connection.c File Reference

#include "postgres.h"
#include "postgres_fdw.h"
#include "access/htup_details.h"
#include "access/xact.h"
#include "catalog/pg_user_mapping.h"
#include "mb/pg_wchar.h"
#include "miscadmin.h"
#include "pgstat.h"
#include "storage/latch.h"
#include "utils/hsearch.h"
#include "utils/inval.h"
#include "utils/memutils.h"
#include "utils/syscache.h"

Include dependency graph for connection.c:

Go to the source code of this file.

Data Structures
struct	ConnCacheEntry

Typedefs
typedef Oid	ConnCacheKey
typedef struct ConnCacheEntry	ConnCacheEntry

Functions
static PGconn *	connect_pg_server (ForeignServer *server, UserMapping *user)
static void	disconnect_pg_server (ConnCacheEntry *entry)
static void	check_conn_params (const char **keywords, const char **values, UserMapping *user)
static void	configure_remote_session (PGconn *conn)
static void	do_sql_command (PGconn *conn, const char *sql)
static void	begin_remote_xact (ConnCacheEntry *entry)
static void	pgfdw_xact_callback (XactEvent event, void *arg)
static void	pgfdw_subxact_callback (SubXactEvent event, SubTransactionId mySubid, SubTransactionId parentSubid, void *arg)
static void	pgfdw_inval_callback (Datum arg, int cacheid, uint32 hashvalue)
static void	pgfdw_reject_incomplete_xact_state_change (ConnCacheEntry *entry)
static bool	pgfdw_cancel_query (PGconn *conn)
static bool	pgfdw_exec_cleanup_query (PGconn *conn, const char *query, bool ignore_errors)
static bool	pgfdw_get_cleanup_result (PGconn *conn, TimestampTz endtime, PGresult **result)
PGconn *	GetConnection (UserMapping *user, bool will_prep_stmt)
void	ReleaseConnection (PGconn *conn)
unsigned int	GetCursorNumber (PGconn *conn)
unsigned int	GetPrepStmtNumber (PGconn *conn)
PGresult *	pgfdw_exec_query (PGconn *conn, const char *query)
PGresult *	pgfdw_get_result (PGconn *conn, const char *query)
void	pgfdw_report_error (int elevel, PGresult *res, PGconn *conn, bool clear, const char *sql)

Variables
static HTAB *	ConnectionHash = NULL
static unsigned int	cursor_number = 0
static unsigned int	prep_stmt_number = 0
static bool	xact_got_connection = false

Typedef Documentation

ConnCacheEntry

typedef struct ConnCacheEntry ConnCacheEntry

ConnCacheKey

typedef Oid ConnCacheKey

Definition at line 46 of file connection.c.

Function Documentation

begin_remote_xact()

static void begin_remote_xact ( ConnCacheEntry *  entry )

static

Definition at line 417 of file connection.c.

References ConnCacheEntry::changing_xact_state, ConnCacheEntry::conn, DEBUG3, do_sql_command(), elog, GetCurrentTransactionNestLevel(), IsolationIsSerializable, snprintf, and ConnCacheEntry::xact_depth.

Referenced by GetConnection().

{
    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;
    }
}

check_conn_params()

static void check_conn_params ( const char **  keywords, const char **  values, UserMapping *  user  )

static

Definition at line 325 of file connection.c.

References ereport, errcode(), errdetail(), errmsg(), ERROR, i, superuser_arg(), and UserMapping::userid.

Referenced by connect_pg_server().

{
    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;
    }

    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.")));
}

configure_remote_session()

static void configure_remote_session ( PGconn *  conn )

static

Definition at line 358 of file connection.c.

References do_sql_command(), and PQserverVersion().

Referenced by connect_pg_server().

{
    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");
}

connect_pg_server()

static PGconn * connect_pg_server ( ForeignServer *  server, UserMapping *  user  )

static

Definition at line 222 of file connection.c.

References check_conn_params(), configure_remote_session(), ConnCacheEntry::conn, CONNECTION_OK, ereport, errcode(), errdetail(), errdetail_internal(), errhint(), errmsg(), ERROR, ExtractConnectionOptions(), GetDatabaseEncodingName(), list_length(), ForeignServer::options, UserMapping::options, palloc(), pchomp(), pfree(), PG_CATCH, PG_END_TRY, PG_RE_THROW, PG_TRY, PQconnectdbParams(), PQconnectionUsedPassword(), PQerrorMessage(), PQfinish(), PQstatus(), ForeignServer::servername, superuser_arg(), UserMapping::userid, and values.

Referenced by GetConnection().

{
    PGconn     *volatile conn = NULL;

    /*
     * Use PG_TRY block to ensure closing connection on error.
     */
    PG_TRY();
    {
        const char **keywords;
        const char **values;
        int         n;

        /*
         * Construct connection params from generic options of ForeignServer
         * and UserMapping.  (Some of them might not be libpq options, in
         * which case we'll just waste a few array slots.)  Add 3 extra slots
         * for fallback_application_name, client_encoding, end marker.
         */
        n = list_length(server->options) + list_length(user->options) + 3;
        keywords = (const char **) palloc(n * sizeof(char *));
        values = (const char **) palloc(n * sizeof(char *));

        n = 0;
        n += ExtractConnectionOptions(server->options,
                                      keywords + n, values + n);
        n += ExtractConnectionOptions(user->options,
                                      keywords + n, values + n);

        /* Use "postgres_fdw" as fallback_application_name. */
        keywords[n] = "fallback_application_name";
        values[n] = "postgres_fdw";
        n++;

        /* Set client_encoding so that libpq can convert encoding properly. */
        keywords[n] = "client_encoding";
        values[n] = GetDatabaseEncodingName();
        n++;

        keywords[n] = values[n] = NULL;

        /* verify connection parameters and make connection */
        check_conn_params(keywords, values, user);

        conn = PQconnectdbParams(keywords, values, false);
        if (!conn || PQstatus(conn) != CONNECTION_OK)
            ereport(ERROR,
                    (errcode(ERRCODE_SQLCLIENT_UNABLE_TO_ESTABLISH_SQLCONNECTION),
                     errmsg("could not connect to server \"%s\"",
                            server->servername),
                     errdetail_internal("%s", pchomp(PQerrorMessage(conn)))));

        /*
         * Check that non-superuser has used password to establish connection;
         * otherwise, he's piggybacking on the postgres server's user
         * identity. See also dblink_security_check() in contrib/dblink.
         */
        if (!superuser_arg(user->userid) && !PQconnectionUsedPassword(conn))
            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.")));

        /* Prepare new session for use */
        configure_remote_session(conn);

        pfree(keywords);
        pfree(values);
    }
    PG_CATCH();
    {
        /* Release PGconn data structure if we managed to create one */
        if (conn)
            PQfinish(conn);
        PG_RE_THROW();
    }
    PG_END_TRY();

    return conn;
}

disconnect_pg_server()

static void disconnect_pg_server ( ConnCacheEntry *  entry )

static

Definition at line 308 of file connection.c.

References ConnCacheEntry::conn, and PQfinish().

Referenced by GetConnection(), pgfdw_reject_incomplete_xact_state_change(), and pgfdw_xact_callback().

{
    if (entry->conn != NULL)
    {
        PQfinish(entry->conn);
        entry->conn = NULL;
    }
}

do_sql_command()

static void do_sql_command ( PGconn *  conn, const char *  sql  )

static

Definition at line 394 of file connection.c.

References ERROR, pgfdw_get_result(), pgfdw_report_error(), PGRES_COMMAND_OK, PQclear(), PQresultStatus(), and PQsendQuery().

Referenced by begin_remote_xact(), configure_remote_session(), pgfdw_subxact_callback(), and pgfdw_xact_callback().

{
    PGresult   *res;

    if (!PQsendQuery(conn, sql))
        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);
}

GetConnection()

PGconn* GetConnection	(	UserMapping *	user,
		bool	will_prep_stmt
	)

Definition at line 107 of file connection.c.

References begin_remote_xact(), CacheMemoryContext, CacheRegisterSyscacheCallback(), ConnCacheEntry::changing_xact_state, ConnCacheEntry::conn, connect_pg_server(), DEBUG3, disconnect_pg_server(), elog, HASHCTL::entrysize, FOREIGNSERVEROID, GetForeignServer(), GetSysCacheHashValue1, HASH_BLOBS, HASH_CONTEXT, hash_create(), HASH_ELEM, HASH_ENTER, hash_search(), ConnCacheEntry::have_error, ConnCacheEntry::have_prep_stmt, HASHCTL::hcxt, ConnCacheEntry::invalidated, ConnCacheEntry::key, HASHCTL::keysize, ConnCacheEntry::mapping_hashvalue, MemSet, ObjectIdGetDatum, pgfdw_inval_callback(), pgfdw_reject_incomplete_xact_state_change(), pgfdw_subxact_callback(), pgfdw_xact_callback(), RegisterSubXactCallback(), RegisterXactCallback(), ConnCacheEntry::server_hashvalue, ForeignServer::serverid, UserMapping::serverid, ForeignServer::servername, UserMapping::umid, UserMapping::userid, USERMAPPINGOID, ConnCacheEntry::xact_depth, and xact_got_connection.

Referenced by create_foreign_modify(), dumpBlobs(), dumpDatabase(), dumpDatabaseConfig(), dumpTableData_copy(), estimate_path_cost_size(), expand_schema_name_patterns(), expand_table_name_patterns(), getTables(), main(), postgresAcquireSampleRowsFunc(), postgresAnalyzeForeignTable(), postgresBeginDirectModify(), postgresBeginForeignScan(), postgresImportForeignSchema(), setup_connection(), StartLogStreamer(), StreamLog(), and StreamLogicalLog().

{
    bool        found;
    ConnCacheEntry *entry;
    ConnCacheKey key;

    /* First time through, initialize connection cache hashtable */
    if (ConnectionHash == NULL)
    {
        HASHCTL     ctl;

        MemSet(&ctl, 0, sizeof(ctl));
        ctl.keysize = sizeof(ConnCacheKey);
        ctl.entrysize = sizeof(ConnCacheEntry);
        /* allocate ConnectionHash in the cache context */
        ctl.hcxt = CacheMemoryContext;
        ConnectionHash = hash_create("postgres_fdw connections", 8,
                                     &ctl,
                                     HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);

        /*
         * Register some callback functions that manage connection cleanup.
         * This should be done just once in each backend.
         */
        RegisterXactCallback(pgfdw_xact_callback, NULL);
        RegisterSubXactCallback(pgfdw_subxact_callback, NULL);
        CacheRegisterSyscacheCallback(FOREIGNSERVEROID,
                                      pgfdw_inval_callback, (Datum) 0);
        CacheRegisterSyscacheCallback(USERMAPPINGOID,
                                      pgfdw_inval_callback, (Datum) 0);
    }

    /* Set flag that we did GetConnection during the current transaction */
    xact_got_connection = true;

    /* Create hash key for the entry.  Assume no pad bytes in key struct */
    key = user->umid;

    /*
     * Find or create cached entry for requested connection.
     */
    entry = hash_search(ConnectionHash, &key, HASH_ENTER, &found);
    if (!found)
    {
        /*
         * We need only clear "conn" here; remaining fields will be filled
         * later when "conn" is set.
         */
        entry->conn = NULL;
    }

    /* Reject further use of connections which failed abort cleanup. */
    pgfdw_reject_incomplete_xact_state_change(entry);

    /*
     * If the connection needs to be remade due to invalidation, disconnect as
     * soon as we're out of all transactions.
     */
    if (entry->conn != NULL && entry->invalidated && entry->xact_depth == 0)
    {
        elog(DEBUG3, "closing connection %p for option changes to take effect",
             entry->conn);
        disconnect_pg_server(entry);
    }

    /*
     * We don't check the health of cached connection here, because it would
     * require some overhead.  Broken connection will be detected when the
     * connection is actually used.
     */

    /*
     * If cache entry doesn't have a connection, we have to establish a new
     * connection.  (If connect_pg_server throws an error, the cache entry
     * will remain in a valid empty state, ie conn == NULL.)
     */
    if (entry->conn == NULL)
    {
        ForeignServer *server = GetForeignServer(user->serverid);

        /* Reset all transient state fields, to be sure all are clean */
        entry->xact_depth = 0;
        entry->have_prep_stmt = false;
        entry->have_error = false;
        entry->changing_xact_state = false;
        entry->invalidated = false;
        entry->server_hashvalue =
            GetSysCacheHashValue1(FOREIGNSERVEROID,
                                  ObjectIdGetDatum(server->serverid));
        entry->mapping_hashvalue =
            GetSysCacheHashValue1(USERMAPPINGOID,
                                  ObjectIdGetDatum(user->umid));

        /* Now try to make the connection */
        entry->conn = connect_pg_server(server, user);

        elog(DEBUG3, "new postgres_fdw connection %p for server \"%s\" (user mapping oid %u, userid %u)",
             entry->conn, server->servername, user->umid, user->userid);
    }

    /*
     * Start a new transaction or subtransaction if needed.
     */
    begin_remote_xact(entry);

    /* Remember if caller will prepare statements */
    entry->have_prep_stmt |= will_prep_stmt;

    return entry->conn;
}

GetCursorNumber()

unsigned int GetCursorNumber

(

PGconn *

conn

)

Definition at line 481 of file connection.c.

References cursor_number.

Referenced by postgresAcquireSampleRowsFunc(), and postgresBeginForeignScan().

{
    return ++cursor_number;
}

GetPrepStmtNumber()

unsigned int GetPrepStmtNumber

(

PGconn *

conn

)

Definition at line 495 of file connection.c.

References prep_stmt_number.

Referenced by prepare_foreign_modify().

{
    return ++prep_stmt_number;
}

pgfdw_cancel_query()

static bool pgfdw_cancel_query ( PGconn *  conn )

static

Definition at line 1022 of file connection.c.

References ereport, errcode(), errmsg(), GetCurrentTimestamp(), pgfdw_get_cleanup_result(), PQcancel(), PQclear(), PQfreeCancel(), PQgetCancel(), TimestampTzPlusMilliseconds, and WARNING.

Referenced by pgfdw_subxact_callback(), and pgfdw_xact_callback().

{
    PGcancel   *cancel;
    char        errbuf[256];
    PGresult   *result = NULL;
    TimestampTz endtime;

    /*
     * 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))
        return false;
    PQclear(result);

    return true;
}

pgfdw_exec_cleanup_query()

static bool pgfdw_exec_cleanup_query ( PGconn *  conn, const char *  query, bool  ignore_errors  )

static

Definition at line 1069 of file connection.c.

References GetCurrentTimestamp(), pgfdw_get_cleanup_result(), pgfdw_report_error(), PGRES_COMMAND_OK, PQclear(), PQresultStatus(), PQsendQuery(), TimestampTzPlusMilliseconds, and WARNING.

Referenced by pgfdw_subxact_callback(), and pgfdw_xact_callback().

{
    PGresult   *result = NULL;
    TimestampTz endtime;

    /*
     * If it takes too long to execute a cleanup query, assume the connection
     * is dead.  It's fairly likely that this is why we aborted in the first
     * place (e.g. statement timeout, user cancel), so the timeout shouldn't
     * be too long.
     */
    endtime = TimestampTzPlusMilliseconds(GetCurrentTimestamp(), 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))
        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;
}

pgfdw_exec_query()

PGresult* pgfdw_exec_query	(	PGconn *	conn,
		const char *	query
	)

Definition at line 508 of file connection.c.

References ERROR, pgfdw_get_result(), pgfdw_report_error(), and PQsendQuery().

Referenced by close_cursor(), fetch_more_data(), finish_foreign_modify(), get_remote_estimate(), postgresAcquireSampleRowsFunc(), postgresAnalyzeForeignTable(), postgresImportForeignSchema(), and postgresReScanForeignScan().

{
    /*
     * 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);
}

pgfdw_get_cleanup_result()

static bool pgfdw_get_cleanup_result ( PGconn *  conn, TimestampTz  endtime, PGresult **  result  )

static

Definition at line 1123 of file connection.c.

References CHECK_FOR_INTERRUPTS, GetCurrentTimestamp(), Min, MyLatch, now(), PG_CATCH, PG_END_TRY, PG_RE_THROW, PG_TRY, PG_WAIT_EXTENSION, PQclear(), PQconsumeInput(), PQgetResult(), PQisBusy(), PQsocket(), ResetLatch(), TimestampDifference(), USECS_PER_SEC, WaitLatchOrSocket(), WL_EXIT_ON_PM_DEATH, WL_LATCH_SET, WL_SOCKET_READABLE, and WL_TIMEOUT.

Referenced by pgfdw_cancel_query(), and pgfdw_exec_cleanup_query().

{
    volatile bool timed_out = false;
    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;
                TimestampTz now = GetCurrentTimestamp();
                long        secs;
                int         microsecs;
                long        cur_timeout;

                /* If timeout has expired, give up, else get sleep time. */
                if (now >= endtime)
                {
                    timed_out = true;
                    goto exit;
                }
                TimestampDifference(now, endtime, &secs, &microsecs);

                /* To protect against clock skew, limit sleep to one minute. */
                cur_timeout = Min(60000, secs * USECS_PER_SEC + microsecs);

                /* 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; treat the same as a timeout */
                        timed_out = 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 (timed_out)
        PQclear(last_res);
    else
        *result = last_res;
    return timed_out;
}

pgfdw_get_result()

PGresult* pgfdw_get_result	(	PGconn *	conn,
		const char *	query
	)

Definition at line 532 of file connection.c.

References CHECK_FOR_INTERRUPTS, ERROR, MyLatch, PG_CATCH, PG_END_TRY, PG_RE_THROW, PG_TRY, PG_WAIT_EXTENSION, pgfdw_report_error(), PQclear(), PQconsumeInput(), PQgetResult(), PQisBusy(), PQsocket(), ResetLatch(), WaitLatchOrSocket(), WL_EXIT_ON_PM_DEATH, WL_LATCH_SET, and WL_SOCKET_READABLE.

Referenced by create_cursor(), do_sql_command(), execute_dml_stmt(), execute_foreign_modify(), pgfdw_exec_query(), and prepare_foreign_modify().

{
    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;
}

pgfdw_inval_callback()

static void pgfdw_inval_callback ( Datum  arg, int  cacheid, uint32  hashvalue  )

static

Definition at line 952 of file connection.c.

References Assert, ConnCacheEntry::conn, FOREIGNSERVEROID, hash_seq_init(), hash_seq_search(), ConnCacheEntry::invalidated, ConnCacheEntry::mapping_hashvalue, ConnCacheEntry::server_hashvalue, and USERMAPPINGOID.

Referenced by GetConnection().

{
    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))
            entry->invalidated = true;
    }
}

pgfdw_reject_incomplete_xact_state_change()

static void pgfdw_reject_incomplete_xact_state_change ( ConnCacheEntry *  entry )

static

Definition at line 988 of file connection.c.

References ConnCacheEntry::changing_xact_state, ConnCacheEntry::conn, disconnect_pg_server(), elog, ereport, errcode(), errmsg(), ERROR, GetForeignServer(), GETSTRUCT, HeapTupleIsValid, ConnCacheEntry::key, ObjectIdGetDatum, ReleaseSysCache(), SearchSysCache1(), ForeignServer::servername, and USERMAPPINGOID.

Referenced by GetConnection(), pgfdw_subxact_callback(), and pgfdw_xact_callback().

{
    HeapTuple   tup;
    Form_pg_user_mapping umform;
    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 */
    tup = SearchSysCache1(USERMAPPINGOID,
                          ObjectIdGetDatum(entry->key));
    if (!HeapTupleIsValid(tup))
        elog(ERROR, "cache lookup failed for user mapping %u", entry->key);
    umform = (Form_pg_user_mapping) GETSTRUCT(tup);
    server = GetForeignServer(umform->umserver);
    ReleaseSysCache(tup);

    ereport(ERROR,
            (errcode(ERRCODE_CONNECTION_EXCEPTION),
             errmsg("connection to server \"%s\" was lost",
                    server->servername)));
}

pgfdw_report_error()

void pgfdw_report_error	(	int	elevel,
		PGresult *	res,
		PGconn *	conn,
		bool	clear,
		const char *	sql
	)

Definition at line 597 of file connection.c.

References ereport, errcode(), errcontext, errdetail_internal(), errhint(), errmsg(), errmsg_internal(), MAKE_SQLSTATE, pchomp(), PG_CATCH, PG_DIAG_CONTEXT, PG_DIAG_MESSAGE_DETAIL, PG_DIAG_MESSAGE_HINT, PG_DIAG_MESSAGE_PRIMARY, PG_DIAG_SQLSTATE, PG_END_TRY, PG_RE_THROW, PG_TRY, PQclear(), PQerrorMessage(), and PQresultErrorField().

Referenced by close_cursor(), create_cursor(), do_sql_command(), execute_dml_stmt(), execute_foreign_modify(), fetch_more_data(), finish_foreign_modify(), get_remote_estimate(), pgfdw_exec_cleanup_query(), pgfdw_exec_query(), pgfdw_get_result(), postgresAcquireSampleRowsFunc(), postgresAnalyzeForeignTable(), postgresImportForeignSchema(), postgresReScanForeignScan(), and prepare_foreign_modify().

{
    /* 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 ? 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_CATCH();
    {
        if (clear)
            PQclear(res);
        PG_RE_THROW();
    }
    PG_END_TRY();
    if (clear)
        PQclear(res);
}

pgfdw_subxact_callback()

static void pgfdw_subxact_callback ( SubXactEvent  event, SubTransactionId  mySubid, SubTransactionId  parentSubid, void *  arg  )

static

Definition at line 838 of file connection.c.

References ConnCacheEntry::changing_xact_state, ConnCacheEntry::conn, do_sql_command(), elog, ERROR, GetCurrentTransactionNestLevel(), hash_seq_init(), hash_seq_search(), ConnCacheEntry::have_error, in_error_recursion_trouble(), pgfdw_cancel_query(), pgfdw_exec_cleanup_query(), pgfdw_reject_incomplete_xact_state_change(), PQTRANS_ACTIVE, PQtransactionStatus(), snprintf, SUBXACT_EVENT_ABORT_SUB, SUBXACT_EVENT_PRE_COMMIT_SUB, ConnCacheEntry::xact_depth, and xact_got_connection.

Referenced by GetConnection().

{
    HASH_SEQ_STATUS scan;
    ConnCacheEntry *entry;
    int         curlevel;

    /* 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;
            do_sql_command(entry->conn, sql);
            entry->changing_xact_state = false;
        }
        else if (in_error_recursion_trouble())
        {
            /*
             * Don't try to clean up the connection if we're already in error
             * recursion trouble.
             */
            entry->changing_xact_state = true;
        }
        else if (!entry->changing_xact_state)
        {
            bool        abort_cleanup_failure = false;

            /* Remember that abort cleanup is in progress. */
            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))
                abort_cleanup_failure = true;
            else
            {
                /* Rollback all remote subtransactions during abort */
                snprintf(sql, sizeof(sql),
                         "ROLLBACK TO SAVEPOINT s%d; RELEASE SAVEPOINT s%d",
                         curlevel, curlevel);
                if (!pgfdw_exec_cleanup_query(entry->conn, sql, false))
                    abort_cleanup_failure = true;
            }

            /* Disarm changing_xact_state if it all worked. */
            entry->changing_xact_state = abort_cleanup_failure;
        }

        /* OK, we're outta that level of subtransaction */
        entry->xact_depth--;
    }
}

pgfdw_xact_callback()

static void pgfdw_xact_callback ( XactEvent  event, void *  arg  )

static

Definition at line 651 of file connection.c.

References ConnCacheEntry::changing_xact_state, ConnCacheEntry::conn, CONNECTION_OK, cursor_number, DEBUG3, disconnect_pg_server(), do_sql_command(), elog, ereport, errcode(), errmsg(), ERROR, hash_seq_init(), hash_seq_search(), ConnCacheEntry::have_error, ConnCacheEntry::have_prep_stmt, in_error_recursion_trouble(), pgfdw_cancel_query(), pgfdw_exec_cleanup_query(), pgfdw_reject_incomplete_xact_state_change(), PQclear(), PQexec(), PQstatus(), PQTRANS_ACTIVE, PQTRANS_IDLE, PQtransactionStatus(), ConnCacheEntry::xact_depth, XACT_EVENT_ABORT, XACT_EVENT_COMMIT, XACT_EVENT_PARALLEL_ABORT, XACT_EVENT_PARALLEL_COMMIT, XACT_EVENT_PARALLEL_PRE_COMMIT, XACT_EVENT_PRE_COMMIT, XACT_EVENT_PRE_PREPARE, XACT_EVENT_PREPARE, and xact_got_connection.

Referenced by GetConnection().

{
    HASH_SEQ_STATUS scan;
    ConnCacheEntry *entry;

    /* 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)
        {
            bool        abort_cleanup_failure = false;

            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;
                    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 remote transactions that modified anything,
                     * 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 modified remote 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:

                    /*
                     * 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)
                        break;

                    /*
                     * 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))
                    {
                        /* Unable to cancel running query. */
                        abort_cleanup_failure = true;
                    }
                    else if (!pgfdw_exec_cleanup_query(entry->conn,
                                                       "ABORT TRANSACTION",
                                                       false))
                    {
                        /* Unable to abort remote transaction. */
                        abort_cleanup_failure = true;
                    }
                    else if (entry->have_prep_stmt && entry->have_error &&
                             !pgfdw_exec_cleanup_query(entry->conn,
                                                       "DEALLOCATE ALL",
                                                       true))
                    {
                        /* Trouble clearing prepared statements. */
                        abort_cleanup_failure = true;
                    }
                    else
                    {
                        entry->have_prep_stmt = false;
                        entry->have_error = false;
                    }

                    /* Disarm changing_xact_state if it all worked. */
                    entry->changing_xact_state = abort_cleanup_failure;
                    break;
            }
        }

        /* Reset state to show we're out of a transaction */
        entry->xact_depth = 0;

        /*
         * If the connection isn't in a good idle state, 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)
        {
            elog(DEBUG3, "discarding connection %p", entry->conn);
            disconnect_pg_server(entry);
        }
    }

    /*
     * 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;
}

ReleaseConnection()

void ReleaseConnection

(

PGconn *

conn

)

Definition at line 460 of file connection.c.

Referenced by estimate_path_cost_size(), finish_foreign_modify(), postgresAcquireSampleRowsFunc(), postgresAnalyzeForeignTable(), postgresEndDirectModify(), postgresEndForeignScan(), and postgresImportForeignSchema().

{
    /*
     * 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.
     */
}

Variable Documentation

ConnectionHash

HTAB* ConnectionHash = NULL

static

Definition at line 66 of file connection.c.

cursor_number

unsigned int cursor_number = 0

static

Definition at line 69 of file connection.c.

Referenced by GetCursorNumber(), and pgfdw_xact_callback().

prep_stmt_number

unsigned int prep_stmt_number = 0

static

Definition at line 70 of file connection.c.

Referenced by GetPrepStmtNumber().

xact_got_connection

bool xact_got_connection = false

static

Definition at line 73 of file connection.c.

Referenced by GetConnection(), pgfdw_subxact_callback(), and pgfdw_xact_callback().