// update the root page of a table or an index
// if succeeded, return true. Vice versa
public bool TryUpdateSchemaRecord(string name, int rootPage)
{
//load both table and index
Catalog_table a = new Catalog_table(_databaseName);
Catalog_index b = new Catalog_index(_databaseName);
//if it's the name of a table
if (a.If_in(name))
{
return(a.Update(name, rootPage));
}
//if it's the name of an index
else if (b.If_in(name))
{
return(b.Update(name, rootPage));
}
//if it's neither index nor table
else
{
return(false);
}
}
// check validation of the statement
public void CheckValidation(IStatement statement)
{
//check validation of createStatement
if (statement.Type == StatementType.CreateStatement)
{
CreateStatement x = (CreateStatement)statement;
//to create a table
if (x.CreateType == CreateType.Table)
{
// primary key not exists
if (x.PrimaryKey == null || x.PrimaryKey == "")
{
throw new KeyNotExistsException($"Table \"{x.TableName}\" does not have a primary key");
}
//to check whether the table has been created before
Catalog_table a = new Catalog_table(_databaseName);
a.AssertNotExist(x.TableName);
}
//to create an index
else
{
// index key not exists
if (x.AttributeName == null || x.AttributeName == "")
{
throw new KeyNotExistsException($"Index \"{x.IndexName}\" does not have a index key");
}
Catalog_table a = new Catalog_table(_databaseName);
Catalog_index b = new Catalog_index(_databaseName);
//to check whether the table exists
bool condition1 = a.If_in(x.TableName);
//to check whether the index has been created before
bool condition2 = !b.If_in(x.IndexName);
//to check whether the attribute is in the attribute list of the table
bool condition3 = a.return_table(x.TableName).Has_attribute(x.AttributeName);
if (!condition1)
{
throw new TableOrIndexNotExistsException($"Table \"\"{x.TableName}\"\" not exists");
}
if (!condition2)
{
throw new TableOrIndexAlreadyExistsException($"Index \"\"{x.IndexName}\"\" not exists");
}
if (!condition3)
{
throw new AttributeNotExistsException($"Attribute \"\"{x.AttributeName}\"\" not exists in table \"\"{x.TableName}\"\"");
}
}
}
//check validation of a drop statement
else if (statement.Type == StatementType.DropStatement)
{
DropStatement x = (DropStatement)statement;
Catalog_table a = new Catalog_table(_databaseName);
Catalog_index b = new Catalog_index(_databaseName);
//to drop a table,we need to check whether the table exists
if (x.TargetType == DropTarget.Table)
{
a.AssertExist(x.TableName);
}
//to drop a index,we need to check whether the index exists
else
{
if (x.TableName != "")
{
b.AssertExist(x.IndexName);
if (b.Of_table(x.IndexName) != x.TableName)
{
throw new AttributeNotExistsException($"Index \"{x.IndexName}\" is not associated with table \"{x.TableName}\"");
}
}
else
{
b.AssertExist(x.IndexName);
}
}
}
//check validation of a select statement
else if (statement.Type == StatementType.SelectStatement)
{
SelectStatement x = (SelectStatement)statement;
//check whether the table is in the tables catalog
Catalog_table a = new Catalog_table(_databaseName);
a.AssertExist(x.FromTable);
if (x.Condition == null)
{
return;
}
else if (x.Condition.AttributeName == "")
{
if (x.Condition.SimpleMinterms.Count == 0)
{
//if the ands is empty and attribute name is emply, the statement means select * from a table
return;
}
else
{
//for each attribute in the egression list(named 'ands')
//check whether the attribute is in the attribute list of this table
foreach (KeyValuePair <string, Expression> expression_piece in x.Condition.SimpleMinterms)
{
if (!a.return_table(x.FromTable).Has_attribute(expression_piece.Key))
{
throw new AttributeNotExistsException($"Attribute \"{expression_piece.Key}\" not exists in table \"{x.FromTable}\"");
}
}
}
}
else
{
//check whether the only attribute is one of the table's attributes
if (!a.return_table(x.FromTable).Has_attribute(x.Condition.AttributeName))
{
throw new AttributeNotExistsException($"Attribute \"{x.Condition.AttributeName}\" not exists in table \"{x.FromTable}\"");
}
}
return;
}
//check validation of a delete statement
else if (statement.Type == StatementType.DeleteStatement)
{
DeleteStatement x = (DeleteStatement)statement;
//check whether the table is in the tables catalog
Catalog_table a = new Catalog_table(_databaseName);
a.AssertExist(x.TableName);
if (x.Condition == null)
{
return;
}
else if (x.Condition.AttributeName == "")
{
if (x.Condition.SimpleMinterms.Count == 0)
{
//if the ands is empty and attribute name is emply, the statement means select * from a table
return;
}
else
{
//for each attribute in the epression list(named 'ands')
//check whether the attribute is in the attribute list of this table
foreach (KeyValuePair <string, Expression> expression_piece in x.Condition.SimpleMinterms)
{
if (!a.return_table(x.TableName).Has_attribute(expression_piece.Key))
{
throw new AttributeNotExistsException($"Attribute \"{expression_piece.Key}\" not exists in table \"{x.TableName}\"");
}
}
}
}
else
{
//check whether the only attribute is one of the table's attributes
if (!a.return_table(x.TableName).Has_attribute(x.Condition.AttributeName))
{
throw new AttributeNotExistsException($"Attribute \"{x.Condition.AttributeName}\" not exists in table \"{x.TableName}\"");
}
}
return;
}
//check validation of an insert statement
else if (statement.Type == StatementType.InsertStatement)
{
InsertStatement x = (InsertStatement)statement;
//check whether the table is in the table list
Catalog_table a = new Catalog_table(_databaseName);
a.AssertExist(x.TableName);
//check if the number of the attributes perfectly match the number of the values
if (x.Values.Count != a.return_table(x.TableName).attribute_list.Count)
{
throw new NumberOfAttributesNotMatchsException($"Number of attributes not matchs. Expected: \"{a.return_table(x.TableName).attribute_list.Count}\"; actual: \"{x.Values.Count}\"");
}
//check whether the type of the inserted data well suits the data definition of each attribute
for (int i = 0; i < x.Values.Count; i++)
{
if (a.return_table(x.TableName).attribute_list[i].type != x.Values[i].Type)
{
throw new TypeOfAttributeNotMatchsException($"Type for attribute \"{a.return_table(x.TableName).attribute_list[i].attribute_name}\" not matches. Expected: \"{a.return_table(x.TableName).attribute_list[i].type}\"; actual: \"{x.Values[i].Type}\"");
}
}
//if all data type suit, return true
return;
}
//check validation of a quit statement
else if (statement.Type == StatementType.QuitStatement)
{
return;
}
//check validation of an exec file statement
else
{
return;
}
}