[pgmoneta#5] SQL: CHECKPOINT

cmake/FindPsqlDevel.cmake

@@ -2,19 +2,41 @@
 # postgresql-server-devel Support
 #
 
+find_program(PG_CONFIG pg_config)
+
+if (NOT PG_CONFIG)
+    message(FATAL_ERROR "pg_config executable not found. Ensure PostgreSQL is installed and pg_config is in your PATH.")
+endif()
+
+# Use pg_config to get the include and library directories
+execute_process(COMMAND ${PG_CONFIG} --includedir
+                OUTPUT_VARIABLE PSQLDEVEL_INCLUDE_DIR
+                OUTPUT_STRIP_TRAILING_WHITESPACE)
+
+execute_process(COMMAND ${PG_CONFIG} --libdir
+                OUTPUT_VARIABLE PSQLDEVEL_LIBRARY_DIR
+                OUTPUT_STRIP_TRAILING_WHITESPACE)
+
 find_path(PSQLDEVEL_INCLUDE_DIR
   NAMES libpq-fe.h
-  PATH_SUFFIXES postgresql
+  PATHS ${PSQLDEVEL_INCLUDE_DIR}
 )
 
 find_library(PSQLDEVEL_LIBRARY
   NAMES pq
+  PATHS ${PSQLDEVEL_LIBRARY_DIR}
 )
 
 include(FindPackageHandleStandardArgs)
 find_package_handle_standard_args(PsqlDevel DEFAULT_MSG
                                   PSQLDEVEL_INCLUDE_DIR PSQLDEVEL_LIBRARY)
 
+if (PSQLDEVEL_INCLUDE_DIR AND PSQLDEVEL_LIBRARY)
+  set(PSQLDEVEL_FOUND TRUE)
+else()
+  set(PSQLDEVEL_FOUND FALSE)
+endif()
+
 if (PSQLDEVEL_FOUND)
   set(PSQLDEVEL_INCLUDE_DIRS ${PSQLDEVEL_INCLUDE_DIR})
   set(PSQLDEVEL_LIBRARIES ${PSQLDEVEL_LIBRARY})

doc/manual/user-03-functions.md

@@ -4,11 +4,12 @@
 
 ## Security
 
-After you create the extension `pgmoneta_ext` using the `postgres` role, you can test all functions as shown below. Some functions may require superuser privileges (For the column `Superuser`, the value is `true`), so if you log in with a role without superuser privileges, the function will return `false`. If you have superuser privileges, it will work as desired.
+After you create the extension `pgmoneta_ext` using the `postgres` role, you can test all functions as shown below. Some functions may require specific privileges (For the column `Privilege`), so if you log in with a role without the specific privileges, the function will return `false`. If you have the specific privileges, it will work as desired.
 
 ## Extension functions
 
-| Function                    | Superuser | Description                                            |
+| Function                    | Privilege                    | Description                                            |
 |-----------------------------|-----------|--------------------------------------------------------|
-| `pgmoneta_ext_version()`    |   false   | Return the version number of `pgmoneta_ext` as a Datum.|
-| `pgmoneta_ext_switch_wal()` |   true    | A function for switching to a new WAL file.            |
+| `pgmoneta_ext_version()`    |   Default                      | Return the version number of `pgmoneta_ext` as a Datum.|
+| `pgmoneta_ext_switch_wal()` | SUPERUSER                   | A function for switching to a new WAL file.            |
+| `pgmoneta_ext_checkpoint()` | SUPERUSER <br>pg_checkpoint | A function which forces a checkpoint. <br>This function can only be executed by a `SUPERUSER` in PostgreSQL 13/14, but can also be executed by `pg_checkpoint` in PostgreSQL 15+. <br>You can use the SQL command `GRANT pg_checkpoint TO repl;` to assign the role in PostgreSQL 15+.|

sql/pgmoneta_ext--0.1.0.sql

@@ -7,4 +7,11 @@ CREATE FUNCTION pgmoneta_ext_switch_wal(OUT success bool,
 ) 
 RETURNS record 
 AS 'MODULE_PATHNAME' 
+LANGUAGE C STRICT;
+
+CREATE FUNCTION pgmoneta_ext_checkpoint(OUT success bool,
+                                        OUT value text
+) 
+RETURNS record 
+AS 'MODULE_PATHNAME' 
 LANGUAGE C STRICT;

src/include/utils.h

@@ -39,14 +39,24 @@ extern "C" {
 #include "fmgr.h"
 
 /* system */
+#include <stdbool.h>
 
 /**
  * Check if the role has superuser privileges.
  * @param roleid The current role's ID
- * @return 0 upon success, otherwise 1
+ * @return The result
  */
-int
-pgmoneta_ext_check_privilege(Oid roleid);
+bool
+pgmoneta_ext_check_superuser(Oid roleid);
+
+/**
+ * Check if the role has specific role.
+ * @param roleid The current role's ID
+ * @param rolename Specific role name
+ * @return The result
+ */
+bool
+pgmoneta_ext_check_role(Oid roleid, const char* rolename);
 
 #ifdef __cplusplus
 }

src/pgmoneta_ext/lib.c

@@ -27,7 +27,7 @@
  *
  */
 
-/* pgmoneta */
+/* pgmoneta_ext */
 #include <pgmoneta_ext.h>
 #include <utils.h>
 
@@ -52,6 +52,7 @@ PG_MODULE_MAGIC;
 
 PG_FUNCTION_INFO_V1(pgmoneta_ext_version);
 PG_FUNCTION_INFO_V1(pgmoneta_ext_switch_wal);
+PG_FUNCTION_INFO_V1(pgmoneta_ext_checkpoint);
 
 Datum
 pgmoneta_ext_version(PG_FUNCTION_ARGS)
@@ -78,15 +79,15 @@ pgmoneta_ext_switch_wal(PG_FUNCTION_ARGS)
    XLogRecPtr recptr;
    bool nulls[2];
    char str_res[1024];
-   int is_superuser;
+   bool is_superuser;
 
    memset(nulls, 0, sizeof(nulls));
 
    roleid = GetUserId();
 
-   is_superuser = pgmoneta_ext_check_privilege(roleid);
+   is_superuser = pgmoneta_ext_check_superuser(roleid);
 
-   if (!is_superuser)
+   if (is_superuser)
    {
       // Request to switch WAL with mark_unimportant set to false.
       recptr = RequestXLogSwitch(false);
@@ -114,5 +115,64 @@ pgmoneta_ext_switch_wal(PG_FUNCTION_ARGS)
    tuple = heap_form_tuple(tupdesc, values, nulls);
    result = HeapTupleGetDatum(tuple);
 
+   PG_RETURN_DATUM(result);
+}
+
+#ifndef RequestCheckpoint
+extern void RequestCheckpoint(int flags);
+#endif
+
+Datum
+pgmoneta_ext_checkpoint(PG_FUNCTION_ARGS)
+{
+   Datum values[2];
+   Datum result;
+   HeapTuple tuple;
+   Oid roleid;
+   TupleDesc tupdesc;
+   bool nulls[2];
+   bool is_superuser;
+   bool is_pg_checkpoint;
+   char cp[1024];
+
+   memset(nulls, 0, sizeof(nulls));
+   memset(&cp, 0, sizeof(cp));
+   is_superuser = false;
+   is_pg_checkpoint = false;
+
+   roleid = GetUserId();
+   is_superuser = pgmoneta_ext_check_superuser(roleid);
+
+#if PG_VERSION_NUM >= 150000
+   is_pg_checkpoint = pgmoneta_ext_check_role(roleid, "pg_checkpoint");
+#endif
+
+   if (is_superuser || is_pg_checkpoint)
+   {
+      // Perform the checkpoint
+      RequestCheckpoint(CHECKPOINT_IMMEDIATE | CHECKPOINT_WAIT | CHECKPOINT_FORCE);
+
+      values[0] = BoolGetDatum(true);
+      snprintf(&cp[0], sizeof(cp), "%s", "CHECKPOINT");
+      values[1] = CStringGetTextDatum(cp);
+   }
+   else
+   {
+      ereport(LOG, errmsg_internal("pgmoneta_ext_checkpoint: Current role is not a superuser"));
+
+      values[0] = BoolGetDatum(false);
+      nulls[1] = true;
+   }
+
+   // Create a tuple descriptor for our result type
+   if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
+   {
+      ereport(ERROR, errmsg_internal("pgmoneta_ext_checkpoint: Return type must be a row type"));
+   }
+
+   // Build the result tuple
+   tuple = heap_form_tuple(tupdesc, values, nulls);
+   result = HeapTupleGetDatum(tuple);
+
    PG_RETURN_DATUM(result);
 }

src/pgmoneta_ext/utils.c

@@ -27,33 +27,37 @@
  *
  */
 
-/* pgmoneta */
+/* pgmoneta_ext */
 #include <utils.h>
 
 /* PostgreSQL */
 #include "access/htup_details.h"
 #include "catalog/pg_authid.h"
+#include "miscadmin.h"
+#include "utils/acl.h"
+#include "utils/builtins.h"
 #include "utils/elog.h"
 #include "utils/errcodes.h"
 #include "utils/relcache.h"
 #include "utils/syscache.h"
 
 /* system */
-#include <stdbool.h>
 
-int
-pgmoneta_ext_check_privilege(Oid roleid)
+bool
+pgmoneta_ext_check_superuser(Oid roleid)
 {
    bool is_superuser;
    HeapTuple roletuple;
    Form_pg_authid roleform;
 
+   is_superuser = false;
+
    // Fetch the role's tuple from pg_authid
    roletuple = SearchSysCache1(AUTHOID, ObjectIdGetDatum(roleid));
    if (!HeapTupleIsValid(roletuple))
    {
-      ereport(ERROR, errmsg_internal("pgmoneta_ext_switch_wal: Role with OID %u does not exist", roleid));
-      return 1;
+      ereport(ERROR, errmsg_internal("pgmoneta_ext_check_superuser: Role with OID %u does not exist", roleid));
+      return false;
    }
 
    // Get the role's superuser attribute
@@ -64,5 +68,43 @@ pgmoneta_ext_check_privilege(Oid roleid)
    // Release the role tuple
    ReleaseSysCache(roletuple);
 
-   return !is_superuser;
+   return is_superuser;
 }
+
+bool
+pgmoneta_ext_check_role(Oid roleid, const char* rolename)
+{
+   bool is_success;
+   HeapTuple roletuple;
+   List* role_oids;
+   ListCell* cell;
+
+   is_success = false;
+
+   roletuple = SearchSysCache1(AUTHOID, ObjectIdGetDatum(roleid));
+   if (!HeapTupleIsValid(roletuple))
+   {
+      ereport(ERROR, errmsg_internal("pgmoneta_ext_check_role: Role with OID %u does not exist", roleid));
+      return false;
+   }
+
+   // Get role OIDs of a given role name
+   Oid role_oid = get_role_oid(rolename, false);
+   role_oids = list_make1_oid(role_oid);
+
+   // Check if the role has the specific privilege
+   foreach (cell, role_oids)
+   {
+      Oid checkpoint_role_oid = lfirst_oid(cell);
+      if (is_member_of_role(roleid, checkpoint_role_oid))
+      {
+         is_success = true;
+         break;
+      }
+   }
+
+   ReleaseSysCache(roletuple);
+   list_free(role_oids);
+
+   return is_success;
+}