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Detailed Description

Retrieve a document from the cluster.

Functions
lcb_error_t	lcb_get3 (lcb_t instance, const void *cookie, const lcb_CMDGET *cmd)
	Spool a single get operation. More...

Macros
#define	LCB_CMDGET_F_CLEAREXP
	If this bit is set in lcb_CMDGET::cmdflags then the expiry time is cleared if lcb_CMDGET::exptime is 0. More...

Function Documentation

lcb_error_t lcb_get3	(	lcb_t	instance,
		const void *	cookie,
		const lcb_CMDGET *	cmd
	)

Spool a single get operation.

Stability

Committed:

Parameters

instance	the handle
cookie	a pointer to be associated with the command
cmd	the command structure

Returns

LCB_SUCCESS if successful, an error code otherwise

Request

lcb_CMDGET cmd = { 0 };
LCB_CMD_SET_KEY(&cmd, "Hello", 5);
lcb_get3(instance, cookie, &cmd);

Response

lcb_install_callback3(instance, LCB_CALLBACK_GET, get_callback);
static void get_callback(lcb_t instance, int cbtype, const lcb_RESPBASE *rb) {
    const lcb_RESPGET *resp = (const lcb_RESPGET*)rb;
    printf("Got response for key: %.*s\n", (int)resp->key, resp->nkey);

    if (resp->rc != LCB_SUCCESS) {
        printf("Couldn't get item: %s\n", lcb_strerror(NULL, resp->rc));
    } else {
        printf("Got value: %.*s\n", (int)resp->nvalue, resp->value);
        printf("Got CAS: 0x%llx\n", resp->cas);
        printf("Got item/formatting flags: 0x%x\n", resp->itmflags);
    }
}

Errors

• LCB_KEY_ENOENT if the item does not exist in the cluster
• LCB_ETMPFAIL if the lcb_CMDGET::lock option was set but the item was already locked. Note that this error may also be returned (as a generic error) if there is a resource constraint within the server itself.

Examples:

example/libeventdirect/main.c, and example/minimal/minimal.c.

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Data Structure Documentation

struct lcb_CMDGET

Command for retrieving a single item.

See also

lcb_get3()

lcb_RESPGET

Note

The cas member should be set to 0 for this operation. If the cas is not 0, lcb_get3() will fail with LCB_OPTIONS_CONFLICT.

Use of the exptime field

• Get And Touch:

  It is possible to retrieve an item and concurrently modify its expiration time (thus keeping it "alive"). The item's expiry time can be set using the exptime field.

• Lock If the lock field is set to non-zero, the exptime field indicates the amount of time the lock should be held for

Examples:

example/libeventdirect/main.c, and example/minimal/minimal.c.

Data Fields
lcb_U32	cmdflags	Common flags for the command. These modify the command itself. Currently the lower 16 bits of this field are reserved, and the higher 16 bits are used for individual commands.
lcb_U32	exptime	Specify the expiration time. This is either an absolute Unix time stamp or a relative offset from now, in seconds. If the value of this number is greater than the value of thirty days in seconds, then it is a Unix timestamp. This field is used in mutation operations (lcb_store3()) to indicate the lifetime of the item. It is used in lcb_get3() with the lcb_CMDGET::lock option to indicate the lock expiration itself.
lcb_U64	cas	The known CAS of the item. This is passed to mutation to commands to ensure the item is only changed if the server-side CAS value matches the one specified here. For other operations (such as lcb_CMDENDURE) this is used to ensure that the item has been persisted/replicated to a number of servers with the value specified here.
lcb_KEYBUF	key	The key for the document itself. This should be set via LCB_CMD_SET_KEY()
lcb_KEYBUF	_hashkey	Stability Volatile:
int	lock	If set to true, the exptime field inside options will take to mean the time the lock should be held. While the lock is held, other operations trying to access the key will fail with an LCB_ETMPFAIL error. The item may be unlocked either via lcb_unlock3() or via a mutation operation with a supplied CAS

struct lcb_RESPGET

Response structure when retrieving a single item.

Examples:

example/libeventdirect/main.c, and example/minimal/minimal.c.

Data Fields
void *	cookie
	Application-defined pointer passed as the cookie parameter when scheduling the command. More...
const void *	key
	Key for request.
lcb_SIZE	nkey
	Size of key.
lcb_CAS	cas
	CAS for response (if applicable)
lcb_error_t	rc
	Status code.
lcb_U16	version
	ABI version for response.
lcb_U16	rflags
	Response specific flags. More...
const void *	value
	Value buffer for the item.
lcb_SIZE	nvalue
	Length of value.
void *	bufh
lcb_U32	itmflags
	User-defined flags for the item.

Field Documentation

void* cookie

Application-defined pointer passed as the cookie parameter when scheduling the command.

lcb_U16 rflags

Response specific flags.

see lcb_RESPFLAGS

Macro Definition Documentation

#define LCB_CMDGET_F_CLEAREXP

If this bit is set in lcb_CMDGET::cmdflags then the expiry time is cleared if lcb_CMDGET::exptime is 0.

This allows get-and-touch with an expiry of 0.