box_dest_receiver

A Postgres DestReceiver implementation that renders query results in a box format, inspired by DuckDB's box renderer. It is meant to be used under the single-user mode as it writes to stdout.

$ ./install/bin/postgres --single -D data  postgres

PostgreSQL stand-alone backend 19devel
backend> SELECT * FROM buzz;
┌─────────────────────┬────────────┐
│ receive_func        │ is_it_good │
├─────────────────────┼────────────┤
│ debugtup            │ f          │
├─────────────────────┼────────────┤
│ box_dr_receive_slot │ t          │
├─────────────────────┼────────────┤
│ ???                 │ NULL       │
└─────────────────────┴────────────┘

Why build this thing

Yeah, I know that single-user mode is primarily for debugging, such a tool does not make too much sense. But right now, that's my main way of running Postgres. I hack the source code, build it, run it with the --single option to test my patch, then keep hacking. Given this niche workflow, the default DestReceiver is a big no-no for me.

How to use it

1. Build the project, we need to know the location of Postgres include directory. It is intended to not invoke pg_config, in case you have multiple Postgres installed. The build procedure only works on macOS.

   $ PG_INCLUDE_DIR=<your Postgres include dir> cargo b -r
   
   # If you want to use pg_config
   $ PG_INCLUDE_DIR=$(pg_config --includedir) cargo b -r

   Then you will get 2 archive files under target/release:

   $ find target/release -name '*.a'
   target/release/libstatic_inline_c_funcs.a
   target/release/libbox_dest_receiver.a 

2. Let Postgres link them:

   LIBS += box_dest_receiver/target/release/libbox_dest_receiver.a
   LIBS += box_dest_receiver/target/release/libstatic_inline_c_funcs.a

   I believe there are better approaches to do this, but I currently don't know.

3. Use this DestReceiver in Postgres

   src/backend/tcop/dest.c

    #include "libpq/libpq.h"
    #include "libpq/pqformat.h"
    
   +#include "box_dest_receiver.h"
   +
    
   /* ----------------
    *             dummy DestReceiver functions
   @@ -130,7 +132,7 @@ CreateDestReceiver(CommandDest dest)
                           return unconstify(DestReceiver *, &donothingDR);
    
                    case DestDebug:
   -                       return unconstify(DestReceiver *, &debugtupDR);
   +                       return box_dr_create(dest);
    
                    case DestSPI:
                           return unconstify(DestReceiver *, &spi_printtupDR);