,0) if none
//    end                   out   Upper time boundary or TVldTimeStamp(0x7FFFFFFF,0) if none
//
//  Specification:-
//  =============
//
//  o Find the next time boundary (either TIMESTART or TIMEEND)
//    outside the current time gate that is potentionally of higher priority.
//
//  Explanation:-
//  ===========
//
//
//  In oder to keep the number of VLDs to a manageable level when doing a
//  Standard Context query, a time gate around the context is imposed and
//  any VLD rejected if it does not overlap the query. However, this
//  implies that the maximum validity of the query result set is also
//  limited by the time gate and hence the interface will again have to
//  query the database when a context outside the time gate is
//  requested. This function attempts to open up the validity of the
//  result set by looking for the nearest start or end of a VLD outside
//  the time gate that is of higher priority. In MINOS, priority is just
//  CREATIONDATE, so the function just looks for VLDs with a higher
//  CREATIONDATE.  For T2K the priority scheme is more complicated:
//  EPOCH,TIMESTART,INSERTDATE and it is not possible to construct a SQL
//  query that only considers higher priority VLDs so the function makes a
//  simplification and only rejects VLDs with a lower EPOCH number.  The
//  consequence of this is that it may accept VLDs that are of a lower
//  priority than the current one and hence the result set validity does
//  not get opened up to its full extent.  All this means is that the
//  interface will have to make another query earlier that it need do but
//  at least it will not miss a VLD boundary and should still keep the current
//  results longer than it would have if this function had not been
//  called.

  SK_DBI_Verbose( "FindTimeBoundaries for table " <<  fTableName
                            << " context " << vc
                            << " task " << task
                            << " Lowest priority VLD creation date: " <<  lowestPriorityVrec.GetCreationDate()
                            << " and EPOCH: " << lowestPriorityVrec.GetEpoch()
                            << " resolve by: " << ( resolveByCreationDate ? "CREATIONDATE" : "EPOCH")
                            << " database " << dbNo << "  ");

//  Set the limits wide open
  start = TVldTimeStamp(0,0);
  end   = TVldTimeStamp(0x7FFFFFFF,0);

//  Construct a Time Gate on the current date.

  const TVldTimeStamp curVTS = vc.GetTimeStamp();
  Int_t timeGate = TDbi::GetTimeGate(this->GetTableName());
  time_t vcSec = curVTS.GetSec() - timeGate;
  TVldTimeStamp startGate(vcSec,0);
  vcSec += 2*timeGate;
  TVldTimeStamp endGate(vcSec,0);
  string startGateString(TDbi::MakeDateTimeString(startGate));
  string endGateString(TDbi::MakeDateTimeString(endGate));

// Extract information for TVldContext.

  DbiDetector::Detector_t    detType(vc.GetDetector());
  DbiSimFlag::SimFlag_t       simFlg(vc.GetSimFlag());

// Use an auto_ptr to manage ownership of TDbiStatement and TSQLStatement
  auto_ptr<TDbiStatement> stmtDb(fCascader.CreateStatement(dbNo));

  for (int i_limit =1; i_limit <= 4; ++i_limit ) {
    TDbiString sql("select ");
    if ( i_limit == 1 ) sql  << "min(TIMESTART) from " << fTableName
                             << "VLD where TIMESTART > '" << endGateString << "' ";
    if ( i_limit == 2 ) sql  << "min(TIMEEND) from " << fTableName
                             << "VLD where TIMEEND > '" << endGateString  << "' ";
    if ( i_limit == 3 ) sql  << "max(TIMESTART) from " << fTableName
                             << "VLD where TIMESTART < '" << startGateString << "' ";
    if ( i_limit == 4 ) sql  << "max(TIMEEND) from " << fTableName
                             << "VLD where TIMEEND < '" << startGateString  << "' ";
    sql << " and DetectorMask & " << static_cast<unsigned int>(detType)
        << " and SimMask & " << static_cast<unsigned int>(simFlg)
        << " and  Task = " << task;
    if ( resolveByCreationDate )
         sql << " and CREATIONDATE >= '" << TDbi::MakeDateTimeString(lowestPriorityVrec.GetCreationDate()) << "'";
    else sql << " and EPOCH >= " << lowestPriorityVrec.GetEpoch();
    SK_DBI_Verbose( "  FindTimeBoundaries query no. " << i_limit
                          << " SQL:" <<sql.c_str() << "  ");

    auto_ptr<TSQLStatement> stmt(stmtDb->ExecuteQuery(sql.c_str()));


//  If the query returns data, convert to a time stamp and trim the limits
    TString date;
    if ( ! stmt.get() || ! stmt->NextResultRow() || stmt->IsNull(0) ) continue;
    date = stmt->GetString(0);
    if ( date.IsNull() ) continue;
    TVldTimeStamp ts(TDbi::MakeTimeStamp(date.Data()));
    SK_DBI_Verbose( "  FindTimeBoundaries query result: " << ts << "  ");
    if ( i_limit <= 2 && ts < end   ) end   = ts;
    if ( i_limit >= 3 && ts > start ) start = ts;

  }

  SK_DBI_Verbose( "FindTimeBoundaries for table " <<  fTableName
                        << " found " << start << " .. " << end << "  ");

}
//.....................................................................

UInt_t TDbiDBProxy::GetNumDb() const {
//
//
//  Purpose:  Return the number of databases in the cascade.

  return fCascader.GetNumDb();

}
//.....................................................................

Bool_t TDbiDBProxy::HasEpoch() const {
  return fMetaValid->HasEpoch();
}
//.....................................................................

TDbiInRowStream*  TDbiDBProxy::QueryAllValidities (UInt_t dbNo,UInt_t seqNo) const {
//
//
//  Purpose:  Apply all validities query to database..
//
//  Arguments:
//    dbNo         in    Database number in cascade (starting at 0).
//    seqNo        in    Just this SEQNO if >0 or all if 0 [default: 0]
//
//  Return:    New TDbiResultSet object.
//             NB  Caller is responsible for deleting..
//
//  Contact:   N. West
//
//  Specification:-
//  =============
//
//  o Ask for every row in associated validity range table and return
//    query results qualifying selection by fSqlCondition if defined.

//  Program Notes:-
//  =============

//  This function is provided to support database maintenance
//  rather than standard TDbi related I/O


// Generate SQL for validity table.

  TDbiString sql;

  sql << "select * from " << fTableName << "VLD";
  if ( fSqlCondition != "" ) sql << " where " << fSqlCondition;
  if ( seqNo > 0 ) {
    if ( fSqlCondition == "" ) sql << " where ";
    else                       sql << " and ";
    sql << "seqno = " << seqNo;
  }
  sql  << ";" << '\0';

  SK_DBI_Verbose( "Database: " << dbNo
                         << " query: " << sql.GetString() << "  ");

//  Apply query and return result..

  TDbiStatement* stmtDb = fCascader.CreateStatement(dbNo);
  return new TDbiInRowStream(stmtDb,sql,fMetaValid,fTableProxy,dbNo);

}



//.....................................................................

TDbiInRowStream*  TDbiDBProxy::QuerySeqNo(UInt_t seqNo, UInt_t dbNo) const {
//
//
//  Purpose:  Apply sequence query to database..
//
//  Arguments:
//    seqNo        in    The sequence number for the query.
//    dbNo         in    Database number in cascade (starting at 0).
//
//  Return:    New TDbiResultSet object.
//             NB  Caller is responsible for deleting..
//
//  Contact:   N. West
//
//  Specification:-
//  =============
//
//  o Apply sequence query to table and return query results

//  Program Notes:-
//  =============

//  None..

// Generate SQL.

  TDbiTimerManager::gTimerManager.RecMainQuery();
  TDbiString sql;
  sql << "select * from " << fTableName << " where "
      << "    SEQNO= " << seqNo;

  if ( TDbiServices::OrderContextQuery() ) sql << " order by ROW_COUNTER";

  SK_DBI_Verbose( "Database: " << dbNo
                         << " SeqNo query: " << sql.c_str() << "  ");

//  Apply query and return result..

  TDbiStatement* stmtDb = fCascader.CreateStatement(dbNo);
  return new TDbiInRowStream(stmtDb,sql,fMetaData,fTableProxy,dbNo);

}

//.....................................................................

TDbiInRowStream*  TDbiDBProxy::QuerySeqNos(SeqList_t& seqNos,
                                       UInt_t dbNo,
                                       const string& sqlData,
                                       const string& fillOpts) const {
//
//
//  Purpose:  Apply query for a list of sequence numbers to database..
//
//  Arguments:
//    seqNos       in    The vector of sequence numbers for the query.
//                       Should be in acsending order, see Program Notes
//    dbNo         in    Database number in cascade (starting at 0).
//    sqlData      in    Optional SQL extension to secondary query.
//    fillOpts     in    Optional fill options (available to TDbiTableRow
//                       objects when filling.
//
//  Return:    New TDbiResultSet object.
//             NB  Caller is responsible for deleting..
//
//  Contact:   N. West
//
//  Specification:-
//  =============
//
//  o Apply sequence query to table and return query results

//  Program Notes:-
//  =============

//  Where possible the SQL query is kept to a minimm by using
//  `BETWEEN' comparison to bracket ranges of numbers.

// Generate SQL.

  if ( seqNos.size() == 0 ) return 0;

  TDbiTimerManager::gTimerManager.RecMainQuery();
  TDbiString sql;
  sql << "select * from " << fTableName << " where ";

  if ( sqlData != "" ) sql << "( ";
  Bool_t first = kTRUE;
  SeqList_t::const_iterator itr1 = seqNos.begin();

  while ( itr1 != seqNos.end() ) {
    UInt_t seq1 = *itr1;
    UInt_t seq2 = seq1;
    SeqList_t::const_iterator itr2 = itr1;
    while ( itr2 != seqNos.end() && seq2 == *itr2 ) {
      ++itr2;
      ++seq2;
    }
    if ( first ) {
      first = kFALSE;
    }
    else {
      sql << "or ";
    }
    if ( seq2 > seq1 + 1) {
      sql << "SEQNO between " << seq1 << " and " << seq2-1 << ' ';
      itr1 = itr2;
    }
    else {
      sql << "SEQNO = " << seq1 << ' ';
      ++itr1;
    }
  }

  if ( sqlData != "" ) sql << ")  and " << "(" << sqlData << ")" << " ";

  sql << "order by SEQNO";

  if ( TDbiServices::OrderContextQuery() ) sql << ",ROW_COUNTER";

  SK_DBI_Verbose( "Database: " << dbNo
                         << " SeqNos query: " << sql.c_str() << "  ");

//  Apply query and return result..

  TDbiStatement* stmtDb = fCascader.CreateStatement(dbNo);
  return new TDbiInRowStream(stmtDb,sql,fMetaData,fTableProxy,dbNo,fillOpts);

}

//.....................................................................

TDbiInRowStream*  TDbiDBProxy::QueryValidity (const TVldContext& vc,
                                          const TDbi::Task& task,
                                          UInt_t dbNo) const {
//
//
//  Purpose:  Apply validity query to database..
//
//  Arguments:
//    vc           in    The Validity Context for the query.
//    task         in    The task of the query.
//    dbNo         in    Database number in cascade (starting at 0).
//
//  Return:    New TDbiResultSet object.
//             NB  Caller is responsible for deleting..
//
//  Contact:   N. West
//
//  Specification:-
//  =============
//
//  o Apply query to associated validity range table and return query
//    results qualifying selection by fSqlCondition if defined.

//  Program Notes:-
//  =============

//  Rather than search over the full table this function places
//  a time gate round the context time and then trims any validity
//  range returned to this gate.  See FindTimeBoundaries to get a
//  more accurate validity range.

//  Construct a search window on the current date.

  const TVldTimeStamp curVTS = vc.GetTimeStamp();
  Int_t timeGate = TDbi::GetTimeGate(this->GetTableName());
  time_t vcSec = curVTS.GetSec() - timeGate;
  TVldTimeStamp startGate(vcSec,0);
  vcSec += 2*timeGate;
  TVldTimeStamp endGate(vcSec,0);

// Extract information for TVldContext.

  string startGateString(TDbi::MakeDateTimeString(startGate));
  string endGateString(TDbi::MakeDateTimeString(endGate));
  DbiDetector::Detector_t    detType(vc.GetDetector());
  DbiSimFlag::SimFlag_t       simFlg(vc.GetSimFlag());

// Generate SQL for context.

  TDbiString context;
  context << "    TimeStart <= '" << endGateString << "' "
          << "and TimeEnd    > '" << startGateString << "' "
          << "and DetectorMask & " << static_cast<unsigned int>(detType)
          << " and SimMask & " << static_cast<unsigned int>(simFlg);

//  Apply query and return result..

  return this->QueryValidity(context.GetString(),task,dbNo);

}
//.....................................................................

TDbiInRowStream*  TDbiDBProxy::QueryValidity (const string& context,
                                          const TDbi::Task& task,
                                          UInt_t dbNo) const {
//
//
//  Purpose:  Apply validity query to database..
//
//  Arguments:
//    context      in    The Validity Context (see TDbiSqlContext)
//    task         in    The task of the query.
//    dbNo         in    Database number in cascade (starting at 0).
//
//  Return:    New TDbiResultSet object.
//             NB  Caller is responsible for deleting..
//
//  Contact:   N. West
//
//  Specification:-
//  =============
//
//  o Apply query to associated validity range table and return query
//    results qualifying selection by fSqlCondition if defined.


// Generate SQL for validity table.

  TDbiString sql;

// In the MINOS  scheme queries are  ordered by creation date (the later the better)
// but if the table has an EPOCH column then the T2K scheme is used (EPOCH,TIMESTART,INSERTDATE)

  string orderByName("CREATIONDATE desc");
  if ( this->HasEpoch() ) orderByName = "EPOCH desc,TIMESTART desc,INSERTDATE desc";
  sql << "select * from " << fTableName << "VLD"
      << " where " ;
  if ( fSqlCondition != ""
      ) sql << fSqlCondition << " and ";
  sql << context;
  if ( task != TDbi::kAnyTask
       ) sql << " and  Task = " << task
             << " order by " << orderByName << ";" << '\0';

  SK_DBI_Verbose( "Database: " << dbNo
                         << " query: " << sql.c_str() << "  ");

//  Apply query and return result..

  TDbiStatement* stmtDb = fCascader.CreateStatement(dbNo);
  return new TDbiInRowStream(stmtDb,sql,fMetaValid,fTableProxy,dbNo);

}
//.....................................................................

TDbiInRowStream*  TDbiDBProxy::QueryValidity (UInt_t seqNo,
                                          UInt_t dbNo) const {
//
//
//  Purpose:  Apply validity query to database..
//
//  Arguments:
//    seqNo        in    The SEQNO of the validity rec.
//
//  Return:    New TDbiResultSet object.
//             NB  Caller is responsible for deleting..
//
//  Contact:   N. West
//
//  Specification:-
//  =============
//
//  o Apply query to associated validity range table and return query
//    results qualifying selection by fSqlCondition if defined.


// Generate SQL for validity table.

  TDbiString sql;
  sql << "select * from " << fTableName << "VLD where ";
  if ( fSqlCondition != "" ) sql << fSqlCondition << " and ";
  sql << "SEQNO = " << seqNo << ";";

  SK_DBI_Verbose( "Database: " << dbNo
                         << " SEQNO query: " << sql.c_str() << "  ");

//  Apply query and return result..

  TDbiStatement* stmtDb = fCascader.CreateStatement(dbNo);
  return new TDbiInRowStream(stmtDb,sql,fMetaValid,fTableProxy,dbNo);

}

//.....................................................................

Bool_t TDbiDBProxy::RemoveSeqNo(UInt_t seqNo,
                               UInt_t dbNo) const {
//
//
//  Purpose:  Remove sequence number in main and auxiliary tables.
//
//  Arguments:
//    seqNo        in    The sequence number to be removed.
//    dbNo         in    Database number in cascade (starting at 0).
//
//  Return:    kTRUE if output successful,otherwise kFALSE.
//
//  Contact:   N. West
//
//  Specification:-
//  =============
//
//  o Remove sequence number in main and auxiliary tables.

//  Program Notes:-
//  =============

//  None.


// Generate SQL to remove SeqNo in main table.
  TDbiString sql;
  sql  << "delete from  " << fTableName
       << " where SEQNO = " << seqNo << ";"
       << '\0';

  SK_DBI_Verbose( "Database: " << dbNo
                        << " RemoveSeqNo SQL: " << sql.c_str() << "  ");

//  Apply query.
  auto_ptr<TDbiStatement> stmtDb(fCascader.CreateStatement(dbNo));
  if ( ! stmtDb.get() ) return false;
  if ( ! stmtDb->ExecuteUpdate(sql.c_str()) || stmtDb->PrintExceptions() ) {
       SK_DBI_Severe( "SQL: " << sql.c_str()
                           << " Failed. " << "  ");
    return false;
  }

// Generate SQL to remove SeqNo in validity table.
  sql.GetString().erase();
  sql << "delete from  " << fTableName
      << "VLD where SEQNO = " << seqNo << ";"
      << '\0';

  SK_DBI_Verbose( "Database: " << dbNo
                        << " RemoveSeqNo SQL: " << sql.c_str() << "  ");

//  Apply query.
  if (  ! stmtDb->ExecuteUpdate(sql.c_str()) ||  stmtDb->PrintExceptions() ) {
       SK_DBI_Severe( "SQL: " << sql.c_str()
                           << " Failed. " << "  ");
    return false;
  }

  return true;

}

//.....................................................................

Bool_t TDbiDBProxy::ReplaceInsertDate(const TVldTimeStamp& ts,
                                     UInt_t SeqNo,
                                     UInt_t dbNo) const{
//
//
//  Purpose:  Replace insertion date for row in auxiliary table.
//
//  Arguments:
//    ts           in    Time stamp for new insertion date.
//    SeqNo        in    The sequence number of the row to be replaced.
//    dbNo         in    Database number in cascade (starting at 0).
//
//  Return:    kTRUE if output successful,otherwise kFALSE.
//
//  Contact:   N. West


// Generate SQL.
  TDbiString sql;
  sql << "update  " << fTableName
      << "VLD set INSERTDATE = \'" << ts.AsString("s")
      << "\' where SEQNO = " << SeqNo << ";"
      << '\0';

  SK_DBI_Verbose( "Database: " << dbNo
                        << " ReplaceInsertDate SQL: "
                        << sql.c_str() << "  ");

//  Apply query.
  auto_ptr<TDbiStatement> stmtDb(fCascader.CreateStatement(dbNo));
  if ( ! stmtDb.get() ) return false;
  if (! stmtDb->ExecuteUpdate(sql.c_str()) || stmtDb->PrintExceptions() ) {
       SK_DBI_Severe( "SQL: " << sql.c_str()
                           << " Failed. " << "  ");
    return false;
  }

  return true;

}
//.....................................................................

Bool_t TDbiDBProxy::ReplaceSeqNo(UInt_t oldSeqNo,
                                UInt_t newSeqNo,
                                UInt_t dbNo) const {
//
//
//  Purpose:  Replace sequence number in main and auxiliary tables.
//
//  Arguments:
//    oldSeqNo     in    The old sequence number.
//    nwSeqNo      in    The new sequence number.
//    dbNo         in    Database number in cascade (starting at 0).
//
//  Return:    kTRUE if output successful,otherwise kFALSE.
//
//  Contact:   N. West
//
//  Specification:-
//  =============
//
//  o Replace sequence number in main and auxiliary tables.

//  Program Notes:-
//  =============

//  None.

  if ( ! fCascader.GetConnection(dbNo) ) {
    SK_DBI_Warn(  "Cannot renumber " << oldSeqNo
       << " no connection to cascade entry " << dbNo << "  ");
    return false;
  }

// Generate SQL to replace SeqNo in validity table.
  TDbiString sql;
  sql << "update  " << fTableName
      << "VLD set SEQNO = " << newSeqNo
      << " where SEQNO = " << oldSeqNo << ";"
      << '\0';

  SK_DBI_Verbose( "Database: " << dbNo
                        << " ReplaceSeqNo SQL: " << sql.c_str() << "  ");

//  Apply query.
  auto_ptr<TDbiStatement> stmtDb(fCascader.CreateStatement(dbNo));
  if ( ! stmtDb.get() ) return false;
  if ( ! stmtDb->ExecuteUpdate(sql.c_str()) || stmtDb->PrintExceptions() ) {
       SK_DBI_Severe( "SQL: " << sql.c_str()
                           << " Failed. " << "  ");
    return false;
  }

// Generate SQL to replace SeqNo in main table.
  sql.GetString().erase();
  sql  << "update  " << fTableName
       << " set SEQNO = " << newSeqNo
       << " where SEQNO = " << oldSeqNo << ";"
       << '\0';

  SK_DBI_Verbose( "Database: " << dbNo
                        << " ReplaceSeqNo SQL: " << sql.c_str() << "  ");

//  Apply query.
  if ( ! stmtDb->ExecuteUpdate(sql.c_str()) || stmtDb->PrintExceptions() ) {
       SK_DBI_Severe( "SQL: " << sql.c_str()
                           << " Failed. " << "  ");
    return false;
  }

  return true;

}

//.....................................................................

void  TDbiDBProxy::StoreMetaData(TDbiTableMetaData& metaData) const {
//
//
//  Purpose:  Store table meta data.
//
//  Arguments:
//    metaData   in    Empty TDbiTableMetaData object apart from table name.



  const char* tableName = metaData.TableName().c_str();
  SK_DBI_Verbose( "Get meta-data for table: " << tableName << "  ");

//  Check each Db in turn until table found and store table meta data.

  for ( UInt_t dbNo = 0; dbNo < fCascader.GetNumDb(); dbNo++ ) {
    TDbiConnection* connection = fCascader.GetConnection(dbNo);
    TSQLServer* server = connection->GetServer();
    if ( ! server ) continue;
    connection->Connect();
    TSQLTableInfo* meta = server->GetTableInfo(tableName);
    if ( ! meta ) {
      connection->DisConnect();
      continue;
    }
    SK_DBI_Verbose( "Meta-data query succeeded on cascade entry " << dbNo << "  ");

    // Clear out any existing data, although there should not be any.
    metaData.Clear();

    const TList* cols =  meta->GetColumns();
    TIter colItr(cols);
    int col = 0;
    while ( TSQLColumnInfo* colInfo = dynamic_cast<TSQLColumnInfo*>(colItr.Next()) ) {

      ++col;
      string name(colInfo->GetName());
      name = UtilString::ToUpper(name);
      metaData.SetColName(name,col);

      TDbiFieldType fldType(colInfo->GetSQLType(),
                           colInfo->GetLength(),
                           colInfo->GetTypeName());

      // For now continue to check for unsigned (even though not supported)
      if ( !colInfo->IsSigned() ) fldType.SetUnsigned();
      metaData.SetColFieldType(fldType,col);

      metaData.SetColIsNullable(col,colInfo->IsNullable());

      SK_DBI_Verbose(  "Column "         << col << " " << name
           << " SQL type "      << colInfo->GetSQLType()
           << " SQL type name " << colInfo->GetTypeName()
           << " DBI type "      << fldType.AsString()
           << " data size: "    << fldType.GetSize()
           << " col size: "     << colInfo->GetLength() << "  ");

    }
    delete meta;
    connection->DisConnect();
    return;
  }
}

//.....................................................................

Bool_t TDbiDBProxy::TableExists(Int_t selectDbNo) const {
//
//
//  Purpose:  Return true if table exists on selected cascade entry
//            or any entry if selectDbNo=-1 (default)


  return fCascader.TableExists(fTableName,selectDbNo);

}