connection.c File Reference

#include "postgres.h"
#include "access/htup_details.h"
#include "access/xact.h"
#include "catalog/pg_user_mapping.h"
#include "commands/defrem.h"
#include "funcapi.h"
#include "mb/pg_wchar.h"
#include "miscadmin.h"
#include "pgstat.h"
#include "postgres_fdw.h"
#include "storage/fd.h"
#include "storage/latch.h"
#include "utils/builtins.h"
#include "utils/datetime.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

Macros
#define	POSTGRES_FDW_GET_CONNECTIONS_COLS   2

Typedefs
typedef Oid	ConnCacheKey
typedef struct ConnCacheEntry	ConnCacheEntry

Functions
	PG_FUNCTION_INFO_V1 (postgres_fdw_get_connections)
	PG_FUNCTION_INFO_V1 (postgres_fdw_disconnect)
	PG_FUNCTION_INFO_V1 (postgres_fdw_disconnect_all)
static void	make_new_connection (ConnCacheEntry *entry, UserMapping *user)
static PGconn *	connect_pg_server (ForeignServer *server, UserMapping *user)
static void	disconnect_pg_server (ConnCacheEntry *entry)
static void	check_conn_params (const char **keywords, const char **values, UserMapping *user)
static void	configure_remote_session (PGconn *conn)
static void	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)
static void	pgfdw_abort_cleanup (ConnCacheEntry *entry, const char *sql, bool toplevel)
static bool	UserMappingPasswordRequired (UserMapping *user)
static bool	disconnect_cached_connections (Oid serverid)
PGconn *	GetConnection (UserMapping *user, bool will_prep_stmt, PgFdwConnState **state)
void	do_sql_command (PGconn *conn, const char *sql)
void	ReleaseConnection (PGconn *conn)
unsigned int	GetCursorNumber (PGconn *conn)
unsigned int	GetPrepStmtNumber (PGconn *conn)
PGresult *	pgfdw_exec_query (PGconn *conn, const char *query, PgFdwConnState *state)
PGresult *	pgfdw_get_result (PGconn *conn, const char *query)
void	pgfdw_report_error (int elevel, PGresult *res, PGconn *conn, bool clear, const char *sql)
Datum	postgres_fdw_get_connections (PG_FUNCTION_ARGS)
Datum	postgres_fdw_disconnect (PG_FUNCTION_ARGS)
Datum	postgres_fdw_disconnect_all (PG_FUNCTION_ARGS)

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

Macro Definition Documentation

POSTGRES_FDW_GET_CONNECTIONS_COLS

#define POSTGRES_FDW_GET_CONNECTIONS_COLS   2

Referenced by postgres_fdw_get_connections().

Typedef Documentation

ConnCacheEntry

typedef struct ConnCacheEntry ConnCacheEntry

ConnCacheKey

typedef Oid ConnCacheKey

Definition at line 49 of file connection.c.

Function Documentation

begin_remote_xact()

static void begin_remote_xact ( ConnCacheEntry *  entry )

static

Definition at line 611 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 515 of file connection.c.

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

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;
    }

    /* ok if the superuser explicitly said so at user mapping creation time */
    if (!UserMappingPasswordRequired(user))
        return;

    ereport(ERROR,
            (errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
             errmsg("password is required"),
             errdetail("Non-superusers must provide a password in the user mapping.")));
}

configure_remote_session()

static void configure_remote_session ( PGconn *  conn )

static

Definition at line 552 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 340 of file connection.c.

References AcquireExternalFD(), 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, pgfdw_application_name, PQconnectdbParams(), PQconnectionUsedPassword(), PQerrorMessage(), PQfinish(), PQstatus(), ReleaseExternalFD(), ForeignServer::servername, superuser_arg(), UserMapping::userid, UserMappingPasswordRequired(), and values.

Referenced by make_new_connection().

{
    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 4 extra slots
         * for application_name, fallback_application_name, client_encoding,
         * end marker.
         */
        n = list_length(server->options) + list_length(user->options) + 4;
        keywords = (const char **) palloc(n * sizeof(char *));
        values = (const char **) palloc(n * sizeof(char *));

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

        /*
         * Use pgfdw_application_name as application_name if set.
         *
         * PQconnectdbParams() processes the parameter arrays from start to
         * end. If any key word is repeated, the last value is used. Therefore
         * note that pgfdw_application_name must be added to the arrays after
         * options of ForeignServer are, so that it can override
         * application_name set in ForeignServer.
         */
        if (pgfdw_application_name && *pgfdw_application_name != '\0')
        {
            keywords[n] = "application_name";
            values[n] = pgfdw_application_name;
            n++;
        }

        /* 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 the set of connection parameters */
        check_conn_params(keywords, values, user);

        /*
         * We must obey fd.c's limit on non-virtual file descriptors.  Assume
         * that a PGconn represents one long-lived FD.  (Doing this here also
         * ensures that VFDs are closed if needed to make room.)
         */
        if (!AcquireExternalFD())
        {
#ifndef WIN32                   /* can't write #if within ereport() macro */
            ereport(ERROR,
                    (errcode(ERRCODE_SQLCLIENT_UNABLE_TO_ESTABLISH_SQLCONNECTION),
                     errmsg("could not connect to server \"%s\"",
                            server->servername),
                     errdetail("There are too many open files on the local server."),
                     errhint("Raise the server's max_files_per_process and/or \"ulimit -n\" limits.")));
#else
            ereport(ERROR,
                    (errcode(ERRCODE_SQLCLIENT_UNABLE_TO_ESTABLISH_SQLCONNECTION),
                     errmsg("could not connect to server \"%s\"",
                            server->servername),
                     errdetail("There are too many open files on the local server."),
                     errhint("Raise the server's max_files_per_process setting.")));
#endif
        }

        /* OK to make connection */
        conn = PQconnectdbParams(keywords, values, false);

        if (!conn)
            ReleaseExternalFD();    /* because the PG_CATCH block won't */

        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 and
         * check_conn_params.
         */
        if (!superuser_arg(user->userid) && UserMappingPasswordRequired(user) &&
            !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 or password_required=false set in the user mapping attributes.")));

        /* 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);
            ReleaseExternalFD();
        }
        PG_RE_THROW();
    }
    PG_END_TRY();

    return conn;
}

disconnect_cached_connections()

static bool disconnect_cached_connections ( Oid  serverid )

static

Definition at line 1578 of file connection.c.

References Assert, ConnCacheEntry::conn, DEBUG3, disconnect_pg_server(), elog, ereport, errmsg(), FSV_MISSING_OK, GetForeignServerExtended(), hash_seq_init(), hash_seq_search(), ConnCacheEntry::invalidated, OidIsValid, ConnCacheEntry::serverid, ForeignServer::servername, WARNING, and ConnCacheEntry::xact_depth.

Referenced by postgres_fdw_disconnect(), and postgres_fdw_disconnect_all().

{
    HASH_SEQ_STATUS scan;
    ConnCacheEntry *entry;
    bool        all = !OidIsValid(serverid);
    bool        result = false;

    /*
     * Connection cache hashtable has not been initialized yet in this
     * session, so return false.
     */
    if (!ConnectionHash)
        return false;

    hash_seq_init(&scan, ConnectionHash);
    while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
    {
        /* Ignore cache entry if no open connection right now. */
        if (!entry->conn)
            continue;

        if (all || entry->serverid == serverid)
        {
            /*
             * Emit a warning because the connection to close is used in the
             * current transaction and cannot be disconnected right now.
             */
            if (entry->xact_depth > 0)
            {
                ForeignServer *server;

                server = GetForeignServerExtended(entry->serverid,
                                                  FSV_MISSING_OK);

                if (!server)
                {
                    /*
                     * If the foreign server was dropped while its connection
                     * was used in the current transaction, the connection
                     * must have been marked as invalid by
                     * pgfdw_inval_callback at the end of DROP SERVER command.
                     */
                    Assert(entry->invalidated);

                    ereport(WARNING,
                            (errmsg("cannot close dropped server connection because it is still in use")));
                }
                else
                    ereport(WARNING,
                            (errmsg("cannot close connection for server \"%s\" because it is still in use",
                                    server->servername)));
            }
            else
            {
                elog(DEBUG3, "discarding connection %p", entry->conn);
                disconnect_pg_server(entry);
                result = true;
            }
        }
    }

    return result;
}

disconnect_pg_server()

static void disconnect_pg_server ( ConnCacheEntry *  entry )

static

Definition at line 477 of file connection.c.

References ConnCacheEntry::conn, PQfinish(), and ReleaseExternalFD().

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

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

do_sql_command()

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

Definition at line 588 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(), pgfdw_xact_callback(), and postgresExecForeignTruncate().

{
    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,
		PgFdwConnState **	state
	)

Definition at line 127 of file connection.c.

References Assert, begin_remote_xact(), CacheRegisterSyscacheCallback(), ConnCacheEntry::conn, CONNECTION_BAD, CopyErrorData(), CurrentMemoryContext, DEBUG3, disconnect_pg_server(), elog, HASHCTL::entrysize, ereport, errdetail_internal(), errmsg_internal(), FlushErrorState(), FOREIGNSERVEROID, FreeErrorData(), HASH_BLOBS, hash_create(), HASH_ELEM, HASH_ENTER, hash_search(), ConnCacheEntry::have_prep_stmt, ConnCacheEntry::invalidated, ConnCacheEntry::key, HASHCTL::keysize, make_new_connection(), MemoryContextSwitchTo(), pchomp(), PgFdwConnState::pendingAreq, PG_CATCH, PG_END_TRY, PG_RE_THROW, PG_TRY, pgfdw_inval_callback(), pgfdw_reject_incomplete_xact_state_change(), pgfdw_subxact_callback(), pgfdw_xact_callback(), PQerrorMessage(), PQstatus(), process_pending_request(), RegisterSubXactCallback(), RegisterXactCallback(), ErrorData::sqlerrcode, ConnCacheEntry::state, UserMapping::umid, USERMAPPINGOID, ConnCacheEntry::xact_depth, and xact_got_connection.

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

{
    bool        found;
    bool        retry = false;
    ConnCacheEntry *entry;
    ConnCacheKey key;
    MemoryContext ccxt = CurrentMemoryContext;

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

        ctl.keysize = sizeof(ConnCacheKey);
        ctl.entrysize = sizeof(ConnCacheEntry);
        ConnectionHash = hash_create("postgres_fdw connections", 8,
                                     &ctl,
                                     HASH_ELEM | HASH_BLOBS);

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

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

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

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

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

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

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

    /*
     * We check the health of the cached connection here when using it.  In
     * cases where we're out of all transactions, if a broken connection is
     * detected, we try to reestablish a new connection later.
     */
    PG_TRY();
    {
        /* Process a pending asynchronous request if any. */
        if (entry->state.pendingAreq)
            process_pending_request(entry->state.pendingAreq);
        /* Start a new transaction or subtransaction if needed. */
        begin_remote_xact(entry);
    }
    PG_CATCH();
    {
        MemoryContext ecxt = MemoryContextSwitchTo(ccxt);
        ErrorData  *errdata = CopyErrorData();

        /*
         * Determine whether to try to reestablish the connection.
         *
         * After a broken connection is detected in libpq, any error other
         * than connection failure (e.g., out-of-memory) can be thrown
         * somewhere between return from libpq and the expected ereport() call
         * in pgfdw_report_error(). In this case, since PQstatus() indicates
         * CONNECTION_BAD, checking only PQstatus() causes the false detection
         * of connection failure. To avoid this, we also verify that the
         * error's sqlstate is ERRCODE_CONNECTION_FAILURE. Note that also
         * checking only the sqlstate can cause another false detection
         * because pgfdw_report_error() may report ERRCODE_CONNECTION_FAILURE
         * for any libpq-originated error condition.
         */
        if (errdata->sqlerrcode != ERRCODE_CONNECTION_FAILURE ||
            PQstatus(entry->conn) != CONNECTION_BAD ||
            entry->xact_depth > 0)
        {
            MemoryContextSwitchTo(ecxt);
            PG_RE_THROW();
        }

        /* Clean up the error state */
        FlushErrorState();
        FreeErrorData(errdata);
        errdata = NULL;

        retry = true;
    }
    PG_END_TRY();

    /*
     * If a broken connection is detected, disconnect it, reestablish a new
     * connection and retry a new remote transaction. If connection failure is
     * reported again, we give up getting a connection.
     */
    if (retry)
    {
        Assert(entry->xact_depth == 0);

        ereport(DEBUG3,
                (errmsg_internal("could not start remote transaction on connection %p",
                                 entry->conn)),
                errdetail_internal("%s", pchomp(PQerrorMessage(entry->conn))));

        elog(DEBUG3, "closing connection %p to reestablish a new one",
             entry->conn);
        disconnect_pg_server(entry);

        if (entry->conn == NULL)
            make_new_connection(entry, user);

        begin_remote_xact(entry);
    }

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

    /* If caller needs access to the per-connection state, return it. */
    if (state)
        *state = &entry->state;

    return entry->conn;
}

GetCursorNumber()

unsigned int GetCursorNumber

(

PGconn *

conn

)

Definition at line 675 of file connection.c.

References cursor_number.

Referenced by postgresAcquireSampleRowsFunc(), and postgresBeginForeignScan().

{
    return ++cursor_number;
}

GetPrepStmtNumber()

unsigned int GetPrepStmtNumber

(

PGconn *

conn

)

Definition at line 689 of file connection.c.

References prep_stmt_number.

Referenced by prepare_foreign_modify().

{
    return ++prep_stmt_number;
}

make_new_connection()

static void make_new_connection ( ConnCacheEntry *  entry, UserMapping *  user  )

static

Definition at line 287 of file connection.c.

References Assert, ConnCacheEntry::changing_xact_state, ConnCacheEntry::conn, connect_pg_server(), DEBUG3, defGetBoolean(), DefElem::defname, elog, FOREIGNSERVEROID, GetForeignServer(), GetSysCacheHashValue1, ConnCacheEntry::have_error, ConnCacheEntry::have_prep_stmt, ConnCacheEntry::invalidated, ConnCacheEntry::keep_connections, lfirst, ConnCacheEntry::mapping_hashvalue, ObjectIdGetDatum, ForeignServer::options, ConnCacheEntry::server_hashvalue, ForeignServer::serverid, UserMapping::serverid, ConnCacheEntry::serverid, ForeignServer::servername, ConnCacheEntry::state, UserMapping::umid, UserMapping::userid, USERMAPPINGOID, and ConnCacheEntry::xact_depth.

Referenced by GetConnection().

{
    ForeignServer *server = GetForeignServer(user->serverid);
    ListCell   *lc;

    Assert(entry->conn == NULL);

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

    /*
     * Determine whether to keep the connection that we're about to make here
     * open even after the transaction using it ends, so that the subsequent
     * transactions can re-use it.
     *
     * It's enough to determine this only when making new connection because
     * all the connections to the foreign server whose keep_connections option
     * is changed will be closed and re-made later.
     *
     * By default, all the connections to any foreign servers are kept open.
     */
    entry->keep_connections = true;
    foreach(lc, server->options)
    {
        DefElem    *def = (DefElem *) lfirst(lc);

        if (strcmp(def->defname, "keep_connections") == 0)
            entry->keep_connections = defGetBoolean(def);
    }

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

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

PG_FUNCTION_INFO_V1() [1/3]

PG_FUNCTION_INFO_V1

(

postgres_fdw_get_connections

)

PG_FUNCTION_INFO_V1() [2/3]

PG_FUNCTION_INFO_V1

(

postgres_fdw_disconnect

)

PG_FUNCTION_INFO_V1() [3/3]

PG_FUNCTION_INFO_V1

(

postgres_fdw_disconnect_all

)

pgfdw_abort_cleanup()

static void pgfdw_abort_cleanup ( ConnCacheEntry *  entry, const char *  sql, bool  toplevel  )

static

Definition at line 1334 of file connection.c.

References ConnCacheEntry::changing_xact_state, ConnCacheEntry::conn, ConnCacheEntry::have_error, ConnCacheEntry::have_prep_stmt, in_error_recursion_trouble(), pgfdw_cancel_query(), pgfdw_exec_cleanup_query(), PQTRANS_ACTIVE, PQtransactionStatus(), and ConnCacheEntry::state.

Referenced by pgfdw_subxact_callback(), and pgfdw_xact_callback().

{
    /*
     * Don't try to clean up the connection if we're already in error
     * recursion trouble.
     */
    if (in_error_recursion_trouble())
        entry->changing_xact_state = true;

    /*
     * If connection is already unsalvageable, don't touch it further.
     */
    if (entry->changing_xact_state)
        return;

    /*
     * Mark this connection as in the process of changing transaction state.
     */
    entry->changing_xact_state = true;

    /* Assume we might have lost track of prepared statements */
    entry->have_error = true;

    /*
     * If a command has been submitted to the remote server by using an
     * asynchronous execution function, the command might not have yet
     * completed.  Check to see if a command is still being processed by the
     * remote server, and if so, request cancellation of the command.
     */
    if (PQtransactionStatus(entry->conn) == PQTRANS_ACTIVE &&
        !pgfdw_cancel_query(entry->conn))
        return;                 /* Unable to cancel running query */

    if (!pgfdw_exec_cleanup_query(entry->conn, sql, false))
        return;                 /* Unable to abort remote transaction */

    if (toplevel)
    {
        if (entry->have_prep_stmt && entry->have_error &&
            !pgfdw_exec_cleanup_query(entry->conn,
                                      "DEALLOCATE ALL",
                                      true))
            return;             /* Trouble clearing prepared statements */

        entry->have_prep_stmt = false;
        entry->have_error = false;
        /* Also reset per-connection state */
        memset(&entry->state, 0, sizeof(entry->state));
    }

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

pgfdw_cancel_query()

static bool pgfdw_cancel_query ( PGconn *  conn )

static

Definition at line 1150 of file connection.c.

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

Referenced by pgfdw_abort_cleanup().

{
    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 1202 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_abort_cleanup().

{
    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,
		PgFdwConnState *	state
	)

Definition at line 702 of file connection.c.

References ERROR, PgFdwConnState::pendingAreq, pgfdw_get_result(), pgfdw_report_error(), PQsendQuery(), and process_pending_request().

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

{
    /* First, process a pending asynchronous request, if any. */
    if (state && state->pendingAreq)
        process_pending_request(state->pendingAreq);

    /*
     * Submit a query.  Since we don't use non-blocking mode, this also can
     * block.  But its risk is relatively small, so we ignore that for now.
     */
    if (!PQsendQuery(conn, query))
        pgfdw_report_error(ERROR, NULL, conn, false, query);

    /* Wait for the result. */
    return pgfdw_get_result(conn, query);
}

pgfdw_get_cleanup_result()

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

static

Definition at line 1251 of file connection.c.

References CHECK_FOR_INTERRUPTS, GetCurrentTimestamp(), MyLatch, now(), PG_CATCH, PG_END_TRY, PG_RE_THROW, PG_TRY, PG_WAIT_EXTENSION, PQclear(), PQconsumeInput(), PQgetResult(), PQisBusy(), PQsocket(), ResetLatch(), TimestampDifferenceMilliseconds(), 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        cur_timeout;

                /* If timeout has expired, give up, else get sleep time. */
                cur_timeout = TimestampDifferenceMilliseconds(now, endtime);
                if (cur_timeout <= 0)
                {
                    timed_out = true;
                    goto exit;
                }

                /* Sleep until there's something to do */
                wc = WaitLatchOrSocket(MyLatch,
                                       WL_LATCH_SET | WL_SOCKET_READABLE |
                                       WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
                                       PQsocket(conn),
                                       cur_timeout, PG_WAIT_EXTENSION);
                ResetLatch(MyLatch);

                CHECK_FOR_INTERRUPTS();

                /* Data available in socket? */
                if (wc & WL_SOCKET_READABLE)
                {
                    if (!PQconsumeInput(conn))
                    {
                        /* connection trouble; 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 730 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(), fetch_more_data(), 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 1065 of file connection.c.

References Assert, ConnCacheEntry::conn, DEBUG3, disconnect_pg_server(), elog, FOREIGNSERVEROID, hash_seq_init(), hash_seq_search(), ConnCacheEntry::invalidated, ConnCacheEntry::mapping_hashvalue, ConnCacheEntry::server_hashvalue, USERMAPPINGOID, and ConnCacheEntry::xact_depth.

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))
        {
            /*
             * Close the connection immediately if it's not used yet in this
             * transaction. Otherwise mark it as invalid so that
             * pgfdw_xact_callback() can close it at the end of this
             * transaction.
             */
            if (entry->xact_depth == 0)
            {
                elog(DEBUG3, "discarding connection %p", entry->conn);
                disconnect_pg_server(entry);
            }
            else
                entry->invalidated = true;
        }
    }
}

pgfdw_reject_incomplete_xact_state_change()

static void pgfdw_reject_incomplete_xact_state_change ( ConnCacheEntry *  entry )

static

Definition at line 1115 of file connection.c.

References ConnCacheEntry::changing_xact_state, ConnCacheEntry::conn, disconnect_pg_server(), ereport, errcode(), errmsg(), ERROR, GetForeignServer(), ConnCacheEntry::serverid, and ForeignServer::servername.

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

{
    ForeignServer *server;

    /* nothing to do for inactive entries and entries of sane state */
    if (entry->conn == NULL || !entry->changing_xact_state)
        return;

    /* make sure this entry is inactive */
    disconnect_pg_server(entry);

    /* find server name to be shown in the message below */
    server = GetForeignServer(entry->serverid);

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

pgfdw_report_error()

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

Definition at line 795 of file connection.c.

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

Referenced by close_cursor(), create_cursor(), deallocate_query(), do_sql_command(), execute_dml_stmt(), execute_foreign_modify(), fetch_more_data(), fetch_more_data_begin(), get_remote_estimate(), pgfdw_exec_cleanup_query(), pgfdw_exec_query(), pgfdw_get_result(), postgresAcquireSampleRowsFunc(), postgresAnalyzeForeignTable(), postgresForeignAsyncNotify(), 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_FINALLY();
    {
        if (clear)
            PQclear(res);
    }
    PG_END_TRY();
}

pgfdw_subxact_callback()

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

static

Definition at line 981 of file connection.c.

References ConnCacheEntry::changing_xact_state, ConnCacheEntry::conn, do_sql_command(), elog, ERROR, GetCurrentTransactionNestLevel(), hash_seq_init(), hash_seq_search(), pgfdw_abort_cleanup(), pgfdw_reject_incomplete_xact_state_change(), 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
        {
            /* Rollback all remote subtransactions during abort */
            snprintf(sql, sizeof(sql),
                     "ROLLBACK TO SAVEPOINT s%d; RELEASE SAVEPOINT s%d",
                     curlevel, curlevel);
            pgfdw_abort_cleanup(entry, sql, false);
        }

        /* 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 850 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, ConnCacheEntry::invalidated, ConnCacheEntry::keep_connections, pgfdw_abort_cleanup(), pgfdw_reject_incomplete_xact_state_change(), PQclear(), PQexec(), PQstatus(), 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)
        {
            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 any remote transactions, since it's not
                     * very reasonable to hold them open until the prepared
                     * transaction is committed.  For the moment, throw error
                     * unconditionally; later we might allow read-only cases.
                     * Note that the error will cause us to come right back
                     * here with event == XACT_EVENT_ABORT, so we'll clean up
                     * the connection state at that point.
                     */
                    ereport(ERROR,
                            (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                             errmsg("cannot PREPARE a transaction that has operated on postgres_fdw foreign tables")));
                    break;
                case XACT_EVENT_PARALLEL_COMMIT:
                case XACT_EVENT_COMMIT:
                case XACT_EVENT_PREPARE:
                    /* Pre-commit should have closed the open transaction */
                    elog(ERROR, "missed cleaning up connection during pre-commit");
                    break;
                case XACT_EVENT_PARALLEL_ABORT:
                case XACT_EVENT_ABORT:

                    pgfdw_abort_cleanup(entry, "ABORT TRANSACTION", true);
                    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, it is marked as
         * invalid or keep_connections option of its server is disabled, then
         * discard it to recover. Next GetConnection will open a new
         * connection.
         */
        if (PQstatus(entry->conn) != CONNECTION_OK ||
            PQtransactionStatus(entry->conn) != PQTRANS_IDLE ||
            entry->changing_xact_state ||
            entry->invalidated ||
            !entry->keep_connections)
        {
            elog(DEBUG3, "discarding connection %p", entry->conn);
            disconnect_pg_server(entry);
        }
    }

    /*
     * 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;
}

postgres_fdw_disconnect()

Datum postgres_fdw_disconnect

(

PG_FUNCTION_ARGS

)

Definition at line 1529 of file connection.c.

References disconnect_cached_connections(), GetForeignServerByName(), PG_GETARG_TEXT_PP, PG_RETURN_BOOL, ForeignServer::serverid, and text_to_cstring().

{
    ForeignServer *server;
    char       *servername;

    servername = text_to_cstring(PG_GETARG_TEXT_PP(0));
    server = GetForeignServerByName(servername, false);

    PG_RETURN_BOOL(disconnect_cached_connections(server->serverid));
}

postgres_fdw_disconnect_all()

Datum postgres_fdw_disconnect_all

(

PG_FUNCTION_ARGS

)

Definition at line 1550 of file connection.c.

References disconnect_cached_connections(), InvalidOid, and PG_RETURN_BOOL.

{
    PG_RETURN_BOOL(disconnect_cached_connections(InvalidOid));
}

postgres_fdw_get_connections()

Datum postgres_fdw_get_connections

(

PG_FUNCTION_ARGS

)

Definition at line 1402 of file connection.c.

References ReturnSetInfo::allowedModes, Assert, BoolGetDatum, CStringGetTextDatum, ReturnSetInfo::econtext, ExprContext::ecxt_per_query_memory, elog, ereport, errcode(), errmsg(), ERROR, FSV_MISSING_OK, get_call_result_type(), GetForeignServerExtended(), hash_seq_init(), hash_seq_search(), IsA, MemoryContextSwitchTo(), MemSet, PG_RETURN_VOID, POSTGRES_FDW_GET_CONNECTIONS_COLS, ReturnSetInfo::returnMode, ForeignServer::servername, ReturnSetInfo::setDesc, ReturnSetInfo::setResult, SFRM_Materialize, tuplestore_begin_heap(), tuplestore_donestoring, tuplestore_putvalues(), TYPEFUNC_COMPOSITE, values, and work_mem.

{
#define POSTGRES_FDW_GET_CONNECTIONS_COLS   2
    ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
    TupleDesc   tupdesc;
    Tuplestorestate *tupstore;
    MemoryContext per_query_ctx;
    MemoryContext oldcontext;
    HASH_SEQ_STATUS scan;
    ConnCacheEntry *entry;

    /* check to see if caller supports us returning a tuplestore */
    if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("set-valued function called in context that cannot accept a set")));
    if (!(rsinfo->allowedModes & SFRM_Materialize))
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("materialize mode required, but it is not allowed in this context")));

    /* Build a tuple descriptor for our result type */
    if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
        elog(ERROR, "return type must be a row type");

    /* Build tuplestore to hold the result rows */
    per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
    oldcontext = MemoryContextSwitchTo(per_query_ctx);

    tupstore = tuplestore_begin_heap(true, false, work_mem);
    rsinfo->returnMode = SFRM_Materialize;
    rsinfo->setResult = tupstore;
    rsinfo->setDesc = tupdesc;

    MemoryContextSwitchTo(oldcontext);

    /* If cache doesn't exist, we return no records */
    if (!ConnectionHash)
    {
        /* clean up and return the tuplestore */
        tuplestore_donestoring(tupstore);

        PG_RETURN_VOID();
    }

    hash_seq_init(&scan, ConnectionHash);
    while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
    {
        ForeignServer *server;
        Datum       values[POSTGRES_FDW_GET_CONNECTIONS_COLS];
        bool        nulls[POSTGRES_FDW_GET_CONNECTIONS_COLS];

        /* We only look for open remote connections */
        if (!entry->conn)
            continue;

        server = GetForeignServerExtended(entry->serverid, FSV_MISSING_OK);

        MemSet(values, 0, sizeof(values));
        MemSet(nulls, 0, sizeof(nulls));

        /*
         * The foreign server may have been dropped in current explicit
         * transaction. It is not possible to drop the server from another
         * session when the connection associated with it is in use in the
         * current transaction, if tried so, the drop query in another session
         * blocks until the current transaction finishes.
         *
         * Even though the server is dropped in the current transaction, the
         * cache can still have associated active connection entry, say we
         * call such connections dangling. Since we can not fetch the server
         * name from system catalogs for dangling connections, instead we show
         * NULL value for server name in output.
         *
         * We could have done better by storing the server name in the cache
         * entry instead of server oid so that it could be used in the output.
         * But the server name in each cache entry requires 64 bytes of
         * memory, which is huge, when there are many cached connections and
         * the use case i.e. dropping the foreign server within the explicit
         * current transaction seems rare. So, we chose to show NULL value for
         * server name in output.
         *
         * Such dangling connections get closed either in next use or at the
         * end of current explicit transaction in pgfdw_xact_callback.
         */
        if (!server)
        {
            /*
             * If the server has been dropped in the current explicit
             * transaction, then this entry would have been invalidated in
             * pgfdw_inval_callback at the end of drop server command. Note
             * that this connection would not have been closed in
             * pgfdw_inval_callback because it is still being used in the
             * current explicit transaction. So, assert that here.
             */
            Assert(entry->conn && entry->xact_depth > 0 && entry->invalidated);

            /* Show null, if no server name was found */
            nulls[0] = true;
        }
        else
            values[0] = CStringGetTextDatum(server->servername);

        values[1] = BoolGetDatum(!entry->invalidated);

        tuplestore_putvalues(tupstore, tupdesc, values, nulls);
    }

    /* clean up and return the tuplestore */
    tuplestore_donestoring(tupstore);

    PG_RETURN_VOID();
}

ReleaseConnection()

void ReleaseConnection

(

PGconn *

conn

)

Definition at line 654 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.
     */
}

UserMappingPasswordRequired()

static bool UserMappingPasswordRequired ( UserMapping *  user )

static

Definition at line 492 of file connection.c.

References defGetBoolean(), DefElem::defname, lfirst, and UserMapping::options.

Referenced by check_conn_params(), and connect_pg_server().

{
    ListCell   *cell;

    foreach(cell, user->options)
    {
        DefElem    *def = (DefElem *) lfirst(cell);

        if (strcmp(def->defname, "password_required") == 0)
            return defGetBoolean(def);
    }

    return true;
}

Variable Documentation

ConnectionHash

HTAB* ConnectionHash = NULL

static

Definition at line 73 of file connection.c.

cursor_number

unsigned int cursor_number = 0

static

Definition at line 76 of file connection.c.

Referenced by GetCursorNumber(), and pgfdw_xact_callback().

prep_stmt_number

unsigned int prep_stmt_number = 0

static

Definition at line 77 of file connection.c.

Referenced by GetPrepStmtNumber().

xact_got_connection

bool xact_got_connection = false

static

Definition at line 80 of file connection.c.

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