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3425730294
This patch introduces table joins. It uses a pretty dumb algorithm- starting with a singleton '__unity__' row consisting of a single boolean value, a cartesian product of all tables in the 'FROM' clause is built. This cartesian product is then filtered through the 'WHERE' clause, again without any smarts just using brute force. This patch required a bunch of busy work to allow for example the ColumnNameExpression having to deal with multiple tables potentially having columns with the same name.
91 lines
3.3 KiB
C++
91 lines
3.3 KiB
C++
/*
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* Copyright (c) 2021, Jan de Visser <jan@de-visser.net>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <LibSQL/AST/AST.h>
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#include <LibSQL/Database.h>
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#include <LibSQL/Meta.h>
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#include <LibSQL/Row.h>
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namespace SQL::AST {
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RefPtr<SQLResult> Select::execute(ExecutionContext& context) const
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{
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NonnullRefPtrVector<ResultColumn> columns;
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for (auto& table_descriptor : table_or_subquery_list()) {
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if (!table_descriptor.is_table())
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TODO();
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auto table = context.database->get_table(table_descriptor.schema_name(), table_descriptor.table_name());
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if (!table) {
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return SQLResult::construct(SQL::SQLCommand::Select, SQL::SQLErrorCode::TableDoesNotExist, table_descriptor.table_name());
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}
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if (result_column_list().size() == 1 && result_column_list()[0].type() == ResultType::All) {
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for (auto& col : table->columns()) {
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columns.append(
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create_ast_node<ResultColumn>(
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create_ast_node<ColumnNameExpression>(table->parent()->name(), table->name(), col.name()),
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""));
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}
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}
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}
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VERIFY(!result_column_list().is_empty());
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if (result_column_list().size() != 1 || result_column_list()[0].type() != ResultType::All) {
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for (auto& col : result_column_list()) {
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if (col.type() == ResultType::All)
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// FIXME can have '*' for example in conjunction with computed columns
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return SQLResult::construct(SQL::SQLCommand::Select, SQL::SQLErrorCode::SyntaxError, "*");
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columns.append(col);
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}
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}
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context.result = SQLResult::construct();
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AK::NonnullRefPtr<TupleDescriptor> descriptor = AK::adopt_ref(*new TupleDescriptor);
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Tuple tuple(descriptor);
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Vector<Tuple> rows;
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descriptor->empend("__unity__");
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tuple.append(Value(SQLType::Boolean, true));
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rows.append(tuple);
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for (auto& table_descriptor : table_or_subquery_list()) {
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if (!table_descriptor.is_table())
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TODO();
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auto table = context.database->get_table(table_descriptor.schema_name(), table_descriptor.table_name());
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if (table->num_columns() == 0)
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continue;
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auto old_descriptor_size = descriptor->size();
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descriptor->extend(table->to_tuple_descriptor());
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for (auto cartesian_row = rows.first(); cartesian_row.size() == old_descriptor_size; cartesian_row = rows.first()) {
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rows.remove(0);
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for (auto& table_row : context.database->select_all(*table)) {
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auto new_row = cartesian_row;
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new_row.extend(table_row);
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rows.append(new_row);
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}
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}
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}
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for (auto& row : rows) {
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context.current_row = &row;
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if (where_clause()) {
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auto where_result = where_clause()->evaluate(context);
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if (context.result->has_error())
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return context.result;
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if (!where_result)
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continue;
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}
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tuple.clear();
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for (auto& col : columns) {
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auto value = col.expression()->evaluate(context);
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if (context.result->has_error())
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return context.result;
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tuple.append(value);
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}
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context.result->append(tuple);
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}
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return context.result;
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}
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}
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