From 96198d94cb7adc664bda341842dc8db671d8be72 Mon Sep 17 00:00:00 2001 From: Robert Haas Date: Thu, 28 Jan 2016 12:05:19 -0500 Subject: [PATCH] Avoid multiple foreign server connections when all use same user mapping. Previously, postgres_fdw's connection cache was keyed by user OID and server OID, but this can lead to multiple connections when it's not really necessary. In particular, if all relevant users are mapped to the public user mapping, then their connection options are certainly the same, so one connection can be used for all of them. While we're cleaning things up here, drop the "server" argument to GetConnection(), which isn't really needed. This saves a few cycles because callers no longer have to look this up; the function itself does, but only when establishing a new connection, not when reusing an existing one. Ashutosh Bapat, with a few small changes by me. --- contrib/postgres_fdw/connection.c | 27 +++++++++++++-------------- contrib/postgres_fdw/postgres_fdw.c | 28 ++++++++++------------------ contrib/postgres_fdw/postgres_fdw.h | 3 +-- src/backend/foreign/foreign.c | 1 + src/include/foreign/foreign.h | 1 + 5 files changed, 26 insertions(+), 34 deletions(-) diff --git a/contrib/postgres_fdw/connection.c b/contrib/postgres_fdw/connection.c index 0c6c3cee30..6e664b0213 100644 --- a/contrib/postgres_fdw/connection.c +++ b/contrib/postgres_fdw/connection.c @@ -24,9 +24,11 @@ /* * Connection cache hash table entry * - * The lookup key in this hash table is the foreign server OID plus the user - * mapping OID. (We use just one connection per user per foreign server, - * so that we can ensure all scans use the same snapshot during a query.) + * 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 @@ -35,11 +37,7 @@ * ourselves, so that rolling back a subtransaction will kill the right * queries and not the wrong ones. */ -typedef struct ConnCacheKey -{ - Oid serverid; /* OID of foreign server */ - Oid userid; /* OID of local user whose mapping we use */ -} ConnCacheKey; +typedef Oid ConnCacheKey; typedef struct ConnCacheEntry { @@ -94,8 +92,7 @@ static void pgfdw_subxact_callback(SubXactEvent event, * mid-transaction anyway. */ PGconn * -GetConnection(ForeignServer *server, UserMapping *user, - bool will_prep_stmt) +GetConnection(UserMapping *user, bool will_prep_stmt) { bool found; ConnCacheEntry *entry; @@ -127,8 +124,7 @@ GetConnection(ForeignServer *server, UserMapping *user, xact_got_connection = true; /* Create hash key for the entry. Assume no pad bytes in key struct */ - key.serverid = server->serverid; - key.userid = user->userid; + key = user->umid; /* * Find or create cached entry for requested connection. @@ -156,12 +152,15 @@ GetConnection(ForeignServer *server, UserMapping *user, */ if (entry->conn == NULL) { + ForeignServer *server = GetForeignServer(user->serverid); + entry->xact_depth = 0; /* just to be sure */ entry->have_prep_stmt = false; entry->have_error = false; entry->conn = connect_pg_server(server, user); - elog(DEBUG3, "new postgres_fdw connection %p for server \"%s\"", - entry->conn, server->servername); + + elog(DEBUG3, "new postgres_fdw connection %p for server \"%s\ (user mapping oid %d, userid %d)", + entry->conn, server->servername, user->umid, user->userid); } /* diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c index 374faf5a25..a237e152c0 100644 --- a/contrib/postgres_fdw/postgres_fdw.c +++ b/contrib/postgres_fdw/postgres_fdw.c @@ -1101,7 +1101,6 @@ postgresBeginForeignScan(ForeignScanState *node, int eflags) RangeTblEntry *rte; Oid userid; ForeignTable *table; - ForeignServer *server; UserMapping *user; int numParams; int i; @@ -1129,14 +1128,13 @@ postgresBeginForeignScan(ForeignScanState *node, int eflags) /* Get info about foreign table. */ fsstate->rel = node->ss.ss_currentRelation; table = GetForeignTable(RelationGetRelid(fsstate->rel)); - server = GetForeignServer(table->serverid); - user = GetUserMapping(userid, server->serverid); + user = GetUserMapping(userid, table->serverid); /* * Get connection to the foreign server. Connection manager will * establish new connection if necessary. */ - fsstate->conn = GetConnection(server, user, false); + fsstate->conn = GetConnection(user, false); /* Assign a unique ID for my cursor */ fsstate->cursor_number = GetCursorNumber(fsstate->conn); @@ -1503,7 +1501,6 @@ postgresBeginForeignModify(ModifyTableState *mtstate, RangeTblEntry *rte; Oid userid; ForeignTable *table; - ForeignServer *server; UserMapping *user; AttrNumber n_params; Oid typefnoid; @@ -1530,11 +1527,10 @@ postgresBeginForeignModify(ModifyTableState *mtstate, /* Get info about foreign table. */ table = GetForeignTable(RelationGetRelid(rel)); - server = GetForeignServer(table->serverid); - user = GetUserMapping(userid, server->serverid); + user = GetUserMapping(userid, table->serverid); /* Open connection; report that we'll create a prepared statement. */ - fmstate->conn = GetConnection(server, user, true); + fmstate->conn = GetConnection(user, true); fmstate->p_name = NULL; /* prepared statement not made yet */ /* Deconstruct fdw_private data. */ @@ -1988,7 +1984,7 @@ estimate_path_cost_size(PlannerInfo *root, appendOrderByClause(&sql, root, baserel, pathkeys); /* Get the remote estimate */ - conn = GetConnection(fpinfo->server, fpinfo->user, false); + conn = GetConnection(fpinfo->user, false); get_remote_estimate(sql.data, conn, &rows, &width, &startup_cost, &total_cost); ReleaseConnection(conn); @@ -2544,7 +2540,6 @@ postgresAnalyzeForeignTable(Relation relation, BlockNumber *totalpages) { ForeignTable *table; - ForeignServer *server; UserMapping *user; PGconn *conn; StringInfoData sql; @@ -2565,9 +2560,8 @@ postgresAnalyzeForeignTable(Relation relation, * owner, even if the ANALYZE was started by some other user. */ table = GetForeignTable(RelationGetRelid(relation)); - server = GetForeignServer(table->serverid); - user = GetUserMapping(relation->rd_rel->relowner, server->serverid); - conn = GetConnection(server, user, false); + user = GetUserMapping(relation->rd_rel->relowner, table->serverid); + conn = GetConnection(user, false); /* * Construct command to get page count for relation. @@ -2626,7 +2620,6 @@ postgresAcquireSampleRowsFunc(Relation relation, int elevel, { PgFdwAnalyzeState astate; ForeignTable *table; - ForeignServer *server; UserMapping *user; PGconn *conn; unsigned int cursor_number; @@ -2657,9 +2650,8 @@ postgresAcquireSampleRowsFunc(Relation relation, int elevel, * owner, even if the ANALYZE was started by some other user. */ table = GetForeignTable(RelationGetRelid(relation)); - server = GetForeignServer(table->serverid); - user = GetUserMapping(relation->rd_rel->relowner, server->serverid); - conn = GetConnection(server, user, false); + user = GetUserMapping(relation->rd_rel->relowner, table->serverid); + conn = GetConnection(user, false); /* * Construct cursor that retrieves whole rows from remote. @@ -2860,7 +2852,7 @@ postgresImportForeignSchema(ImportForeignSchemaStmt *stmt, Oid serverOid) */ server = GetForeignServer(serverOid); mapping = GetUserMapping(GetUserId(), server->serverid); - conn = GetConnection(server, mapping, false); + conn = GetConnection(mapping, false); /* Don't attempt to import collation if remote server hasn't got it */ if (PQserverVersion(conn) < 90100) diff --git a/contrib/postgres_fdw/postgres_fdw.h b/contrib/postgres_fdw/postgres_fdw.h index 8553536047..59e9f60c04 100644 --- a/contrib/postgres_fdw/postgres_fdw.h +++ b/contrib/postgres_fdw/postgres_fdw.h @@ -60,8 +60,7 @@ extern int set_transmission_modes(void); extern void reset_transmission_modes(int nestlevel); /* in connection.c */ -extern PGconn *GetConnection(ForeignServer *server, UserMapping *user, - bool will_prep_stmt); +extern PGconn *GetConnection(UserMapping *user, bool will_prep_stmt); extern void ReleaseConnection(PGconn *conn); extern unsigned int GetCursorNumber(PGconn *conn); extern unsigned int GetPrepStmtNumber(PGconn *conn); diff --git a/src/backend/foreign/foreign.c b/src/backend/foreign/foreign.c index 14e082b5b8..c24b11b685 100644 --- a/src/backend/foreign/foreign.c +++ b/src/backend/foreign/foreign.c @@ -193,6 +193,7 @@ GetUserMapping(Oid userid, Oid serverid) MappingUserName(userid)))); um = (UserMapping *) palloc(sizeof(UserMapping)); + um->umid = HeapTupleGetOid(tp); um->userid = userid; um->serverid = serverid; diff --git a/src/include/foreign/foreign.h b/src/include/foreign/foreign.h index 2c1ada1b12..5dc2c90f3c 100644 --- a/src/include/foreign/foreign.h +++ b/src/include/foreign/foreign.h @@ -55,6 +55,7 @@ typedef struct ForeignServer typedef struct UserMapping { + Oid umid; /* Oid of user mapping */ Oid userid; /* local user Oid */ Oid serverid; /* server Oid */ List *options; /* useoptions as DefElem list */