query postgres in openresty

nginx.conf

worker_processes 1;


events {
    worker_connections 64;
}

http {
    send_timeout 1s;
    server_tokens off;
    client_body_buffer_size   128k;

    upstream database {
        postgres_server  localhost:5432 dbname=test
                         user=adminpassword=test123;
        postgres_keepalive max=80 mode=single overflow=ignore;
    }
    
    lua_package_path "$prefix/?.luac;$prefix/?.lua;;";

    include mime.types;
    
    log_format access '$remote_addr - $remote_user [$time_local] "$request" $status $body_bytes_sent $request_time $request_body';
    
    include ngx_php_win.conf;
    include ngx_lua_win.conf;
}

ngx_lua_win.conf

server {
        listen 80;
        access_log off;#/var/log/nginx/access.log access;
        gzip on;
        gzip_types  text/plain application/x-javascript text/css application/xml;

        location /postgres {
            internal;
            default_type text/html;
            set_by_lua $query_sql 'return ngx.unescape_uri(ngx.var.arg_sql)';
            postgres_pass   database;
            rds_json          on;
            postgres_query  $query_sql;
        }
        
        location /hello {
            access_log off;
            default_type text/html;
            content_by_lua '
                ngx.say("<p>hello, world</p>")
            ';
        }
}

query_db.lua

function query_from_db(sql)
   local res = ngx.location.capture('/postgres',
        { args = {sql = sql } }
    )
   
   local status = res.status
   local body = json.decode(res.body)

   if status == 200 then
       status = true
   else
       status = false
   end
    return status, body
end

function client_heartbeat(mid)
    common.query_from_db("BEGIN")
    local sql = [[UPDATE clients SET update_time = now() WHERE midn = ']] .. mid .. [[']]
    common.query_from_db(sql)
    common.query_from_db("COMMIT")
end