Figures & Pics in Docs

An action item from this session in PGCon 2016 user unconference was that I (Heikki) would try to draw an illustration of the GIN index using ASCII art, to see how well ASCII art works in practice for diagrams like that. Here's what I came up with:

********************************************************************************************
*                                                                                          *
* +----------+                                            +-----------------+              *
* | Metapage |                                            |                 |              *
* +----+-----+   +---------------------------------+      |          +---+  |              *
*      |         |                                 |      |       -->|   |  |              *
*      |         |                         +---+   |      | +---+/   +---+  |              *
*      |         |                      -->|   +----------->|   +           |              *
*      |         |                +---+/   +---+   |      | +---+\   +---+  |              *
*      |         |             -->|   +            |      |       -->|   |  |              *
*      |         |            /   +---+\   +---+   |      |          +---+  |              *
*      |         |           /          -->|   |   |      |                 |              *
*      |         |          /              +---+   |      | Posting tree    |              *
*      |         |         /                       |      +-----------------+              *
*      |         |        /                +---+   |                                       *
*      |         |       /              -->|   |   |                                       *
*      |         | +---+/         +---+/   +---+   |                                       *
*      |         | |   +--------->|   +            |                                       *
*      |         | +---+\         +---+\   +---+   |                                       *
*      |         |       \              -->|   +------->                                   *
*      |         |        \                +---+   |                                       *
*      |         |         \                       |                                       *
*      |         |          \              +---+   |                                       *
*      |         |           \          -->|   |   |                                       *
*      |         |            \   +---+/   +---+   |                                       *
*      |         |             -->|   +            |                                       *
*      |         |                +---+\   +---+   |                                       *
*      |         |                      -->|   |   |                                       *
*      |         |                         +---+   |                                       *
*      |         |                                 |                                       *
*      |         | Entry tree                      |                                       *
*      |         +---------------------------------+                                       *
*      |                                                                                   *
*  +---|------------------+                                                                *
*  |   V                  |                                                                *
*  | +---+  +---+  +---+  |                                                                *
*  | |   |->|   |->|   |  |                                                                *
*  | +---+  +---+  +---+  |                                                                *
*  |                      |                                                                *
*  | Fast update list     |                                                                *
*  +----------------------+                                                                *
*                                                                                          *
********************************************************************************************