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68 lines
1.8 KiB
Text
68 lines
1.8 KiB
Text
/*
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* PREF_FUNC_recover --
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* Recovery function for FUNC.
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*
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* PUBLIC: int PREF_FUNC_recover
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* PUBLIC: __P((dbenv *, DBT *, DB_LSN *, db_recops));
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*/
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int
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PREF_FUNC_recover(dbenv, dbtp, lsnp, op)
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dbenv *dbenv;
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DBT *dbtp;
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DB_LSN *lsnp;
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db_recops op;
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{
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PREF_DUP_args *argp;
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int cmp_n, cmp_p, modified, ret;
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#ifdef DEBUG_RECOVER
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(void)PREF_DUP_print(dbenv, dbtp, lsnp, op);
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#endif
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argp = NULL;
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if ((ret = PREF_DUP_read(dbenv, dbtp->data, &argp)) != 0)
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goto out;
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modified = 0;
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cmp_n = 0;
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cmp_p = 0;
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/*
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* The function now needs to calculate cmp_n and cmp_p based
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* on whatever is in argp (usually an LSN representing the state
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* of an object BEFORE the operation described in this record was
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* applied) and whatever other information the function needs,
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* e.g., the LSN of the object as it exists now.
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*
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* cmp_p should be set to 0 if the current state of the object
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* is believed to be same as the state of the object BEFORE the
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* described operation was applied. For example, if you had an
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* LSN in the log record (argp->prevlsn) and a current LSN of the
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* object (curlsn), you might want to do:
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*
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* cmp_p = log_compare(curlsn, argp->prevlsn);
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*
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* Similarly, cmp_n should be set to 0 if the current state
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* of the object reflects the object AFTER this operation has
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* been applied. Thus, if you can figure out an object's current
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* LSN, yo might set cmp_n as:
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*
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* cmp_n = log_compare(lsnp, curlsn);
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*/
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if (cmp_p == 0 && DB_REDO(op)) {
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/* Need to redo update described. */
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modified = 1;
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} else if (cmp_n == 0 && !DB_REDO(op)) {
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/* Need to undo update described. */
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modified = 1;
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}
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/* Allow for following LSN pointers through a transaction. */
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*lsnp = argp->prev_lsn;
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ret = 0;
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out: if (argp != NULL)
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free(argp);
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return (ret);
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}
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