private static IRowCursor QueryAllMatches(SystemTransaction transaction, TableName tableName, SystemTable table,
IList<string> columns, SqlObject val)
{
// Try and find an index on these columns
SystemIndexSetDataSource indexSet = transaction.FindIndexOn(tableName, columns);
// If index found
if (indexSet != null)
// Query the index and find all matches
return indexSet.Select(SelectableRange.Is(val));
// Otherwise no index, so scan the table for matches
// Make an Expression for the operation;
// (column1, column2, ...columnn) = val
Expression compExp;
int sz = columns.Count;
if (sz > 1) {
FunctionExpression cfunExp = new FunctionExpression("composite_fetch");
for (int i = 0; i < sz; ++i) {
Expression varRef = new FetchVariableExpression(new Variable(tableName, columns[i]));
cfunExp.Parameters.Add(varRef);
}
compExp = cfunExp;
} else if (sz == 1) {
compExp = new FetchVariableExpression(new Variable(tableName, columns[0]));
} else {
throw new ApplicationException("Invalid columns list size");
}
// Equality test
FunctionExpression funExp = new FunctionExpression("@is_sql");
funExp.Parameters.Add(compExp);
funExp.Parameters.Add(new FetchStaticExpression(val));
// Create a query processor and perform the scan operation
QueryProcessor processor = new QueryProcessor(transaction);
ITable result = processor.FilterByScan(table, funExp);
// Return the row cursor
return result.GetRowCursor();
}
public Expression OnAfterWalk(Expression expression)
{
if (expression is SelectExpression) {
SelectExpression selectExp = (SelectExpression)expression;
// Exiting select, we expand the select output list to a complete
// form.
int sz = selectExp.Output.Count;
// Create a list of all forward referencable variables in the join
// graph
List<FetchVariableExpression> varList = new List<FetchVariableExpression>();
optimizer.PopulateVariables(varList, selectExp.Join);
// The unique table name of this select
TableName uniqueTableName = selectExp.UniqueName;
if (uniqueTableName == null)
throw new SystemException("Select must have a unique name.");
List<Expression> newOutList = new List<Expression>();
for (int i = 0; i < sz; ++i) {
// The Expression
SelectOutput selectOut = selectExp.Output[i];
// Is this a glob type?
if (selectOut.Expression is FetchGlobExpression) {
// Get the glob string
string str = ((FetchGlobExpression)selectOut.Expression).GlobString;
// Search the referencable list for matches,
bool matchFound = false;
foreach(FetchVariableExpression varExp in varList) {
Variable v = varExp.Variable;
// Found a match, add it to the list
if (optimizer.GlobMatch(str, v)) {
SqlType returnType = varExp.ReturnType;
Expression globExp = new FetchVariableExpression(v);
globExp = new AliasVariableNameExpression(globExp, v);
globExp.ReturnType = returnType;
newOutList.Add(globExp);
matchFound = true;
}
}
// If we searched the whole referencable list and no matches,
// we report the error. This doesn't apply to the general
// glob "*" which is valid for results with no columns.
if (!str.Equals("*") && !matchFound)
throw new SqlParseException("'" + str + "' does not match anything", selectOut.Expression);
} else {
// The makes sure all other types of output from a select are
// named variable references.
// If this is an alias, we need to make sure we qualify it with
// this table name
if (selectOut.Expression is AliasVariableNameExpression) {
// Rewrite this alias name with the new unique table id
Variable v = selectOut.Alias;
if (v.TableName != null)
throw new SqlParseException("Incorrect alias format", selectOut.Expression);
v = new Variable(uniqueTableName, v.Name);
selectOut.Alias = v;
}
// If it's not a fetchvar operation, we need to assign a
// unique alias name for this value
else if (!(selectOut.Expression is FetchVariableExpression)) {
string label = (string)selectOut.Expression.GetArgument("label");
if (label == null)
label = "nolabel";
selectOut = new SelectOutput(
new AliasVariableNameExpression(selectOut.Expression, new Variable(uniqueTableName, "#" + newOutList.Count + "#" + label)),
selectOut.Alias);
}
// If it's a regular fetch variable operation, we need to
// forward qualify it and label it.
else {
selectOut.Expression = QualifyExpression(selectOut.Expression, varList, true);
Variable var = ((FetchVariableExpression)selectOut.Expression).Variable;
SqlType returnType = selectOut.Expression.ReturnType;
selectOut.Expression = new AliasVariableNameExpression(selectOut.Expression, var);
selectOut.Expression.ReturnType = returnType;
}
// Add it to the new select output list
newOutList.Add(selectOut.Expression);
}
}
// new_out_list is now the new expanded select output list
sz = newOutList.Count;
selectExp.Output.Clear();
for (int i = 0; i < sz; ++i) {
selectExp.Output.Add(new SelectOutput(newOutList[i]));
}
// Set the qualified flag for each select statement,
selectExp.IsQualified = true;
}
return expression;
}
private void PopulateVariables(IList<FetchVariableExpression> varList, Expression joinGraph)
{
// Exit early if join graph is null
if (joinGraph == null)
return;
if (joinGraph is JoinExpression) {
// Search the left and right for matching terms
JoinExpression joinExp = (JoinExpression)joinGraph;
PopulateVariables(varList, joinExp.Left);
PopulateVariables(varList, joinExp.Right);
} else if (joinGraph is FetchTableExpression) {
// This must be fully qualified
TableName table_name = ((FetchTableExpression)joinGraph).TableName;
PopulateVariables(varList, table_name);
} else if (joinGraph is AliasTableNameExpression) {
AliasTableNameExpression aliasExp = (AliasTableNameExpression)joinGraph;
TableName alias_name = aliasExp.Alias;
// We find any that match in the child,
List<FetchVariableExpression> newList = new List<FetchVariableExpression>();
PopulateVariables(newList, aliasExp.Child);
// And rewrite them with this table name alias
int sz = newList.Count;
for (int i = 0; i < sz; ++i) {
FetchVariableExpression varExp = newList[i];
Variable v = varExp.Variable;
FetchVariableExpression newVarExp = (FetchVariableExpression) varExp.Clone();
newVarExp.Variable = new Variable(alias_name, v.Name);
newVarExp.ReturnType = varExp.ReturnType;
varList.Add(newVarExp);
}
} else if (joinGraph is SelectExpression) {
// For nested selects, we resolve against the select output only
SelectExpression selectExp = (SelectExpression)joinGraph;
int sz = selectExp.Output.Count;
for (int i = 0; i < sz; ++i) {
Expression op = selectExp.Output[i].Expression;
Variable v;
SqlType varType;
if (op is FetchVariableExpression) {
FetchVariableExpression varExp = (FetchVariableExpression)op;
v = varExp.Variable;
varType = varExp.ReturnType;
} else if (op is AliasVariableNameExpression) {
AliasVariableNameExpression aliasExp = (AliasVariableNameExpression)op;
v = aliasExp.Alias;
varType = aliasExp.ReturnType;
} else {
throw new ApplicationException("Unknown output object in SELECT");
}
if (v != null) {
FetchVariableExpression varExp = new FetchVariableExpression(v);
varExp.ReturnType = varType;
varList.Add(varExp);
}
}
}
}
public void PopulateVariables(IList<FetchVariableExpression> varList, TableName tableName)
{
ITable tsource = transaction.GetTable(tableName);
int sz = tsource.Columns.Count;
for (int i = 0; i < sz; ++i) {
TableColumn column = tsource.Columns[i];
string columnName = column.Name;
// The variable name,
FetchVariableExpression varExp = new FetchVariableExpression(new Variable(tableName, columnName));
// The type,
SqlType returnType = column.Type;
varExp.ReturnType = returnType;
varList.Add(varExp);
}
}