innobase/ha/ha0ha.cc

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/** @file ha/ha0ha.cc
 The hash table with external chains

 Created 8/22/1994 Heikki Tuuri
 *************************************************************************/

#include "ha0ha.h"

#include <sys/types.h>

#ifdef UNIV_DEBUG
#include "buf0buf.h"
#endif /* UNIV_DEBUG */
#include "btr0sea.h"
#include "page0page.h"

#if defined UNIV_AHI_DEBUG || defined UNIV_DEBUG
/** Maximum number of records in a page */
static const ulint MAX_N_POINTERS = UNIV_PAGE_SIZE_MAX / REC_N_NEW_EXTRA_BYTES;
#endif /* UNIV_AHI_DEBUG || UNIV_DEBUG */

/** Creates a hash table with at least n array cells.  The actual number
 of cells is chosen to be a prime number slightly bigger than n.
 @return own: created table */
hash_table_t *ib_create(ulint n,       /*!< in: number of array cells */
                        latch_id_t id, /*!< in: latch ID */
                        ulint n_sync_obj,
                        /*!< in: number of mutexes to protect the
                        hash table: must be a power of 2, or 0 */
                        ulint type) /*!< in: type of datastructure for which
                                    MEM_HEAP_FOR_PAGE_HASH */
{
  hash_table_t *table;

  ut_a(type == MEM_HEAP_FOR_BTR_SEARCH || type == MEM_HEAP_FOR_PAGE_HASH);

  ut_ad(ut_is_2pow(n_sync_obj));
  table = hash_create(n);

  /* Creating MEM_HEAP_BTR_SEARCH type heaps can potentially fail,
  but in practise it never should in this case, hence the asserts. */

  if (n_sync_obj == 0) {
    table->heap = mem_heap_create_typed(
        ut_min(static_cast<ulint>(4096), MEM_MAX_ALLOC_IN_BUF / 2 -
                                             MEM_BLOCK_HEADER_SIZE -
                                             MEM_SPACE_NEEDED(0)),
        type);
    ut_a(table->heap);

    return (table);
  }

  if (type == MEM_HEAP_FOR_PAGE_HASH) {
    /* We create a hash table protected by rw_locks for
    buf_pool->page_hash. */
    hash_create_sync_obj(table, HASH_TABLE_SYNC_RW_LOCK, id, n_sync_obj);
  } else {
    hash_create_sync_obj(table, HASH_TABLE_SYNC_MUTEX, id, n_sync_obj);
  }

  table->heaps =
      static_cast<mem_heap_t **>(ut_malloc_nokey(n_sync_obj * sizeof(void *)));

  for (ulint i = 0; i < n_sync_obj; i++) {
    table->heaps[i] = mem_heap_create_typed(
        ut_min(static_cast<ulint>(4096), MEM_MAX_ALLOC_IN_BUF / 2 -
                                             MEM_BLOCK_HEADER_SIZE -
                                             MEM_SPACE_NEEDED(0)),
        type);
    ut_a(table->heaps[i]);
  }

  return (table);
}

/** Recreate a hash table with at least n array cells. The actual number
of cells is chosen to be a prime number slightly bigger than n.
The new cells are all cleared. The heaps are recreated.
The sync objects are reused.
@param[in,out]	table	hash table to be resuzed (to be freed later)
@param[in]	n	number of array cells
@return	resized new table */
hash_table_t *ib_recreate(hash_table_t *table, ulint n) {
  /* This function is for only page_hash for now */
  ut_ad(table->type == HASH_TABLE_SYNC_RW_LOCK);
  ut_ad(table->n_sync_obj > 0);

  hash_table_t *new_table = hash_create(n);

  new_table->type = table->type;
  new_table->n_sync_obj = table->n_sync_obj;
  new_table->sync_obj = table->sync_obj;

  for (ulint i = 0; i < table->n_sync_obj; i++) {
    mem_heap_free(table->heaps[i]);
  }
  ut_free(table->heaps);

  new_table->heaps = static_cast<mem_heap_t **>(
      ut_malloc_nokey(new_table->n_sync_obj * sizeof(void *)));

  for (ulint i = 0; i < new_table->n_sync_obj; i++) {
    new_table->heaps[i] = mem_heap_create_typed(
        ut_min(static_cast<ulint>(4096), MEM_MAX_ALLOC_IN_BUF / 2 -
                                             MEM_BLOCK_HEADER_SIZE -
                                             MEM_SPACE_NEEDED(0)),
        MEM_HEAP_FOR_PAGE_HASH);
    ut_a(new_table->heaps[i]);
  }

  return (new_table);
}

/** Empties a hash table and frees the memory heaps. */
void ha_clear(hash_table_t *table) /*!< in, own: hash table */
{
  ut_ad(table->magic_n == HASH_TABLE_MAGIC_N);
  ut_ad(!table->adaptive || btr_search_own_all(RW_LOCK_X));

  for (ulint i = 0; i < table->n_sync_obj; i++) {
    mem_heap_free(table->heaps[i]);
  }

  ut_free(table->heaps);

  switch (table->type) {
    case HASH_TABLE_SYNC_MUTEX:
      for (ulint i = 0; i < table->n_sync_obj; ++i) {
        mutex_destroy(&table->sync_obj.mutexes[i]);
      }
      ut_free(table->sync_obj.mutexes);
      table->sync_obj.mutexes = nullptr;
      break;

    case HASH_TABLE_SYNC_RW_LOCK:
      for (ulint i = 0; i < table->n_sync_obj; ++i) {
        rw_lock_free(&table->sync_obj.rw_locks[i]);
      }

      ut_free(table->sync_obj.rw_locks);
      table->sync_obj.rw_locks = nullptr;
      break;

    case HASH_TABLE_SYNC_NONE:
      /* do nothing */
      break;
  }

  table->n_sync_obj = 0;
  table->type = HASH_TABLE_SYNC_NONE;

  /* Clear the hash table. */
  ulint n = hash_get_n_cells(table);

  for (ulint i = 0; i < n; i++) {
    hash_get_nth_cell(table, i)->node = nullptr;
  }
}

/** Inserts an entry into a hash table. If an entry with the same fold number
 is found, its node is updated to point to the new data, and no new node
 is inserted. If btr_search_enabled is set to FALSE, we will only allow
 updating existing nodes, but no new node is allowed to be added.
 @return true if succeed, false if no more memory could be allocated */
ibool ha_insert_for_fold_func(
    hash_table_t *table, /*!< in: hash table */
    ulint fold,          /*!< in: folded value of data; if a node with
                         the same fold value already exists, it is
                         updated to point to the same data, and no new
                         node is created! */
#if defined UNIV_AHI_DEBUG || defined UNIV_DEBUG
    buf_block_t *block, /*!< in: buffer block containing the data */
#endif                  /* UNIV_AHI_DEBUG || UNIV_DEBUG */
    const rec_t *data)  /*!< in: data, must not be NULL */
{
  hash_cell_t *cell;
  ha_node_t *node;
  ha_node_t *prev_node;
  ulint hash;

  ut_ad(data);
  ut_ad(table);
  ut_ad(table->magic_n == HASH_TABLE_MAGIC_N);
#if defined UNIV_AHI_DEBUG || defined UNIV_DEBUG
  ut_a(block->frame == page_align(data));
#endif /* UNIV_AHI_DEBUG || UNIV_DEBUG */
  hash_assert_can_modify(table, fold);
  ut_ad(btr_search_enabled);

  hash = hash_calc_hash(fold, table);

  cell = hash_get_nth_cell(table, hash);

  prev_node = static_cast<ha_node_t *>(cell->node);

  while (prev_node != nullptr) {
    if (prev_node->fold == fold) {
#if defined UNIV_AHI_DEBUG || defined UNIV_DEBUG
      if (table->adaptive) {
        buf_block_t *prev_block = prev_node->block;
        ut_a(prev_block->frame == page_align(prev_node->data));
        ut_a(os_atomic_decrement_ulint(&prev_block->n_pointers, 1) <
             MAX_N_POINTERS);
        ut_a(os_atomic_increment_ulint(&block->n_pointers, 1) < MAX_N_POINTERS);
      }

      prev_node->block = block;
#endif /* UNIV_AHI_DEBUG || UNIV_DEBUG */
      prev_node->data = data;

      return (TRUE);
    }

    prev_node = prev_node->next;
  }

  /* We have to allocate a new chain node */

  node = static_cast<ha_node_t *>(
      mem_heap_alloc(hash_get_heap(table, fold), sizeof(ha_node_t)));

  if (node == nullptr) {
    /* It was a btr search type memory heap and at the moment
    no more memory could be allocated: return */

    ut_ad(hash_get_heap(table, fold)->type & MEM_HEAP_BTR_SEARCH);

    return (FALSE);
  }

  ha_node_set_data(node, block, data);

#if defined UNIV_AHI_DEBUG || defined UNIV_DEBUG
  if (table->adaptive) {
    ut_a(os_atomic_increment_ulint(&block->n_pointers, 1) < MAX_N_POINTERS);
  }
#endif /* UNIV_AHI_DEBUG || UNIV_DEBUG */

  node->fold = fold;

  node->next = nullptr;

  prev_node = static_cast<ha_node_t *>(cell->node);

  if (prev_node == nullptr) {
    cell->node = node;

    return (TRUE);
  }

  while (prev_node->next != nullptr) {
    prev_node = prev_node->next;
  }

  prev_node->next = node;

  return (TRUE);
}

#ifdef UNIV_DEBUG
/** Verify if latch corresponding to the hash table is x-latched
@param[in]	table		hash table */
static void ha_btr_search_latch_x_locked(const hash_table_t *table) {
  ulint i;
  for (i = 0; i < btr_ahi_parts; ++i) {
    if (btr_search_sys->hash_tables[i] == table) {
      break;
    }
  }

  ut_ad(i < btr_ahi_parts);
  ut_ad(rw_lock_own(btr_search_latches[i], RW_LOCK_X));
}
#endif /* UNIV_DEBUG */

/** Deletes a hash node. */
void ha_delete_hash_node(hash_table_t *table, /*!< in: hash table */
                         ha_node_t *del_node) /*!< in: node to be deleted */
{
  ut_ad(table);
  ut_ad(table->magic_n == HASH_TABLE_MAGIC_N);
  ut_d(ha_btr_search_latch_x_locked(table));
  ut_ad(btr_search_enabled);
#if defined UNIV_AHI_DEBUG || defined UNIV_DEBUG
  if (table->adaptive) {
    ut_a(del_node->block->frame = page_align(del_node->data));
    ut_a(os_atomic_decrement_ulint(&del_node->block->n_pointers, 1) <
         MAX_N_POINTERS);
  }
#endif /* UNIV_AHI_DEBUG || UNIV_DEBUG */

  HASH_DELETE_AND_COMPACT(ha_node_t, next, table, del_node);
}

/** Looks for an element when we know the pointer to the data, and updates
 the pointer to data, if found.
 @return true if found */
ibool ha_search_and_update_if_found_func(
    hash_table_t *table, /*!< in/out: hash table */
    ulint fold,          /*!< in: folded value of the searched data */
    const rec_t *data,   /*!< in: pointer to the data */
#if defined UNIV_AHI_DEBUG || defined UNIV_DEBUG
    buf_block_t *new_block, /*!< in: block containing new_data */
#endif                      /* UNIV_AHI_DEBUG || UNIV_DEBUG */
    const rec_t *new_data)  /*!< in: new pointer to the data */
{
  ha_node_t *node;

  ut_ad(table);
  ut_ad(table->magic_n == HASH_TABLE_MAGIC_N);
  hash_assert_can_modify(table, fold);
#if defined UNIV_AHI_DEBUG || defined UNIV_DEBUG
  ut_a(new_block->frame == page_align(new_data));
#endif /* UNIV_AHI_DEBUG || UNIV_DEBUG */

  ut_d(ha_btr_search_latch_x_locked(table));

  if (!btr_search_enabled) {
    return (FALSE);
  }

  node = ha_search_with_data(table, fold, data);

  if (node) {
#if defined UNIV_AHI_DEBUG || defined UNIV_DEBUG
    if (table->adaptive) {
      ut_a(os_atomic_decrement_ulint(&node->block->n_pointers, 1) <
           MAX_N_POINTERS);
      ut_a(os_atomic_increment_ulint(&new_block->n_pointers, 1) <
           MAX_N_POINTERS);
    }

    node->block = new_block;
#endif /* UNIV_AHI_DEBUG || UNIV_DEBUG */
    node->data = new_data;

    return (TRUE);
  }

  return (FALSE);
}

/** Removes from the chain determined by fold all nodes whose data pointer
 points to the page given. */
void ha_remove_all_nodes_to_page(hash_table_t *table, /*!< in: hash table */
                                 ulint fold,          /*!< in: fold value */
                                 const page_t *page)  /*!< in: buffer page */
{
  ha_node_t *node;

  ut_ad(table);
  ut_ad(table->magic_n == HASH_TABLE_MAGIC_N);
  hash_assert_can_modify(table, fold);
  ut_ad(btr_search_enabled);

  node = ha_chain_get_first(table, fold);

  while (node) {
    if (page_align(ha_node_get_data(node)) == page) {
      /* Remove the hash node */

      ha_delete_hash_node(table, node);

      /* Start again from the first node in the chain
      because the deletion may compact the heap of
      nodes and move other nodes! */

      node = ha_chain_get_first(table, fold);
    } else {
      node = ha_chain_get_next(node);
    }
  }
#ifdef UNIV_DEBUG
  /* Check that all nodes really got deleted */

  node = ha_chain_get_first(table, fold);

  while (node) {
    ut_a(page_align(ha_node_get_data(node)) != page);

    node = ha_chain_get_next(node);
  }
#endif /* UNIV_DEBUG */
}

#if defined UNIV_AHI_DEBUG || defined UNIV_DEBUG
/** Validates a given range of the cells in hash table.
 @return true if ok */
ibool ha_validate(hash_table_t *table, /*!< in: hash table */
                  ulint start_index,   /*!< in: start index */
                  ulint end_index)     /*!< in: end index */
{
  ibool ok = TRUE;
  ulint i;

  ut_ad(table);
  ut_ad(table->magic_n == HASH_TABLE_MAGIC_N);
  ut_a(start_index <= end_index);
  ut_a(start_index < hash_get_n_cells(table));
  ut_a(end_index < hash_get_n_cells(table));

  for (i = start_index; i <= end_index; i++) {
    ha_node_t *node;
    hash_cell_t *cell;

    cell = hash_get_nth_cell(table, i);

    for (node = static_cast<ha_node_t *>(cell->node); node != nullptr;
         node = node->next) {
      if (hash_calc_hash(node->fold, table) != i) {
        ib::error(ER_IB_MSG_522) << "Hash table node fold value " << node->fold
                                 << " does not match the"
                                    " cell number "
                                 << i << ".";

        ok = FALSE;
      }
    }
  }

  return (ok);
}
#endif /* defined UNIV_AHI_DEBUG || defined UNIV_DEBUG */

/** Prints info of a hash table. */
void ha_print_info(FILE *file,          /*!< in: file where to print */
                   hash_table_t *table) /*!< in: hash table */
{
#ifdef UNIV_DEBUG
/* Some of the code here is disabled for performance reasons in production
builds, see http://bugs.mysql.com/36941 */
#define PRINT_USED_CELLS
#endif /* UNIV_DEBUG */

#ifdef PRINT_USED_CELLS
  hash_cell_t *cell;
  ulint cells = 0;
  ulint i;
#endif /* PRINT_USED_CELLS */
  ulint n_bufs;

  ut_ad(table);
  ut_ad(table->magic_n == HASH_TABLE_MAGIC_N);
#ifdef PRINT_USED_CELLS
  for (i = 0; i < hash_get_n_cells(table); i++) {
    cell = hash_get_nth_cell(table, i);

    if (cell->node) {
      cells++;
    }
  }
#endif /* PRINT_USED_CELLS */

  fprintf(file, "Hash table size %lu", (ulong)hash_get_n_cells(table));

#ifdef PRINT_USED_CELLS
  fprintf(file, ", used cells %lu", (ulong)cells);
#endif /* PRINT_USED_CELLS */

  if (table->heaps == nullptr && table->heap != nullptr) {
    /* This calculation is intended for the adaptive hash
    index: how many buffer frames we have reserved? */

    n_bufs = UT_LIST_GET_LEN(table->heap->base) - 1;

    if (table->heap->free_block) {
      n_bufs++;
    }

    fprintf(file, ", node heap has %lu buffer(s)\n", (ulong)n_bufs);
  }
}