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https://git.postgresql.org/git/postgresql.git
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1868 lines
56 KiB
C
1868 lines
56 KiB
C
/*-------------------------------------------------------------------------
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*
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* connection.c
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* Connection management functions for postgres_fdw
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*
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* Portions Copyright (c) 2012-2022, PostgreSQL Global Development Group
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*
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* IDENTIFICATION
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* contrib/postgres_fdw/connection.c
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "access/htup_details.h"
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#include "access/xact.h"
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#include "catalog/pg_user_mapping.h"
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#include "commands/defrem.h"
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#include "funcapi.h"
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#include "mb/pg_wchar.h"
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#include "miscadmin.h"
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#include "pgstat.h"
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#include "postgres_fdw.h"
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#include "storage/fd.h"
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#include "storage/latch.h"
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#include "utils/builtins.h"
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#include "utils/datetime.h"
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#include "utils/hsearch.h"
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#include "utils/inval.h"
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#include "utils/memutils.h"
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#include "utils/syscache.h"
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/*
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* Connection cache hash table entry
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*
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* The lookup key in this hash table is the user mapping OID. We use just one
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* connection per user mapping ID, which ensures that all the scans use the
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* same snapshot during a query. Using the user mapping OID rather than
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* the foreign server OID + user OID avoids creating multiple connections when
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* the public user mapping applies to all user OIDs.
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*
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* The "conn" pointer can be NULL if we don't currently have a live connection.
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* When we do have a connection, xact_depth tracks the current depth of
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* transactions and subtransactions open on the remote side. We need to issue
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* commands at the same nesting depth on the remote as we're executing at
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* ourselves, so that rolling back a subtransaction will kill the right
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* queries and not the wrong ones.
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*/
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typedef Oid ConnCacheKey;
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typedef struct ConnCacheEntry
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{
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ConnCacheKey key; /* hash key (must be first) */
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PGconn *conn; /* connection to foreign server, or NULL */
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/* Remaining fields are invalid when conn is NULL: */
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int xact_depth; /* 0 = no xact open, 1 = main xact open, 2 =
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* one level of subxact open, etc */
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bool have_prep_stmt; /* have we prepared any stmts in this xact? */
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bool have_error; /* have any subxacts aborted in this xact? */
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bool changing_xact_state; /* xact state change in process */
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bool parallel_commit; /* do we commit (sub)xacts in parallel? */
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bool invalidated; /* true if reconnect is pending */
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bool keep_connections; /* setting value of keep_connections
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* server option */
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Oid serverid; /* foreign server OID used to get server name */
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uint32 server_hashvalue; /* hash value of foreign server OID */
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uint32 mapping_hashvalue; /* hash value of user mapping OID */
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PgFdwConnState state; /* extra per-connection state */
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} ConnCacheEntry;
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/*
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* Connection cache (initialized on first use)
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*/
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static HTAB *ConnectionHash = NULL;
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/* for assigning cursor numbers and prepared statement numbers */
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static unsigned int cursor_number = 0;
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static unsigned int prep_stmt_number = 0;
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/* tracks whether any work is needed in callback functions */
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static bool xact_got_connection = false;
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/*
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* SQL functions
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*/
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PG_FUNCTION_INFO_V1(postgres_fdw_get_connections);
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PG_FUNCTION_INFO_V1(postgres_fdw_disconnect);
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PG_FUNCTION_INFO_V1(postgres_fdw_disconnect_all);
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/* prototypes of private functions */
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static void make_new_connection(ConnCacheEntry *entry, UserMapping *user);
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static PGconn *connect_pg_server(ForeignServer *server, UserMapping *user);
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static void disconnect_pg_server(ConnCacheEntry *entry);
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static void check_conn_params(const char **keywords, const char **values, UserMapping *user);
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static void configure_remote_session(PGconn *conn);
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static void do_sql_command_begin(PGconn *conn, const char *sql);
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static void do_sql_command_end(PGconn *conn, const char *sql,
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bool consume_input);
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static void begin_remote_xact(ConnCacheEntry *entry);
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static void pgfdw_xact_callback(XactEvent event, void *arg);
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static void pgfdw_subxact_callback(SubXactEvent event,
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SubTransactionId mySubid,
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SubTransactionId parentSubid,
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void *arg);
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static void pgfdw_inval_callback(Datum arg, int cacheid, uint32 hashvalue);
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static void pgfdw_reject_incomplete_xact_state_change(ConnCacheEntry *entry);
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static void pgfdw_reset_xact_state(ConnCacheEntry *entry, bool toplevel);
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static bool pgfdw_cancel_query(PGconn *conn);
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static bool pgfdw_exec_cleanup_query(PGconn *conn, const char *query,
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bool ignore_errors);
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static bool pgfdw_get_cleanup_result(PGconn *conn, TimestampTz endtime,
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PGresult **result, bool *timed_out);
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static void pgfdw_abort_cleanup(ConnCacheEntry *entry, bool toplevel);
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static void pgfdw_finish_pre_commit_cleanup(List *pending_entries);
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static void pgfdw_finish_pre_subcommit_cleanup(List *pending_entries,
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int curlevel);
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static bool UserMappingPasswordRequired(UserMapping *user);
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static bool disconnect_cached_connections(Oid serverid);
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/*
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* Get a PGconn which can be used to execute queries on the remote PostgreSQL
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* server with the user's authorization. A new connection is established
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* if we don't already have a suitable one, and a transaction is opened at
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* the right subtransaction nesting depth if we didn't do that already.
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*
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* will_prep_stmt must be true if caller intends to create any prepared
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* statements. Since those don't go away automatically at transaction end
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* (not even on error), we need this flag to cue manual cleanup.
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*
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* If state is not NULL, *state receives the per-connection state associated
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* with the PGconn.
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*/
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PGconn *
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GetConnection(UserMapping *user, bool will_prep_stmt, PgFdwConnState **state)
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{
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bool found;
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bool retry = false;
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ConnCacheEntry *entry;
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ConnCacheKey key;
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MemoryContext ccxt = CurrentMemoryContext;
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/* First time through, initialize connection cache hashtable */
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if (ConnectionHash == NULL)
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{
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HASHCTL ctl;
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ctl.keysize = sizeof(ConnCacheKey);
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ctl.entrysize = sizeof(ConnCacheEntry);
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ConnectionHash = hash_create("postgres_fdw connections", 8,
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&ctl,
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HASH_ELEM | HASH_BLOBS);
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/*
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* Register some callback functions that manage connection cleanup.
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* This should be done just once in each backend.
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*/
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RegisterXactCallback(pgfdw_xact_callback, NULL);
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RegisterSubXactCallback(pgfdw_subxact_callback, NULL);
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CacheRegisterSyscacheCallback(FOREIGNSERVEROID,
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pgfdw_inval_callback, (Datum) 0);
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CacheRegisterSyscacheCallback(USERMAPPINGOID,
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pgfdw_inval_callback, (Datum) 0);
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}
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/* Set flag that we did GetConnection during the current transaction */
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xact_got_connection = true;
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/* Create hash key for the entry. Assume no pad bytes in key struct */
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key = user->umid;
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/*
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* Find or create cached entry for requested connection.
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*/
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entry = hash_search(ConnectionHash, &key, HASH_ENTER, &found);
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if (!found)
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{
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/*
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* We need only clear "conn" here; remaining fields will be filled
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* later when "conn" is set.
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*/
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entry->conn = NULL;
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}
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/* Reject further use of connections which failed abort cleanup. */
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pgfdw_reject_incomplete_xact_state_change(entry);
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/*
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* If the connection needs to be remade due to invalidation, disconnect as
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* soon as we're out of all transactions.
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*/
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if (entry->conn != NULL && entry->invalidated && entry->xact_depth == 0)
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{
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elog(DEBUG3, "closing connection %p for option changes to take effect",
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entry->conn);
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disconnect_pg_server(entry);
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}
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/*
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* If cache entry doesn't have a connection, we have to establish a new
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* connection. (If connect_pg_server throws an error, the cache entry
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* will remain in a valid empty state, ie conn == NULL.)
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*/
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if (entry->conn == NULL)
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make_new_connection(entry, user);
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/*
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* We check the health of the cached connection here when using it. In
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* cases where we're out of all transactions, if a broken connection is
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* detected, we try to reestablish a new connection later.
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*/
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PG_TRY();
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{
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/* Process a pending asynchronous request if any. */
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if (entry->state.pendingAreq)
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process_pending_request(entry->state.pendingAreq);
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/* Start a new transaction or subtransaction if needed. */
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begin_remote_xact(entry);
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}
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PG_CATCH();
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{
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MemoryContext ecxt = MemoryContextSwitchTo(ccxt);
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ErrorData *errdata = CopyErrorData();
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/*
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* Determine whether to try to reestablish the connection.
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*
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* After a broken connection is detected in libpq, any error other
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* than connection failure (e.g., out-of-memory) can be thrown
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* somewhere between return from libpq and the expected ereport() call
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* in pgfdw_report_error(). In this case, since PQstatus() indicates
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* CONNECTION_BAD, checking only PQstatus() causes the false detection
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* of connection failure. To avoid this, we also verify that the
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* error's sqlstate is ERRCODE_CONNECTION_FAILURE. Note that also
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* checking only the sqlstate can cause another false detection
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* because pgfdw_report_error() may report ERRCODE_CONNECTION_FAILURE
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* for any libpq-originated error condition.
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*/
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if (errdata->sqlerrcode != ERRCODE_CONNECTION_FAILURE ||
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PQstatus(entry->conn) != CONNECTION_BAD ||
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entry->xact_depth > 0)
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{
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MemoryContextSwitchTo(ecxt);
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PG_RE_THROW();
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}
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/* Clean up the error state */
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FlushErrorState();
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FreeErrorData(errdata);
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errdata = NULL;
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retry = true;
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}
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PG_END_TRY();
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/*
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* If a broken connection is detected, disconnect it, reestablish a new
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* connection and retry a new remote transaction. If connection failure is
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* reported again, we give up getting a connection.
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*/
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if (retry)
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{
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Assert(entry->xact_depth == 0);
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ereport(DEBUG3,
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(errmsg_internal("could not start remote transaction on connection %p",
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entry->conn)),
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errdetail_internal("%s", pchomp(PQerrorMessage(entry->conn))));
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elog(DEBUG3, "closing connection %p to reestablish a new one",
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entry->conn);
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disconnect_pg_server(entry);
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if (entry->conn == NULL)
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make_new_connection(entry, user);
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begin_remote_xact(entry);
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}
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/* Remember if caller will prepare statements */
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entry->have_prep_stmt |= will_prep_stmt;
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/* If caller needs access to the per-connection state, return it. */
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if (state)
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*state = &entry->state;
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return entry->conn;
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}
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/*
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* Reset all transient state fields in the cached connection entry and
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* establish new connection to the remote server.
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*/
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static void
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make_new_connection(ConnCacheEntry *entry, UserMapping *user)
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{
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ForeignServer *server = GetForeignServer(user->serverid);
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ListCell *lc;
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Assert(entry->conn == NULL);
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/* Reset all transient state fields, to be sure all are clean */
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entry->xact_depth = 0;
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entry->have_prep_stmt = false;
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entry->have_error = false;
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entry->changing_xact_state = false;
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entry->invalidated = false;
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entry->serverid = server->serverid;
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entry->server_hashvalue =
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GetSysCacheHashValue1(FOREIGNSERVEROID,
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ObjectIdGetDatum(server->serverid));
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entry->mapping_hashvalue =
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GetSysCacheHashValue1(USERMAPPINGOID,
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ObjectIdGetDatum(user->umid));
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memset(&entry->state, 0, sizeof(entry->state));
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/*
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* Determine whether to keep the connection that we're about to make here
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* open even after the transaction using it ends, so that the subsequent
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* transactions can re-use it.
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*
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* By default, all the connections to any foreign servers are kept open.
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*
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* Also determine whether to commit (sub)transactions opened on the remote
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* server in parallel at (sub)transaction end, which is disabled by
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* default.
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*
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* Note: it's enough to determine these only when making a new connection
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* because if these settings for it are changed, it will be closed and
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* re-made later.
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*/
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entry->keep_connections = true;
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entry->parallel_commit = false;
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foreach(lc, server->options)
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{
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DefElem *def = (DefElem *) lfirst(lc);
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if (strcmp(def->defname, "keep_connections") == 0)
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entry->keep_connections = defGetBoolean(def);
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else if (strcmp(def->defname, "parallel_commit") == 0)
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entry->parallel_commit = defGetBoolean(def);
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}
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/* Now try to make the connection */
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entry->conn = connect_pg_server(server, user);
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elog(DEBUG3, "new postgres_fdw connection %p for server \"%s\" (user mapping oid %u, userid %u)",
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entry->conn, server->servername, user->umid, user->userid);
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}
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/*
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* Connect to remote server using specified server and user mapping properties.
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*/
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static PGconn *
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connect_pg_server(ForeignServer *server, UserMapping *user)
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{
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PGconn *volatile conn = NULL;
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/*
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* Use PG_TRY block to ensure closing connection on error.
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*/
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PG_TRY();
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{
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const char **keywords;
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const char **values;
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char *appname = NULL;
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int n;
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/*
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* Construct connection params from generic options of ForeignServer
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* and UserMapping. (Some of them might not be libpq options, in
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* which case we'll just waste a few array slots.) Add 4 extra slots
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* for application_name, fallback_application_name, client_encoding,
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* end marker.
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*/
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n = list_length(server->options) + list_length(user->options) + 4;
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keywords = (const char **) palloc(n * sizeof(char *));
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values = (const char **) palloc(n * sizeof(char *));
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n = 0;
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n += ExtractConnectionOptions(server->options,
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keywords + n, values + n);
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n += ExtractConnectionOptions(user->options,
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keywords + n, values + n);
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/*
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* Use pgfdw_application_name as application_name if set.
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*
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* PQconnectdbParams() processes the parameter arrays from start to
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* end. If any key word is repeated, the last value is used. Therefore
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* note that pgfdw_application_name must be added to the arrays after
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* options of ForeignServer are, so that it can override
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* application_name set in ForeignServer.
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*/
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if (pgfdw_application_name && *pgfdw_application_name != '\0')
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{
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keywords[n] = "application_name";
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values[n] = pgfdw_application_name;
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n++;
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}
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/*
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* Search the parameter arrays to find application_name setting, and
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* replace escape sequences in it with status information if found.
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* The arrays are searched backwards because the last value is used if
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* application_name is repeatedly set.
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*/
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for (int i = n - 1; i >= 0; i--)
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{
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if (strcmp(keywords[i], "application_name") == 0 &&
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*(values[i]) != '\0')
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{
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/*
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* Use this application_name setting if it's not empty string
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* even after any escape sequences in it are replaced.
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*/
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appname = process_pgfdw_appname(values[i]);
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if (appname[0] != '\0')
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{
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values[i] = appname;
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break;
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}
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/*
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* This empty application_name is not used, so we set
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* values[i] to NULL and keep searching the array to find the
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* next one.
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*/
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values[i] = NULL;
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pfree(appname);
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appname = NULL;
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}
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}
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/* Use "postgres_fdw" as fallback_application_name */
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keywords[n] = "fallback_application_name";
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values[n] = "postgres_fdw";
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n++;
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/* Set client_encoding so that libpq can convert encoding properly. */
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keywords[n] = "client_encoding";
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values[n] = GetDatabaseEncodingName();
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n++;
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keywords[n] = values[n] = NULL;
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/* verify the set of connection parameters */
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check_conn_params(keywords, values, user);
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/*
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* We must obey fd.c's limit on non-virtual file descriptors. Assume
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* that a PGconn represents one long-lived FD. (Doing this here also
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* ensures that VFDs are closed if needed to make room.)
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*/
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if (!AcquireExternalFD())
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{
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#ifndef WIN32 /* can't write #if within ereport() macro */
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ereport(ERROR,
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(errcode(ERRCODE_SQLCLIENT_UNABLE_TO_ESTABLISH_SQLCONNECTION),
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errmsg("could not connect to server \"%s\"",
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server->servername),
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errdetail("There are too many open files on the local server."),
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errhint("Raise the server's max_files_per_process and/or \"ulimit -n\" limits.")));
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#else
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ereport(ERROR,
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(errcode(ERRCODE_SQLCLIENT_UNABLE_TO_ESTABLISH_SQLCONNECTION),
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errmsg("could not connect to server \"%s\"",
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server->servername),
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errdetail("There are too many open files on the local server."),
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errhint("Raise the server's max_files_per_process setting.")));
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#endif
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}
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/* OK to make connection */
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conn = PQconnectdbParams(keywords, values, false);
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if (!conn)
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ReleaseExternalFD(); /* because the PG_CATCH block won't */
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if (!conn || PQstatus(conn) != CONNECTION_OK)
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ereport(ERROR,
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(errcode(ERRCODE_SQLCLIENT_UNABLE_TO_ESTABLISH_SQLCONNECTION),
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errmsg("could not connect to server \"%s\"",
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server->servername),
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errdetail_internal("%s", pchomp(PQerrorMessage(conn)))));
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/*
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* Check that non-superuser has used password to establish connection;
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* otherwise, he's piggybacking on the postgres server's user
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* identity. See also dblink_security_check() in contrib/dblink and
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* check_conn_params.
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*/
|
|
if (!superuser_arg(user->userid) && UserMappingPasswordRequired(user) &&
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!PQconnectionUsedPassword(conn))
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ereport(ERROR,
|
|
(errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
|
|
errmsg("password is required"),
|
|
errdetail("Non-superuser cannot connect if the server does not request a password."),
|
|
errhint("Target server's authentication method must be changed or password_required=false set in the user mapping attributes.")));
|
|
|
|
/* Prepare new session for use */
|
|
configure_remote_session(conn);
|
|
|
|
if (appname != NULL)
|
|
pfree(appname);
|
|
pfree(keywords);
|
|
pfree(values);
|
|
}
|
|
PG_CATCH();
|
|
{
|
|
/* Release PGconn data structure if we managed to create one */
|
|
if (conn)
|
|
{
|
|
PQfinish(conn);
|
|
ReleaseExternalFD();
|
|
}
|
|
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)
|
|
{
|
|
PQfinish(entry->conn);
|
|
entry->conn = NULL;
|
|
ReleaseExternalFD();
|
|
}
|
|
}
|
|
|
|
/*
|
|
* 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;
|
|
}
|
|
|
|
/*
|
|
* For non-superusers, insist that the connstr specify a password. 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;
|
|
|
|
/* 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 is required"),
|
|
errdetail("Non-superusers must provide a password in the 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 UTC
|
|
* (quoted, because very old servers are picky about case).
|
|
*/
|
|
do_sql_command(conn, "SET timezone = 'UTC'");
|
|
|
|
/*
|
|
* 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, sql);
|
|
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.
|
|
*
|
|
* This function is interruptible by signals.
|
|
*
|
|
* 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);
|
|
|
|
/*
|
|
* 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(ERROR, NULL, conn, false, query);
|
|
|
|
/* Wait for the result. */
|
|
return pgfdw_get_result(conn, query);
|
|
}
|
|
|
|
/*
|
|
* Wait for the result from a prior asynchronous execution function call.
|
|
*
|
|
* This function offers quick responsiveness by checking for any interruptions.
|
|
*
|
|
* This function emulates PQexec()'s behavior of returning the last result
|
|
* when there are many.
|
|
*
|
|
* Caller is responsible for the error handling on the result.
|
|
*/
|
|
PGresult *
|
|
pgfdw_get_result(PGconn *conn, const char *query)
|
|
{
|
|
PGresult *volatile last_res = NULL;
|
|
|
|
/* In what follows, do not leak any PGresults on an error. */
|
|
PG_TRY();
|
|
{
|
|
for (;;)
|
|
{
|
|
PGresult *res;
|
|
|
|
while (PQisBusy(conn))
|
|
{
|
|
int wc;
|
|
|
|
/* Sleep until there's something to do */
|
|
wc = WaitLatchOrSocket(MyLatch,
|
|
WL_LATCH_SET | WL_SOCKET_READABLE |
|
|
WL_EXIT_ON_PM_DEATH,
|
|
PQsocket(conn),
|
|
-1L, PG_WAIT_EXTENSION);
|
|
ResetLatch(MyLatch);
|
|
|
|
CHECK_FOR_INTERRUPTS();
|
|
|
|
/* Data available in socket? */
|
|
if (wc & WL_SOCKET_READABLE)
|
|
{
|
|
if (!PQconsumeInput(conn))
|
|
pgfdw_report_error(ERROR, NULL, conn, false, query);
|
|
}
|
|
}
|
|
|
|
res = PQgetResult(conn);
|
|
if (res == NULL)
|
|
break; /* query is complete */
|
|
|
|
PQclear(last_res);
|
|
last_res = res;
|
|
}
|
|
}
|
|
PG_CATCH();
|
|
{
|
|
PQclear(last_res);
|
|
PG_RE_THROW();
|
|
}
|
|
PG_END_TRY();
|
|
|
|
return last_res;
|
|
}
|
|
|
|
/*
|
|
* 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, PQexec 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;
|
|
|
|
/* 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 = PQexec(entry->conn, "DEALLOCATE ALL");
|
|
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 */
|
|
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)
|
|
{
|
|
Assert(event == XACT_EVENT_PARALLEL_PRE_COMMIT ||
|
|
event == XACT_EVENT_PRE_COMMIT);
|
|
pgfdw_finish_pre_commit_cleanup(pending_entries);
|
|
}
|
|
|
|
/*
|
|
* 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;
|
|
|
|
/* 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 */
|
|
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)
|
|
{
|
|
Assert(event == SUBXACT_EVENT_PRE_COMMIT_SUB);
|
|
pgfdw_finish_pre_subcommit_cleanup(pending_entries, curlevel);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* 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)
|
|
{
|
|
PGcancel *cancel;
|
|
char errbuf[256];
|
|
PGresult *result = NULL;
|
|
TimestampTz endtime;
|
|
bool timed_out;
|
|
|
|
/*
|
|
* If it takes too long to cancel the query and discard the result, assume
|
|
* the connection is dead.
|
|
*/
|
|
endtime = TimestampTzPlusMilliseconds(GetCurrentTimestamp(), 30000);
|
|
|
|
/*
|
|
* Issue cancel request. Unfortunately, there's no good way to limit the
|
|
* amount of time that we might block inside PQgetCancel().
|
|
*/
|
|
if ((cancel = PQgetCancel(conn)))
|
|
{
|
|
if (!PQcancel(cancel, errbuf, sizeof(errbuf)))
|
|
{
|
|
ereport(WARNING,
|
|
(errcode(ERRCODE_CONNECTION_FAILURE),
|
|
errmsg("could not send cancel request: %s",
|
|
errbuf)));
|
|
PQfreeCancel(cancel);
|
|
return false;
|
|
}
|
|
PQfreeCancel(cancel);
|
|
}
|
|
|
|
/* Get and discard the result of the query. */
|
|
if (pgfdw_get_cleanup_result(conn, endtime, &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)
|
|
{
|
|
PGresult *result = NULL;
|
|
TimestampTz endtime;
|
|
bool timed_out;
|
|
|
|
/*
|
|
* 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(), 30000);
|
|
|
|
/*
|
|
* 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;
|
|
}
|
|
|
|
/* Get the result of the query. */
|
|
if (pgfdw_get_cleanup_result(conn, endtime, &result, &timed_out))
|
|
{
|
|
if (timed_out)
|
|
ereport(WARNING,
|
|
(errmsg("could not get query result due to timeout"),
|
|
query ? errcontext("remote SQL command: %s", query) : 0));
|
|
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 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. Returns true if the timeout expired or connection trouble
|
|
* occurred, false otherwise. Sets *result except in case of a timeout.
|
|
* Sets timed_out to true only when the timeout expired.
|
|
*/
|
|
static bool
|
|
pgfdw_get_cleanup_result(PGconn *conn, TimestampTz endtime, PGresult **result,
|
|
bool *timed_out)
|
|
{
|
|
volatile bool failed = false;
|
|
PGresult *volatile last_res = NULL;
|
|
|
|
*timed_out = false;
|
|
|
|
/* In what follows, do not leak any PGresults on an error. */
|
|
PG_TRY();
|
|
{
|
|
for (;;)
|
|
{
|
|
PGresult *res;
|
|
|
|
while (PQisBusy(conn))
|
|
{
|
|
int wc;
|
|
TimestampTz now = GetCurrentTimestamp();
|
|
long cur_timeout;
|
|
|
|
/* If timeout has expired, give up, else get sleep time. */
|
|
cur_timeout = TimestampDifferenceMilliseconds(now, endtime);
|
|
if (cur_timeout <= 0)
|
|
{
|
|
*timed_out = true;
|
|
failed = true;
|
|
goto exit;
|
|
}
|
|
|
|
/* 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, PG_WAIT_EXTENSION);
|
|
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 */
|
|
|
|
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);
|
|
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;
|
|
}
|
|
|
|
/*
|
|
* 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);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* List active foreign server connections.
|
|
*
|
|
* This function takes no input parameter and returns setof record made of
|
|
* 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 the connections can get invalidated in pgfdw_inval_callback.
|
|
*
|
|
* No records are returned when there are no cached connections at all.
|
|
*/
|
|
Datum
|
|
postgres_fdw_get_connections(PG_FUNCTION_ARGS)
|
|
{
|
|
#define POSTGRES_FDW_GET_CONNECTIONS_COLS 2
|
|
ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
|
|
HASH_SEQ_STATUS scan;
|
|
ConnCacheEntry *entry;
|
|
|
|
SetSingleFuncCall(fcinfo, 0);
|
|
|
|
/* If cache doesn't exist, we return no records */
|
|
if (!ConnectionHash)
|
|
PG_RETURN_VOID();
|
|
|
|
hash_seq_init(&scan, ConnectionHash);
|
|
while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
|
|
{
|
|
ForeignServer *server;
|
|
Datum values[POSTGRES_FDW_GET_CONNECTIONS_COLS];
|
|
bool nulls[POSTGRES_FDW_GET_CONNECTIONS_COLS];
|
|
|
|
/* We only look for open remote connections */
|
|
if (!entry->conn)
|
|
continue;
|
|
|
|
server = GetForeignServerExtended(entry->serverid, FSV_MISSING_OK);
|
|
|
|
MemSet(values, 0, sizeof(values));
|
|
MemSet(nulls, 0, sizeof(nulls));
|
|
|
|
/*
|
|
* 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[0] = true;
|
|
}
|
|
else
|
|
values[0] = CStringGetTextDatum(server->servername);
|
|
|
|
values[1] = BoolGetDatum(!entry->invalidated);
|
|
|
|
tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
|
|
}
|
|
|
|
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;
|
|
}
|