JetGetSecondaryIndexBookmark Function

Applies to: Windows | Windows Server

JetGetSecondaryIndexBookmark Function

The JetGetSecondaryIndexBookmark function retrieves a special bookmark for the secondary index entry at the current position of a cursor. This bookmark can then be used to efficiently reposition that cursor back to the same index entry using JetGotoSecondaryIndexBookmark. This is most useful when repositioning on a secondary index that contains duplicate keys or that contains multiple index entries for the same record.

Windows XP:  JetGetSecondaryIndexBookmark is introduced in Windows XP.

    JET_ERR JET_API JetGetSecondaryIndexBookmark(
      __in          JET_SESID sesid,
      __in          JET_TABLEID tableid,
      __out_opt     void* pvSecondaryKey,
      __in          unsigned long cbSecondaryKeyMax,
      __out_opt     unsigned long* pcbSecondaryKeyActual,
      __out_opt      void* pvPrimaryBookmark,
      __in          unsigned long cbPrimaryBookmarkMax,
      __out_opt     unsigned long* pcbPrimaryKeyActual,
      __in          const JET_GRBIT grbit
    );

Parameters

sesid

The session to use for this call.

tableid

The cursor to use for this call.

pvSecondaryKey

The output buffer that receives the secondary key.

cbSecondaryKeyMax

The maximum size, in bytes, of the output buffer for the secondary key.

pcbSecondaryKeyActual

Receives the actual size in bytes of the secondary key.

If this parameter is NULL, the actual size of the secondary key will not be returned.

If the output buffer is too small, the actual size of the secondary key will still be returned. That means that this number will be larger than the size of the output buffer.

pvPrimaryBookmark

The output buffer that receives the primary key bookmark.

cbPrimaryBookmarkMax

The maximum size, in bytes, of the output buffer for the primary key bookmark.

pcbPrimaryKeyActual

Receives the actual size, in bytes, of the primary key bookmark.

If this parameter is NULL then the actual size of the primary key bookmark will not be returned.

If the output buffer is too small, the actual size of the primary key bookmark will still be returned. That means that this number will be larger than the size of the output buffer.

grbit

Reserved for future use.

Return Value

This function returns the JET_ERR datatype with one of the following return codes. For more information about the possible ESE errors, see Extensible Storage Engine Errors and Error Handling Parameters.

On success, the secondary index bookmark for the index entry at the current position of a cursor will be returned in the output buffers. No change to the database state will occur.

On failure, the state of the output buffers and the actual size of the secondary index bookmark will be undefined unless JET_errBufferTooSmall was returned. In the event that JET_errBufferTooSmall is returned, the output buffers will contain as much of the secondary index bookmark as will fit in the space provided and the actual size of the secondary index bookmark will be accurate. In any case, no change to the database state will occur.

Remarks

Bookmarks should generally be treated as opaque chunks of data. No attempt should be made to exploit the internal structure of this data. However, the following properties can be known about all ESENT bookmarks:

• A bookmark uniquely identifies a record in a given table.

• The bookmark of a record will not change for the lifetime of that record.

• The bookmark of a record is the same as the key of that record on the primary index over the table containing that record. If no primary index is defined over that table, the database engine will create its own bookmark for the record.

• Bookmarks may be compared against each other using memcmp to establish their relative ordering in the primary index over the table of the source records. If no primary index is defined over that table, the relative ordering of bookmarks from that table is not meaningful.

• It is meaningless to compare bookmarks of records from different tables against each other.

• A bookmark is always less than or equal to JET_cbBookmarkMost (256) bytes in length prior to Windows Vista. On Windows Vista and later releases, bookmarks can be larger. The maximum size of a bookmark is equal to the current value of JET_paramKeyMost + 1.

Keys should generally be treated as opaque chunks of data. No attempt should be made to exploit the internal structure of this data. However, the following properties can be known about all ESENT keys:

• Keys may be compared against each other using memcmp to establish their relative ordering in the originating index over the table of the source index entries.

• It is meaningless to compare keys of index entries from different indexes against each other.

• A key is always less than or equal to JET_cbKeyMost (255) bytes in length prior to Windows Vista. On Windows Vista and later releases, keys can be larger. The maximum size of a key is equal to the current value of JET_paramKeyMost.

Requirements

See Also

JET_ERR
JET_GRBIT
JET_SESID
JET_TABLEID
JetGetBookmark
JetGotoSecondaryIndexBookmark
JetRetrieveKey
memcmp