c-treeDB API API for C

ctdbMergeSessionDictionary

Compare and merge c-treeDB API session dictionaries.

Declaration

ctdbEXPORT CTDBRET ctdbDECL ctdbMergeSessionDictionary (CTHANDLE src, CTHANDLE dst, mergeFunPtr mrgfun, logFunPtr logfun);

Description

Parameters

src: handle of an exclusively open session where the session dictionary is the dictionary containing the entry to be merged.
dst: handle of an exclusively open session where the session dictionary is the target dictionary for the merge.
mrgfun: function that the c-treeDB API engine calls to perform the comparison and set the actions on the compared items.
The function prototype is:

CTDBRET (ctdbDECL *mergeFunPtr) (pCTDBLIST src_list, pCTDBLIST dst_list);

mrgfun must return either an error code (in which case the ctdbMergeSessionDictionary () function will fail with that error code) or CTDBRET_OK if no error occurred.

The c-treeDB API engine will pass two lists (CTDBLIST) containing items of type MERGEINFO. One per each dictionary entry.

The MERGEINFO structure is defined as follows:

struct tagMERGEINFO

{

DICTDATA info;

NINT todo;

};

info contains the dictionary record.
todo must be set to the action to perform on that entry.
src_list contains the elements from the source dictionary
dst_list contains the elements from the target dictionary.

The function must set for each entry the action to be performed on that entry as follows:

Source List Actions	Description
DIFF_SRC_IGNORE	Ignore the record in the source list and do not copy it on the target dictionary
DIFF_SRC_COPY2DST	Copy the record to the target dictionary for entries on the dst_list.
Destination List Actions	Description
DIFF_DST_KEEP	Keep the entry as it is.
DIFF_DST_REMOVE	Remove the entry.
DIFF_DST_REWRITE	Replace the dest record on disk with the one in the list (in case we merge only some information). Note: This cannot change the UID.

For example, to replace an entry on the target dictionary with one from the source dictionary, the todo of the item in dsl_list must be set to DIFF_DST_REMOVE, the todo of the item in src_list to DIFF_SRC_COPY2DST.

logfun: the function called to return additional information about errors.
The function prototype is:

VOID (ctdbDECL*logFunPtr) (NINT lvl, pTEXT mesg, CTDBRET error, pTEXT extra);

lvl: number indication the error message level. (1 indicating fewer and higher level messages to 3 indicating more numerous detailed messages.)
mesg: the error message
error: the error code
extra: extra information such as the table or database name.

Note: Depending on where an error occurred, this function could be called multiple times with different lvl and mesg.

Return Values

See c-tree Plus Error Codes for a complete listing of valid c-tree Plus error values.

Example

Please review the source code for ctsqlmdd.c, FairCom DB SQL Database Move Utility, for a complete implementation using this c-treeDB API function.