/*------------------------------------------------------------------------- * * postgres_fdw.c * Foreign-data wrapper for remote PostgreSQL servers * * Portions Copyright (c) 2012-2013, PostgreSQL Global Development Group * * IDENTIFICATION * contrib/postgres_fdw/postgres_fdw.c * *------------------------------------------------------------------------- */ #include "postgres.h" #include "postgres_fdw.h" #include "access/htup.h" #include "commands/defrem.h" #include "commands/explain.h" #include "commands/vacuum.h" #include "foreign/fdwapi.h" #include "funcapi.h" #include "miscadmin.h" #include "optimizer/cost.h" #include "optimizer/pathnode.h" #include "optimizer/planmain.h" #include "parser/parsetree.h" #include "utils/builtins.h" #include "utils/guc.h" #include "utils/lsyscache.h" #include "utils/memutils.h" PG_MODULE_MAGIC; /* Default CPU cost to start up a foreign query. */ #define DEFAULT_FDW_STARTUP_COST 100.0 /* Default CPU cost to process 1 row (above and beyond cpu_tuple_cost). */ #define DEFAULT_FDW_TUPLE_COST 0.01 /* * FDW-specific planner information kept in RelOptInfo.fdw_private for a * foreign table. This information is collected by postgresGetForeignRelSize. */ typedef struct PgFdwRelationInfo { /* XXX underdocumented, but a lot of this shouldn't be here anyway */ StringInfoData sql; Cost startup_cost; Cost total_cost; List *remote_conds; List *param_conds; List *local_conds; List *param_numbers; /* Cached catalog information. */ ForeignTable *table; ForeignServer *server; } PgFdwRelationInfo; /* * Indexes of FDW-private information stored in fdw_private list. * * We store various information in ForeignScan.fdw_private to pass it from * planner to executor. Specifically there is: * * 1) SELECT statement text to be sent to the remote server * 2) IDs of PARAM_EXEC Params used in the SELECT statement * * These items are indexed with the enum FdwPrivateIndex, so an item can be * fetched with list_nth(). For example, to get the SELECT statement: * sql = strVal(list_nth(fdw_private, FdwPrivateSelectSql)); */ enum FdwPrivateIndex { /* SQL statement to execute remotely (as a String node) */ FdwPrivateSelectSql, /* Integer list of param IDs of PARAM_EXEC Params used in SQL stmt */ FdwPrivateExternParamIds, /* # of elements stored in the list fdw_private */ FdwPrivateNum }; /* * Execution state of a foreign scan using postgres_fdw. */ typedef struct PgFdwExecutionState { Relation rel; /* relcache entry for the foreign table */ AttInMetadata *attinmeta; /* attribute datatype conversion metadata */ List *fdw_private; /* FDW-private information from planner */ /* for remote query execution */ PGconn *conn; /* connection for the scan */ unsigned int cursor_number; /* quasi-unique ID for my cursor */ bool cursor_exists; /* have we created the cursor? */ bool extparams_done; /* have we converted PARAM_EXTERN params? */ int numParams; /* number of parameters passed to query */ Oid *param_types; /* array of types of query parameters */ const char **param_values; /* array of values of query parameters */ /* for storing result tuples */ HeapTuple *tuples; /* array of currently-retrieved tuples */ int num_tuples; /* # of tuples in array */ int next_tuple; /* index of next one to return */ /* batch-level state, for optimizing rewinds and avoiding useless fetch */ int fetch_ct_2; /* Min(# of fetches done, 2) */ bool eof_reached; /* true if last fetch reached EOF */ /* working memory contexts */ MemoryContext batch_cxt; /* context holding current batch of tuples */ MemoryContext temp_cxt; /* context for per-tuple temporary data */ } PgFdwExecutionState; /* * Workspace for analyzing a foreign table. */ typedef struct PgFdwAnalyzeState { Relation rel; /* relcache entry for the foreign table */ AttInMetadata *attinmeta; /* attribute datatype conversion metadata */ /* collected sample rows */ HeapTuple *rows; /* array of size targrows */ int targrows; /* target # of sample rows */ int numrows; /* # of sample rows collected */ /* for random sampling */ double samplerows; /* # of rows fetched */ double rowstoskip; /* # of rows to skip before next sample */ double rstate; /* random state */ /* working memory contexts */ MemoryContext anl_cxt; /* context for per-analyze lifespan data */ MemoryContext temp_cxt; /* context for per-tuple temporary data */ } PgFdwAnalyzeState; /* * Identify the attribute where data conversion fails. */ typedef struct ConversionLocation { Relation rel; /* foreign table's relcache entry */ AttrNumber cur_attno; /* attribute number being processed, or 0 */ } ConversionLocation; /* * SQL functions */ extern Datum postgres_fdw_handler(PG_FUNCTION_ARGS); PG_FUNCTION_INFO_V1(postgres_fdw_handler); /* * FDW callback routines */ static void postgresGetForeignRelSize(PlannerInfo *root, RelOptInfo *baserel, Oid foreigntableid); static void postgresGetForeignPaths(PlannerInfo *root, RelOptInfo *baserel, Oid foreigntableid); static ForeignScan *postgresGetForeignPlan(PlannerInfo *root, RelOptInfo *baserel, Oid foreigntableid, ForeignPath *best_path, List *tlist, List *scan_clauses); static void postgresExplainForeignScan(ForeignScanState *node, ExplainState *es); static void postgresBeginForeignScan(ForeignScanState *node, int eflags); static TupleTableSlot *postgresIterateForeignScan(ForeignScanState *node); static void postgresReScanForeignScan(ForeignScanState *node); static void postgresEndForeignScan(ForeignScanState *node); static bool postgresAnalyzeForeignTable(Relation relation, AcquireSampleRowsFunc *func, BlockNumber *totalpages); /* * Helper functions */ static void get_remote_estimate(const char *sql, PGconn *conn, double *rows, int *width, Cost *startup_cost, Cost *total_cost); static void create_cursor(ForeignScanState *node); static void fetch_more_data(ForeignScanState *node); static void close_cursor(PGconn *conn, unsigned int cursor_number); static int postgresAcquireSampleRowsFunc(Relation relation, int elevel, HeapTuple *rows, int targrows, double *totalrows, double *totaldeadrows); static void analyze_row_processor(PGresult *res, int row, PgFdwAnalyzeState *astate); static HeapTuple make_tuple_from_result_row(PGresult *res, int row, Relation rel, AttInMetadata *attinmeta, MemoryContext temp_context); static void conversion_error_callback(void *arg); /* * Foreign-data wrapper handler function: return a struct with pointers * to my callback routines. */ Datum postgres_fdw_handler(PG_FUNCTION_ARGS) { FdwRoutine *routine = makeNode(FdwRoutine); /* Required handler functions. */ routine->GetForeignRelSize = postgresGetForeignRelSize; routine->GetForeignPaths = postgresGetForeignPaths; routine->GetForeignPlan = postgresGetForeignPlan; routine->ExplainForeignScan = postgresExplainForeignScan; routine->BeginForeignScan = postgresBeginForeignScan; routine->IterateForeignScan = postgresIterateForeignScan; routine->ReScanForeignScan = postgresReScanForeignScan; routine->EndForeignScan = postgresEndForeignScan; /* Optional handler functions. */ routine->AnalyzeForeignTable = postgresAnalyzeForeignTable; PG_RETURN_POINTER(routine); } /* * postgresGetForeignRelSize * Estimate # of rows and width of the result of the scan * * Here we estimate number of rows returned by the scan in two steps. In the * first step, we execute remote EXPLAIN command to obtain the number of rows * returned from remote side. In the second step, we calculate the selectivity * of the filtering done on local side, and modify first estimate. * * We have to get some catalog objects and generate remote query string here, * so we store such expensive information in FDW private area of RelOptInfo and * pass them to subsequent functions for reuse. */ static void postgresGetForeignRelSize(PlannerInfo *root, RelOptInfo *baserel, Oid foreigntableid) { bool use_remote_estimate = false; ListCell *lc; PgFdwRelationInfo *fpinfo; StringInfo sql; ForeignTable *table; ForeignServer *server; Selectivity sel; double rows; int width; Cost startup_cost; Cost total_cost; Cost run_cost; QualCost qpqual_cost; Cost cpu_per_tuple; List *remote_conds; List *param_conds; List *local_conds; List *param_numbers; /* * We use PgFdwRelationInfo to pass various information to subsequent * functions. */ fpinfo = palloc0(sizeof(PgFdwRelationInfo)); initStringInfo(&fpinfo->sql); sql = &fpinfo->sql; /* * Determine whether we use remote estimate or not. Note that per-table * setting overrides per-server setting. */ table = GetForeignTable(foreigntableid); server = GetForeignServer(table->serverid); foreach(lc, server->options) { DefElem *def = (DefElem *) lfirst(lc); if (strcmp(def->defname, "use_remote_estimate") == 0) { use_remote_estimate = defGetBoolean(def); break; } } foreach(lc, table->options) { DefElem *def = (DefElem *) lfirst(lc); if (strcmp(def->defname, "use_remote_estimate") == 0) { use_remote_estimate = defGetBoolean(def); break; } } /* * Construct remote query which consists of SELECT, FROM, and WHERE * clauses. Conditions which contain any Param node are excluded because * placeholder can't be used in EXPLAIN statement. Such conditions are * appended later. */ classifyConditions(root, baserel, &remote_conds, ¶m_conds, &local_conds, ¶m_numbers); deparseSimpleSql(sql, root, baserel, local_conds); if (list_length(remote_conds) > 0) appendWhereClause(sql, true, remote_conds, root); /* * If the table or the server is configured to use remote estimates, * connect to the foreign server and execute EXPLAIN with the quals that * don't contain any Param nodes. Otherwise, estimate rows using whatever * statistics we have locally, in a way similar to ordinary tables. */ if (use_remote_estimate) { RangeTblEntry *rte; Oid userid; UserMapping *user; PGconn *conn; /* * Identify which user to do the remote access as. This should match * what ExecCheckRTEPerms() does. If we fail due to lack of * permissions, the query would have failed at runtime anyway. */ rte = planner_rt_fetch(baserel->relid, root); userid = rte->checkAsUser ? rte->checkAsUser : GetUserId(); user = GetUserMapping(userid, server->serverid); conn = GetConnection(server, user); get_remote_estimate(sql->data, conn, &rows, &width, &startup_cost, &total_cost); ReleaseConnection(conn); /* * Estimate selectivity of conditions which were not used in remote * EXPLAIN by calling clauselist_selectivity(). The best we can do * for these conditions is to estimate selectivity on the basis of * local statistics. */ sel = clauselist_selectivity(root, param_conds, baserel->relid, JOIN_INNER, NULL); sel *= clauselist_selectivity(root, local_conds, baserel->relid, JOIN_INNER, NULL); /* * Add in the eval cost of those conditions, too. */ cost_qual_eval(&qpqual_cost, param_conds, root); startup_cost += qpqual_cost.startup; total_cost += qpqual_cost.per_tuple * rows; cost_qual_eval(&qpqual_cost, local_conds, root); startup_cost += qpqual_cost.startup; total_cost += qpqual_cost.per_tuple * rows; /* Report estimated numbers to planner. */ baserel->rows = clamp_row_est(rows * sel); baserel->width = width; } else { /* * Estimate rows from the result of the last ANALYZE, using all * conditions specified in original query. * * If the foreign table has never been ANALYZEd, it will have relpages * and reltuples equal to zero, which most likely has nothing to do * with reality. We can't do a whole lot about that if we're not * allowed to consult the remote server, but we can use a hack similar * to plancat.c's treatment of empty relations: use a minimum size * estimate of 10 pages, and divide by the column-datatype-based width * estimate to get the corresponding number of tuples. */ if (baserel->pages == 0 && baserel->tuples == 0) { baserel->pages = 10; baserel->tuples = (10 * BLCKSZ) / (baserel->width + sizeof(HeapTupleHeaderData)); } set_baserel_size_estimates(root, baserel); /* Cost as though this were a seqscan, which is pessimistic. */ startup_cost = 0; run_cost = 0; run_cost += seq_page_cost * baserel->pages; startup_cost += baserel->baserestrictcost.startup; cpu_per_tuple = cpu_tuple_cost + baserel->baserestrictcost.per_tuple; run_cost += cpu_per_tuple * baserel->tuples; total_cost = startup_cost + run_cost; } /* * Finish deparsing remote query by adding conditions which were unusable * in remote EXPLAIN since they contain Param nodes. */ if (list_length(param_conds) > 0) appendWhereClause(sql, !(list_length(remote_conds) > 0), param_conds, root); /* * Store obtained information into FDW-private area of RelOptInfo so it's * available to subsequent functions. */ fpinfo->startup_cost = startup_cost; fpinfo->total_cost = total_cost; fpinfo->remote_conds = remote_conds; fpinfo->param_conds = param_conds; fpinfo->local_conds = local_conds; fpinfo->param_numbers = param_numbers; fpinfo->table = table; fpinfo->server = server; baserel->fdw_private = (void *) fpinfo; } /* * postgresGetForeignPaths * Create possible scan paths for a scan on the foreign table */ static void postgresGetForeignPaths(PlannerInfo *root, RelOptInfo *baserel, Oid foreigntableid) { PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *) baserel->fdw_private; ForeignPath *path; ListCell *lc; double fdw_startup_cost = DEFAULT_FDW_STARTUP_COST; double fdw_tuple_cost = DEFAULT_FDW_TUPLE_COST; Cost startup_cost; Cost total_cost; List *fdw_private; /* * Check for user override of fdw_startup_cost, fdw_tuple_cost values */ foreach(lc, fpinfo->server->options) { DefElem *d = (DefElem *) lfirst(lc); if (strcmp(d->defname, "fdw_startup_cost") == 0) fdw_startup_cost = strtod(defGetString(d), NULL); else if (strcmp(d->defname, "fdw_tuple_cost") == 0) fdw_tuple_cost = strtod(defGetString(d), NULL); } /* * We have cost values which are estimated on remote side, so adjust them * for better estimate which respect various stuffs to complete the scan, * such as sending query, transferring result, and local filtering. */ startup_cost = fpinfo->startup_cost; total_cost = fpinfo->total_cost; /*---------- * Adjust costs with factors of the corresponding foreign server: * - add cost to establish connection to both startup and total * - add cost to manipulate on remote, and transfer result to total * - add cost to manipulate tuples on local side to total *---------- */ startup_cost += fdw_startup_cost; total_cost += fdw_startup_cost; total_cost += fdw_tuple_cost * baserel->rows; total_cost += cpu_tuple_cost * baserel->rows; /* * Build the fdw_private list that will be available to the executor. * Items in the list must match enum FdwPrivateIndex, above. */ fdw_private = list_make2(makeString(fpinfo->sql.data), fpinfo->param_numbers); /* * Create simplest ForeignScan path node and add it to baserel. This path * corresponds to SeqScan path of regular tables (though depending on what * baserestrict conditions we were able to send to remote, there might * actually be an indexscan happening there). */ path = create_foreignscan_path(root, baserel, baserel->rows, startup_cost, total_cost, NIL, /* no pathkeys */ NULL, /* no outer rel either */ fdw_private); add_path(baserel, (Path *) path); /* * XXX We can consider sorted path or parameterized path here if we know * that foreign table is indexed on remote end. For this purpose, we * might have to support FOREIGN INDEX to represent possible sets of sort * keys and/or filtering. Or we could just try some join conditions and * see if remote side estimates using them as markedly cheaper. Note that * executor functions need work to support internal Params before we can * try generating any parameterized paths, though. */ } /* * postgresGetForeignPlan * Create ForeignScan plan node which implements selected best path */ static ForeignScan * postgresGetForeignPlan(PlannerInfo *root, RelOptInfo *baserel, Oid foreigntableid, ForeignPath *best_path, List *tlist, List *scan_clauses) { PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *) baserel->fdw_private; Index scan_relid = baserel->relid; List *fdw_private = best_path->fdw_private; List *remote_exprs = NIL; List *local_exprs = NIL; ListCell *lc; /* * Separate the scan_clauses into those that can be executed remotely and * those that can't. For now, we accept only remote clauses that were * previously determined to be safe by classifyClauses (so, only * baserestrictinfo clauses can be used that way). * * This code must match "extract_actual_clauses(scan_clauses, false)" * except for the additional decision about remote versus local execution. */ foreach(lc, scan_clauses) { RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc); Assert(IsA(rinfo, RestrictInfo)); /* Ignore any pseudoconstants, they're dealt with elsewhere */ if (rinfo->pseudoconstant) continue; /* Either simple or parameterized remote clauses are OK now */ if (list_member_ptr(fpinfo->remote_conds, rinfo) || list_member_ptr(fpinfo->param_conds, rinfo)) remote_exprs = lappend(remote_exprs, rinfo->clause); else local_exprs = lappend(local_exprs, rinfo->clause); } /* * Create the ForeignScan node from target list, local filtering * expressions, remote filtering expressions, and FDW private information. * * Note that the remote_exprs are stored in the fdw_exprs field of the * finished plan node; we can't keep them in private state because then * they wouldn't be subject to later planner processing. * * XXX Currently, the remote_exprs aren't actually used at runtime, so we * don't need to store them at all. But we'll keep this behavior for a * little while for debugging reasons. */ return make_foreignscan(tlist, local_exprs, scan_relid, remote_exprs, fdw_private); } /* * postgresExplainForeignScan * Produce extra output for EXPLAIN */ static void postgresExplainForeignScan(ForeignScanState *node, ExplainState *es) { List *fdw_private; char *sql; if (es->verbose) { fdw_private = ((ForeignScan *) node->ss.ps.plan)->fdw_private; sql = strVal(list_nth(fdw_private, FdwPrivateSelectSql)); ExplainPropertyText("Remote SQL", sql, es); } } /* * postgresBeginForeignScan * Initiate an executor scan of a foreign PostgreSQL table. */ static void postgresBeginForeignScan(ForeignScanState *node, int eflags) { ForeignScan *fsplan = (ForeignScan *) node->ss.ps.plan; EState *estate = node->ss.ps.state; PgFdwExecutionState *festate; RangeTblEntry *rte; Oid userid; ForeignTable *table; ForeignServer *server; UserMapping *user; List *param_numbers; int numParams; int i; /* * Do nothing in EXPLAIN (no ANALYZE) case. node->fdw_state stays NULL. */ if (eflags & EXEC_FLAG_EXPLAIN_ONLY) return; /* * We'll save private state in node->fdw_state. */ festate = (PgFdwExecutionState *) palloc0(sizeof(PgFdwExecutionState)); node->fdw_state = (void *) festate; /* * Identify which user to do the remote access as. This should match what * ExecCheckRTEPerms() does. */ rte = rt_fetch(fsplan->scan.scanrelid, estate->es_range_table); userid = rte->checkAsUser ? rte->checkAsUser : GetUserId(); /* Get info about foreign table. */ festate->rel = node->ss.ss_currentRelation; table = GetForeignTable(RelationGetRelid(festate->rel)); server = GetForeignServer(table->serverid); user = GetUserMapping(userid, server->serverid); /* * Get connection to the foreign server. Connection manager will * establish new connection if necessary. */ festate->conn = GetConnection(server, user); /* Assign a unique ID for my cursor */ festate->cursor_number = GetCursorNumber(festate->conn); festate->cursor_exists = false; /* Get private info created by planner functions. */ festate->fdw_private = fsplan->fdw_private; /* Create contexts for batches of tuples and per-tuple temp workspace. */ festate->batch_cxt = AllocSetContextCreate(estate->es_query_cxt, "postgres_fdw tuple data", ALLOCSET_DEFAULT_MINSIZE, ALLOCSET_DEFAULT_INITSIZE, ALLOCSET_DEFAULT_MAXSIZE); festate->temp_cxt = AllocSetContextCreate(estate->es_query_cxt, "postgres_fdw temporary data", ALLOCSET_SMALL_MINSIZE, ALLOCSET_SMALL_INITSIZE, ALLOCSET_SMALL_MAXSIZE); /* Get info we'll need for data conversion. */ festate->attinmeta = TupleDescGetAttInMetadata(RelationGetDescr(festate->rel)); /* * Allocate buffer for query parameters, if the remote conditions use any. * * We use a parameter slot for each PARAM_EXTERN parameter, even though * not all of them may get sent to the remote server. This allows us to * refer to Params by their original number rather than remapping, and it * doesn't cost much. Slots that are not actually used get filled with * null values that are arbitrarily marked as being of type int4. */ param_numbers = (List *) list_nth(festate->fdw_private, FdwPrivateExternParamIds); if (param_numbers != NIL) { ParamListInfo params = estate->es_param_list_info; numParams = params ? params->numParams : 0; } else numParams = 0; festate->numParams = numParams; if (numParams > 0) { /* we initially fill all slots with value = NULL, type = int4 */ festate->param_types = (Oid *) palloc(numParams * sizeof(Oid)); festate->param_values = (const char **) palloc0(numParams * sizeof(char *)); for (i = 0; i < numParams; i++) festate->param_types[i] = INT4OID; } else { festate->param_types = NULL; festate->param_values = NULL; } festate->extparams_done = false; } /* * postgresIterateForeignScan * Retrieve next row from the result set, or clear tuple slot to indicate * EOF. */ static TupleTableSlot * postgresIterateForeignScan(ForeignScanState *node) { PgFdwExecutionState *festate = (PgFdwExecutionState *) node->fdw_state; TupleTableSlot *slot = node->ss.ss_ScanTupleSlot; /* * If this is the first call after Begin or ReScan, we need to create the * cursor on the remote side. */ if (!festate->cursor_exists) create_cursor(node); /* * Get some more tuples, if we've run out. */ if (festate->next_tuple >= festate->num_tuples) { /* No point in another fetch if we already detected EOF, though. */ if (!festate->eof_reached) fetch_more_data(node); /* If we didn't get any tuples, must be end of data. */ if (festate->next_tuple >= festate->num_tuples) return ExecClearTuple(slot); } /* * Return the next tuple. */ ExecStoreTuple(festate->tuples[festate->next_tuple++], slot, InvalidBuffer, false); return slot; } /* * postgresReScanForeignScan * Restart the scan. */ static void postgresReScanForeignScan(ForeignScanState *node) { PgFdwExecutionState *festate = (PgFdwExecutionState *) node->fdw_state; char sql[64]; PGresult *res; /* * Note: we assume that PARAM_EXTERN params don't change over the life of * the query, so no need to reset extparams_done. */ /* If we haven't created the cursor yet, nothing to do. */ if (!festate->cursor_exists) return; /* * If any internal parameters affecting this node have changed, we'd * better destroy and recreate the cursor. Otherwise, rewinding it should * be good enough. If we've only fetched zero or one batch, we needn't * even rewind the cursor, just rescan what we have. */ if (node->ss.ps.chgParam != NULL) { festate->cursor_exists = false; snprintf(sql, sizeof(sql), "CLOSE c%u", festate->cursor_number); } else if (festate->fetch_ct_2 > 1) { snprintf(sql, sizeof(sql), "MOVE BACKWARD ALL IN c%u", festate->cursor_number); } else { /* Easy: just rescan what we already have in memory, if anything */ festate->next_tuple = 0; return; } /* * We don't use a PG_TRY block here, so be careful not to throw error * without releasing the PGresult. */ res = PQexec(festate->conn, sql); if (PQresultStatus(res) != PGRES_COMMAND_OK) pgfdw_report_error(ERROR, res, true, sql); PQclear(res); /* Now force a fresh FETCH. */ festate->tuples = NULL; festate->num_tuples = 0; festate->next_tuple = 0; festate->fetch_ct_2 = 0; festate->eof_reached = false; } /* * postgresEndForeignScan * Finish scanning foreign table and dispose objects used for this scan */ static void postgresEndForeignScan(ForeignScanState *node) { PgFdwExecutionState *festate = (PgFdwExecutionState *) node->fdw_state; /* if festate is NULL, we are in EXPLAIN; nothing to do */ if (festate == NULL) return; /* Close the cursor if open, to prevent accumulation of cursors */ if (festate->cursor_exists) close_cursor(festate->conn, festate->cursor_number); /* Release remote connection */ ReleaseConnection(festate->conn); festate->conn = NULL; /* MemoryContexts will be deleted automatically. */ } /* * Estimate costs of executing given SQL statement. */ static void get_remote_estimate(const char *sql, PGconn *conn, double *rows, int *width, Cost *startup_cost, Cost *total_cost) { PGresult *volatile res = NULL; /* PGresult must be released before leaving this function. */ PG_TRY(); { StringInfoData buf; char *line; char *p; int n; /* * Execute EXPLAIN remotely on given SQL statement. */ initStringInfo(&buf); appendStringInfo(&buf, "EXPLAIN %s", sql); res = PQexec(conn, buf.data); if (PQresultStatus(res) != PGRES_TUPLES_OK) pgfdw_report_error(ERROR, res, false, buf.data); /* * Extract cost numbers for topmost plan node. Note we search for a * left paren from the end of the line to avoid being confused by * other uses of parentheses. */ line = PQgetvalue(res, 0, 0); p = strrchr(line, '('); if (p == NULL) elog(ERROR, "could not interpret EXPLAIN output: \"%s\"", line); n = sscanf(p, "(cost=%lf..%lf rows=%lf width=%d)", startup_cost, total_cost, rows, width); if (n != 4) elog(ERROR, "could not interpret EXPLAIN output: \"%s\"", line); PQclear(res); res = NULL; } PG_CATCH(); { if (res) PQclear(res); PG_RE_THROW(); } PG_END_TRY(); } /* * Create cursor for node's query with current parameter values. */ static void create_cursor(ForeignScanState *node) { PgFdwExecutionState *festate = (PgFdwExecutionState *) node->fdw_state; int numParams = festate->numParams; Oid *types = festate->param_types; const char **values = festate->param_values; PGconn *conn = festate->conn; char *sql; StringInfoData buf; PGresult *res; /* * Construct array of external parameter values in text format. Since * there might be random unconvertible stuff in the ParamExternData array, * take care to convert only values we actually need. * * Note that we leak the memory for the value strings until end of query; * this doesn't seem like a big problem, and in any case we might need to * recreate the cursor after a rescan, so we could need to re-use the * values anyway. */ if (numParams > 0 && !festate->extparams_done) { ParamListInfo params = node->ss.ps.state->es_param_list_info; int nestlevel; List *param_numbers; ListCell *lc; nestlevel = set_transmission_modes(); param_numbers = (List *) list_nth(festate->fdw_private, FdwPrivateExternParamIds); foreach(lc, param_numbers) { int paramno = lfirst_int(lc); ParamExternData *prm = ¶ms->params[paramno - 1]; /* give hook a chance in case parameter is dynamic */ if (!OidIsValid(prm->ptype) && params->paramFetch != NULL) params->paramFetch(params, paramno); /* * Force the remote server to infer a type for this parameter. * Since we explicitly cast every parameter (see deparse.c), the * "inference" is trivial and will produce the desired result. * This allows us to avoid assuming that the remote server has the * same OIDs we do for the parameters' types. * * We'd not need to pass a type array to PQexecParams at all, * except that there may be unused holes in the array, which * will have to be filled with something or the remote server will * complain. We arbitrarily set them to INT4OID earlier. */ types[paramno - 1] = InvalidOid; /* * Get string representation of each parameter value by invoking * type-specific output function, unless the value is null. */ if (prm->isnull) values[paramno - 1] = NULL; else { Oid out_func; bool isvarlena; getTypeOutputInfo(prm->ptype, &out_func, &isvarlena); values[paramno - 1] = OidOutputFunctionCall(out_func, prm->value); } } reset_transmission_modes(nestlevel); festate->extparams_done = true; } /* Construct the DECLARE CURSOR command */ sql = strVal(list_nth(festate->fdw_private, FdwPrivateSelectSql)); initStringInfo(&buf); appendStringInfo(&buf, "DECLARE c%u CURSOR FOR\n%s", festate->cursor_number, sql); /* * We don't use a PG_TRY block here, so be careful not to throw error * without releasing the PGresult. */ res = PQexecParams(conn, buf.data, numParams, types, values, NULL, NULL, 0); if (PQresultStatus(res) != PGRES_COMMAND_OK) pgfdw_report_error(ERROR, res, true, sql); PQclear(res); /* Mark the cursor as created, and show no tuples have been retrieved */ festate->cursor_exists = true; festate->tuples = NULL; festate->num_tuples = 0; festate->next_tuple = 0; festate->fetch_ct_2 = 0; festate->eof_reached = false; /* Clean up */ pfree(buf.data); } /* * Fetch some more rows from the node's cursor. */ static void fetch_more_data(ForeignScanState *node) { PgFdwExecutionState *festate = (PgFdwExecutionState *) node->fdw_state; PGresult *volatile res = NULL; MemoryContext oldcontext; /* * We'll store the tuples in the batch_cxt. First, flush the previous * batch. */ festate->tuples = NULL; MemoryContextReset(festate->batch_cxt); oldcontext = MemoryContextSwitchTo(festate->batch_cxt); /* PGresult must be released before leaving this function. */ PG_TRY(); { PGconn *conn = festate->conn; char sql[64]; int fetch_size; int numrows; int i; /* The fetch size is arbitrary, but shouldn't be enormous. */ fetch_size = 100; snprintf(sql, sizeof(sql), "FETCH %d FROM c%u", fetch_size, festate->cursor_number); res = PQexec(conn, sql); /* On error, report the original query, not the FETCH. */ if (PQresultStatus(res) != PGRES_TUPLES_OK) pgfdw_report_error(ERROR, res, false, strVal(list_nth(festate->fdw_private, FdwPrivateSelectSql))); /* Convert the data into HeapTuples */ numrows = PQntuples(res); festate->tuples = (HeapTuple *) palloc0(numrows * sizeof(HeapTuple)); festate->num_tuples = numrows; festate->next_tuple = 0; for (i = 0; i < numrows; i++) { festate->tuples[i] = make_tuple_from_result_row(res, i, festate->rel, festate->attinmeta, festate->temp_cxt); } /* Update fetch_ct_2 */ if (festate->fetch_ct_2 < 2) festate->fetch_ct_2++; /* Must be EOF if we didn't get as many tuples as we asked for. */ festate->eof_reached = (numrows < fetch_size); PQclear(res); res = NULL; } PG_CATCH(); { if (res) PQclear(res); PG_RE_THROW(); } PG_END_TRY(); MemoryContextSwitchTo(oldcontext); } /* * Force assorted GUC parameters to settings that ensure that we'll output * data values in a form that is unambiguous to the remote server. * * This is rather expensive and annoying to do once per row, but there's * little choice if we want to be sure values are transmitted accurately; * we can't leave the settings in place between rows for fear of affecting * user-visible computations. * * We use the equivalent of a function SET option to allow the settings to * persist only until the caller calls reset_transmission_modes(). If an * error is thrown in between, guc.c will take care of undoing the settings. * * The return value is the nestlevel that must be passed to * reset_transmission_modes() to undo things. */ int set_transmission_modes(void) { int nestlevel = NewGUCNestLevel(); /* * The values set here should match what pg_dump does. See also * configure_remote_session in connection.c. */ if (DateStyle != USE_ISO_DATES) (void) set_config_option("datestyle", "ISO", PGC_USERSET, PGC_S_SESSION, GUC_ACTION_SAVE, true, 0); if (IntervalStyle != INTSTYLE_POSTGRES) (void) set_config_option("intervalstyle", "postgres", PGC_USERSET, PGC_S_SESSION, GUC_ACTION_SAVE, true, 0); if (extra_float_digits < 3) (void) set_config_option("extra_float_digits", "3", PGC_USERSET, PGC_S_SESSION, GUC_ACTION_SAVE, true, 0); return nestlevel; } /* * Undo the effects of set_transmission_modes(). */ void reset_transmission_modes(int nestlevel) { AtEOXact_GUC(true, nestlevel); } /* * Utility routine to close a cursor. */ static void close_cursor(PGconn *conn, unsigned int cursor_number) { char sql[64]; PGresult *res; snprintf(sql, sizeof(sql), "CLOSE c%u", cursor_number); /* * We don't use a PG_TRY block here, so be careful not to throw error * without releasing the PGresult. */ res = PQexec(conn, sql); if (PQresultStatus(res) != PGRES_COMMAND_OK) pgfdw_report_error(ERROR, res, true, sql); PQclear(res); } /* * postgresAnalyzeForeignTable * Test whether analyzing this foreign table is supported */ static bool postgresAnalyzeForeignTable(Relation relation, AcquireSampleRowsFunc *func, BlockNumber *totalpages) { ForeignTable *table; ForeignServer *server; UserMapping *user; PGconn *conn; StringInfoData sql; PGresult *volatile res = NULL; /* Return the row-analysis function pointer */ *func = postgresAcquireSampleRowsFunc; /* * Now we have to get the number of pages. It's annoying that the ANALYZE * API requires us to return that now, because it forces some duplication * of effort between this routine and postgresAcquireSampleRowsFunc. But * it's probably not worth redefining that API at this point. */ /* * Get the connection to use. We do the remote access as the table's * 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); /* * Construct command to get page count for relation. */ initStringInfo(&sql); deparseAnalyzeSizeSql(&sql, relation); /* In what follows, do not risk leaking any PGresults. */ PG_TRY(); { res = PQexec(conn, sql.data); if (PQresultStatus(res) != PGRES_TUPLES_OK) pgfdw_report_error(ERROR, res, false, sql.data); if (PQntuples(res) != 1 || PQnfields(res) != 1) elog(ERROR, "unexpected result from deparseAnalyzeSizeSql query"); *totalpages = strtoul(PQgetvalue(res, 0, 0), NULL, 10); PQclear(res); res = NULL; } PG_CATCH(); { if (res) PQclear(res); PG_RE_THROW(); } PG_END_TRY(); ReleaseConnection(conn); return true; } /* * Acquire a random sample of rows from foreign table managed by postgres_fdw. * * We fetch the whole table from the remote side and pick out some sample rows. * * Selected rows are returned in the caller-allocated array rows[], * which must have at least targrows entries. * The actual number of rows selected is returned as the function result. * We also count the total number of rows in the table and return it into * *totalrows. Note that *totaldeadrows is always set to 0. * * Note that the returned list of rows is not always in order by physical * position in the table. Therefore, correlation estimates derived later * may be meaningless, but it's OK because we don't use the estimates * currently (the planner only pays attention to correlation for indexscans). */ static int postgresAcquireSampleRowsFunc(Relation relation, int elevel, HeapTuple *rows, int targrows, double *totalrows, double *totaldeadrows) { PgFdwAnalyzeState astate; ForeignTable *table; ForeignServer *server; UserMapping *user; PGconn *conn; unsigned int cursor_number; StringInfoData sql; PGresult *volatile res = NULL; /* Initialize workspace state */ astate.rel = relation; astate.attinmeta = TupleDescGetAttInMetadata(RelationGetDescr(relation)); astate.rows = rows; astate.targrows = targrows; astate.numrows = 0; astate.samplerows = 0; astate.rowstoskip = -1; /* -1 means not set yet */ astate.rstate = anl_init_selection_state(targrows); /* Remember ANALYZE context, and create a per-tuple temp context */ astate.anl_cxt = CurrentMemoryContext; astate.temp_cxt = AllocSetContextCreate(CurrentMemoryContext, "postgres_fdw temporary data", ALLOCSET_SMALL_MINSIZE, ALLOCSET_SMALL_INITSIZE, ALLOCSET_SMALL_MAXSIZE); /* * Get the connection to use. We do the remote access as the table's * 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); /* * Construct cursor that retrieves whole rows from remote. */ cursor_number = GetCursorNumber(conn); initStringInfo(&sql); appendStringInfo(&sql, "DECLARE c%u CURSOR FOR ", cursor_number); deparseAnalyzeSql(&sql, relation); /* In what follows, do not risk leaking any PGresults. */ PG_TRY(); { res = PQexec(conn, sql.data); if (PQresultStatus(res) != PGRES_COMMAND_OK) pgfdw_report_error(ERROR, res, false, sql.data); PQclear(res); res = NULL; /* Retrieve and process rows a batch at a time. */ for (;;) { char fetch_sql[64]; int fetch_size; int numrows; int i; /* Allow users to cancel long query */ CHECK_FOR_INTERRUPTS(); /* * XXX possible future improvement: if rowstoskip is large, we * could issue a MOVE rather than physically fetching the rows, * then just adjust rowstoskip and samplerows appropriately. */ /* The fetch size is arbitrary, but shouldn't be enormous. */ fetch_size = 100; /* Fetch some rows */ snprintf(fetch_sql, sizeof(fetch_sql), "FETCH %d FROM c%u", fetch_size, cursor_number); res = PQexec(conn, fetch_sql); /* On error, report the original query, not the FETCH. */ if (PQresultStatus(res) != PGRES_TUPLES_OK) pgfdw_report_error(ERROR, res, false, sql.data); /* Process whatever we got. */ numrows = PQntuples(res); for (i = 0; i < numrows; i++) analyze_row_processor(res, i, &astate); PQclear(res); res = NULL; /* Must be EOF if we didn't get all the rows requested. */ if (numrows < fetch_size) break; } /* Close the cursor, just to be tidy. */ close_cursor(conn, cursor_number); } PG_CATCH(); { if (res) PQclear(res); PG_RE_THROW(); } PG_END_TRY(); ReleaseConnection(conn); /* We assume that we have no dead tuple. */ *totaldeadrows = 0.0; /* We've retrieved all living tuples from foreign server. */ *totalrows = astate.samplerows; /* * Emit some interesting relation info */ ereport(elevel, (errmsg("\"%s\": table contains %.0f rows, %d rows in sample", RelationGetRelationName(relation), astate.samplerows, astate.numrows))); return astate.numrows; } /* * Collect sample rows from the result of query. * - Use all tuples in sample until target # of samples are collected. * - Subsequently, replace already-sampled tuples randomly. */ static void analyze_row_processor(PGresult *res, int row, PgFdwAnalyzeState *astate) { int targrows = astate->targrows; int pos; /* array index to store tuple in */ MemoryContext oldcontext; /* Always increment sample row counter. */ astate->samplerows += 1; /* * Determine the slot where this sample row should be stored. Set pos to * negative value to indicate the row should be skipped. */ if (astate->numrows < targrows) { /* First targrows rows are always included into the sample */ pos = astate->numrows++; } else { /* * Now we start replacing tuples in the sample until we reach the end * of the relation. Same algorithm as in acquire_sample_rows in * analyze.c; see Jeff Vitter's paper. */ if (astate->rowstoskip < 0) astate->rowstoskip = anl_get_next_S(astate->samplerows, targrows, &astate->rstate); if (astate->rowstoskip <= 0) { /* Choose a random reservoir element to replace. */ pos = (int) (targrows * anl_random_fract()); Assert(pos >= 0 && pos < targrows); heap_freetuple(astate->rows[pos]); } else { /* Skip this tuple. */ pos = -1; } astate->rowstoskip -= 1; } if (pos >= 0) { /* * Create sample tuple from current result row, and store it in the * position determined above. The tuple has to be created in anl_cxt. */ oldcontext = MemoryContextSwitchTo(astate->anl_cxt); astate->rows[pos] = make_tuple_from_result_row(res, row, astate->rel, astate->attinmeta, astate->temp_cxt); MemoryContextSwitchTo(oldcontext); } } /* * Create a tuple from the specified row of the PGresult. * * rel is the local representation of the foreign table, attinmeta is * conversion data for the rel's tupdesc, and temp_context is a working * context that can be reset after each tuple. */ static HeapTuple make_tuple_from_result_row(PGresult *res, int row, Relation rel, AttInMetadata *attinmeta, MemoryContext temp_context) { HeapTuple tuple; TupleDesc tupdesc = RelationGetDescr(rel); Form_pg_attribute *attrs = tupdesc->attrs; Datum *values; bool *nulls; ConversionLocation errpos; ErrorContextCallback errcallback; MemoryContext oldcontext; int i; int j; Assert(row < PQntuples(res)); /* * Do the following work in a temp context that we reset after each tuple. * This cleans up not only the data we have direct access to, but any * cruft the I/O functions might leak. */ oldcontext = MemoryContextSwitchTo(temp_context); values = (Datum *) palloc(tupdesc->natts * sizeof(Datum)); nulls = (bool *) palloc(tupdesc->natts * sizeof(bool)); /* * Set up and install callback to report where conversion error occurs. */ errpos.rel = rel; errpos.cur_attno = 0; errcallback.callback = conversion_error_callback; errcallback.arg = (void *) &errpos; errcallback.previous = error_context_stack; error_context_stack = &errcallback; /* * i indexes columns in the relation, j indexes columns in the PGresult. * We assume dropped columns are not represented in the PGresult. */ for (i = 0, j = 0; i < tupdesc->natts; i++) { char *valstr; /* skip dropped columns. */ if (attrs[i]->attisdropped) { values[i] = (Datum) 0; nulls[i] = true; continue; } /* convert value to internal representation */ if (PQgetisnull(res, row, j)) { valstr = NULL; nulls[i] = true; } else { valstr = PQgetvalue(res, row, j); nulls[i] = false; } /* Note: apply the input function even to nulls, to support domains */ errpos.cur_attno = i + 1; values[i] = InputFunctionCall(&attinmeta->attinfuncs[i], valstr, attinmeta->attioparams[i], attinmeta->atttypmods[i]); errpos.cur_attno = 0; j++; } /* Uninstall error context callback. */ error_context_stack = errcallback.previous; /* check result and tuple descriptor have the same number of columns */ if (j != PQnfields(res)) elog(ERROR, "remote query result does not match the foreign table"); /* * Build the result tuple in caller's memory context. */ MemoryContextSwitchTo(oldcontext); tuple = heap_form_tuple(tupdesc, values, nulls); /* Clean up */ MemoryContextReset(temp_context); return tuple; } /* * Callback function which is called when error occurs during column value * conversion. Print names of column and relation. */ static void conversion_error_callback(void *arg) { ConversionLocation *errpos = (ConversionLocation *) arg; TupleDesc tupdesc = RelationGetDescr(errpos->rel); if (errpos->cur_attno > 0 && errpos->cur_attno <= tupdesc->natts) errcontext("column \"%s\" of foreign table \"%s\"", NameStr(tupdesc->attrs[errpos->cur_attno - 1]->attname), RelationGetRelationName(errpos->rel)); }