As always, there are some functions that just don't fit anywhere.
Frees memory allocated by libpq.
void PQfreemem(void *ptr);
Frees memory allocated by libpq, particularly
PQnotifies. It is particularly important that
this function, rather than
used on Microsoft Windows. This is because allocating memory in a
DLL and releasing it in the application works only if
multithreaded/single-threaded, release/debug, and static/dynamic
flags are the same for the DLL and the application. On
non-Microsoft Windows platforms, this function is the same as the
standard library function
Frees the data structures allocated by
void PQconninfoFree(PQconninfoOption *connOptions);
PQfreemem will not do for
this, since the array contains references to subsidiary
Prepares the encrypted form of a PostgreSQL password.
char * PQencryptPassword(const char *passwd, const char *user);
This function is intended to be used by client applications that
wish to send commands like ALTER USER joe
PASSWORD 'pwd'. It is good practice not to send the original
cleartext password in such a command, because it might be exposed
in command logs, activity displays, and so on. Instead, use this
function to convert the password to encrypted form before it is
sent. The arguments are the cleartext password, and the SQL name of
the user it is for. The return value is a string allocated by
malloc, or NULL if out of memory. The caller can assume the
string doesn't contain any special characters that would require
PQfreemem to free the
result when done with it.
Constructs an empty PGresult object with the given status.
PGresult *PQmakeEmptyPGresult(PGconn *conn, ExecStatusType status);
This is libpq's internal
function to allocate and initialize an empty PGresult object. This function returns NULL if memory could not be allocated. It is exported
because some applications find it useful to generate result objects
(particularly objects with error status) themselves. If conn is not null and status indicates an error, the current error
message of the specified connection is copied into the PGresult. Also, if conn is not null, any event procedures registered
in the connection are copied into the PGresult. (They do not get PGEVT_RESULTCREATE calls, but see
PQfireResultCreateEvents.) Note that
PQclear should eventually be called on the
object, just as with a PGresult
returned by libpq itself.
Fires a PGEVT_RESULTCREATE event (see Section 31.13) for each event procedure registered in the PGresult object. Returns non-zero for success, zero if any event procedure fails.
int PQfireResultCreateEvents(PGconn *conn, PGresult *res);
The conn argument is passed through to event procedures but not used directly. It can be NULL if the event procedures won't use it.
Event procedures that have already received a PGEVT_RESULTCREATE or PGEVT_RESULTCOPY event for this object are not fired again.
The main reason that this function is separate from
PQmakeEmptyPGresult is that it is often
appropriate to create a PGresult and
fill it with data before invoking the event procedures.
Makes a copy of a PGresult object.
The copy is not linked to the source result in any way and
PQclear must be called when the copy
is no longer needed. If the function fails, NULL is returned.
PGresult *PQcopyResult(const PGresult *src, int flags);
This is not intended to make an exact copy. The returned result is always put into PGRES_TUPLES_OK status, and does not copy any error message in the source. (It does copy the command status string, however.) The flags argument determines what else is copied. It is a bitwise OR of several flags. PG_COPYRES_ATTRS specifies copying the source result's attributes (column definitions). PG_COPYRES_TUPLES specifies copying the source result's tuples. (This implies copying the attributes, too.) PG_COPYRES_NOTICEHOOKS specifies copying the source result's notify hooks. PG_COPYRES_EVENTS specifies copying the source result's events. (But any instance data associated with the source is not copied.)
Sets the attributes of a PGresult object.
int PQsetResultAttrs(PGresult *res, int numAttributes, PGresAttDesc *attDescs);
The provided attDescs are copied into the result. If the attDescs pointer is NULL or numAttributes is less than one, the request is ignored and the function succeeds. If res already contains attributes, the function will fail. If the function fails, the return value is zero. If the function succeeds, the return value is non-zero.
Sets a tuple field value of a PGresult object.
int PQsetvalue(PGresult *res, int tup_num, int field_num, char *value, int len);
The function will automatically grow the result's internal
tuples array as needed. However, the tup_num argument must be less than or equal to
PQntuples, meaning this function can
only grow the tuples array one tuple at a time. But any field of
any existing tuple can be modified in any order. If a value at
field_num already exists, it will be
overwritten. If len is -1 or value is NULL, the field
value will be set to an SQL null value. The value is copied into the result's private storage,
thus is no longer needed after the function returns. If the
function fails, the return value is zero. If the function succeeds,
the return value is non-zero.
Allocate subsidiary storage for a PGresult object.
void *PQresultAlloc(PGresult *res, size_t nBytes);
Any memory allocated with this function will be freed when
res is cleared. If the function fails,
the return value is NULL. The result is
guaranteed to be adequately aligned for any type of data, just as
Return the version of libpq that is being used.
The result of this function can be used to determine, at run
time, if specific functionality is available in the currently
loaded version of libpq. The function can be used, for example, to
determine which connection options are available for
PQconnectdb or if the hex bytea output added in
PostgreSQL 9.0 is supported.
The number is formed by converting the major, minor, and revision numbers into two-decimal-digit numbers and appending them together. For example, version 9.1 will be returned as 90100, and version 9.1.2 will be returned as 90102 (leading zeroes are not shown).
Note: This function appeared in PostgreSQL version 9.1, so it cannot be used to detect required functionality in earlier versions, since linking to it will create a link dependency on version 9.1.
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