How can I ensure that a materialized view is always up to date?

Question

I\'ll need to invoke REFRESH MATERIALIZED VIEW on each change to the tables involved, right? I\'m surprised to not find much discussion of this on the web.

Answer 1

Let me point out three things on the previous answer by MatheusOl - the pglater technology.

1. As the last element of long_options array it should include "{0, 0, 0, 0}" element as pointed at https://linux.die.net/man/3/getopt_long by the phrase "The last element of the array has to be filled with zeros." So, it should read -

   static struct option long_options[] =     {
         //......
         {"help", no_argument, NULL, '?'},
         {0, 0, 0, 0} 
   };
   

2. On the malloc/free thing -- one free(for char listen = malloc(...);) is missing. Anyhow, malloc caused pglater process to crash on CentOS (but not on Ubuntu - I don't know why). So, I recommend using char array and assign the array name to the char pointer(to both char and char**). You many need to force type conversion while you do that(pointer assignment).

   char block4[100];
   ...
   password_prompt = block4;
   ...
   char block1[500];
   const char **keywords = (const char **)&block1;
   ...
   char block3[300];
   char *listen = block3;
   sprintf(listen, "listen %s", id);
   PQfreemem(id);
   res = PQexec(db, listen);
   

3. Use below table to calculate timeout where md is mature_duration which is the time difference between the latest refresh(lr) time point and current time.

   when md >= callback_delay(cd) ==> timeout: 0

   when md + PING_INTERVAL >= cd ==> timeout: cd-md[=cd-(now-lr)]

   when md + PING_INTERVAL < cd ==> timeout: PI

To implement this algorithm(3rd point), you should init 'lr' as follows -

res = PQexec(db, command);
latest_refresh = time(0);
if (PQresultStatus(res) == PGRES_COMMAND_OK) {