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postgres_fdw: Extend postgres_fdw_get_connections to return user name.

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This commit adds a "user_name" output column to
the postgres_fdw_get_connections function, returning the name
of the local user mapped to the foreign server for each connection.
If a public mapping is used, it returns "public."

This helps identify postgres_fdw connections more easily,
such as determining which connections are invalid, closed,
or used within the current transaction.

No extension version bump is needed, as commit c297a47c5f
already handled it for v18~.

Author: Hayato Kuroda
Reviewed-by: Fujii Masao
Discussion: https://postgr.es/m/b492a935-6c7e-8c08-e485-3c1d64d7d10f@oss.nttdata.com
This commit is contained in:
Fujii Masao
2024-09-18 12:51:48 +09:00
parent b14e9ce7d5
commit 4f08ab5545
5 changed files with 81 additions and 26 deletions
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57
contrib/postgres_fdw/connection.c
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@ -1997,8 +1997,8 @@ pgfdw_finish_abort_cleanup(List *pending_entries, List *cancel_requested,
/* Number of output arguments (columns) for various API versions */
#define POSTGRES_FDW_GET_CONNECTIONS_COLS_V1_1 2
#define POSTGRES_FDW_GET_CONNECTIONS_COLS_V1_2 4
#define POSTGRES_FDW_GET_CONNECTIONS_COLS 4 /* maximum of above */
#define POSTGRES_FDW_GET_CONNECTIONS_COLS_V1_2 5
#define POSTGRES_FDW_GET_CONNECTIONS_COLS 5 /* maximum of above */
/*
* Internal function used by postgres_fdw_get_connections variants.
@ -2014,10 +2014,13 @@ pgfdw_finish_abort_cleanup(List *pending_entries, List *cancel_requested,
*
* For API version 1.2 and later, this function takes an input parameter
* to check a connection status and returns the following
* additional values along with the two values from version 1.1:
* additional values along with the three values from version 1.1:
*
* - user_name - the local user name of the active connection. In case the
* user mapping is dropped but the connection is still active, then the
* user name will be NULL in the output.
* - used_in_xact - true if the connection is used in the current transaction.
* - closed: true if the connection is closed.
* - closed - true if the connection is closed.
*
* No records are returned when there are no cached connections at all.
*/
@ -2056,6 +2059,7 @@ postgres_fdw_get_connections_internal(FunctionCallInfo fcinfo,
ForeignServer *server;
Datum values[POSTGRES_FDW_GET_CONNECTIONS_COLS] = {0};
bool nulls[POSTGRES_FDW_GET_CONNECTIONS_COLS] = {0};
int i = 0;
/* We only look for open remote connections */
if (!entry->conn)
@ -2100,28 +2104,61 @@ postgres_fdw_get_connections_internal(FunctionCallInfo fcinfo,
Assert(entry->conn && entry->xact_depth > 0 && entry->invalidated);
/* Show null, if no server name was found */
nulls[0] = true;
nulls[i++] = true;
}
else
values[0] = CStringGetTextDatum(server->servername);
values[i++] = CStringGetTextDatum(server->servername);
values[1] = BoolGetDatum(!entry->invalidated);
if (api_version >= PGFDW_V1_2)
{
HeapTuple tp;
/* Use the system cache to obtain the user mapping */
tp = SearchSysCache1(USERMAPPINGOID, ObjectIdGetDatum(entry->key));
/*
* Just like in the foreign server case, user mappings can also be
* dropped in the current explicit transaction. Therefore, the
* similar check as in the server case is required.
*/
if (!HeapTupleIsValid(tp))
{
/*
* If we reach here, this entry must have been invalidated in
* pgfdw_inval_callback, same as in the server case.
*/
Assert(entry->conn && entry->xact_depth > 0 &&
entry->invalidated);
nulls[i++] = true;
}
else
{
Oid userid;
userid = ((Form_pg_user_mapping) GETSTRUCT(tp))->umuser;
values[i++] = CStringGetTextDatum(MappingUserName(userid));
ReleaseSysCache(tp);
}
}
values[i++] = BoolGetDatum(!entry->invalidated);
if (api_version >= PGFDW_V1_2)
{
bool check_conn = PG_GETARG_BOOL(0);
/* Is this connection used in the current transaction? */
values[2] = BoolGetDatum(entry->xact_depth > 0);
values[i++] = BoolGetDatum(entry->xact_depth > 0);
/*
* If a connection status check is requested and supported, return
* whether the connection is closed. Otherwise, return NULL.
*/
if (check_conn && pgfdw_conn_checkable())
values[3] = BoolGetDatum(pgfdw_conn_check(entry->conn) != 0);
values[i++] = BoolGetDatum(pgfdw_conn_check(entry->conn) != 0);
else
nulls[3] = true;
nulls[i++] = true;
}
tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);