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
It is particularly important that this function, rather than
free(), be 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
Frees the data structures allocated by
void PQconninfoFree(PQconninfoOption *connOptions);
PQfreemem will not do for this, since
the array contains references to subsidiary strings.
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 escaping. Use
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
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 for
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.