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980ec41fe7
Fix race condition which could result in freeing a struct that is still in use by another thread. Detailed revision comments: r2537 | inaam | 2008-07-15 20:46:03 +0300 (Tue, 15 Jul 2008) | 12 lines branches/5.1 issue# 4 Fixed a timing hole where a thread dropping an index can free the in-memory index struct while another thread is still using that structure to remove entries from adaptive hash index belonging to one of the pages that belongs to the index being dropped. The fix is to have a reference counter in the index struct and to wait for this counter to drop to zero beforing freeing the struct. Reviewed by: Heikki r2543 | inaam | 2008-07-22 18:57:43 +0300 (Tue, 22 Jul 2008) | 7 lines branches/5.1: Removed UNIV_INLINE qualifier from btr_search_info_get_ref_count(). Otherwise compilation failed on non-debug builds. Pointed by: Vasil
255 lines
8.6 KiB
C
255 lines
8.6 KiB
C
/************************************************************************
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The index tree adaptive search
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(c) 1996 Innobase Oy
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Created 2/17/1996 Heikki Tuuri
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*************************************************************************/
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#ifndef btr0sea_h
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#define btr0sea_h
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#include "univ.i"
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#include "rem0rec.h"
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#include "dict0dict.h"
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#include "btr0types.h"
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#include "mtr0mtr.h"
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#include "ha0ha.h"
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/*********************************************************************
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Creates and initializes the adaptive search system at a database start. */
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void
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btr_search_sys_create(
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/*==================*/
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ulint hash_size); /* in: hash index hash table size */
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/************************************************************************
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Returns search info for an index. */
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UNIV_INLINE
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btr_search_t*
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btr_search_get_info(
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/*================*/
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/* out: search info; search mutex reserved */
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dict_index_t* index); /* in: index */
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/*********************************************************************
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Creates and initializes a search info struct. */
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btr_search_t*
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btr_search_info_create(
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/*===================*/
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/* out, own: search info struct */
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mem_heap_t* heap); /* in: heap where created */
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/*********************************************************************
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Returns the value of ref_count. The value is protected by
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btr_search_latch. */
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ulint
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btr_search_info_get_ref_count(
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/*==========================*/
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/* out: ref_count value. */
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btr_search_t* info); /* in: search info. */
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/*************************************************************************
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Updates the search info. */
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UNIV_INLINE
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void
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btr_search_info_update(
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/*===================*/
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dict_index_t* index, /* in: index of the cursor */
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btr_cur_t* cursor);/* in: cursor which was just positioned */
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/**********************************************************************
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Tries to guess the right search position based on the hash search info
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of the index. Note that if mode is PAGE_CUR_LE, which is used in inserts,
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and the function returns TRUE, then cursor->up_match and cursor->low_match
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both have sensible values. */
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ibool
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btr_search_guess_on_hash(
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/*=====================*/
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/* out: TRUE if succeeded */
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dict_index_t* index, /* in: index */
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btr_search_t* info, /* in: index search info */
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dtuple_t* tuple, /* in: logical record */
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ulint mode, /* in: PAGE_CUR_L, ... */
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ulint latch_mode, /* in: BTR_SEARCH_LEAF, ... */
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btr_cur_t* cursor, /* out: tree cursor */
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ulint has_search_latch,/* in: latch mode the caller
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currently has on btr_search_latch:
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RW_S_LATCH, RW_X_LATCH, or 0 */
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mtr_t* mtr); /* in: mtr */
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/************************************************************************
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Moves or deletes hash entries for moved records. If new_page is already hashed,
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then the hash index for page, if any, is dropped. If new_page is not hashed,
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and page is hashed, then a new hash index is built to new_page with the same
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parameters as page (this often happens when a page is split). */
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void
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btr_search_move_or_delete_hash_entries(
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/*===================================*/
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page_t* new_page, /* in: records are copied
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to this page */
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page_t* page, /* in: index page */
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dict_index_t* index); /* in: record descriptor */
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/************************************************************************
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Drops a page hash index. */
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void
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btr_search_drop_page_hash_index(
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/*============================*/
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page_t* page); /* in: index page, s- or x-latched */
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/************************************************************************
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Drops a page hash index when a page is freed from a fseg to the file system.
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Drops possible hash index if the page happens to be in the buffer pool. */
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void
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btr_search_drop_page_hash_when_freed(
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/*=================================*/
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ulint space, /* in: space id */
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ulint page_no); /* in: page number */
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/************************************************************************
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Updates the page hash index when a single record is inserted on a page. */
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void
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btr_search_update_hash_node_on_insert(
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/*==================================*/
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btr_cur_t* cursor);/* in: cursor which was positioned to the
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place to insert using btr_cur_search_...,
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and the new record has been inserted next
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to the cursor */
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/************************************************************************
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Updates the page hash index when a single record is inserted on a page. */
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void
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btr_search_update_hash_on_insert(
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/*=============================*/
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btr_cur_t* cursor);/* in: cursor which was positioned to the
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place to insert using btr_cur_search_...,
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and the new record has been inserted next
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to the cursor */
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/************************************************************************
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Updates the page hash index when a single record is deleted from a page. */
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void
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btr_search_update_hash_on_delete(
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/*=============================*/
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btr_cur_t* cursor);/* in: cursor which was positioned on the
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record to delete using btr_cur_search_...,
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the record is not yet deleted */
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/************************************************************************
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Validates the search system. */
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ibool
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btr_search_validate(void);
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/*======================*/
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/* out: TRUE if ok */
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/* The search info struct in an index */
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struct btr_search_struct{
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ulint ref_count; /* Number of blocks in this index tree
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that have search index built
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i.e. block->index points to this index.
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Protected by btr_search_latch except
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when during initialization in
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btr_search_info_create(). */
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/* The following fields are not protected by any latch.
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Unfortunately, this means that they must be aligned to
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the machine word, i.e., they cannot be turned into bit-fields. */
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page_t* root_guess; /* the root page frame when it was last time
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fetched, or NULL */
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ulint hash_analysis; /* when this exceeds BTR_SEARCH_HASH_ANALYSIS,
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the hash analysis starts; this is reset if no
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success noticed */
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ibool last_hash_succ; /* TRUE if the last search would have
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succeeded, or did succeed, using the hash
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index; NOTE that the value here is not exact:
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it is not calculated for every search, and the
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calculation itself is not always accurate! */
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ulint n_hash_potential;
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/* number of consecutive searches
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which would have succeeded, or did succeed,
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using the hash index;
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the range is 0 .. BTR_SEARCH_BUILD_LIMIT + 5 */
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/*----------------------*/
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ulint n_fields; /* recommended prefix length for hash search:
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number of full fields */
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ulint n_bytes; /* recommended prefix: number of bytes in
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an incomplete field;
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see also BTR_PAGE_MAX_REC_SIZE */
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ibool left_side; /* TRUE or FALSE, depending on whether
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the leftmost record of several records with
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the same prefix should be indexed in the
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hash index */
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/*----------------------*/
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#ifdef UNIV_SEARCH_PERF_STAT
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ulint n_hash_succ; /* number of successful hash searches thus
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far */
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ulint n_hash_fail; /* number of failed hash searches */
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ulint n_patt_succ; /* number of successful pattern searches thus
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far */
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ulint n_searches; /* number of searches */
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#endif /* UNIV_SEARCH_PERF_STAT */
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#ifdef UNIV_DEBUG
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ulint magic_n; /* magic number */
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# define BTR_SEARCH_MAGIC_N 1112765
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#endif /* UNIV_DEBUG */
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};
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/* The hash index system */
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typedef struct btr_search_sys_struct btr_search_sys_t;
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struct btr_search_sys_struct{
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hash_table_t* hash_index;
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};
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extern btr_search_sys_t* btr_search_sys;
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/* The latch protecting the adaptive search system: this latch protects the
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(1) hash index;
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(2) columns of a record to which we have a pointer in the hash index;
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but does NOT protect:
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(3) next record offset field in a record;
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(4) next or previous records on the same page.
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Bear in mind (3) and (4) when using the hash index.
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*/
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extern rw_lock_t* btr_search_latch_temp;
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#define btr_search_latch (*btr_search_latch_temp)
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#ifdef UNIV_SEARCH_PERF_STAT
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extern ulint btr_search_n_succ;
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extern ulint btr_search_n_hash_fail;
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#endif /* UNIV_SEARCH_PERF_STAT */
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/* After change in n_fields or n_bytes in info, this many rounds are waited
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before starting the hash analysis again: this is to save CPU time when there
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is no hope in building a hash index. */
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#define BTR_SEARCH_HASH_ANALYSIS 17
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/* Limit of consecutive searches for trying a search shortcut on the search
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pattern */
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#define BTR_SEARCH_ON_PATTERN_LIMIT 3
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/* Limit of consecutive searches for trying a search shortcut using the hash
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index */
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#define BTR_SEARCH_ON_HASH_LIMIT 3
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/* We do this many searches before trying to keep the search latch over calls
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from MySQL. If we notice someone waiting for the latch, we again set this
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much timeout. This is to reduce contention. */
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#define BTR_SEA_TIMEOUT 10000
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#ifndef UNIV_NONINL
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#include "btr0sea.ic"
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#endif
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#endif
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