message: Removed outdated explanation in src README.
diff: @@ -10,7 +10,7 @@ The planner can be found in the [planner](https://github.com/cwida/duckdb/tree/m
  The optimizer can be found in the [optimizer](https://github.com/cwida/duckdb/tree/master/src/optimizer) folder. The optimizer takes the Logical Query Plan generated by the `Planner` and translates it into a logically equivalent but (hopefully) faster to execute Logical Query Plan. Examples of optimizations that are performed are predicate pushdown, expression rewriting and join ordering. Both cost-based and rule-based optimizations are performed.
  # Execution
  -The execution layer can be found in the [execution](https://github.com/cwida/duckdb/tree/master/src/execution) folder. The execution layer first takes the Logical Query Plan resulting from the `Optimizer` and converts it into a Physical Query Plan consisting of `PhysicalOperators`. The `PhysicalOperators` are then executed using a push-based execution model. The `GetChunk()` method is called on the root of the operator tree, which recursively calls `GetChunk()` on its children until a root node is reached. The root node then emits chunks that result from e.g. a base table scan, which propagate through the plan until the chunk reaches the output. This is repeated until the data sources have been exhausted, after which point the query execution is finished.
  +The execution layer can be found in the [execution](https://github.com/cwida/duckdb/tree/master/src/execution) folder. The execution layer first takes the Logical Query Plan resulting from the `Optimizer` and converts it into a Physical Query Plan consisting of `PhysicalOperators`. The `PhysicalOperators` are then executed using a push-based execution model.
  # Catalog
  The catalog management can be found in the [catalog](https://github.com/cwida/duckdb/tree/master/src/catalog) folder. The catalog keeps track of the the tables, schemas and functions that are contained in the database. The `Catalog` is used by the `Binder` in the planning phase to resolve symbols (e.g. "table_name") to the actual tables and columns that exist in the database.
  