* pgviz
*** visualize foreign-key relations in postgresql

This program produces diagrams of graphs where the nodes are tables and the
edges are foreign-key relations. There is a small query language to specify the
tables that should be included in the diagram.

Using the [[https://github.com/devrimgunduz/pagila][Pagila]] schema as an example:

#+begin_src
pgviz --out pagila.svg "(graph (within 2 (table film)))"
#+end_src

produces

[[.images/pagila.svg]]

** Query language

The query language uses s-expressions and includes the following functions:

- ~graph <q: query> <s0: subgraph> ...~ :: produces a ~graph~ with top level nodes
  matching ~q~ and any number of included subgraphs
- ~subgraph <label: string> <g: graph> ...~ :: produces a ~subgraph~ with the
  provided label that contains the provided graph
- ~within <n: integer> <q: query>~ :: produces a ~query~ that includes all
  tables within ~n~ edges of tables matching ~q~
- ~schema <s: schema name> ...~ :: produces a ~query~ that includes all tables
  contained by the provided schemas
- ~table <t: table name> ...~ :: procudes a ~query~ that includes tables whose
  name is equal to any of the provided table names
- ~and <q0: query> <q1: query> ...~ :: produces a ~query~ that include tables
  that match all of the provided queries
- ~or <q0: query> <q1: query> ...~ :: produces a ~query~ that includes tables
  that match any of the provided queries
- ~- <lhs: query> <rhs: query>~ :: produces a ~query~ that includes tables that
  match ~lhs~, but do not match ~rhs~

** Colors

Columns have background colors that indicate certain attributes, for example:
nullable columns are gray, unique columns are green, primary key columns are
blue, columns that are both nullable and unique are a darker green.

** Installation

*** Cargo

~cd~ into ~src~ and ~cargo build~ as usual. ~graphviz~ is a runtime dependency.

*** Nix

~nix build~ will compile the binary that references a nix-pinned graphviz. You
can also run it directly with

#+begin_src 
nix run "github:tstat/pgviz" -- <args>
#+end_src

or add it to your nix registry with

#+begin_src 
nix registry add pgviz "github:tstat/pgviz"
#+end_src

then you can run it with ~nix run pgviz -- <args>~