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LibSQL: Allow expressions and column names in SELECT ... FROM

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Up to now the only ``SELECT`` statement that worked was ``SELECT *
FROM <table>``. This commit allows a column list consisting of
column names and expressions in addition to ``*``. ``WHERE``
still doesn't work though.
This commit is contained in:
Jan de Visser 2021-09-16 22:29:19 +02:00 • committed by Andreas Kling
parent f33a288ca4
commit fe50598a03
8 changed files with 90 additions and 20 deletions
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3
Userland/Libraries/LibSQL/AST/AST.h
View file

@ -298,7 +298,7 @@ private:
struct ExecutionContext {
NonnullRefPtr<Database> database;
RefPtr<SQLResult> result { nullptr };
Tuple current_row {};
Tuple* current_row { nullptr };
};
class Expression : public ASTNode {
@ -429,6 +429,7 @@ public:
const String& schema_name() const { return m_schema_name; }
const String& table_name() const { return m_table_name; }
const String& column_name() const { return m_column_name; }
virtual Value evaluate(ExecutionContext&) const override;
private:
String m_schema_name;

13
Userland/Libraries/LibSQL/AST/Expression.cpp
View file

@ -87,4 +87,17 @@ Value UnaryOperatorExpression::evaluate(ExecutionContext& context) const
VERIFY_NOT_REACHED();
}
Value ColumnNameExpression::evaluate(ExecutionContext& context) const
{
auto& descriptor = *context.current_row->descriptor();
VERIFY(context.current_row->size() == descriptor.size());
for (auto ix = 0u; ix < context.current_row->size(); ix++) {
auto& column_descriptor = descriptor[ix];
if (column_descriptor.name == column_name())
return { (*context.current_row)[ix] };
}
// TODO: Error handling.
VERIFY_NOT_REACHED();
}
}

44
Userland/Libraries/LibSQL/AST/Select.cpp
View file

@ -14,22 +14,36 @@ namespace SQL::AST {
RefPtr<SQLResult> Select::execute(ExecutionContext& context) const
{
if (table_or_subquery_list().size() == 1 && table_or_subquery_list()[0].is_table()) {
if (result_column_list().size() == 1 && result_column_list()[0].type() == ResultType::All) {
auto table = context.database->get_table(table_or_subquery_list()[0].schema_name(), table_or_subquery_list()[0].table_name());
if (!table) {
return SQLResult::construct(SQL::SQLCommand::Select, SQL::SQLErrorCode::TableDoesNotExist, table_or_subquery_list()[0].table_name());
}
NonnullRefPtr<TupleDescriptor> descriptor = table->to_tuple_descriptor();
context.result = SQLResult::construct();
for (auto& row : context.database->select_all(*table)) {
Tuple tuple(descriptor);
for (auto ix = 0u; ix < descriptor->size(); ix++) {
tuple[ix] = row[ix];
}
context.result->append(tuple);
}
return context.result;
auto table = context.database->get_table(table_or_subquery_list()[0].schema_name(), table_or_subquery_list()[0].table_name());
if (!table) {
return SQLResult::construct(SQL::SQLCommand::Select, SQL::SQLErrorCode::TableDoesNotExist, table_or_subquery_list()[0].table_name());
}
NonnullRefPtrVector<ResultColumn> columns;
if (result_column_list().size() == 1 && result_column_list()[0].type() == ResultType::All) {
for (auto& col : table->columns()) {
columns.append(
create_ast_node<ResultColumn>(
create_ast_node<ColumnNameExpression>(table->parent()->name(), table->name(), col.name()),
""));
}
} else {
for (auto& col : result_column_list()) {
columns.append(col);
}
}
context.result = SQLResult::construct();
AK::NonnullRefPtr<TupleDescriptor> descriptor = AK::adopt_ref(*new TupleDescriptor);
for (auto& row : context.database->select_all(*table)) {
context.current_row = &row;
Tuple tuple(descriptor);
for (auto& col : columns) {
auto value = col.expression()->evaluate(context);
tuple.append(value);
}
context.result->append(tuple);
}
return context.result;
}
return SQLResult::construct();
}