Re: [PATCH] psql: add \dcs to list all constraints

Here a few comments to v2:

== listConstraints() == 

It looks like that a WHERE condition can be potentially added to the "if
(!showAllkinds)" block even if there is no WHERE clause at all. I'm not
sure if this path is even possible, but perhaps a more defensive
approach here wouldn't be a bad idea, e.g.

...
bool have_where = false;

if (!showSystem && !pattern)
{
        appendPQExpBufferStr(&buf,
                             "WHERE n.nspname <> 'pg_catalog' \n"
                             "  AND n.nspname <> 'information_schema' \n");
        have_where = true;
}

if (!validateSQLNamePattern(&buf, pattern,
                have_where, false,
                "n.nspname", "cst.conname", NULL,
                "pg_catalog.pg_table_is_visible(cst.conrelid)",
                &have_where, 3))       
{

if (!showAllkinds)
{
        appendPQExpBuffer(&buf, " %s cst.contype in (",
                          have_where ? "AND" : "WHERE");
...

What do you think?

== Patch name ==

It'd be better if you format your patch name with the version upfront, e.g.

$ git format-patch -1 -v3

I've tried a few more edge cases and so far everything is working as

expected

postgres=# \set ECHO_HIDDEN on

postgres=# \dcs 🐘*
/******** QUERY *********/
... 

FROM pg_catalog.pg_constraint cst
     JOIN pg_catalog.pg_namespace n ON n.oid = cst.connamespace
     JOIN pg_catalog.pg_class c on c.oid = cst.conrelid