row0undo.h

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/** @file include/row0undo.h
 Row undo
 
 Created 1/8/1997 Heikki Tuuri
 *******************************************************/
 
#ifndef row0undo_h
#define row0undo_h
 
#include "btr0pcur.h"
#include "btr0types.h"
#include "dict0types.h"
#include "mtr0mtr.h"
#include "que0types.h"
#include "row0types.h"
#include "trx0sys.h"
#include "trx0types.h"
#include "univ.i"
 
/** Converts an implicit lock on the record to explicit in case of partial
 rollback.
@param[in]      cursor          cursor to record
@param[in]      node            undo node */
void row_convert_impl_to_expl_if_needed(btr_cur_t *cursor, undo_node_t *node);
 
/** Creates a row undo node to a query graph.
@param[in]      trx              transaction
@param[in]      parent           parent node, i.e., a thr node
@param[in]      heap             memory heap where created
@param[in]      partial_rollback true if partial rollback
@return         undo node */
undo_node_t *row_undo_node_create(trx_t *trx, que_thr_t *parent,
                                  mem_heap_t *heap, bool partial_rollback);
 
/** Looks for the clustered index record when node has the row reference.
 The pcur in node is used in the search. If found, stores the row to node,
 and stores the position of pcur, and detaches it. The pcur must be closed
 by the caller in any case.
 @return true if found; NOTE the node->pcur must be closed by the
 caller, regardless of the return value */
[[nodiscard]] bool row_undo_search_clust_to_pcur(
    undo_node_t *node); /*!< in/out: row undo node */
/** Undoes a row operation in a table. This is a high-level function used
 in SQL execution graphs.
 @return query thread to run next or NULL */
que_thr_t *row_undo_step(que_thr_t *thr); /*!< in: query thread */
 
/* A single query thread will try to perform the undo for all successive
versions of a clustered index record, if the transaction has modified it
several times during the execution which is rolled back. It may happen
that the task is transferred to another query thread, if the other thread
is assigned to handle an undo log record in the chain of different versions
of the record, and the other thread happens to get the x-latch to the
clustered index record at the right time.
        If a query thread notices that the clustered index record it is looking
for is missing, or the roll ptr field in the record does not point to the
undo log record the thread was assigned to handle, then it gives up the undo
task for that undo log record, and fetches the next. This situation can occur
just in the case where the transaction modified the same record several times
and another thread is currently doing the undo for successive versions of
that index record. */
 
/** Execution state of an undo node */
enum undo_exec {
  UNDO_NODE_FETCH_NEXT = 1, /*!< we should fetch the next
                            undo log record */
  UNDO_NODE_INSERT,         /*!< undo a fresh insert of a
                            row to a table */
  UNDO_NODE_MODIFY          /*!< undo a modify operation
                            (DELETE or UPDATE) on a row
                            of a table */
};
 
/** Undo node structure */
struct undo_node_t {
  que_common_t common;      /*!< node type: QUE_NODE_UNDO */
  enum undo_exec state;     /*!< node execution state */
  trx_t *trx;               /*!< trx for which undo is done */
  roll_ptr_t roll_ptr;      /*!< roll pointer to undo log record */
  trx_undo_rec_t *undo_rec; /*!< undo log record */
  undo_no_t undo_no;        /*!< undo number of the record */
  ulint rec_type;           /*!< undo log record type: TRX_UNDO_INSERT_REC,
                           ... */
  trx_id_t new_trx_id;      /*!< trx id to restore to clustered index
                        record */
  btr_pcur_t pcur;          /*!< persistent cursor used in searching the
                            clustered index record */
  dict_table_t *table;      /*!< table where undo is done */
  ulint cmpl_info;          /*!< compiler analysis of an update */
  upd_t *update;            /*!< update vector for a clustered index
                            record */
  dtuple_t *ref;            /*!< row reference to the next row to handle */
  dtuple_t *row;            /*!< a copy (also fields copied to heap) of the
                            row to handle */
  row_ext_t *ext;           /*!< NULL, or prefixes of the externally
                            stored columns of the row */
  dtuple_t *undo_row;       /*!< NULL, or the row after undo */
  row_ext_t *undo_ext;      /*!< NULL, or prefixes of the externally
                           stored columns of undo_row */
  dict_index_t *index;      /*!< the next index whose record should be
                            handled */
  mem_heap_t *heap;         /*!< memory heap used as auxiliary storage for
                            row; this must be emptied after undo is tried
                            on a row */
  bool partial;             /*!< true if partial rollback */
};
 
#endif