// Merge //
public static MergePlan RenderMergePlan(Workspace Home, HScriptParser.Crudam_mergeContext context)
{
// Get the data sources //
DataSet data1 = VisitorHelper.GetData(Home, context.merge_source()[0].full_table_name());
DataSet data2 = VisitorHelper.GetData(Home, context.merge_source()[1].full_table_name());
// Get the aliases //
string alias1 = (context.merge_source()[0].IDENTIFIER() ?? context.merge_source()[0].full_table_name().table_name().IDENTIFIER()).GetText();
string alias2 = (context.merge_source()[1].IDENTIFIER() ?? context.merge_source()[1].full_table_name().table_name().IDENTIFIER()).GetText();
// Build the registers; the join functions only use static registers //
StaticRegister mem1 = new StaticRegister(null);
StaticRegister mem2 = new StaticRegister(null);
// Create our expression builder //
ExpressionVisitor exp_vis = new ExpressionVisitor(null, Home);
exp_vis.AddSchema(alias1, data1.Columns, mem1);
exp_vis.AddSchema(alias2, data2.Columns, mem2);
// Get the equality keys //
Key eq1 = new Key();
Key eq2 = new Key();
foreach (HScriptParser.Merge_equi_predicateContext ctx in context.merge_equi_predicate())
{
string a1 = ctx.table_variable()[0].IDENTIFIER()[0].GetText();
string a2 = ctx.table_variable()[1].IDENTIFIER()[0].GetText();
string c1 = ctx.table_variable()[0].IDENTIFIER()[1].GetText();
string c2 = ctx.table_variable()[1].IDENTIFIER()[1].GetText();
int idx1 = -1;
int idx2 = -1;
if (a1 == alias1 && a2 == alias2)
{
// Look up indicides //
idx1 = data1.Columns.ColumnIndex(c1);
idx2 = data2.Columns.ColumnIndex(c2);
// Check for invalid keys //
if (idx1 == -1)
throw new Exception(string.Format("Column '{0}' does not exist in '{1}'", c1, alias1));
if (idx2 == -1)
throw new Exception(string.Format("Column '{0}' does not exist in '{1}'", c2, alias2));
}
else if (a1 == alias2 && a2 == alias1)
{
// Look up indicides //
idx1 = data1.Columns.ColumnIndex(c2);
idx2 = data2.Columns.ColumnIndex(c1);
// Check for invalid keys //
if (idx1 == -1)
throw new Exception(string.Format("Column '{0}' does not exist in '{1}'", c2, idx1));
if (idx2 == -1)
throw new Exception(string.Format("Column '{0}' does not exist in '{1}'", c1, idx2));
}
else
throw new Exception("Aliases passed are invalid");
// add the keys //
eq1.Add(idx1);
eq2.Add(idx2);
}
// Get the predicate //
Predicate where = VisitorHelper.GetWhere(exp_vis, context.where_clause());
// Get the list of expressions //
FNodeSet nodes = VisitorHelper.GetReturnStatement(exp_vis, context.return_action().expression_or_wildcard_set());
// Get the output cursor //
RecordWriter out_data = VisitorHelper.GetWriter(Home, nodes.Columns, context.return_action());
// Get the join method //
MergeMethod method = VisitorHelper.GetMergeMethod(context.merge_type());
// Find the best algorithm //
MergeAlgorithm alg = MergeAlgorithm.SortMerge;
if (context.merge_algorithm() != null)
{
string suggest_alg = exp_vis.ToNode(context.merge_algorithm().expression()).Evaluate().valueSTRING.ToUpper();
if (suggest_alg == "NL")
alg = MergeAlgorithm.NestedLoop;
else if (suggest_alg == "SM")
alg = MergeAlgorithm.SortMerge;
else if (suggest_alg == "HT")
alg = MergeAlgorithm.HashTable;
}
if (eq1.Count == 0)
alg = MergeAlgorithm.NestedLoop;
return new MergePlan(method, alg, out_data, nodes, where, data1, data2, eq1, eq2, mem1, mem2);
}