hash0hash.h

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/** @file include/hash0hash.h
 The simple hash table utility
 
 Created 5/20/1997 Heikki Tuuri
 *******************************************************/
 
#ifndef hash0hash_h
#define hash0hash_h
 
#include <stddef.h>
 
#include "mem0mem.h"
#include "univ.i"
#include "ut0rnd.h"
#ifndef UNIV_HOTBACKUP
#include "sync0rw.h"
#endif /* !UNIV_HOTBACKUP */
 
class hash_table_t;
struct hash_cell_t;
 
typedef void *hash_node_t;
 
/* Different types of hash_table based on the synchronization
method used for it. */
enum hash_table_sync_t {
  HASH_TABLE_SYNC_NONE = 0, /*!< Don't use any internal
                            synchronization objects for
                            this hash_table. */
  HASH_TABLE_SYNC_RW_LOCK   /*!< Use rw_locks to control
                            access to this hash_table. */
};
 
struct hash_cell_t {
  void *node; /*!< hash chain node, NULL if none */
};
 
#ifndef UNIV_HOTBACKUP
 
/** Creates a sync object array to protect a hash table.
@param[in]      table           hash table
@param[in]      id              latch ID
@param[in]      n_sync_obj      number of sync objects, must be a power of 2 */
void hash_create_sync_obj(hash_table_t *table, latch_id_t id,
                          size_t n_sync_obj);
#endif /* !UNIV_HOTBACKUP */
 
/** Calculates the cell index from a hashed value for a specified hash table.
@param[in]      hash_value      hashed value
@param[in]      table           hash table
@return cell index for specified hash table*/
static inline uint64_t hash_calc_cell_id(uint64_t hash_value,
                                         hash_table_t *table);
 
/** Gets the nth cell in a hash table.
@param[in]      table   hash table
@param[in]      n       cell index
@return pointer to cell */
static inline hash_cell_t *hash_get_nth_cell(hash_table_t *table, size_t n);
 
/** Inserts a struct to a hash table. */
 
#define HASH_INSERT(TYPE, NAME, TABLE, HASH_VALUE, DATA)                    \
  do {                                                                      \
    hash_cell_t *cell3333;                                                  \
    TYPE *struct3333;                                                       \
    const uint64_t hash_value3333 = HASH_VALUE;                             \
                                                                            \
    hash_assert_can_modify(TABLE, hash_value3333);                          \
                                                                            \
    (DATA)->NAME = NULL;                                                    \
                                                                            \
    cell3333 =                                                              \
        hash_get_nth_cell(TABLE, hash_calc_cell_id(hash_value3333, TABLE)); \
                                                                            \
    if (cell3333->node == NULL) {                                           \
      cell3333->node = DATA;                                                \
    } else {                                                                \
      struct3333 = (TYPE *)cell3333->node;                                  \
                                                                            \
      while (struct3333->NAME != NULL) {                                    \
        struct3333 = (TYPE *)struct3333->NAME;                              \
      }                                                                     \
                                                                            \
      struct3333->NAME = DATA;                                              \
    }                                                                       \
  } while (0)
 
#ifdef UNIV_HASH_DEBUG
#define HASH_ASSERT_VALID(DATA) ut_a((void *)(DATA) != (void *)-1)
#define HASH_INVALIDATE(DATA, NAME) *(void **)(&DATA->NAME) = (void *)-1
#else
#define HASH_ASSERT_VALID(DATA) \
  do {                          \
  } while (0)
#define HASH_INVALIDATE(DATA, NAME) \
  do {                              \
  } while (0)
#endif
 
/** Deletes a struct from a hash table. */
 
#define HASH_DELETE(TYPE, NAME, TABLE, HASH_VALUE, DATA)                    \
  do {                                                                      \
    hash_cell_t *cell3333;                                                  \
    TYPE *struct3333;                                                       \
    const uint64_t hash_value3333 = HASH_VALUE;                             \
                                                                            \
    hash_assert_can_modify(TABLE, hash_value3333);                          \
                                                                            \
    cell3333 =                                                              \
        hash_get_nth_cell(TABLE, hash_calc_cell_id(hash_value3333, TABLE)); \
                                                                            \
    if (cell3333->node == DATA) {                                           \
      HASH_ASSERT_VALID(DATA->NAME);                                        \
      cell3333->node = DATA->NAME;                                          \
    } else {                                                                \
      struct3333 = (TYPE *)cell3333->node;                                  \
                                                                            \
      while (struct3333->NAME != DATA) {                                    \
        struct3333 = (TYPE *)struct3333->NAME;                              \
        ut_a(struct3333);                                                   \
      }                                                                     \
                                                                            \
      struct3333->NAME = DATA->NAME;                                        \
    }                                                                       \
    HASH_INVALIDATE(DATA, NAME);                                            \
  } while (0)
 
/** Gets the first struct in a hash chain, NULL if none. */
 
static inline void *&hash_get_first(hash_table_t *table, size_t cell_id) {
  return hash_get_nth_cell(table, cell_id)->node;
}
 
/** Gets the next struct in a hash chain, NULL if none. */
 
#define HASH_GET_NEXT(NAME, DATA) ((DATA)->NAME)
 
/** Looks for a struct in a hash table. */
#define HASH_SEARCH(NAME, TABLE, HASH_VALUE, TYPE, DATA, ASSERTION, TEST)      \
  {                                                                            \
    const uint64_t hash_value3333 = HASH_VALUE;                                \
                                                                               \
    hash_assert_can_search(TABLE, hash_value3333);                             \
                                                                               \
    (DATA) =                                                                   \
        (TYPE)hash_get_first(TABLE, hash_calc_cell_id(hash_value3333, TABLE)); \
    HASH_ASSERT_VALID(DATA);                                                   \
                                                                               \
    while ((DATA) != NULL) {                                                   \
      ASSERTION;                                                               \
      if (TEST) {                                                              \
        break;                                                                 \
      } else {                                                                 \
        HASH_ASSERT_VALID(HASH_GET_NEXT(NAME, DATA));                          \
        (DATA) = (TYPE)HASH_GET_NEXT(NAME, DATA);                              \
      }                                                                        \
    }                                                                          \
  }
 
/** Looks for an item in all hash cells. */
#define HASH_SEARCH_ALL(NAME, TABLE, TYPE, DATA, ASSERTION, TEST) \
  do {                                                            \
    size_t i3333;                                                 \
                                                                  \
    for (i3333 = (TABLE)->get_n_cells(); i3333--;) {              \
      (DATA) = (TYPE)hash_get_first(TABLE, i3333);                \
                                                                  \
      while ((DATA) != NULL) {                                    \
        HASH_ASSERT_VALID(DATA);                                  \
        ASSERTION;                                                \
                                                                  \
        if (TEST) {                                               \
          break;                                                  \
        }                                                         \
                                                                  \
        (DATA) = (TYPE)HASH_GET_NEXT(NAME, DATA);                 \
      }                                                           \
                                                                  \
      if ((DATA) != NULL) {                                       \
        break;                                                    \
      }                                                           \
    }                                                             \
  } while (0)
 
/** Clears a hash table so that all the cells become empty. */
static inline void hash_table_clear(
    hash_table_t *table); /*!< in/out: hash table */
 
/** Returns the number of cells in a hash table.
 @return number of cells */
static inline size_t hash_get_n_cells(hash_table_t *table); /*!< in: table */
 
/** Deletes a struct which is stored in the heap of the hash table, and compacts
 the heap. The hash value must be stored in the struct NODE in a field named
 'hash_value'. */
#define HASH_DELETE_AND_COMPACT(TYPE, NAME, TABLE, NODE)                  \
  do {                                                                    \
    TYPE *node111;                                                        \
    TYPE *top_node111;                                                    \
    hash_cell_t *cell111;                                                 \
    uint64_t hash_value111;                                               \
                                                                          \
    hash_value111 = (NODE)->hash_value;                                   \
                                                                          \
    HASH_DELETE(TYPE, NAME, TABLE, hash_value111, NODE);                  \
                                                                          \
    top_node111 =                                                         \
        (TYPE *)mem_heap_get_top(hash_get_heap(TABLE), sizeof(TYPE));     \
                                                                          \
    /* If the node to remove is not the top node in the heap, compact the \
    heap of nodes by moving the top node in the place of NODE. */         \
                                                                          \
    if (NODE != top_node111) {                                            \
      /* Copy the top node in place of NODE */                            \
                                                                          \
      *(NODE) = *top_node111;                                             \
                                                                          \
      cell111 = hash_get_nth_cell(                                        \
          TABLE, hash_calc_cell_id(top_node111->hash_value, TABLE));      \
                                                                          \
      /* Look for the pointer to the top node, to update it */            \
                                                                          \
      if (cell111->node == top_node111) {                                 \
        /* The top node is the first in the chain */                      \
                                                                          \
        cell111->node = NODE;                                             \
      } else {                                                            \
        /* We have to look for the predecessor of the top                 \
        node */                                                           \
        node111 = static_cast<TYPE *>(cell111->node);                     \
                                                                          \
        while (top_node111 != HASH_GET_NEXT(NAME, node111)) {             \
          node111 = static_cast<TYPE *>(HASH_GET_NEXT(NAME, node111));    \
        }                                                                 \
                                                                          \
        /* Now we have the predecessor node */                            \
                                                                          \
        node111->NAME = NODE;                                             \
      }                                                                   \
    }                                                                     \
                                                                          \
    /* Free the space occupied by the top node */                         \
                                                                          \
    mem_heap_free_top(hash_get_heap(TABLE), sizeof(TYPE));                \
  } while (0)
 
#ifndef UNIV_HOTBACKUP
/** Move all hash table entries from OLD_TABLE to NEW_TABLE. */
 
#define HASH_MIGRATE(OLD_TABLE, NEW_TABLE, NODE_TYPE, PTR_NAME, HASH_FUNC)  \
  do {                                                                      \
    size_t i2222;                                                           \
    size_t cell_count2222;                                                  \
                                                                            \
    cell_count2222 = hash_get_n_cells(OLD_TABLE);                           \
                                                                            \
    for (i2222 = 0; i2222 < cell_count2222; i2222++) {                      \
      NODE_TYPE *node2222 =                                                 \
          static_cast<NODE_TYPE *>(hash_get_first((OLD_TABLE), i2222));     \
                                                                            \
      while (node2222) {                                                    \
        NODE_TYPE *next2222 = static_cast<NODE_TYPE *>(node2222->PTR_NAME); \
        uint64_t hash_value2222 = HASH_FUNC(node2222);                      \
                                                                            \
        HASH_INSERT(NODE_TYPE, PTR_NAME, (NEW_TABLE), hash_value2222,       \
                    node2222);                                              \
                                                                            \
        node2222 = next2222;                                                \
      }                                                                     \
    }                                                                       \
  } while (0)
 
/** Gets the sync object index for a hash value in a hash table.
@param[in]      table       hash table
@param[in]      hash_value  hash value
@return index */
static inline uint64_t hash_get_sync_obj_index(hash_table_t *table,
                                               uint64_t hash_value);
 
/** Gets the heap for a hash value in a hash table.
@param[in]      table   hash table
@return mem heap */
static inline mem_heap_t *hash_get_heap(hash_table_t *table);
 
/** Gets the nth rw_lock in a hash table.
@param[in]      table   hash table
@param[in]      i       index of the rw_lock
@return rw_lock */
static inline rw_lock_t *hash_get_nth_lock(hash_table_t *table, size_t i);
 
/** Gets the rw_lock for a hash value in a hash table.
@param[in]      table       hash table
@param[in]      hash_value  hash value
@return rw_lock */
static inline rw_lock_t *hash_get_lock(hash_table_t *table,
                                       uint64_t hash_value);
 
/** If not appropriate rw_lock for a hash value in a hash table,
relock S-lock the another rw_lock until appropriate for a hash value.
@param[in]      hash_lock       latched rw_lock to be confirmed
@param[in]      table           hash table
@param[in]      hash_value      hash value
@return latched rw_lock */
static inline rw_lock_t *hash_lock_s_confirm(rw_lock_t *hash_lock,
                                             hash_table_t *table,
                                             uint64_t hash_value);
 
/** If not appropriate rw_lock for a hash value in a hash table,
relock X-lock the another rw_lock until appropriate for a hash value.
@param[in]      hash_lock       latched rw_lock to be confirmed
@param[in]      table           hash table
@param[in]      hash_value      hash value
@return latched rw_lock */
static inline rw_lock_t *hash_lock_x_confirm(rw_lock_t *hash_lock,
                                             hash_table_t *table,
                                             uint64_t hash_value);
 
#ifdef UNIV_DEBUG
 
/** Verifies that the current thread holds X-latch on all shards.
Assumes type==HASH_TABLE_SYNC_RW_LOCK.
@param[in]  table the table in question
@return true iff the current thread holds X-latch on all shards*/
bool hash_lock_has_all_x(const hash_table_t *table);
 
#endif /* UNIV_DEBUG */
 
/** Reserves all the locks of a hash table, in an ascending order. */
void hash_lock_x_all(hash_table_t *table); /*!< in: hash table */
 
/** Releases all the locks of a hash table, in an ascending order. */
void hash_unlock_x_all(hash_table_t *table); /*!< in: hash table */
 
/** Releases all but passed in lock of a hash table,
@param[in] table Hash table
@param[in] keep_lock Lock to keep */
void hash_unlock_x_all_but(hash_table_t *table, rw_lock_t *keep_lock);
 
#else /* !UNIV_HOTBACKUP */
#define hash_get_heap(table) ((table)->heap)
#define hash_lock_x_all(t) ((void)0)
#define hash_unlock_x_all(t) ((void)0)
#define hash_unlock_x_all_but(t, l) ((void)0)
#endif /* !UNIV_HOTBACKUP */
 
/* The hash table structure */
class hash_table_t {
 public:
  hash_table_t(size_t n) {
    const auto prime = ut::find_prime(n);
    cells = ut::make_unique<hash_cell_t[]>(prime);
    set_n_cells(prime);
 
    /* Initialize the cell array */
    hash_table_clear(this);
  }
  ~hash_table_t() { ut_ad(magic_n == HASH_TABLE_MAGIC_N); }
 
  /** Returns number of cells in cells[] array.
   If type==HASH_TABLE_SYNC_RW_LOCK it can be used:
  - without any latches to peek a value, before hash_lock_[sx]_confirm
  - when holding S-latch for at least one n_sync_obj to get the "real" value
  @return value of n_cells
  */
  size_t get_n_cells() { return n_cells.load(std::memory_order_relaxed); }
 
  /** Returns a helper class for calculating fast modulo n_cells.
   If type==HASH_TABLE_SYNC_RW_LOCK it can be used:
  - without any latches to peek a value, before hash_lock_[sx]_confirm
  - when holding S-latch for at least one n_sync_obj to get the "real" value */
  const ut::fast_modulo_t get_n_cells_fast_modulo() {
    return n_cells_fast_modulo.load();
  }
 
  /** Sets the number of n_cells, to the provided one.
  If type==HASH_TABLE_SYNC_RW_LOCK it can be used only when holding x-latches on
  all shards.
  @param[in]  n   The new size of cells[] array
  */
  void set_n_cells(size_t n) {
#ifndef UNIV_HOTBACKUP
    ut_ad(type == HASH_TABLE_SYNC_NONE || hash_lock_has_all_x(this));
#endif
    n_cells.store(n);
    n_cells_fast_modulo.store(n);
  }
 
 public:
  /** Either:
  a) HASH_TABLE_SYNC_NONE in which case n_sync_obj is 0 and rw_locks is nullptr
  or
  b) HASH_TABLE_SYNC_RW_LOCK in which case n_sync_obj > 0 is the number of
  rw_locks elements, each of which protects a disjoint fraction of cells.
  The default type of hash_table is HASH_TABLE_SYNC_NONE i.e.: the caller is
  responsible for access control to the table. */
  enum hash_table_sync_t type = HASH_TABLE_SYNC_NONE;
 
#if defined UNIV_AHI_DEBUG || defined UNIV_DEBUG
#ifndef UNIV_HOTBACKUP
  /* true if this is the hash table of the adaptive hash index */
  bool adaptive = false;
#endif /* !UNIV_HOTBACKUP */
#endif /* UNIV_AHI_DEBUG || UNIV_DEBUG */
 private:
  /** The number of cells in the hash table.
  If type==HASH_TABLE_SYNC_RW_LOCK it is:
  - modified when holding X-latches on all n_sync_obj
  - read
    - without any latches to peek a value, before hash_lock_[sx]_confirm
    - when holding S-latch for at least one n_sync_obj to get the "real" value
  */
  std::atomic<size_t> n_cells;
  /** Utility to calculate the modulo n_cells fast. It is set together with
  n_cells. It can be read without latches in parallel to set_n_cells, and as it
  is a complex object, it is not set atomically. Because of this the
  multi-threaded version is used. */
  ut::mt_fast_modulo_t n_cells_fast_modulo;
 
 public:
  /** The pointer to the array of cells.
  If type==HASH_TABLE_SYNC_RW_LOCK it is:
  - modified when holding X-latches on all n_sync_obj
  - read when holding an S-latch for at least one n_sync_obj
  */
  ut::unique_ptr<hash_cell_t[]> cells;
#ifndef UNIV_HOTBACKUP
  /** if rw_locks != nullptr, then it's their number (must be a power of two).
  Otherwise, 0. Is zero iff the type is HASH_TABLE_SYNC_NONE. */
  size_t n_sync_obj = 0;
  /** nullptr, or an array of n_sync_obj rw_locks used to protect segments of
  the hash table. Is nullptr iff the type is HASH_TABLE_SYNC_NONE. */
  rw_lock_t *rw_locks = nullptr;
 
#endif /* !UNIV_HOTBACKUP */
  mem_heap_t *heap = nullptr;
#ifdef UNIV_DEBUG
  static constexpr uint32_t HASH_TABLE_MAGIC_N = 76561114;
  uint32_t magic_n = HASH_TABLE_MAGIC_N;
#endif /* UNIV_DEBUG */
};
 
#include "hash0hash.ic"
 
#endif