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postgres/contrib/postgres_fdw/connection.c
Fujii Masao fe186bda78 postgres_fdw: Extend postgres_fdw_get_connections to return remote backend PID. 
This commit adds a new "remote_backend_pid" output column to
the postgres_fdw_get_connections function. It returns the process ID of
the remote backend, on the foreign server, handling the connection.

This enhancement is useful for troubleshooting, monitoring, and reporting.
For example, if a connection is unexpectedly closed by the foreign server,
the remote backend's PID can help diagnose the cause.

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

Author: Sagar Dilip Shedge <sagar.shedge92@gmail.com>
Reviewed-by: Fujii Masao <masao.fujii@gmail.com>
Discussion: https://postgr.es/m/CAPhYifF25q5xUQWXETfKwhc0YVa_6+tfG9Kw4bCvCjpCWxYs2A@mail.gmail.com
2025-03-03 08:51:30 +09:00

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/*-------------------------------------------------------------------------
*
* connection.c
* Connection management functions for postgres_fdw
*
* Portions Copyright (c) 2012-2025, PostgreSQL Global Development Group
*
* IDENTIFICATION
* contrib/postgres_fdw/connection.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#if HAVE_POLL_H
#include <poll.h>
#endif
#include "access/xact.h"
#include "catalog/pg_user_mapping.h"
#include "commands/defrem.h"
#include "common/base64.h"
#include "funcapi.h"
#include "libpq/libpq-be.h"
#include "libpq/libpq-be-fe-helpers.h"
#include "mb/pg_wchar.h"
#include "miscadmin.h"
#include "pgstat.h"
#include "postgres_fdw.h"
#include "storage/latch.h"
#include "utils/builtins.h"
#include "utils/hsearch.h"
#include "utils/inval.h"
#include "utils/syscache.h"
/*
* Connection cache hash table entry
*
* The lookup key in this hash table is the user mapping OID. We use just one
* connection per user mapping ID, which ensures that all the scans use the
* same snapshot during a query. Using the user mapping OID rather than
* the foreign server OID + user OID avoids creating multiple connections when
* the public user mapping applies to all user OIDs.
*
* The "conn" pointer can be NULL if we don't currently have a live connection.
* When we do have a connection, xact_depth tracks the current depth of
* transactions and subtransactions open on the remote side. We need to issue
* commands at the same nesting depth on the remote as we're executing at
* ourselves, so that rolling back a subtransaction will kill the right
* queries and not the wrong ones.
*/
typedef Oid ConnCacheKey;
typedef struct ConnCacheEntry
{
ConnCacheKey key; /* hash key (must be first) */
PGconn *conn; /* connection to foreign server, or NULL */
/* Remaining fields are invalid when conn is NULL: */
int xact_depth; /* 0 = no xact open, 1 = main xact open, 2 =
* one level of subxact open, etc */
bool have_prep_stmt; /* have we prepared any stmts in this xact? */
bool have_error; /* have any subxacts aborted in this xact? */
bool changing_xact_state; /* xact state change in process */
bool parallel_commit; /* do we commit (sub)xacts in parallel? */
bool parallel_abort; /* do we abort (sub)xacts in parallel? */
bool invalidated; /* true if reconnect is pending */
bool keep_connections; /* setting value of keep_connections
* server option */
Oid serverid; /* foreign server OID used to get server name */
uint32 server_hashvalue; /* hash value of foreign server OID */
uint32 mapping_hashvalue; /* hash value of user mapping OID */
PgFdwConnState state; /* extra per-connection state */
} ConnCacheEntry;
/*
* Connection cache (initialized on first use)
*/
static HTAB *ConnectionHash = NULL;
/* for assigning cursor numbers and prepared statement numbers */
static unsigned int cursor_number = 0;
static unsigned int prep_stmt_number = 0;
/* tracks whether any work is needed in callback functions */
static bool xact_got_connection = false;
/* custom wait event values, retrieved from shared memory */
static uint32 pgfdw_we_cleanup_result = 0;
static uint32 pgfdw_we_connect = 0;
static uint32 pgfdw_we_get_result = 0;
/*
* Milliseconds to wait to cancel an in-progress query or execute a cleanup
* query; if it takes longer than 30 seconds to do these, we assume the
* connection is dead.
*/
#define CONNECTION_CLEANUP_TIMEOUT 30000
/*
* Milliseconds to wait before issuing another cancel request. This covers
* the race condition where the remote session ignored our cancel request
* because it arrived while idle.
*/
#define RETRY_CANCEL_TIMEOUT 1000
/* Macro for constructing abort command to be sent */
#define CONSTRUCT_ABORT_COMMAND(sql, entry, toplevel) \
do { \
if (toplevel) \
snprintf((sql), sizeof(sql), \
"ABORT TRANSACTION"); \
else \
snprintf((sql), sizeof(sql), \
"ROLLBACK TO SAVEPOINT s%d; RELEASE SAVEPOINT s%d", \
(entry)->xact_depth, (entry)->xact_depth); \
} while(0)
/*
* Extension version number, for supporting older extension versions' objects
*/
enum pgfdwVersion
{
PGFDW_V1_1 = 0,
PGFDW_V1_2,
};
/*
* SQL functions
*/
PG_FUNCTION_INFO_V1(postgres_fdw_get_connections);
PG_FUNCTION_INFO_V1(postgres_fdw_get_connections_1_2);
PG_FUNCTION_INFO_V1(postgres_fdw_disconnect);
PG_FUNCTION_INFO_V1(postgres_fdw_disconnect_all);
/* prototypes of private functions */
static void make_new_connection(ConnCacheEntry *entry, UserMapping *user);
static PGconn *connect_pg_server(ForeignServer *server, UserMapping *user);
static void disconnect_pg_server(ConnCacheEntry *entry);
static void check_conn_params(const char **keywords, const char **values, UserMapping *user);
static void configure_remote_session(PGconn *conn);
static void do_sql_command_begin(PGconn *conn, const char *sql);
static void do_sql_command_end(PGconn *conn, const char *sql,
bool consume_input);
static void begin_remote_xact(ConnCacheEntry *entry);
static void pgfdw_xact_callback(XactEvent event, void *arg);
static void pgfdw_subxact_callback(SubXactEvent event,
SubTransactionId mySubid,
SubTransactionId parentSubid,
void *arg);
static void pgfdw_inval_callback(Datum arg, int cacheid, uint32 hashvalue);
static void pgfdw_reject_incomplete_xact_state_change(ConnCacheEntry *entry);
static void pgfdw_reset_xact_state(ConnCacheEntry *entry, bool toplevel);
static bool pgfdw_cancel_query(PGconn *conn);
static bool pgfdw_cancel_query_begin(PGconn *conn, TimestampTz endtime);
static bool pgfdw_cancel_query_end(PGconn *conn, TimestampTz endtime,
TimestampTz retrycanceltime,
bool consume_input);
static bool pgfdw_exec_cleanup_query(PGconn *conn, const char *query,
bool ignore_errors);
static bool pgfdw_exec_cleanup_query_begin(PGconn *conn, const char *query);
static bool pgfdw_exec_cleanup_query_end(PGconn *conn, const char *query,
TimestampTz endtime,
bool consume_input,
bool ignore_errors);
static bool pgfdw_get_cleanup_result(PGconn *conn, TimestampTz endtime,
TimestampTz retrycanceltime,
PGresult **result, bool *timed_out);
static void pgfdw_abort_cleanup(ConnCacheEntry *entry, bool toplevel);
static bool pgfdw_abort_cleanup_begin(ConnCacheEntry *entry, bool toplevel,
List **pending_entries,
List **cancel_requested);
static void pgfdw_finish_pre_commit_cleanup(List *pending_entries);
static void pgfdw_finish_pre_subcommit_cleanup(List *pending_entries,
int curlevel);
static void pgfdw_finish_abort_cleanup(List *pending_entries,
List *cancel_requested,
bool toplevel);
static void pgfdw_security_check(const char **keywords, const char **values,
UserMapping *user, PGconn *conn);
static bool UserMappingPasswordRequired(UserMapping *user);
static bool UseScramPassthrough(ForeignServer *server, UserMapping *user);
static bool disconnect_cached_connections(Oid serverid);
static void postgres_fdw_get_connections_internal(FunctionCallInfo fcinfo,
enum pgfdwVersion api_version);
static int pgfdw_conn_check(PGconn *conn);
static bool pgfdw_conn_checkable(void);
/*
* Get a PGconn which can be used to execute queries on the remote PostgreSQL
* server with the user's authorization. A new connection is established
* if we don't already have a suitable one, and a transaction is opened at
* the right subtransaction nesting depth if we didn't do that already.
*
* will_prep_stmt must be true if caller intends to create any prepared
* statements. Since those don't go away automatically at transaction end
* (not even on error), we need this flag to cue manual cleanup.
*
* If state is not NULL, *state receives the per-connection state associated
* with the PGconn.
*/
PGconn *
GetConnection(UserMapping *user, bool will_prep_stmt, PgFdwConnState **state)
{
bool found;
bool retry = false;
ConnCacheEntry *entry;
ConnCacheKey key;
MemoryContext ccxt = CurrentMemoryContext;
/* First time through, initialize connection cache hashtable */
if (ConnectionHash == NULL)
{
HASHCTL ctl;
if (pgfdw_we_get_result == 0)
pgfdw_we_get_result =
WaitEventExtensionNew("PostgresFdwGetResult");
ctl.keysize = sizeof(ConnCacheKey);
ctl.entrysize = sizeof(ConnCacheEntry);
ConnectionHash = hash_create("postgres_fdw connections", 8,
&ctl,
HASH_ELEM | HASH_BLOBS);
/*
* Register some callback functions that manage connection cleanup.
* This should be done just once in each backend.
*/
RegisterXactCallback(pgfdw_xact_callback, NULL);
RegisterSubXactCallback(pgfdw_subxact_callback, NULL);
CacheRegisterSyscacheCallback(FOREIGNSERVEROID,
pgfdw_inval_callback, (Datum) 0);
CacheRegisterSyscacheCallback(USERMAPPINGOID,
pgfdw_inval_callback, (Datum) 0);
}
/* Set flag that we did GetConnection during the current transaction */
xact_got_connection = true;
/* Create hash key for the entry. Assume no pad bytes in key struct */
key = user->umid;
/*
* Find or create cached entry for requested connection.
*/
entry = hash_search(ConnectionHash, &key, HASH_ENTER, &found);
if (!found)
{
/*
* We need only clear "conn" here; remaining fields will be filled
* later when "conn" is set.
*/
entry->conn = NULL;
}
/* Reject further use of connections which failed abort cleanup. */
pgfdw_reject_incomplete_xact_state_change(entry);
/*
* If the connection needs to be remade due to invalidation, disconnect as
* soon as we're out of all transactions.
*/
if (entry->conn != NULL && entry->invalidated && entry->xact_depth == 0)
{
elog(DEBUG3, "closing connection %p for option changes to take effect",
entry->conn);
disconnect_pg_server(entry);
}
/*
* If cache entry doesn't have a connection, we have to establish a new
* connection. (If connect_pg_server throws an error, the cache entry
* will remain in a valid empty state, ie conn == NULL.)
*/
if (entry->conn == NULL)
make_new_connection(entry, user);
/*
* We check the health of the cached connection here when using it. In
* cases where we're out of all transactions, if a broken connection is
* detected, we try to reestablish a new connection later.
*/
PG_TRY();
{
/* Process a pending asynchronous request if any. */
if (entry->state.pendingAreq)
process_pending_request(entry->state.pendingAreq);
/* Start a new transaction or subtransaction if needed. */
begin_remote_xact(entry);
}
PG_CATCH();
{
MemoryContext ecxt = MemoryContextSwitchTo(ccxt);
ErrorData *errdata = CopyErrorData();
/*
* Determine whether to try to reestablish the connection.
*
* After a broken connection is detected in libpq, any error other
* than connection failure (e.g., out-of-memory) can be thrown
* somewhere between return from libpq and the expected ereport() call
* in pgfdw_report_error(). In this case, since PQstatus() indicates
* CONNECTION_BAD, checking only PQstatus() causes the false detection
* of connection failure. To avoid this, we also verify that the
* error's sqlstate is ERRCODE_CONNECTION_FAILURE. Note that also
* checking only the sqlstate can cause another false detection
* because pgfdw_report_error() may report ERRCODE_CONNECTION_FAILURE
* for any libpq-originated error condition.
*/
if (errdata->sqlerrcode != ERRCODE_CONNECTION_FAILURE ||
PQstatus(entry->conn) != CONNECTION_BAD ||
entry->xact_depth > 0)
{
MemoryContextSwitchTo(ecxt);
PG_RE_THROW();
}
/* Clean up the error state */
FlushErrorState();
FreeErrorData(errdata);
errdata = NULL;
retry = true;
}
PG_END_TRY();
/*
* If a broken connection is detected, disconnect it, reestablish a new
* connection and retry a new remote transaction. If connection failure is
* reported again, we give up getting a connection.
*/
if (retry)
{
Assert(entry->xact_depth == 0);
ereport(DEBUG3,
(errmsg_internal("could not start remote transaction on connection %p",
entry->conn)),
errdetail_internal("%s", pchomp(PQerrorMessage(entry->conn))));
elog(DEBUG3, "closing connection %p to reestablish a new one",
entry->conn);
disconnect_pg_server(entry);
make_new_connection(entry, user);
begin_remote_xact(entry);
}
/* Remember if caller will prepare statements */
entry->have_prep_stmt |= will_prep_stmt;
/* If caller needs access to the per-connection state, return it. */
if (state)
*state = &entry->state;
return entry->conn;
}
/*
* Reset all transient state fields in the cached connection entry and
* establish new connection to the remote server.
*/
static void
make_new_connection(ConnCacheEntry *entry, UserMapping *user)
{
ForeignServer *server = GetForeignServer(user->serverid);
ListCell *lc;
Assert(entry->conn == NULL);
/* Reset all transient state fields, to be sure all are clean */
entry->xact_depth = 0;
entry->have_prep_stmt = false;
entry->have_error = false;
entry->changing_xact_state = false;
entry->invalidated = false;
entry->serverid = server->serverid;
entry->server_hashvalue =
GetSysCacheHashValue1(FOREIGNSERVEROID,
ObjectIdGetDatum(server->serverid));
entry->mapping_hashvalue =
GetSysCacheHashValue1(USERMAPPINGOID,
ObjectIdGetDatum(user->umid));
memset(&entry->state, 0, sizeof(entry->state));
/*
* Determine whether to keep the connection that we're about to make here
* open even after the transaction using it ends, so that the subsequent
* transactions can re-use it.
*
* By default, all the connections to any foreign servers are kept open.
*
* Also determine whether to commit/abort (sub)transactions opened on the
* remote server in parallel at (sub)transaction end, which is disabled by
* default.
*
* Note: it's enough to determine these only when making a new connection
* because if these settings for it are changed, it will be closed and
* re-made later.
*/
entry->keep_connections = true;
entry->parallel_commit = false;
entry->parallel_abort = false;
foreach(lc, server->options)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "keep_connections") == 0)
entry->keep_connections = defGetBoolean(def);
else if (strcmp(def->defname, "parallel_commit") == 0)
entry->parallel_commit = defGetBoolean(def);
else if (strcmp(def->defname, "parallel_abort") == 0)
entry->parallel_abort = defGetBoolean(def);
}
/* Now try to make the connection */
entry->conn = connect_pg_server(server, user);
elog(DEBUG3, "new postgres_fdw connection %p for server \"%s\" (user mapping oid %u, userid %u)",
entry->conn, server->servername, user->umid, user->userid);
}
/*
* Check that non-superuser has used password or delegated credentials
* to establish connection; otherwise, he's piggybacking on the
* postgres server's user identity. See also dblink_security_check()
* in contrib/dblink and check_conn_params.
*/
static void
pgfdw_security_check(const char **keywords, const char **values, UserMapping *user, PGconn *conn)
{
/* Superusers bypass the check */
if (superuser_arg(user->userid))
return;
#ifdef ENABLE_GSS
/* Connected via GSSAPI with delegated credentials- all good. */
if (PQconnectionUsedGSSAPI(conn) && be_gssapi_get_delegation(MyProcPort))
return;
#endif
/* Ok if superuser set PW required false. */
if (!UserMappingPasswordRequired(user))
return;
/* Connected via PW, with PW required true, and provided non-empty PW. */
if (PQconnectionUsedPassword(conn))
{
/* ok if params contain a non-empty password */
for (int i = 0; keywords[i] != NULL; i++)
{
if (strcmp(keywords[i], "password") == 0 && values[i][0] != '\0')
return;
}
}
ereport(ERROR,
(errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
errmsg("password or GSSAPI delegated credentials required"),
errdetail("Non-superuser cannot connect if the server does not request a password or use GSSAPI with delegated credentials."),
errhint("Target server's authentication method must be changed or password_required=false set in the user mapping attributes.")));
}
/*
* Connect to remote server using specified server and user mapping properties.
*/
static PGconn *
connect_pg_server(ForeignServer *server, UserMapping *user)
{
PGconn *volatile conn = NULL;
/*
* Use PG_TRY block to ensure closing connection on error.
*/
PG_TRY();
{
const char **keywords;
const char **values;
char *appname = NULL;
int n;
/*
* Construct connection params from generic options of ForeignServer
* and UserMapping. (Some of them might not be libpq options, in
* which case we'll just waste a few array slots.) Add 4 extra slots
* for application_name, fallback_application_name, client_encoding,
* end marker.
*/
n = list_length(server->options) + list_length(user->options) + 4 + 2;
keywords = (const char **) palloc(n * sizeof(char *));
values = (const char **) palloc(n * sizeof(char *));
n = 0;
n += ExtractConnectionOptions(server->options,
keywords + n, values + n);
n += ExtractConnectionOptions(user->options,
keywords + n, values + n);
/*
* Use pgfdw_application_name as application_name if set.
*
* PQconnectdbParams() processes the parameter arrays from start to
* end. If any key word is repeated, the last value is used. Therefore
* note that pgfdw_application_name must be added to the arrays after
* options of ForeignServer are, so that it can override
* application_name set in ForeignServer.
*/
if (pgfdw_application_name && *pgfdw_application_name != '\0')
{
keywords[n] = "application_name";
values[n] = pgfdw_application_name;
n++;
}
/*
* Search the parameter arrays to find application_name setting, and
* replace escape sequences in it with status information if found.
* The arrays are searched backwards because the last value is used if
* application_name is repeatedly set.
*/
for (int i = n - 1; i >= 0; i--)
{
if (strcmp(keywords[i], "application_name") == 0 &&
*(values[i]) != '\0')
{
/*
* Use this application_name setting if it's not empty string
* even after any escape sequences in it are replaced.
*/
appname = process_pgfdw_appname(values[i]);
if (appname[0] != '\0')
{
values[i] = appname;
break;
}
/*
* This empty application_name is not used, so we set
* values[i] to NULL and keep searching the array to find the
* next one.
*/
values[i] = NULL;
pfree(appname);
appname = NULL;
}
}
/* Use "postgres_fdw" as fallback_application_name */
keywords[n] = "fallback_application_name";
values[n] = "postgres_fdw";
n++;
/* Set client_encoding so that libpq can convert encoding properly. */
keywords[n] = "client_encoding";
values[n] = GetDatabaseEncodingName();
n++;
if (MyProcPort->has_scram_keys && UseScramPassthrough(server, user))
{
int len;
int encoded_len;
keywords[n] = "scram_client_key";
len = pg_b64_enc_len(sizeof(MyProcPort->scram_ClientKey));
/* don't forget the zero-terminator */
values[n] = palloc0(len + 1);
encoded_len = pg_b64_encode((const char *) MyProcPort->scram_ClientKey,
sizeof(MyProcPort->scram_ClientKey),
(char *) values[n], len);
if (encoded_len < 0)
elog(ERROR, "could not encode SCRAM client key");
n++;
keywords[n] = "scram_server_key";
len = pg_b64_enc_len(sizeof(MyProcPort->scram_ServerKey));
/* don't forget the zero-terminator */
values[n] = palloc0(len + 1);
encoded_len = pg_b64_encode((const char *) MyProcPort->scram_ServerKey,
sizeof(MyProcPort->scram_ServerKey),
(char *) values[n], len);
if (encoded_len < 0)
elog(ERROR, "could not encode SCRAM server key");
n++;
}
keywords[n] = values[n] = NULL;
/*
* Verify the set of connection parameters only if scram pass-through
* is not being used because the password is not necessary.
*/
if (!(MyProcPort->has_scram_keys && UseScramPassthrough(server, user)))
check_conn_params(keywords, values, user);
/* first time, allocate or get the custom wait event */
if (pgfdw_we_connect == 0)
pgfdw_we_connect = WaitEventExtensionNew("PostgresFdwConnect");
/* OK to make connection */
conn = libpqsrv_connect_params(keywords, values,
false, /* expand_dbname */
pgfdw_we_connect);
if (!conn || PQstatus(conn) != CONNECTION_OK)
ereport(ERROR,
(errcode(ERRCODE_SQLCLIENT_UNABLE_TO_ESTABLISH_SQLCONNECTION),
errmsg("could not connect to server \"%s\"",
server->servername),
errdetail_internal("%s", pchomp(PQerrorMessage(conn)))));
/*
* Perform post-connection security checks only if scram pass-through
* is not being used because the password is not necessary.
*/
if (!(MyProcPort->has_scram_keys && UseScramPassthrough(server, user)))
pgfdw_security_check(keywords, values, user, conn);
/* Prepare new session for use */
configure_remote_session(conn);
if (appname != NULL)
pfree(appname);
pfree(keywords);
pfree(values);
}
PG_CATCH();
{
libpqsrv_disconnect(conn);
PG_RE_THROW();
}
PG_END_TRY();
return conn;
}
/*
* Disconnect any open connection for a connection cache entry.
*/
static void
disconnect_pg_server(ConnCacheEntry *entry)
{
if (entry->conn != NULL)
{
libpqsrv_disconnect(entry->conn);
entry->conn = NULL;
}
}
/*
* Return true if the password_required is defined and false for this user
* mapping, otherwise false. The mapping has been pre-validated.
*/
static bool
UserMappingPasswordRequired(UserMapping *user)
{
ListCell *cell;
foreach(cell, user->options)
{
DefElem *def = (DefElem *) lfirst(cell);
if (strcmp(def->defname, "password_required") == 0)
return defGetBoolean(def);
}
return true;
}
static bool
UseScramPassthrough(ForeignServer *server, UserMapping *user)
{
ListCell *cell;
foreach(cell, server->options)
{
DefElem *def = (DefElem *) lfirst(cell);
if (strcmp(def->defname, "use_scram_passthrough") == 0)
return defGetBoolean(def);
}
foreach(cell, user->options)
{
DefElem *def = (DefElem *) lfirst(cell);
if (strcmp(def->defname, "use_scram_passthrough") == 0)
return defGetBoolean(def);
}
return false;
}
/*
* For non-superusers, insist that the connstr specify a password or that the
* user provided their own GSSAPI delegated credentials. This
* prevents a password from being picked up from .pgpass, a service file, the
* environment, etc. We don't want the postgres user's passwords,
* certificates, etc to be accessible to non-superusers. (See also
* dblink_connstr_check in contrib/dblink.)
*/
static void
check_conn_params(const char **keywords, const char **values, UserMapping *user)
{
int i;
/* no check required if superuser */
if (superuser_arg(user->userid))
return;
#ifdef ENABLE_GSS
/* ok if the user provided their own delegated credentials */
if (be_gssapi_get_delegation(MyProcPort))
return;
#endif
/* ok if params contain a non-empty password */
for (i = 0; keywords[i] != NULL; i++)
{
if (strcmp(keywords[i], "password") == 0 && values[i][0] != '\0')
return;
}
/* ok if the superuser explicitly said so at user mapping creation time */
if (!UserMappingPasswordRequired(user))
return;
ereport(ERROR,
(errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
errmsg("password or GSSAPI delegated credentials required"),
errdetail("Non-superusers must delegate GSSAPI credentials, provide a password, or enable SCRAM pass-through in user mapping.")));
}
/*
* Issue SET commands to make sure remote session is configured properly.
*
* We do this just once at connection, assuming nothing will change the
* values later. Since we'll never send volatile function calls to the
* remote, there shouldn't be any way to break this assumption from our end.
* It's possible to think of ways to break it at the remote end, eg making
* a foreign table point to a view that includes a set_config call ---
* but once you admit the possibility of a malicious view definition,
* there are any number of ways to break things.
*/
static void
configure_remote_session(PGconn *conn)
{
int remoteversion = PQserverVersion(conn);
/* Force the search path to contain only pg_catalog (see deparse.c) */
do_sql_command(conn, "SET search_path = pg_catalog");
/*
* Set remote timezone; this is basically just cosmetic, since all
* transmitted and returned timestamptzs should specify a zone explicitly
* anyway. However it makes the regression test outputs more predictable.
*
* We don't risk setting remote zone equal to ours, since the remote
* server might use a different timezone database. Instead, use GMT
* (quoted, because very old servers are picky about case). That's
* guaranteed to work regardless of the remote's timezone database,
* because pg_tzset() hard-wires it (at least in PG 9.2 and later).
*/
do_sql_command(conn, "SET timezone = 'GMT'");
/*
* Set values needed to ensure unambiguous data output from remote. (This
* logic should match what pg_dump does. See also set_transmission_modes
* in postgres_fdw.c.)
*/
do_sql_command(conn, "SET datestyle = ISO");
if (remoteversion >= 80400)
do_sql_command(conn, "SET intervalstyle = postgres");
if (remoteversion >= 90000)
do_sql_command(conn, "SET extra_float_digits = 3");
else
do_sql_command(conn, "SET extra_float_digits = 2");
}
/*
* Convenience subroutine to issue a non-data-returning SQL command to remote
*/
void
do_sql_command(PGconn *conn, const char *sql)
{
do_sql_command_begin(conn, sql);
do_sql_command_end(conn, sql, false);
}
static void
do_sql_command_begin(PGconn *conn, const char *sql)
{
if (!PQsendQuery(conn, sql))
pgfdw_report_error(ERROR, NULL, conn, false, sql);
}
static void
do_sql_command_end(PGconn *conn, const char *sql, bool consume_input)
{
PGresult *res;
/*
* If requested, consume whatever data is available from the socket. (Note
* that if all data is available, this allows pgfdw_get_result to call
* PQgetResult without forcing the overhead of WaitLatchOrSocket, which
* would be large compared to the overhead of PQconsumeInput.)
*/
if (consume_input && !PQconsumeInput(conn))
pgfdw_report_error(ERROR, NULL, conn, false, sql);
res = pgfdw_get_result(conn);
if (PQresultStatus(res) != PGRES_COMMAND_OK)
pgfdw_report_error(ERROR, res, conn, true, sql);
PQclear(res);
}
/*
* Start remote transaction or subtransaction, if needed.
*
* Note that we always use at least REPEATABLE READ in the remote session.
* This is so that, if a query initiates multiple scans of the same or
* different foreign tables, we will get snapshot-consistent results from
* those scans. A disadvantage is that we can't provide sane emulation of
* READ COMMITTED behavior --- it would be nice if we had some other way to
* control which remote queries share a snapshot.
*/
static void
begin_remote_xact(ConnCacheEntry *entry)
{
int curlevel = GetCurrentTransactionNestLevel();
/* Start main transaction if we haven't yet */
if (entry->xact_depth <= 0)
{
const char *sql;
elog(DEBUG3, "starting remote transaction on connection %p",
entry->conn);
if (IsolationIsSerializable())
sql = "START TRANSACTION ISOLATION LEVEL SERIALIZABLE";
else
sql = "START TRANSACTION ISOLATION LEVEL REPEATABLE READ";
entry->changing_xact_state = true;
do_sql_command(entry->conn, sql);
entry->xact_depth = 1;
entry->changing_xact_state = false;
}
/*
* If we're in a subtransaction, stack up savepoints to match our level.
* This ensures we can rollback just the desired effects when a
* subtransaction aborts.
*/
while (entry->xact_depth < curlevel)
{
char sql[64];
snprintf(sql, sizeof(sql), "SAVEPOINT s%d", entry->xact_depth + 1);
entry->changing_xact_state = true;
do_sql_command(entry->conn, sql);
entry->xact_depth++;
entry->changing_xact_state = false;
}
}
/*
* Release connection reference count created by calling GetConnection.
*/
void
ReleaseConnection(PGconn *conn)
{
/*
* Currently, we don't actually track connection references because all
* cleanup is managed on a transaction or subtransaction basis instead. So
* there's nothing to do here.
*/
}
/*
* Assign a "unique" number for a cursor.
*
* These really only need to be unique per connection within a transaction.
* For the moment we ignore the per-connection point and assign them across
* all connections in the transaction, but we ask for the connection to be
* supplied in case we want to refine that.
*
* Note that even if wraparound happens in a very long transaction, actual
* collisions are highly improbable; just be sure to use %u not %d to print.
*/
unsigned int
GetCursorNumber(PGconn *conn)
{
return ++cursor_number;
}
/*
* Assign a "unique" number for a prepared statement.
*
* This works much like GetCursorNumber, except that we never reset the counter
* within a session. That's because we can't be 100% sure we've gotten rid
* of all prepared statements on all connections, and it's not really worth
* increasing the risk of prepared-statement name collisions by resetting.
*/
unsigned int
GetPrepStmtNumber(PGconn *conn)
{
return ++prep_stmt_number;
}
/*
* Submit a query and wait for the result.
*
* Since we don't use non-blocking mode, this can't process interrupts while
* pushing the query text to the server. That risk is relatively small, so we
* ignore that for now.
*
* Caller is responsible for the error handling on the result.
*/
PGresult *
pgfdw_exec_query(PGconn *conn, const char *query, PgFdwConnState *state)
{
/* First, process a pending asynchronous request, if any. */
if (state && state->pendingAreq)
process_pending_request(state->pendingAreq);
if (!PQsendQuery(conn, query))
return NULL;
return pgfdw_get_result(conn);
}
/*
* Wrap libpqsrv_get_result_last(), adding wait event.
*
* Caller is responsible for the error handling on the result.
*/
PGresult *
pgfdw_get_result(PGconn *conn)
{
return libpqsrv_get_result_last(conn, pgfdw_we_get_result);
}
/*
* Report an error we got from the remote server.
*
* elevel: error level to use (typically ERROR, but might be less)
* res: PGresult containing the error
* conn: connection we did the query on
* clear: if true, PQclear the result (otherwise caller will handle it)
* sql: NULL, or text of remote command we tried to execute
*
* Note: callers that choose not to throw ERROR for a remote error are
* responsible for making sure that the associated ConnCacheEntry gets
* marked with have_error = true.
*/
void
pgfdw_report_error(int elevel, PGresult *res, PGconn *conn,
bool clear, const char *sql)
{
/* If requested, PGresult must be released before leaving this function. */
PG_TRY();
{
char *diag_sqlstate = PQresultErrorField(res, PG_DIAG_SQLSTATE);
char *message_primary = PQresultErrorField(res, PG_DIAG_MESSAGE_PRIMARY);
char *message_detail = PQresultErrorField(res, PG_DIAG_MESSAGE_DETAIL);
char *message_hint = PQresultErrorField(res, PG_DIAG_MESSAGE_HINT);
char *message_context = PQresultErrorField(res, PG_DIAG_CONTEXT);
int sqlstate;
if (diag_sqlstate)
sqlstate = MAKE_SQLSTATE(diag_sqlstate[0],
diag_sqlstate[1],
diag_sqlstate[2],
diag_sqlstate[3],
diag_sqlstate[4]);
else
sqlstate = ERRCODE_CONNECTION_FAILURE;
/*
* If we don't get a message from the PGresult, try the PGconn. This
* is needed because for connection-level failures, PQgetResult may
* just return NULL, not a PGresult at all.
*/
if (message_primary == NULL)
message_primary = pchomp(PQerrorMessage(conn));
ereport(elevel,
(errcode(sqlstate),
(message_primary != NULL && message_primary[0] != '\0') ?
errmsg_internal("%s", message_primary) :
errmsg("could not obtain message string for remote error"),
message_detail ? errdetail_internal("%s", message_detail) : 0,
message_hint ? errhint("%s", message_hint) : 0,
message_context ? errcontext("%s", message_context) : 0,
sql ? errcontext("remote SQL command: %s", sql) : 0));
}
PG_FINALLY();
{
if (clear)
PQclear(res);
}
PG_END_TRY();
}
/*
* pgfdw_xact_callback --- cleanup at main-transaction end.
*
* This runs just late enough that it must not enter user-defined code
* locally. (Entering such code on the remote side is fine. Its remote
* COMMIT TRANSACTION may run deferred triggers.)
*/
static void
pgfdw_xact_callback(XactEvent event, void *arg)
{
HASH_SEQ_STATUS scan;
ConnCacheEntry *entry;
List *pending_entries = NIL;
List *cancel_requested = NIL;
/* Quick exit if no connections were touched in this transaction. */
if (!xact_got_connection)
return;
/*
* Scan all connection cache entries to find open remote transactions, and
* close them.
*/
hash_seq_init(&scan, ConnectionHash);
while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
{
PGresult *res;
/* Ignore cache entry if no open connection right now */
if (entry->conn == NULL)
continue;
/* If it has an open remote transaction, try to close it */
if (entry->xact_depth > 0)
{
elog(DEBUG3, "closing remote transaction on connection %p",
entry->conn);
switch (event)
{
case XACT_EVENT_PARALLEL_PRE_COMMIT:
case XACT_EVENT_PRE_COMMIT:
/*
* If abort cleanup previously failed for this connection,
* we can't issue any more commands against it.
*/
pgfdw_reject_incomplete_xact_state_change(entry);
/* Commit all remote transactions during pre-commit */
entry->changing_xact_state = true;
if (entry->parallel_commit)
{
do_sql_command_begin(entry->conn, "COMMIT TRANSACTION");
pending_entries = lappend(pending_entries, entry);
continue;
}
do_sql_command(entry->conn, "COMMIT TRANSACTION");
entry->changing_xact_state = false;
/*
* If there were any errors in subtransactions, and we
* made prepared statements, do a DEALLOCATE ALL to make
* sure we get rid of all prepared statements. This is
* annoying and not terribly bulletproof, but it's
* probably not worth trying harder.
*
* DEALLOCATE ALL only exists in 8.3 and later, so this
* constrains how old a server postgres_fdw can
* communicate with. We intentionally ignore errors in
* the DEALLOCATE, so that we can hobble along to some
* extent with older servers (leaking prepared statements
* as we go; but we don't really support update operations
* pre-8.3 anyway).
*/
if (entry->have_prep_stmt && entry->have_error)
{
res = pgfdw_exec_query(entry->conn, "DEALLOCATE ALL",
NULL);
PQclear(res);
}
entry->have_prep_stmt = false;
entry->have_error = false;
break;
case XACT_EVENT_PRE_PREPARE:
/*
* We disallow any remote transactions, since it's not
* very reasonable to hold them open until the prepared
* transaction is committed. For the moment, throw error
* unconditionally; later we might allow read-only cases.
* Note that the error will cause us to come right back
* here with event == XACT_EVENT_ABORT, so we'll clean up
* the connection state at that point.
*/
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot PREPARE a transaction that has operated on postgres_fdw foreign tables")));
break;
case XACT_EVENT_PARALLEL_COMMIT:
case XACT_EVENT_COMMIT:
case XACT_EVENT_PREPARE:
/* Pre-commit should have closed the open transaction */
elog(ERROR, "missed cleaning up connection during pre-commit");
break;
case XACT_EVENT_PARALLEL_ABORT:
case XACT_EVENT_ABORT:
/* Rollback all remote transactions during abort */
if (entry->parallel_abort)
{
if (pgfdw_abort_cleanup_begin(entry, true,
&pending_entries,
&cancel_requested))
continue;
}
else
pgfdw_abort_cleanup(entry, true);
break;
}
}
/* Reset state to show we're out of a transaction */
pgfdw_reset_xact_state(entry, true);
}
/* If there are any pending connections, finish cleaning them up */
if (pending_entries || cancel_requested)
{
if (event == XACT_EVENT_PARALLEL_PRE_COMMIT ||
event == XACT_EVENT_PRE_COMMIT)
{
Assert(cancel_requested == NIL);
pgfdw_finish_pre_commit_cleanup(pending_entries);
}
else
{
Assert(event == XACT_EVENT_PARALLEL_ABORT ||
event == XACT_EVENT_ABORT);
pgfdw_finish_abort_cleanup(pending_entries, cancel_requested,
true);
}
}
/*
* Regardless of the event type, we can now mark ourselves as out of the
* transaction. (Note: if we are here during PRE_COMMIT or PRE_PREPARE,
* this saves a useless scan of the hashtable during COMMIT or PREPARE.)
*/
xact_got_connection = false;
/* Also reset cursor numbering for next transaction */
cursor_number = 0;
}
/*
* pgfdw_subxact_callback --- cleanup at subtransaction end.
*/
static void
pgfdw_subxact_callback(SubXactEvent event, SubTransactionId mySubid,
SubTransactionId parentSubid, void *arg)
{
HASH_SEQ_STATUS scan;
ConnCacheEntry *entry;
int curlevel;
List *pending_entries = NIL;
List *cancel_requested = NIL;
/* Nothing to do at subxact start, nor after commit. */
if (!(event == SUBXACT_EVENT_PRE_COMMIT_SUB ||
event == SUBXACT_EVENT_ABORT_SUB))
return;
/* Quick exit if no connections were touched in this transaction. */
if (!xact_got_connection)
return;
/*
* Scan all connection cache entries to find open remote subtransactions
* of the current level, and close them.
*/
curlevel = GetCurrentTransactionNestLevel();
hash_seq_init(&scan, ConnectionHash);
while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
{
char sql[100];
/*
* We only care about connections with open remote subtransactions of
* the current level.
*/
if (entry->conn == NULL || entry->xact_depth < curlevel)
continue;
if (entry->xact_depth > curlevel)
elog(ERROR, "missed cleaning up remote subtransaction at level %d",
entry->xact_depth);
if (event == SUBXACT_EVENT_PRE_COMMIT_SUB)
{
/*
* If abort cleanup previously failed for this connection, we
* can't issue any more commands against it.
*/
pgfdw_reject_incomplete_xact_state_change(entry);
/* Commit all remote subtransactions during pre-commit */
snprintf(sql, sizeof(sql), "RELEASE SAVEPOINT s%d", curlevel);
entry->changing_xact_state = true;
if (entry->parallel_commit)
{
do_sql_command_begin(entry->conn, sql);
pending_entries = lappend(pending_entries, entry);
continue;
}
do_sql_command(entry->conn, sql);
entry->changing_xact_state = false;
}
else
{
/* Rollback all remote subtransactions during abort */
if (entry->parallel_abort)
{
if (pgfdw_abort_cleanup_begin(entry, false,
&pending_entries,
&cancel_requested))
continue;
}
else
pgfdw_abort_cleanup(entry, false);
}
/* OK, we're outta that level of subtransaction */
pgfdw_reset_xact_state(entry, false);
}
/* If there are any pending connections, finish cleaning them up */
if (pending_entries || cancel_requested)
{
if (event == SUBXACT_EVENT_PRE_COMMIT_SUB)
{
Assert(cancel_requested == NIL);
pgfdw_finish_pre_subcommit_cleanup(pending_entries, curlevel);
}
else
{
Assert(event == SUBXACT_EVENT_ABORT_SUB);
pgfdw_finish_abort_cleanup(pending_entries, cancel_requested,
false);
}
}
}
/*
* Connection invalidation callback function
*
* After a change to a pg_foreign_server or pg_user_mapping catalog entry,
* close connections depending on that entry immediately if current transaction
* has not used those connections yet. Otherwise, mark those connections as
* invalid and then make pgfdw_xact_callback() close them at the end of current
* transaction, since they cannot be closed in the midst of the transaction
* using them. Closed connections will be remade at the next opportunity if
* necessary.
*
* Although most cache invalidation callbacks blow away all the related stuff
* regardless of the given hashvalue, connections are expensive enough that
* it's worth trying to avoid that.
*
* NB: We could avoid unnecessary disconnection more strictly by examining
* individual option values, but it seems too much effort for the gain.
*/
static void
pgfdw_inval_callback(Datum arg, int cacheid, uint32 hashvalue)
{
HASH_SEQ_STATUS scan;
ConnCacheEntry *entry;
Assert(cacheid == FOREIGNSERVEROID || cacheid == USERMAPPINGOID);
/* ConnectionHash must exist already, if we're registered */
hash_seq_init(&scan, ConnectionHash);
while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
{
/* Ignore invalid entries */
if (entry->conn == NULL)
continue;
/* hashvalue == 0 means a cache reset, must clear all state */
if (hashvalue == 0 ||
(cacheid == FOREIGNSERVEROID &&
entry->server_hashvalue == hashvalue) ||
(cacheid == USERMAPPINGOID &&
entry->mapping_hashvalue == hashvalue))
{
/*
* Close the connection immediately if it's not used yet in this
* transaction. Otherwise mark it as invalid so that
* pgfdw_xact_callback() can close it at the end of this
* transaction.
*/
if (entry->xact_depth == 0)
{
elog(DEBUG3, "discarding connection %p", entry->conn);
disconnect_pg_server(entry);
}
else
entry->invalidated = true;
}
}
}
/*
* Raise an error if the given connection cache entry is marked as being
* in the middle of an xact state change. This should be called at which no
* such change is expected to be in progress; if one is found to be in
* progress, it means that we aborted in the middle of a previous state change
* and now don't know what the remote transaction state actually is.
* Such connections can't safely be further used. Re-establishing the
* connection would change the snapshot and roll back any writes already
* performed, so that's not an option, either. Thus, we must abort.
*/
static void
pgfdw_reject_incomplete_xact_state_change(ConnCacheEntry *entry)
{
ForeignServer *server;
/* nothing to do for inactive entries and entries of sane state */
if (entry->conn == NULL || !entry->changing_xact_state)
return;
/* make sure this entry is inactive */
disconnect_pg_server(entry);
/* find server name to be shown in the message below */
server = GetForeignServer(entry->serverid);
ereport(ERROR,
(errcode(ERRCODE_CONNECTION_EXCEPTION),
errmsg("connection to server \"%s\" was lost",
server->servername)));
}
/*
* Reset state to show we're out of a (sub)transaction.
*/
static void
pgfdw_reset_xact_state(ConnCacheEntry *entry, bool toplevel)
{
if (toplevel)
{
/* Reset state to show we're out of a transaction */
entry->xact_depth = 0;
/*
* If the connection isn't in a good idle state, it is marked as
* invalid or keep_connections option of its server is disabled, then
* discard it to recover. Next GetConnection will open a new
* connection.
*/
if (PQstatus(entry->conn) != CONNECTION_OK ||
PQtransactionStatus(entry->conn) != PQTRANS_IDLE ||
entry->changing_xact_state ||
entry->invalidated ||
!entry->keep_connections)
{
elog(DEBUG3, "discarding connection %p", entry->conn);
disconnect_pg_server(entry);
}
}
else
{
/* Reset state to show we're out of a subtransaction */
entry->xact_depth--;
}
}
/*
* Cancel the currently-in-progress query (whose query text we do not have)
* and ignore the result. Returns true if we successfully cancel the query
* and discard any pending result, and false if not.
*
* It's not a huge problem if we throw an ERROR here, but if we get into error
* recursion trouble, we'll end up slamming the connection shut, which will
* necessitate failing the entire toplevel transaction even if subtransactions
* were used. Try to use WARNING where we can.
*
* XXX: if the query was one sent by fetch_more_data_begin(), we could get the
* query text from the pendingAreq saved in the per-connection state, then
* report the query using it.
*/
static bool
pgfdw_cancel_query(PGconn *conn)
{
TimestampTz now = GetCurrentTimestamp();
TimestampTz endtime;
TimestampTz retrycanceltime;
/*
* If it takes too long to cancel the query and discard the result, assume
* the connection is dead.
*/
endtime = TimestampTzPlusMilliseconds(now, CONNECTION_CLEANUP_TIMEOUT);
/*
* Also, lose patience and re-issue the cancel request after a little bit.
* (This serves to close some race conditions.)
*/
retrycanceltime = TimestampTzPlusMilliseconds(now, RETRY_CANCEL_TIMEOUT);
if (!pgfdw_cancel_query_begin(conn, endtime))
return false;
return pgfdw_cancel_query_end(conn, endtime, retrycanceltime, false);
}
/*
* Submit a cancel request to the given connection, waiting only until
* the given time.
*
* We sleep interruptibly until we receive confirmation that the cancel
* request has been accepted, and if it is, return true; if the timeout
* lapses without that, or the request fails for whatever reason, return
* false.
*/
static bool
pgfdw_cancel_query_begin(PGconn *conn, TimestampTz endtime)
{
const char *errormsg = libpqsrv_cancel(conn, endtime);
if (errormsg != NULL)
ereport(WARNING,
errcode(ERRCODE_CONNECTION_FAILURE),
errmsg("could not send cancel request: %s", errormsg));
return errormsg == NULL;
}
static bool
pgfdw_cancel_query_end(PGconn *conn, TimestampTz endtime,
TimestampTz retrycanceltime, bool consume_input)
{
PGresult *result;
bool timed_out;
/*
* If requested, consume whatever data is available from the socket. (Note
* that if all data is available, this allows pgfdw_get_cleanup_result to
* call PQgetResult without forcing the overhead of WaitLatchOrSocket,
* which would be large compared to the overhead of PQconsumeInput.)
*/
if (consume_input && !PQconsumeInput(conn))
{
ereport(WARNING,
(errcode(ERRCODE_CONNECTION_FAILURE),
errmsg("could not get result of cancel request: %s",
pchomp(PQerrorMessage(conn)))));
return false;
}
/* Get and discard the result of the query. */
if (pgfdw_get_cleanup_result(conn, endtime, retrycanceltime,
&result, &timed_out))
{
if (timed_out)
ereport(WARNING,
(errmsg("could not get result of cancel request due to timeout")));
else
ereport(WARNING,
(errcode(ERRCODE_CONNECTION_FAILURE),
errmsg("could not get result of cancel request: %s",
pchomp(PQerrorMessage(conn)))));
return false;
}
PQclear(result);
return true;
}
/*
* Submit a query during (sub)abort cleanup and wait up to 30 seconds for the
* result. If the query is executed without error, the return value is true.
* If the query is executed successfully but returns an error, the return
* value is true if and only if ignore_errors is set. If the query can't be
* sent or times out, the return value is false.
*
* It's not a huge problem if we throw an ERROR here, but if we get into error
* recursion trouble, we'll end up slamming the connection shut, which will
* necessitate failing the entire toplevel transaction even if subtransactions
* were used. Try to use WARNING where we can.
*/
static bool
pgfdw_exec_cleanup_query(PGconn *conn, const char *query, bool ignore_errors)
{
TimestampTz endtime;
/*
* If it takes too long to execute a cleanup query, assume the connection
* is dead. It's fairly likely that this is why we aborted in the first
* place (e.g. statement timeout, user cancel), so the timeout shouldn't
* be too long.
*/
endtime = TimestampTzPlusMilliseconds(GetCurrentTimestamp(),
CONNECTION_CLEANUP_TIMEOUT);
if (!pgfdw_exec_cleanup_query_begin(conn, query))
return false;
return pgfdw_exec_cleanup_query_end(conn, query, endtime,
false, ignore_errors);
}
static bool
pgfdw_exec_cleanup_query_begin(PGconn *conn, const char *query)
{
Assert(query != NULL);
/*
* Submit a query. Since we don't use non-blocking mode, this also can
* block. But its risk is relatively small, so we ignore that for now.
*/
if (!PQsendQuery(conn, query))
{
pgfdw_report_error(WARNING, NULL, conn, false, query);
return false;
}
return true;
}
static bool
pgfdw_exec_cleanup_query_end(PGconn *conn, const char *query,
TimestampTz endtime, bool consume_input,
bool ignore_errors)
{
PGresult *result;
bool timed_out;
Assert(query != NULL);
/*
* If requested, consume whatever data is available from the socket. (Note
* that if all data is available, this allows pgfdw_get_cleanup_result to
* call PQgetResult without forcing the overhead of WaitLatchOrSocket,
* which would be large compared to the overhead of PQconsumeInput.)
*/
if (consume_input && !PQconsumeInput(conn))
{
pgfdw_report_error(WARNING, NULL, conn, false, query);
return false;
}
/* Get the result of the query. */
if (pgfdw_get_cleanup_result(conn, endtime, endtime, &result, &timed_out))
{
if (timed_out)
ereport(WARNING,
(errmsg("could not get query result due to timeout"),
errcontext("remote SQL command: %s", query)));
else
pgfdw_report_error(WARNING, NULL, conn, false, query);
return false;
}
/* Issue a warning if not successful. */
if (PQresultStatus(result) != PGRES_COMMAND_OK)
{
pgfdw_report_error(WARNING, result, conn, true, query);
return ignore_errors;
}
PQclear(result);
return true;
}
/*
* Get, during abort cleanup, the result of a query that is in progress.
* This might be a query that is being interrupted by a cancel request or by
* transaction abort, or it might be a query that was initiated as part of
* transaction abort to get the remote side back to the appropriate state.
*
* endtime is the time at which we should give up and assume the remote side
* is dead. retrycanceltime is the time at which we should issue a fresh
* cancel request (pass the same value as endtime if this is not wanted).
*
* Returns true if the timeout expired or connection trouble occurred,
* false otherwise. Sets *result except in case of a true result.
* Sets *timed_out to true only when the timeout expired.
*/
static bool
pgfdw_get_cleanup_result(PGconn *conn, TimestampTz endtime,
TimestampTz retrycanceltime,
PGresult **result,
bool *timed_out)
{
volatile bool failed = false;
PGresult *volatile last_res = NULL;
*result = NULL;
*timed_out = false;
/* In what follows, do not leak any PGresults on an error. */
PG_TRY();
{
int canceldelta = RETRY_CANCEL_TIMEOUT * 2;
for (;;)
{
PGresult *res;
while (PQisBusy(conn))
{
int wc;
TimestampTz now = GetCurrentTimestamp();
long cur_timeout;
/* If timeout has expired, give up. */
if (now >= endtime)
{
*timed_out = true;
failed = true;
goto exit;
}
/* If we need to re-issue the cancel request, do that. */
if (now >= retrycanceltime)
{
/* We ignore failure to issue the repeated request. */
(void) libpqsrv_cancel(conn, endtime);
/* Recompute "now" in case that took measurable time. */
now = GetCurrentTimestamp();
/* Adjust re-cancel timeout in increasing steps. */
retrycanceltime = TimestampTzPlusMilliseconds(now,
canceldelta);
canceldelta += canceldelta;
}
/* If timeout has expired, give up, else get sleep time. */
cur_timeout = TimestampDifferenceMilliseconds(now,
Min(endtime,
retrycanceltime));
if (cur_timeout <= 0)
{
*timed_out = true;
failed = true;
goto exit;
}
/* first time, allocate or get the custom wait event */
if (pgfdw_we_cleanup_result == 0)
pgfdw_we_cleanup_result = WaitEventExtensionNew("PostgresFdwCleanupResult");
/* Sleep until there's something to do */
wc = WaitLatchOrSocket(MyLatch,
WL_LATCH_SET | WL_SOCKET_READABLE |
WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
PQsocket(conn),
cur_timeout, pgfdw_we_cleanup_result);
ResetLatch(MyLatch);
CHECK_FOR_INTERRUPTS();
/* Data available in socket? */
if (wc & WL_SOCKET_READABLE)
{
if (!PQconsumeInput(conn))
{
/* connection trouble */
failed = true;
goto exit;
}
}
}
res = PQgetResult(conn);
if (res == NULL)
break; /* query is complete */
PQclear(last_res);
last_res = res;
}
exit: ;
}
PG_CATCH();
{
PQclear(last_res);
PG_RE_THROW();
}
PG_END_TRY();
if (failed)
PQclear(last_res);
else
*result = last_res;
return failed;
}
/*
* Abort remote transaction or subtransaction.
*
* "toplevel" should be set to true if toplevel (main) transaction is
* rollbacked, false otherwise.
*
* Set entry->changing_xact_state to false on success, true on failure.
*/
static void
pgfdw_abort_cleanup(ConnCacheEntry *entry, bool toplevel)
{
char sql[100];
/*
* Don't try to clean up the connection if we're already in error
* recursion trouble.
*/
if (in_error_recursion_trouble())
entry->changing_xact_state = true;
/*
* If connection is already unsalvageable, don't touch it further.
*/
if (entry->changing_xact_state)
return;
/*
* Mark this connection as in the process of changing transaction state.
*/
entry->changing_xact_state = true;
/* Assume we might have lost track of prepared statements */
entry->have_error = true;
/*
* If a command has been submitted to the remote server by using an
* asynchronous execution function, the command might not have yet
* completed. Check to see if a command is still being processed by the
* remote server, and if so, request cancellation of the command.
*/
if (PQtransactionStatus(entry->conn) == PQTRANS_ACTIVE &&
!pgfdw_cancel_query(entry->conn))
return; /* Unable to cancel running query */
CONSTRUCT_ABORT_COMMAND(sql, entry, toplevel);
if (!pgfdw_exec_cleanup_query(entry->conn, sql, false))
return; /* Unable to abort remote (sub)transaction */
if (toplevel)
{
if (entry->have_prep_stmt && entry->have_error &&
!pgfdw_exec_cleanup_query(entry->conn,
"DEALLOCATE ALL",
true))
return; /* Trouble clearing prepared statements */
entry->have_prep_stmt = false;
entry->have_error = false;
}
/*
* If pendingAreq of the per-connection state is not NULL, it means that
* an asynchronous fetch begun by fetch_more_data_begin() was not done
* successfully and thus the per-connection state was not reset in
* fetch_more_data(); in that case reset the per-connection state here.
*/
if (entry->state.pendingAreq)
memset(&entry->state, 0, sizeof(entry->state));
/* Disarm changing_xact_state if it all worked */
entry->changing_xact_state = false;
}
/*
* Like pgfdw_abort_cleanup, submit an abort command or cancel request, but
* don't wait for the result.
*
* Returns true if the abort command or cancel request is successfully issued,
* false otherwise. If the abort command is successfully issued, the given
* connection cache entry is appended to *pending_entries. Otherwise, if the
* cancel request is successfully issued, it is appended to *cancel_requested.
*/
static bool
pgfdw_abort_cleanup_begin(ConnCacheEntry *entry, bool toplevel,
List **pending_entries, List **cancel_requested)
{
/*
* Don't try to clean up the connection if we're already in error
* recursion trouble.
*/
if (in_error_recursion_trouble())
entry->changing_xact_state = true;
/*
* If connection is already unsalvageable, don't touch it further.
*/
if (entry->changing_xact_state)
return false;
/*
* Mark this connection as in the process of changing transaction state.
*/
entry->changing_xact_state = true;
/* Assume we might have lost track of prepared statements */
entry->have_error = true;
/*
* If a command has been submitted to the remote server by using an
* asynchronous execution function, the command might not have yet
* completed. Check to see if a command is still being processed by the
* remote server, and if so, request cancellation of the command.
*/
if (PQtransactionStatus(entry->conn) == PQTRANS_ACTIVE)
{
TimestampTz endtime;
endtime = TimestampTzPlusMilliseconds(GetCurrentTimestamp(),
CONNECTION_CLEANUP_TIMEOUT);
if (!pgfdw_cancel_query_begin(entry->conn, endtime))
return false; /* Unable to cancel running query */
*cancel_requested = lappend(*cancel_requested, entry);
}
else
{
char sql[100];
CONSTRUCT_ABORT_COMMAND(sql, entry, toplevel);
if (!pgfdw_exec_cleanup_query_begin(entry->conn, sql))
return false; /* Unable to abort remote transaction */
*pending_entries = lappend(*pending_entries, entry);
}
return true;
}
/*
* Finish pre-commit cleanup of connections on each of which we've sent a
* COMMIT command to the remote server.
*/
static void
pgfdw_finish_pre_commit_cleanup(List *pending_entries)
{
ConnCacheEntry *entry;
List *pending_deallocs = NIL;
ListCell *lc;
Assert(pending_entries);
/*
* Get the result of the COMMIT command for each of the pending entries
*/
foreach(lc, pending_entries)
{
entry = (ConnCacheEntry *) lfirst(lc);
Assert(entry->changing_xact_state);
/*
* We might already have received the result on the socket, so pass
* consume_input=true to try to consume it first
*/
do_sql_command_end(entry->conn, "COMMIT TRANSACTION", true);
entry->changing_xact_state = false;
/* Do a DEALLOCATE ALL in parallel if needed */
if (entry->have_prep_stmt && entry->have_error)
{
/* Ignore errors (see notes in pgfdw_xact_callback) */
if (PQsendQuery(entry->conn, "DEALLOCATE ALL"))
{
pending_deallocs = lappend(pending_deallocs, entry);
continue;
}
}
entry->have_prep_stmt = false;
entry->have_error = false;
pgfdw_reset_xact_state(entry, true);
}
/* No further work if no pending entries */
if (!pending_deallocs)
return;
/*
* Get the result of the DEALLOCATE command for each of the pending
* entries
*/
foreach(lc, pending_deallocs)
{
PGresult *res;
entry = (ConnCacheEntry *) lfirst(lc);
/* Ignore errors (see notes in pgfdw_xact_callback) */
while ((res = PQgetResult(entry->conn)) != NULL)
{
PQclear(res);
/* Stop if the connection is lost (else we'll loop infinitely) */
if (PQstatus(entry->conn) == CONNECTION_BAD)
break;
}
entry->have_prep_stmt = false;
entry->have_error = false;
pgfdw_reset_xact_state(entry, true);
}
}
/*
* Finish pre-subcommit cleanup of connections on each of which we've sent a
* RELEASE command to the remote server.
*/
static void
pgfdw_finish_pre_subcommit_cleanup(List *pending_entries, int curlevel)
{
ConnCacheEntry *entry;
char sql[100];
ListCell *lc;
Assert(pending_entries);
/*
* Get the result of the RELEASE command for each of the pending entries
*/
snprintf(sql, sizeof(sql), "RELEASE SAVEPOINT s%d", curlevel);
foreach(lc, pending_entries)
{
entry = (ConnCacheEntry *) lfirst(lc);
Assert(entry->changing_xact_state);
/*
* We might already have received the result on the socket, so pass
* consume_input=true to try to consume it first
*/
do_sql_command_end(entry->conn, sql, true);
entry->changing_xact_state = false;
pgfdw_reset_xact_state(entry, false);
}
}
/*
* Finish abort cleanup of connections on each of which we've sent an abort
* command or cancel request to the remote server.
*/
static void
pgfdw_finish_abort_cleanup(List *pending_entries, List *cancel_requested,
bool toplevel)
{
List *pending_deallocs = NIL;
ListCell *lc;
/*
* For each of the pending cancel requests (if any), get and discard the
* result of the query, and submit an abort command to the remote server.
*/
if (cancel_requested)
{
foreach(lc, cancel_requested)
{
ConnCacheEntry *entry = (ConnCacheEntry *) lfirst(lc);
TimestampTz now = GetCurrentTimestamp();
TimestampTz endtime;
TimestampTz retrycanceltime;
char sql[100];
Assert(entry->changing_xact_state);
/*
* Set end time. You might think we should do this before issuing
* cancel request like in normal mode, but that is problematic,
* because if, for example, it took longer than 30 seconds to
* process the first few entries in the cancel_requested list, it
* would cause a timeout error when processing each of the
* remaining entries in the list, leading to slamming that entry's
* connection shut.
*/
endtime = TimestampTzPlusMilliseconds(now,
CONNECTION_CLEANUP_TIMEOUT);
retrycanceltime = TimestampTzPlusMilliseconds(now,
RETRY_CANCEL_TIMEOUT);
if (!pgfdw_cancel_query_end(entry->conn, endtime,
retrycanceltime, true))
{
/* Unable to cancel running query */
pgfdw_reset_xact_state(entry, toplevel);
continue;
}
/* Send an abort command in parallel if needed */
CONSTRUCT_ABORT_COMMAND(sql, entry, toplevel);
if (!pgfdw_exec_cleanup_query_begin(entry->conn, sql))
{
/* Unable to abort remote (sub)transaction */
pgfdw_reset_xact_state(entry, toplevel);
}
else
pending_entries = lappend(pending_entries, entry);
}
}
/* No further work if no pending entries */
if (!pending_entries)
return;
/*
* Get the result of the abort command for each of the pending entries
*/
foreach(lc, pending_entries)
{
ConnCacheEntry *entry = (ConnCacheEntry *) lfirst(lc);
TimestampTz endtime;
char sql[100];
Assert(entry->changing_xact_state);
/*
* Set end time. We do this now, not before issuing the command like
* in normal mode, for the same reason as for the cancel_requested
* entries.
*/
endtime = TimestampTzPlusMilliseconds(GetCurrentTimestamp(),
CONNECTION_CLEANUP_TIMEOUT);
CONSTRUCT_ABORT_COMMAND(sql, entry, toplevel);
if (!pgfdw_exec_cleanup_query_end(entry->conn, sql, endtime,
true, false))
{
/* Unable to abort remote (sub)transaction */
pgfdw_reset_xact_state(entry, toplevel);
continue;
}
if (toplevel)
{
/* Do a DEALLOCATE ALL in parallel if needed */
if (entry->have_prep_stmt && entry->have_error)
{
if (!pgfdw_exec_cleanup_query_begin(entry->conn,
"DEALLOCATE ALL"))
{
/* Trouble clearing prepared statements */
pgfdw_reset_xact_state(entry, toplevel);
}
else
pending_deallocs = lappend(pending_deallocs, entry);
continue;
}
entry->have_prep_stmt = false;
entry->have_error = false;
}
/* Reset the per-connection state if needed */
if (entry->state.pendingAreq)
memset(&entry->state, 0, sizeof(entry->state));
/* We're done with this entry; unset the changing_xact_state flag */
entry->changing_xact_state = false;
pgfdw_reset_xact_state(entry, toplevel);
}
/* No further work if no pending entries */
if (!pending_deallocs)
return;
Assert(toplevel);
/*
* Get the result of the DEALLOCATE command for each of the pending
* entries
*/
foreach(lc, pending_deallocs)
{
ConnCacheEntry *entry = (ConnCacheEntry *) lfirst(lc);
TimestampTz endtime;
Assert(entry->changing_xact_state);
Assert(entry->have_prep_stmt);
Assert(entry->have_error);
/*
* Set end time. We do this now, not before issuing the command like
* in normal mode, for the same reason as for the cancel_requested
* entries.
*/
endtime = TimestampTzPlusMilliseconds(GetCurrentTimestamp(),
CONNECTION_CLEANUP_TIMEOUT);
if (!pgfdw_exec_cleanup_query_end(entry->conn, "DEALLOCATE ALL",
endtime, true, true))
{
/* Trouble clearing prepared statements */
pgfdw_reset_xact_state(entry, toplevel);
continue;
}
entry->have_prep_stmt = false;
entry->have_error = false;
/* Reset the per-connection state if needed */
if (entry->state.pendingAreq)
memset(&entry->state, 0, sizeof(entry->state));
/* We're done with this entry; unset the changing_xact_state flag */
entry->changing_xact_state = false;
pgfdw_reset_xact_state(entry, toplevel);
}
}
/* 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 6
#define POSTGRES_FDW_GET_CONNECTIONS_COLS 6 /* maximum of above */
/*
* Internal function used by postgres_fdw_get_connections variants.
*
* For API version 1.1, this function takes no input parameter and
* returns a set of records with the following values:
*
* - server_name - server name of active connection. In case the foreign server
* is dropped but still the connection is active, then the server name will
* be NULL in output.
* - valid - true/false representing whether the connection is valid or not.
* Note that connections can become invalid in pgfdw_inval_callback.
*
* 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 four 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.
* - remote_backend_pid - process ID of the remote backend, on the foreign
* server, handling the connection.
*
* No records are returned when there are no cached connections at all.
*/
static void
postgres_fdw_get_connections_internal(FunctionCallInfo fcinfo,
enum pgfdwVersion api_version)
{
ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
HASH_SEQ_STATUS scan;
ConnCacheEntry *entry;
InitMaterializedSRF(fcinfo, 0);
/* If cache doesn't exist, we return no records */
if (!ConnectionHash)
return;
/* Check we have the expected number of output arguments */
switch (rsinfo->setDesc->natts)
{
case POSTGRES_FDW_GET_CONNECTIONS_COLS_V1_1:
if (api_version != PGFDW_V1_1)
elog(ERROR, "incorrect number of output arguments");
break;
case POSTGRES_FDW_GET_CONNECTIONS_COLS_V1_2:
if (api_version != PGFDW_V1_2)
elog(ERROR, "incorrect number of output arguments");
break;
default:
elog(ERROR, "incorrect number of output arguments");
}
hash_seq_init(&scan, ConnectionHash);
while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
{
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)
continue;
server = GetForeignServerExtended(entry->serverid, FSV_MISSING_OK);
/*
* The foreign server may have been dropped in current explicit
* transaction. It is not possible to drop the server from another
* session when the connection associated with it is in use in the
* current transaction, if tried so, the drop query in another session
* blocks until the current transaction finishes.
*
* Even though the server is dropped in the current transaction, the
* cache can still have associated active connection entry, say we
* call such connections dangling. Since we can not fetch the server
* name from system catalogs for dangling connections, instead we show
* NULL value for server name in output.
*
* We could have done better by storing the server name in the cache
* entry instead of server oid so that it could be used in the output.
* But the server name in each cache entry requires 64 bytes of
* memory, which is huge, when there are many cached connections and
* the use case i.e. dropping the foreign server within the explicit
* current transaction seems rare. So, we chose to show NULL value for
* server name in output.
*
* Such dangling connections get closed either in next use or at the
* end of current explicit transaction in pgfdw_xact_callback.
*/
if (!server)
{
/*
* If the server has been dropped in the current explicit
* transaction, then this entry would have been invalidated in
* pgfdw_inval_callback at the end of drop server command. Note
* that this connection would not have been closed in
* pgfdw_inval_callback because it is still being used in the
* current explicit transaction. So, assert that here.
*/
Assert(entry->conn && entry->xact_depth > 0 && entry->invalidated);
/* Show null, if no server name was found */
nulls[i++] = true;
}
else
values[i++] = CStringGetTextDatum(server->servername);
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[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[i++] = BoolGetDatum(pgfdw_conn_check(entry->conn) != 0);
else
nulls[i++] = true;
/* Return process ID of remote backend */
values[i++] = Int32GetDatum(PQbackendPID(entry->conn));
}
tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
}
}
/*
* List active foreign server connections.
*
* The SQL API of this function has changed multiple times, and will likely
* do so again in future. To support the case where a newer version of this
* loadable module is being used with an old SQL declaration of the function,
* we continue to support the older API versions.
*/
Datum
postgres_fdw_get_connections_1_2(PG_FUNCTION_ARGS)
{
postgres_fdw_get_connections_internal(fcinfo, PGFDW_V1_2);
PG_RETURN_VOID();
}
Datum
postgres_fdw_get_connections(PG_FUNCTION_ARGS)
{
postgres_fdw_get_connections_internal(fcinfo, PGFDW_V1_1);
PG_RETURN_VOID();
}
/*
* Disconnect the specified cached connections.
*
* This function discards the open connections that are established by
* postgres_fdw from the local session to the foreign server with
* the given name. Note that there can be multiple connections to
* the given server using different user mappings. If the connections
* are used in the current local transaction, they are not disconnected
* and warning messages are reported. This function returns true
* if it disconnects at least one connection, otherwise false. If no
* foreign server with the given name is found, an error is reported.
*/
Datum
postgres_fdw_disconnect(PG_FUNCTION_ARGS)
{
ForeignServer *server;
char *servername;
servername = text_to_cstring(PG_GETARG_TEXT_PP(0));
server = GetForeignServerByName(servername, false);
PG_RETURN_BOOL(disconnect_cached_connections(server->serverid));
}
/*
* Disconnect all the cached connections.
*
* This function discards all the open connections that are established by
* postgres_fdw from the local session to the foreign servers.
* If the connections are used in the current local transaction, they are
* not disconnected and warning messages are reported. This function
* returns true if it disconnects at least one connection, otherwise false.
*/
Datum
postgres_fdw_disconnect_all(PG_FUNCTION_ARGS)
{
PG_RETURN_BOOL(disconnect_cached_connections(InvalidOid));
}
/*
* Workhorse to disconnect cached connections.
*
* This function scans all the connection cache entries and disconnects
* the open connections whose foreign server OID matches with
* the specified one. If InvalidOid is specified, it disconnects all
* the cached connections.
*
* This function emits a warning for each connection that's used in
* the current transaction and doesn't close it. It returns true if
* it disconnects at least one connection, otherwise false.
*
* Note that this function disconnects even the connections that are
* established by other users in the same local session using different
* user mappings. This leads even non-superuser to be able to close
* the connections established by superusers in the same local session.
*
* XXX As of now we don't see any security risk doing this. But we should
* set some restrictions on that, for example, prevent non-superuser
* from closing the connections established by superusers even
* in the same session?
*/
static bool
disconnect_cached_connections(Oid serverid)
{
HASH_SEQ_STATUS scan;
ConnCacheEntry *entry;
bool all = !OidIsValid(serverid);
bool result = false;
/*
* Connection cache hashtable has not been initialized yet in this
* session, so return false.
*/
if (!ConnectionHash)
return false;
hash_seq_init(&scan, ConnectionHash);
while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
{
/* Ignore cache entry if no open connection right now. */
if (!entry->conn)
continue;
if (all || entry->serverid == serverid)
{
/*
* Emit a warning because the connection to close is used in the
* current transaction and cannot be disconnected right now.
*/
if (entry->xact_depth > 0)
{
ForeignServer *server;
server = GetForeignServerExtended(entry->serverid,
FSV_MISSING_OK);
if (!server)
{
/*
* If the foreign server was dropped while its connection
* was used in the current transaction, the connection
* must have been marked as invalid by
* pgfdw_inval_callback at the end of DROP SERVER command.
*/
Assert(entry->invalidated);
ereport(WARNING,
(errmsg("cannot close dropped server connection because it is still in use")));
}
else
ereport(WARNING,
(errmsg("cannot close connection for server \"%s\" because it is still in use",
server->servername)));
}
else
{
elog(DEBUG3, "discarding connection %p", entry->conn);
disconnect_pg_server(entry);
result = true;
}
}
}
return result;
}
/*
* Check if the remote server closed the connection.
*
* Returns 1 if the connection is closed, -1 if an error occurred,
* and 0 if it's not closed or if the connection check is unavailable
* on this platform.
*/
static int
pgfdw_conn_check(PGconn *conn)
{
int sock = PQsocket(conn);
if (PQstatus(conn) != CONNECTION_OK || sock == -1)
return -1;
#if (defined(HAVE_POLL) && defined(POLLRDHUP))
{
struct pollfd input_fd;
int result;
input_fd.fd = sock;
input_fd.events = POLLRDHUP;
input_fd.revents = 0;
do
result = poll(&input_fd, 1, 0);
while (result < 0 && errno == EINTR);
if (result < 0)
return -1;
return (input_fd.revents &
(POLLRDHUP | POLLHUP | POLLERR | POLLNVAL)) ? 1 : 0;
}
#else
return 0;
#endif
}
/*
* Check if connection status checking is available on this platform.
*
* Returns true if available, false otherwise.
*/
static bool
pgfdw_conn_checkable(void)
{
#if (defined(HAVE_POLL) && defined(POLLRDHUP))
return true;
#else
return false;
#endif
}
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