// Register an expression that will be used in a query
// An expression is the RHS of an attribute assignment (not just a function)
// Can only be Rename, Project, Open, Aggregate: only last two needed
public bool RegisterExpression(ExpressionEval expr, int naccum)
{
if (!(expr.IsOpen || expr.HasFold))
{
return(true);
}
// Check whether new registration or update (to new evaluator)
// TODO: check it's the same expr
var updating = ExprDict.ContainsKey(expr.Serial);
var name = SqlGen.FuncName(expr);
ExprDict[expr.Serial] = expr;
Logger.WriteLine(3, $"Register {name} upd={updating} nacc={naccum} expr={expr}");
if (updating)
{
return(true);
}
// notify database, set up callbacks
// may require sql to register (PG)
// FIX: would be better in PostgresDatabase, but does not have access to sql gen (and data types).
var args = expr.Lookup.Columns.Select(c => ToSqlCommon[c.DataType.BaseType]).ToArray();
var retn = ToSqlCommon[expr.ReturnType.BaseType];
if (expr.HasFold)
{
// note: type must match low level wrappers
var stype = DataTypes.Number;
var init = NumberValue.Zero;
var col0 = new DataColumn[] { DataColumn.Create("_state_", stype) };
OptionalExpressionSql(_sqlgen.CreateFunction(name, col0.Concat(expr.Lookup.Columns).ToArray(), stype));
OptionalExpressionSql(_sqlgen.CreateFunction(name + "F", col0, expr.ReturnType));
OptionalExpressionSql(_sqlgen.CreateAggregate(name, expr.Lookup.Columns, stype, init, name, name + "F"));
return(FunctionCreator.CreateAggFunction(name, expr.Serial, naccum, args, retn));
}
// expr.IsOpen
OptionalExpressionSql(_sqlgen.CreateFunction(name, expr.Lookup.Columns, expr.ReturnType));
return(FunctionCreator.CreateFunction(name, FuncTypes.Open, expr.Serial, args, retn));
}
///-------------------------------------------------------------------
///
/// Catalog info
///
// Construct and return a heading for a database table
// return null if not found or error
// TODO:
public DataHeading GetTableHeading(string table)
{
Tuple <string, SqlCommonType>[] columns;
// optional sql
var sql = SqlGen.GetColumns(table);
var optsql = sql.Length > 0;
Logger.WriteLine(3, "GetTableHeading {0}", optsql ? sql : table);
if (optsql)
{
Logger.WriteLine(2, ">>>(th){0}", sql);
}
Logger.Assert(_database != null, "gth");
var ok = _database.GetTableColumns(optsql ? sql : table, out columns);
if (!ok || columns.Length == 0)
{
return(null);
}
var cols = columns.Select(c => DataColumn.Create(c.Item1, FromSqlCommon[c.Item2]));
return(DataHeading.Create(cols)); // ignore column order
}
//--- factories
DataTableSql()
{
_database = SqlTarget.Current;
_gen = SqlTarget.Current.SqlGen;
}
