<para>

When the <structfield>ampredlocks</> flag is not set, any scan using that

index access method within a serializable transaction will acquire a

non-blocking predicate lock on the full index. This will generate a

nonblocking predicate lock on the full index. This will generate a

read-write conflict with the insert of any tuple into that index by a

concurrent serializable transaction. If certain patterns of read-write

conflicts are detected among a set of concurrent serializable

<para>

As mentioned in <xref linkend="xact-serializable">, Serializable

transactions are just Repeatable Read transactions which add

non-blocking monitoring for dangerous patterns of read/write conflicts.

nonblocking monitoring for dangerous patterns of read/write conflicts.

When a pattern is detected which could cause a cycle in the apparent

order of execution, one of the transactions involved is rolled back to

break the cycle.

{

if (!pg_set_noblock(MyProcPort->sock))

ereport(COMMERROR,

(errmsg("could not set socket tonon-blocking mode: %m")));

(errmsg("could not set socket tononblocking mode: %m")));

}

{

if (fcntl(postmaster_alive_fds[POSTMASTER_FD_WATCH],F_SETFL,O_NONBLOCK))

ereport(FATAL,

(errcode_for_socket_access(),

errmsg_internal("could not set postmaster death monitoring pipe tonon-blocking mode: %m")));

errmsg_internal("could not set postmaster death monitoring pipe tononblocking mode: %m")));

charsebuf[256];

printfPQExpBuffer(&conn->errorMessage,

libpq_gettext("could not restorenon-blocking mode on socket: %s\n"),

libpq_gettext("could not restorenonblocking mode on socket: %s\n"),

pqStrerror(errno,sebuf,sizeof(sebuf)));

ret=STATUS_ERROR;

}

if (!pg_set_noblock(conn->sock))

{

appendPQExpBuffer(&conn->errorMessage,

libpq_gettext("could not set socket tonon-blocking mode: %s\n"),

libpq_gettext("could not set socket tononblocking mode: %s\n"),

SOCK_STRERROR(SOCK_ERRNO,sebuf,sizeof(sebuf)));

pqDropConnection(conn);

conn->addr_cur=addr_cur->ai_next;