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mariadb/sql/opt_sum.cc
unknown 01d03e7b4b This changeset is largely a handler cleanup changeset (WL#3281), but includes fixes and cleanups that was found necessary while testing the handler changes 
Changes that requires code changes in other code of other storage engines.
(Note that all changes are very straightforward and one should find all issues
by compiling a --debug build and fixing all compiler errors and all
asserts in field.cc while running the test suite),

- New optional handler function introduced: reset()
  This is called after every DML statement to make it easy for a handler to
  statement specific cleanups.
  (The only case it's not called is if force the file to be closed)

- handler::extra(HA_EXTRA_RESET) is removed. Code that was there before
  should be moved to handler::reset()

- table->read_set contains a bitmap over all columns that are needed
  in the query.  read_row() and similar functions only needs to read these
  columns
- table->write_set contains a bitmap over all columns that will be updated
  in the query. write_row() and update_row() only needs to update these
  columns.
  The above bitmaps should now be up to date in all context
  (including ALTER TABLE, filesort()).

  The handler is informed of any changes to the bitmap after
  fix_fields() by calling the virtual function
  handler::column_bitmaps_signal(). If the handler does caching of
  these bitmaps (instead of using table->read_set, table->write_set),
  it should redo the caching in this code. as the signal() may be sent
  several times, it's probably best to set a variable in the signal
  and redo the caching on read_row() / write_row() if the variable was
  set.

- Removed the read_set and write_set bitmap objects from the handler class

- Removed all column bit handling functions from the handler class.
  (Now one instead uses the normal bitmap functions in my_bitmap.c instead
  of handler dedicated bitmap functions)

- field->query_id is removed. One should instead instead check
  table->read_set and table->write_set if a field is used in the query.

- handler::extra(HA_EXTRA_RETRIVE_ALL_COLS) and
  handler::extra(HA_EXTRA_RETRIEVE_PRIMARY_KEY) are removed. One should now
  instead use table->read_set to check for which columns to retrieve.

- If a handler needs to call Field->val() or Field->store() on columns
  that are not used in the query, one should install a temporary
  all-columns-used map while doing so. For this, we provide the following
  functions:

  my_bitmap_map *old_map= dbug_tmp_use_all_columns(table, table->read_set);
  field->val();
  dbug_tmp_restore_column_map(table->read_set, old_map);

  and similar for the write map:

  my_bitmap_map *old_map= dbug_tmp_use_all_columns(table, table->write_set);
  field->val();
  dbug_tmp_restore_column_map(table->write_set, old_map);

  If this is not done, you will sooner or later hit a DBUG_ASSERT
  in the field store() / val() functions.
  (For not DBUG binaries, the dbug_tmp_restore_column_map() and
  dbug_tmp_restore_column_map() are inline dummy functions and should
  be optimized away be the compiler).

- If one needs to temporary set the column map for all binaries (and not
  just to avoid the DBUG_ASSERT() in the Field::store() / Field::val()
  methods) one should use the functions tmp_use_all_columns() and
  tmp_restore_column_map() instead of the above dbug_ variants.

- All 'status' fields in the handler base class (like records,
  data_file_length etc) are now stored in a 'stats' struct. This makes
  it easier to know what status variables are provided by the base
  handler.  This requires some trivial variable names in the extra()
  function.

- New virtual function handler::records().  This is called to optimize
  COUNT(*) if (handler::table_flags() & HA_HAS_RECORDS()) is true.
  (stats.records is not supposed to be an exact value. It's only has to
  be 'reasonable enough' for the optimizer to be able to choose a good
  optimization path).

- Non virtual handler::init() function added for caching of virtual
  constants from engine.

- Removed has_transactions() virtual method. Now one should instead return
  HA_NO_TRANSACTIONS in table_flags() if the table handler DOES NOT support
  transactions.

- The 'xxxx_create_handler()' function now has a MEM_ROOT_root argument
  that is to be used with 'new handler_name()' to allocate the handler
  in the right area.  The xxxx_create_handler() function is also
  responsible for any initialization of the object before returning.

  For example, one should change:

  static handler *myisam_create_handler(TABLE_SHARE *table)
  {
    return new ha_myisam(table);
  }

  ->

  static handler *myisam_create_handler(TABLE_SHARE *table, MEM_ROOT *mem_root)
  {
    return new (mem_root) ha_myisam(table);
  }

- New optional virtual function: use_hidden_primary_key().
  This is called in case of an update/delete when
  (table_flags() and HA_PRIMARY_KEY_REQUIRED_FOR_DELETE) is defined
  but we don't have a primary key. This allows the handler to take precisions
  in remembering any hidden primary key to able to update/delete any
  found row. The default handler marks all columns to be read.

- handler::table_flags() now returns a ulonglong (to allow for more flags).

- New/changed table_flags()
  - HA_HAS_RECORDS	    Set if ::records() is supported
  - HA_NO_TRANSACTIONS	    Set if engine doesn't support transactions
  - HA_PRIMARY_KEY_REQUIRED_FOR_DELETE
                            Set if we should mark all primary key columns for
			    read when reading rows as part of a DELETE
			    statement. If there is no primary key,
			    all columns are marked for read.
  - HA_PARTIAL_COLUMN_READ  Set if engine will not read all columns in some
			    cases (based on table->read_set)
 - HA_PRIMARY_KEY_ALLOW_RANDOM_ACCESS
   			    Renamed to HA_PRIMARY_KEY_REQUIRED_FOR_POSITION.
 - HA_DUPP_POS              Renamed to HA_DUPLICATE_POS
 - HA_REQUIRES_KEY_COLUMNS_FOR_DELETE
			    Set this if we should mark ALL key columns for
			    read when when reading rows as part of a DELETE
			    statement. In case of an update we will mark
			    all keys for read for which key part changed
			    value.
  - HA_STATS_RECORDS_IS_EXACT
			     Set this if stats.records is exact.
			     (This saves us some extra records() calls
			     when optimizing COUNT(*))
			    

- Removed table_flags()
  - HA_NOT_EXACT_COUNT     Now one should instead use HA_HAS_RECORDS if
			   handler::records() gives an exact count() and
			   HA_STATS_RECORDS_IS_EXACT if stats.records is exact.
  - HA_READ_RND_SAME	   Removed (no one supported this one)

- Removed not needed functions ha_retrieve_all_cols() and ha_retrieve_all_pk()

- Renamed handler::dupp_pos to handler::dup_pos

- Removed not used variable handler::sortkey


Upper level handler changes:

- ha_reset() now does some overall checks and calls ::reset()
- ha_table_flags() added. This is a cached version of table_flags(). The
  cache is updated on engine creation time and updated on open.


MySQL level changes (not obvious from the above):

- DBUG_ASSERT() added to check that column usage matches what is set
  in the column usage bit maps. (This found a LOT of bugs in current
  column marking code).

- In 5.1 before, all used columns was marked in read_set and only updated
  columns was marked in write_set. Now we only mark columns for which we
  need a value in read_set.

- Column bitmaps are created in open_binary_frm() and open_table_from_share().
  (Before this was in table.cc)

- handler::table_flags() calls are replaced with handler::ha_table_flags()

- For calling field->val() you must have the corresponding bit set in
  table->read_set. For calling field->store() you must have the
  corresponding bit set in table->write_set. (There are asserts in
  all store()/val() functions to catch wrong usage)

- thd->set_query_id is renamed to thd->mark_used_columns and instead
  of setting this to an integer value, this has now the values:
  MARK_COLUMNS_NONE, MARK_COLUMNS_READ, MARK_COLUMNS_WRITE
  Changed also all variables named 'set_query_id' to mark_used_columns.

- In filesort() we now inform the handler of exactly which columns are needed
  doing the sort and choosing the rows.

- The TABLE_SHARE object has a 'all_set' column bitmap one can use
  when one needs a column bitmap with all columns set.
  (This is used for table->use_all_columns() and other places)

- The TABLE object has 3 column bitmaps:
  - def_read_set     Default bitmap for columns to be read
  - def_write_set    Default bitmap for columns to be written
  - tmp_set          Can be used as a temporary bitmap when needed.
  The table object has also two pointer to bitmaps read_set and write_set
  that the handler should use to find out which columns are used in which way.

- count() optimization now calls handler::records() instead of using
  handler->stats.records (if (table_flags() & HA_HAS_RECORDS) is true).

- Added extra argument to Item::walk() to indicate if we should also
  traverse sub queries.

- Added TABLE parameter to cp_buffer_from_ref()

- Don't close tables created with CREATE ... SELECT but keep them in
  the table cache. (Faster usage of newly created tables).


New interfaces:

- table->clear_column_bitmaps() to initialize the bitmaps for tables
  at start of new statements.

- table->column_bitmaps_set() to set up new column bitmaps and signal
  the handler about this.

- table->column_bitmaps_set_no_signal() for some few cases where we need
  to setup new column bitmaps but don't signal the handler (as the handler
  has already been signaled about these before). Used for the momement
  only in opt_range.cc when doing ROR scans.

- table->use_all_columns() to install a bitmap where all columns are marked
  as use in the read and the write set.

- table->default_column_bitmaps() to install the normal read and write
  column bitmaps, but not signaling the handler about this.
  This is mainly used when creating TABLE instances.

- table->mark_columns_needed_for_delete(),
  table->mark_columns_needed_for_delete() and
  table->mark_columns_needed_for_insert() to allow us to put additional
  columns in column usage maps if handler so requires.
  (The handler indicates what it neads in handler->table_flags())

- table->prepare_for_position() to allow us to tell handler that it
  needs to read primary key parts to be able to store them in
  future table->position() calls.
  (This replaces the table->file->ha_retrieve_all_pk function)

- table->mark_auto_increment_column() to tell handler are going to update
  columns part of any auto_increment key.

- table->mark_columns_used_by_index() to mark all columns that is part of
  an index.  It will also send extra(HA_EXTRA_KEYREAD) to handler to allow
  it to quickly know that it only needs to read colums that are part
  of the key.  (The handler can also use the column map for detecting this,
  but simpler/faster handler can just monitor the extra() call).

- table->mark_columns_used_by_index_no_reset() to in addition to other columns,
  also mark all columns that is used by the given key.

- table->restore_column_maps_after_mark_index() to restore to default
  column maps after a call to table->mark_columns_used_by_index().

- New item function register_field_in_read_map(), for marking used columns
  in table->read_map. Used by filesort() to mark all used columns

- Maintain in TABLE->merge_keys set of all keys that are used in query.
  (Simplices some optimization loops)

- Maintain Field->part_of_key_not_clustered which is like Field->part_of_key
  but the field in the clustered key is not assumed to be part of all index.
  (used in opt_range.cc for faster loops)

-  dbug_tmp_use_all_columns(), dbug_tmp_restore_column_map()
   tmp_use_all_columns() and tmp_restore_column_map() functions to temporally
   mark all columns as usable.  The 'dbug_' version is primarily intended
   inside a handler when it wants to just call Field:store() & Field::val()
   functions, but don't need the column maps set for any other usage.
   (ie:: bitmap_is_set() is never called)

- We can't use compare_records() to skip updates for handlers that returns
  a partial column set and the read_set doesn't cover all columns in the
  write set. The reason for this is that if we have a column marked only for
  write we can't in the MySQL level know if the value changed or not.
  The reason this worked before was that MySQL marked all to be written
  columns as also to be read. The new 'optimal' bitmaps exposed this 'hidden
  bug'.

- open_table_from_share() does not anymore setup temporary MEM_ROOT
  object as a thread specific variable for the handler. Instead we
  send the to-be-used MEMROOT to get_new_handler().
  (Simpler, faster code)



Bugs fixed:

- Column marking was not done correctly in a lot of cases.
  (ALTER TABLE, when using triggers, auto_increment fields etc)
  (Could potentially result in wrong values inserted in table handlers
  relying on that the old column maps or field->set_query_id was correct)
  Especially when it comes to triggers, there may be cases where the
  old code would cause lost/wrong values for NDB and/or InnoDB tables.

- Split thd->options flag OPTION_STATUS_NO_TRANS_UPDATE to two flags:
  OPTION_STATUS_NO_TRANS_UPDATE and OPTION_KEEP_LOG.
  This allowed me to remove some wrong warnings about:
  "Some non-transactional changed tables couldn't be rolled back"

- Fixed handling of INSERT .. SELECT and CREATE ... SELECT that wrongly reset
  (thd->options & OPTION_STATUS_NO_TRANS_UPDATE) which caused us to loose
  some warnings about
  "Some non-transactional changed tables couldn't be rolled back")

- Fixed use of uninitialized memory in ha_ndbcluster.cc::delete_table()
  which could cause delete_table to report random failures.

- Fixed core dumps for some tests when running with --debug

- Added missing FN_LIBCHAR in mysql_rm_tmp_tables()
  (This has probably caused us to not properly remove temporary files after
  crash)

- slow_logs was not properly initialized, which could maybe cause
  extra/lost entries in slow log.

- If we get an duplicate row on insert, change column map to read and
  write all columns while retrying the operation. This is required by
  the definition of REPLACE and also ensures that fields that are only
  part of UPDATE are properly handled.  This fixed a bug in NDB and
  REPLACE where REPLACE wrongly copied some column values from the replaced
  row.

- For table handler that doesn't support NULL in keys, we would give an error
  when creating a primary key with NULL fields, even after the fields has been
  automaticly converted to NOT NULL.

- Creating a primary key on a SPATIAL key, would fail if field was not
  declared as NOT NULL.


Cleanups:

- Removed not used condition argument to setup_tables

- Removed not needed item function reset_query_id_processor().

- Field->add_index is removed. Now this is instead maintained in
  (field->flags & FIELD_IN_ADD_INDEX)

- Field->fieldnr is removed (use field->field_index instead)

- New argument to filesort() to indicate that it should return a set of
  row pointers (not used columns). This allowed me to remove some references
  to sql_command in filesort and should also enable us to return column
  results in some cases where we couldn't before.

- Changed column bitmap handling in opt_range.cc to be aligned with TABLE
  bitmap, which allowed me to use bitmap functions instead of looping over
  all fields to create some needed bitmaps. (Faster and smaller code)

- Broke up found too long lines

- Moved some variable declaration at start of function for better code
  readability.

- Removed some not used arguments from functions.
  (setup_fields(), mysql_prepare_insert_check_table())

- setup_fields() now takes an enum instead of an int for marking columns
   usage.

- For internal temporary tables, use handler::write_row(),
  handler::delete_row() and handler::update_row() instead of
  handler::ha_xxxx() for faster execution.

- Changed some constants to enum's and define's.

- Using separate column read and write sets allows for easier checking
  of timestamp field was set by statement.

- Remove calls to free_io_cache() as this is now done automaticly in ha_reset()

- Don't build table->normalized_path as this is now identical to table->path
  (after bar's fixes to convert filenames)

- Fixed some missed DBUG_PRINT(.."%lx") to use "0x%lx" to make it easier to
  do comparision with the 'convert-dbug-for-diff' tool.


Things left to do in 5.1:

- We wrongly log failed CREATE TABLE ... SELECT in some cases when using
  row based logging (as shown by testcase binlog_row_mix_innodb_myisam.result)
  Mats has promised to look into this.

- Test that my fix for CREATE TABLE ... SELECT is indeed correct.
  (I added several test cases for this, but in this case it's better that
  someone else also tests this throughly).
  Lars has promosed to do this.


BitKeeper/etc/ignore:
  added mysys/test_bitmap
include/base64.h:
  Removed my_global.h, as this must be included first in any program
include/heap.h:
  Added heap_reset() (Required by new handler interface)
include/my_base.h:
  Removed HA_EXTRA_RESET. MySQL will now call ::reset() instead of ::extra(HA_EXTRA_RESET).
  HA_EXTRA_RETRIVE_ALL_COLS and HA_EXTRA_RETRIVE_PRIMARY key are deleted as the column bitmaps makes these unnecessary
include/my_bitmap.h:
  Remove my_pthread.h (should be included at upper level)
  Introduced my_bitmap_map typedef to make it the bitmap handling more like a black box
  Added bitmap_is_overlapping(), bitmap_test_and_clear(), bitmap_copy() and bitmap_cmp()
  Made bitmap_set_bit(), bitmap_flip_bit(), bitmap_clear_bit() return void
include/myisam.h:
  Added mi_reset() (Required by new handler interface)
include/myisammrg.h:
  Added myrg_reset() (Required by new handler interface)
include/mysql_com.h:
  Added flag FIELD_IN_ADD_INDEX to be able to remove Field->add_index
mysql-test/extra/binlog_tests/mix_innodb_myisam_binlog.test:
  Added testing of CREATE ... SELECT in a mixed environment
  (This found some bugs that Mats is going to fix shortly)
mysql-test/install_test_db.sh:
  Simplify ldata usage
  Added --tmpdir=. option to mysqld bootstrap (Removed some warnings when TMPDIR was wrongly set)
mysql-test/mysql-test-run.pl:
  Added --tmpdir=. to bootstrap
mysql-test/mysql-test-run.sh:
  Use copy instead of INSTALL_DB for master and slave databases.
  (Speeds up startup time a lot!)
  Remove snapshot directories at startup (removes some strange warnings)
mysql-test/r/binlog_row_mix_innodb_myisam.result:
  Added testing of CREATE ... SELECT in a mixed environment
  (This found some bugs that Mats is going to fix shortly)
mysql-test/r/binlog_stm_mix_innodb_myisam.result:
  Added testing of CREATE ... SELECT in a mixed environment
mysql-test/r/create.result:
  Some extra tests of warnings and number of tables opened by CREATE ... SELECT
mysql-test/r/federated.result:
  Drop some left over tables
  Added testing of multiple table update and multiple table delete (with and without keys)
mysql-test/r/func_gconcat.result:
  Enable some disabled tests (converted them slightly to be predictable)
mysql-test/r/func_time.result:
  Added drop of test function
mysql-test/r/innodb_mysql.result:
  Added tests for CREATE ... SELECT
mysql-test/r/insert.result:
  More tests
  Added testing of duplicate columns in insert
mysql-test/r/loaddata.result:
  Added testing LOAD DATA ... SET ...
mysql-test/r/multi_update.result:
  Test multi updates and deletes using primary key and without
mysql-test/r/ndb_index_unique.result:
  Better error message
mysql-test/r/ndb_replace.result:
  New correct result after fixing REPLACE handling with NDB
mysql-test/r/rpl_ddl.result:
  Now we don't get these (wrong) warnings anymore
mysql-test/r/view_grant.result:
  Drop used views
mysql-test/t/create.test:
  Some extra tests of warnings and number of tables opened by CREATE ... SELECT
mysql-test/t/federated.test:
  Drop some left over tables
  Added testing of multiple table update and multiple table delete (with and without keys)
mysql-test/t/func_gconcat.test:
  Enable some disabled tests (converted them slightly to be predictable)
mysql-test/t/func_time.test:
  Added drop of test function
mysql-test/t/innodb_mysql.test:
  Added tests for CREATE ... SELECT
mysql-test/t/insert.test:
  More tests
  Added testing of duplicate columns in insert
mysql-test/t/loaddata.test:
  Added testing LOAD DATA ... SET ...
mysql-test/t/multi_update.test:
  Test multi updates and deletes using primary key and without
mysql-test/t/view_grant.test:
  Drop used views
mysql-test/valgrind.supp:
  Added supression of not needed warnings when printing stack trace
mysys/base64.c:
  Include my_global.h first
mysys/my_bitmap.c:
  Added bitmap_is_overlapping(), bitmap_test_and_clear() and bitmap_copy()
  Changed logic of bitmap handling to be a bit more efficent (Did this together with Mikael Ronström)
  Now the 'extra, not used bits' in the bitmap are assumed to have a 'random value' and the bitmap functions are free to change them whenever needed.
  Changed how mutex is allocated to make 'bitmap_free()' function simpler.
mysys/thr_lock.c:
  Added 0x before thread pointers (for easier comparison of DBUG traces)
sql/event.cc:
  Ensure 'use_all_columns()' is used for event tables
  Don't print warning that event table is damaged if it doesn't exists.
sql/field.cc:
  Added ASSERT_COLUMN_MARKED_FOR_WRITE in all store() methods and ASSERT_COLUMN_MARKED_FOR_READ in all val() methods to catch wrong setting if table->read_set and table->write_set
  (Rest of changes are only indentation cleanups)
sql/field.h:
  Removed Field->query_id (replaced by table->read_set and table->write_set)
  Removed Field->fieldnr (use Field->field_index instead)
  Removed Field->add_index (Use Field->flags instead)
  Add Field->part_of_key_not_clustered (for usage in opt_range.cc)
sql/filesort.cc:
  Added paramater sort_postion to filesort() to force sorting by position instead of storing all fields in the result set.
  This allowed me to remove checking of sql_command.
  Create a temporary column bitmap for fields that are used by the sorting process.
  Use column bitmaps instead of query_id
sql/ha_berkeley.cc:
  Update to 'newer' table handler interface
sql/ha_berkeley.h:
  Update to 'newer' table handler interface
sql/ha_federated.cc:
  Update to 'newer' table handler interface
  Only read columns that are needed from remote server.
  In case of eq ranges, don't generate two conditions in the WHERE clause
  (this can still be optimized, but would require a bigger code change)
  Use 'simpler to use' XXXX_LEN' macros
  A bit simpler logic in ::write_row() when creating statements.
  In update, only include test of fields actually read.
  (This greatly simplifies the queries sent by the federated engine)
  Similar changes done for delete_row()
sql/ha_federated.h:
  Update to 'newer' table handler interface
  Changed XXX_LEN macros to use sizeof(...)-1, to simplify usage in ha_federated.cc
  Added HA_PRIMARY_KEY_REQUIRED_FOR_DELETE to tell MySQL to read all primary key columns in case of DELETE
sql/ha_heap.cc:
  Update to 'newer' table handler interface
sql/ha_heap.h:
  Update to 'newer' table handler interface
sql/ha_innodb.cc:
  Update to 'newer' table handler interface
  - Update innobase_create_handler() to new interface
  - Removed HA_NOT_EXACT_COUNT (not needed)
  - Renamed HA_PRIMARY_KEY_ALLOW_RANDOM_ACCESS to HA_PRIMARY_KEY_REQUIRED_FOR_POSITION.
  - Prefixed base status variables with 'stats'
  - Use table column bitmaps instead of ha_get_bit_in_read_set()
  - Added ::reset(), with code from ::extra(HA_EXTRA_RESET)
  - Removed HA_EXTRA_RETRIVE_ALL_COLS and HA_EXTRA_RETRIEVE_PRIMARY_KEY as
    the table->read_set and table->write_set bitmaps now are accurate
sql/ha_innodb.h:
  Update to 'newer' table handler interface
  - table_flags are now ulonglong
  - Added reset() method
  - Removed not needed ha_retrieve_all_cols() and ha_retrieve_all_pk() columns.
  - Made build_template() a class function to be able to easier access class variables
sql/ha_myisam.cc:
  Update to 'newer' table handler interface
sql/ha_myisam.h:
  Update to 'newer' table handler interface
sql/ha_myisammrg.cc:
  Update to 'newer' table handler interface
sql/ha_myisammrg.h:
  Update to 'newer' table handler interface
sql/ha_ndbcluster.cc:
  Update to 'newer' table handler interface
  Fixed use_blob_value() to be accurate
  In ::complemented_read() we have to check both the read and write bitmap as the old code did mark all changed columns also in the read map
  Correct dumping of field data with DBUG_DUMP
  Prefix addresses in DBUG_PRINT with 0x
  Fixed usage of not initialized memory
  Update to use field->flags & FIELD_IN_ADD_INDEX instead of field->add_index.
sql/ha_ndbcluster.h:
  Update to 'newer' table handler interface
sql/ha_ndbcluster_binlog.cc:
  Mark usage of all columns in ndbcluster binlog tables
  false -> FALSE, true -> TRUE
  Use table->s->all_set instead of creating a temporary bitmap.
sql/ha_partition.cc:
  Update to 'newer' table handler interface
  Added memroot to initialise_partitions() and related functions to get faster memory allocation.
  partition_create_handler() is now responsible for initialisation of the partition object
  Some trivial optimizations and indentation fixes
  Ensure that table_flags() are up to date
  Removed documentation for removed HA_EXTRA flags
  Fixed 'strange' usage of m_file[i] in new_handlers_from_part_info()that worked in current code 'by chance'
sql/ha_partition.h:
  Update to 'newer' table handler interface
sql/handler.cc:
  create_xxx handler now takes MEMROOT as an argument to simplify memory allocation.
  Much simpler get_new_handler()
  (Initialization of the object is now handled by the create method for the engine)
  Moved all allocation of bitmap handling to the TABLE object (in table.cc)
  Added column_bitmaps_signal() to signal column usage changes.
  Changed binlog_log_row() to use the exiusting all_set bitmap in the table object.
  Added ha_reset() function to test that the file object is ok at end of statement and call handler::reset()
  Added use_hidden_primary_key() to signal handler that we we are going to read and update + delete the row and the handler should thus remember the position for the row
sql/handler.h:
  Added HA_NO_TRANSACTIONS, HA_PARTIAL_COLUMN_READ, HA_REQUIRES_KEY_COLUMNS_FOR_DELETE,HA_PRIMARY_KEY_REQUIRED_FOR_DELETE and HA_HAS_RECORDS
  Removed HA_NOT_EXACT_COUNT, HA_READ_RND_SAME
  HA_DUPP_POS -> HA_DUPLICATE_POS
  HA_NOT_EXACT_COUNT replaced by HA_STATS_RECORDS_IS_EXACT, HA_HAS_RECORDS and records()
  HA_PRIMARY_KEY_ALLOW_RANDOM_ACCESS renamed to HA_PRIMARY_KEY_REQUIRED_FOR_POSITION
  Added future row type 'ROW_TYPE_PAGES'
  Added MEM_ROOT to handlerton 'create' function
  Added ha_statistics, a structure for all status variable in the base handler class.
  Moved all status variables in the handler class into a stats structs to improve readability.
  ha_table_flags() is now a cached (not virtual) version of table_flags()
  reset() doesn't anymore call extra(HA_EXTRA_RESET) but is a function of it's own.
  Renamed dupp_ref to dup_ref
  Renamed not used handler::sortkey
  Moved read_set and write_set to TABLE structure
  handler::init() function added for cacheing of virtual constants from engine.
sql/item.cc:
  Added register_field_in_read_map() for marking used columns in expression.
  This is used by filesort() for creating an optimal column bitmap while retrieving columns for sorting.
  Initalize value.cs_info.character_set_client to fix core dump bug with --debug
  set_query_id -> mark_used_columns
  Mark used columns in read_set OR write_set.
sql/item.h:
  Removed reset_query_id_processor() as it's not needed anymore.
  Added register_field_in_read_map()
  Added extra argument to Item::walk() to indicate if we should also
  traverse sub queries.
sql/item_cmpfunc.cc:
  Temporary mark used columns to be read/writable
  Update Item::walk to new interface
sql/item_cmpfunc.h:
  Added extra argument to Item::walk() to indicate if we should also traverse sub queries.
sql/item_func.cc:
  Update Item::walk() to new interface
  table_flags() -> ha_table_flags()
sql/item_func.h:
  Update Item::walk() to new interface
sql/item_row.cc:
  Update Item::walk() to new interface
sql/item_row.h:
  Update Item::walk() to new interface
sql/item_strfunc.h:
  Update Item::walk() to new interface
sql/item_subselect.cc:
  Added Item_subselect::walk()
  (It was a bug it was missing before. Not sure what kind of bugs this could have caused)
sql/item_subselect.h:
  Update Item::walk() to new interface
sql/item_sum.cc:
  Update Item::walk() to new interface
  Updates for new handler interace
sql/item_sum.h:
  Update Item::walk() to new interface
sql/key.cc:
  Updates for new handler interace
sql/log.cc:
  Mark all columns used for log tables
  Split options flag
  Ensured that second argument to trans_register_ha is a bool
sql/log_event.cc:
  Fixed comments to be withing 79 characters
  Use OPTION_KEEP_LOG instead of OPTION_STATUS_NO_TRANS_UPDATE to remove wrong warnings
  Updates for new handler interface
  Use 0x%lx instead of %p (portability problem)
sql/mysql_priv.h:
  Added OPTION_KEEP_LOG to indicate that we should replicate the binlog even on rollback
  Removed not used 'conds' argument to setup_tables
sql/mysqld.cc:
  Indentation fixes and removed old comment
sql/opt_range.cc:
  Update to new handler and bitmap interface.
  Fixed calls to cp_buffer_from_ref() and walk() (new argument).
  Create new temporary bitmaps for ror scans.
  (Needed because of handler changes and to get more accurate column bitmaps than before)
  Remove not needed file->ha_reset() call before file->close().
  Some trivial optimization and indentation fixes.
  Use Field->part_of_key_not_clustered() to check if field is part of a key, instead of looping over all key parts.
  
  Added flag 'in_ror_merged_scan' to allow ::get_next() to know that we need a special column bitmap to only fetch pointer to record.
  This is needed because ror scan uses the same TABLE object but different file objects, which creates problem for the column bitmap handling.
  (This is a temporary solution. A better one would be to allocate an own TABLE object for ROR scans)
  
  Optimized bitmap handling in ror scans:
  - Start bitmap at position 0, not 1
  - Use same bitmap size as in TABLE
  - Use table->read_set and table->write_set to create column bitmaps instead of looping over all fields in table
sql/opt_range.h:
  Added 'in_ror_merged_scan' to indicate if we are doing a ROR scan
  Added temporary column bitmaps used in ROR scans
sql/opt_sum.cc:
  Added get_ext_record_count() which is used in COUNT() optimization if handler has HA_HAS_RECORDS
  Note that we don't call this if handler has HA_STATS_RECORDS_IS_EXACT set.
sql/protocol.cc:
  We need to mark columns as readable in ::store() as we sometimes return default value for fields to the user
sql/records.cc:
  Updates for new handler interface
sql/set_var.cc:
  Handle splitting OPTION_STATUS_NO_TRANS_UPDATE to two flags
sql/share/errmsg.txt:
  Fixed wrong
sql/sp.cc:
  Mark that we are using all columns for the proc table
  Update call to setup_tables() to use new prototype
sql/sp_head.cc:
  Removed QQ comment
sql/spatial.cc:
  Removed wrong QQ comment
sql/sql_acl.cc:
  Mark that we need all columns for acl tables
  Supply memroot to some 'new' calls.
  Indentation fixes
sql/sql_base.cc:
  set_query_id removed
  Ensure we call ha_reset() at end of each statement
  Mark read columns in read_set and changed columns in write_set (Before all columns was marked in read set)
  Fixed marking of some columns that was not proplerly marked before
  Maintain in TABLE->merge_keys set of all keys that are used in some way
  Removed not used 'conds' argument from setup_tables()
  Remove not used setting of 'dupp_field' in insert_fields()
  Added missing FN_LIBCHAR in mysql_rm_tmp_tables()
  (This has probably caused us to not properly remove temporary files after crash)
sql/sql_bitmap.h:
  Added is_overlapping()
sql/sql_class.cc:
  Slow_logs was not properly initialized, which could maybe cause extra/lost entries in slow log.
  set_query_id -> mark_used_columns
  Simpler variable usage in pack_row()  (cleanup)
  Moved some variable declartion at start of function for better code readability
sql/sql_class.h:
  Added enum_mark_columns
  Updated comments
  Renamed dupp_field -> dup_field
  Added virtual function 'can_rollback_data()' to select_insert() to be used in CREATE ... SELECT to optimize use of OPTION_STATUS_NO_TRANS_UPDATE.
  (This fixes a bug in CREATE ... SELECT where we did give wrong warnings when using non transacational tables)
sql/sql_delete.cc:
  Updates to new handler interface
  Call table->mark_columns_needed_for_delete() to allow us to put additional columns in column usage maps if handler so requires.
  Call table->prepare_for_position() to tell handler that we are going to call ha_position().
  Removed call to free_io_cache(). (io_cache is now removed in ha_reset()).
  Fixed calls to setup_tables()
sql/sql_do.cc:
  Update call to setup_fields()
sql/sql_handler.cc:
  Tell handler tables to always read all columns.
  Use temporary column map when storing value in field for later index usage
sql/sql_help.cc:
  Makr all used fields to be read
  Update call to setup_fields()
sql/sql_insert.cc:
  Tell handler we are going to update the auto_increment column
  dupp_field -> dup_field
  Set column usage bits for timestamp field.
  Call table->mark_columns_needed_for_insert() and table->mark_auto_increment_column()
  Removed not used argument from mysql_prepare_insert_check_table().
  
  If we get an duplicate row on insert, change column map to read and write all columns while retrying the operatation.
  This is required by the definition of REPLACE and also ensures that fields that are only part of UPDATE are properly handled.
  This fixed a bug in NDB and REPLACE where REPLACE wrongly copied some column values from the replaced row.
  
  Setup new bitmaps for delayed insert rows
  Remove reseting of next_number_fields as it will be reset on next call to handler_insert()
  
  Fixed usage of thd->options and OPTION_STATUS_NO_TRANS_UPDATE.
  The issue was that one should not to reset this flag as it may be set by a previous statement.
  The way it was now used caused us to loose some warnings and get other wrong warnings when using non transactional tables mixed with transactional.
  I fixed it by introducing 'select_insert::can_rollback_data' to inform send_error() that the given statement can be rolled back (which in case of CREATE TABLE can always be done)
  Don't close tables created with CREATE ... SELECT but keep them in the table cache.
  
  Moved out MY_HOOKS from inside function (better readability)
sql/sql_load.cc:
  Update to use new handler and column marking interface
  Update using setup_tables()
sql/sql_olap.cc:
  Update calls to setup_tables
  Use enums instead of constants to setup_fields()
sql/sql_parse.cc:
  Handle OPTION_KEEP_LOG:
  - Set it on CREATE TEMPORARY TABLE / DROP TABLE
  - Reset it when OPTION_STATUS_NO_TRANS_UPDATE is reset
  - Don't set it for CREATE ... SELECT (this is handled in select_create class)
  Remove reseting of OPTION_STATUS_NO_TRANS_UPDATE in begin_trans() as this should already be reset.
  If in autocommit mode, reset OPTION_KEEP_LOG and OPTION_STATUS_NO_TRANS_UPDATE to not give warnings in future commands
sql/sql_partition.cc:
  Update walk() usage
  Trivial indentation fixes
sql/sql_plugin.cc:
  Mark all columns as used for plugins
sql/sql_prepare.cc:
  Added assert to find out hidden bugs in character_set_client (got an error in debug binary when this not set correctly)
  Updates for new handler interface
  Update calls to setup_fields()
sql/sql_repl.cc:
  Indentation fixes
sql/sql_select.cc:
  Update call to setup_tables() and setup_fields()
  Remove some old disabled code
  Update to new hadler interface
  Indentation cleanups
  Added column bitmaps for temporary tables.
  Remove updating of the removed slots in the Field class
  Added TABLE argument to cp_buffer_from_ref() (To be able to install temporary column maps)
  For internal temporary tables, use handler::write_row(), handler::delete_row() and handler::update_row() instead of handler::ha_xxxx() for faster execution.
sql/sql_select.h:
  Indentaition fixes.
  Install temporary column usage maps when needed
  Added TABLE element to cp_buffer_from_ref()
sql/sql_show.cc:
  Update to new handler interface
  Mark all columns used for internal tables.
  Style fixes.
  Added support for 'future' ROW_TYPE_PAGES.
  Don't allocate TMP_TABLE_PARAM with calloc. The 'init()' function will initialize the structure properly.
sql/sql_table.cc:
  Update to new handler interface
  Simple my_snprintf -> strmake()
  Changed some constants to defines
  Don't test for NULL in primary key (as we a couple of line above force the PRIMARY KEY to be NOT NULL)
  Change field->add_index to use field->flags & FIELD_IN_ADD_INDEX
  Mark all columns as used for ALTER TABLE
  Style fixes
  Update call to filesort()
sql/sql_trigger.h:
  Added friend functions to be able to test if triggers exists for table we are going to insert/update or delete in.
sql/sql_udf.cc:
  Mark all columns as used for udf system table.
sql/sql_union.cc:
  Update call to walk()
  Update to new handler interface
sql/sql_update.cc:
  Remove query_id argument from compare_record()
  Use column bitmaps instead of query_id.
  We can't use compare_records() to skip updates for handlers that returns a partial column set and the read_set doesn't cover all columns in the write set, because compare_record() can't in this case know if a not read column changed value.
  Update call to setup_fields()
  Using separate column read and write sets allows for easier checking of timestamp field was set by statement.
  Removed call to free_io_cache() as this is now done in ha_reset()
  Call table->mark_columns_needed_for_update() and table->prepare_for_position()
  Style fixes
sql/sql_view.cc:
  Style fixes
sql/table.cc:
  Remove implicitely include 'errno.h'
  Remove code for building normalized path, as this is now identical to 'path'
  Remove field->fieldnr
  Added update of field->part_of_key_not_clustered()
  Create column bitmaps in TABLE and TABLE_SHARE
  Don't setup a temporary MEM_ROOT object as a thread specific variable for the handler. Instead we send the to-be-used MEMROOT to get_new_handler()
  Update to new handler interface
  Update call to walk()
  Added new functions:
  - st_table::clear_column_bitmaps()
  - st_table::prepare_for_position()
  - st_table::mark_columns_used_by_index()
  - st_table::restore_column_maps_after_mark_index()
  - st_table::mark_columns_used_by_index_no_reset()
  - st_table::mark_auto_increment_column()
  - st_table::mark_columns_needed_for_delete()
  - st_table::mark_columns_needed_for_update()
  - st_table::mark_columns_needed_for_insert()
sql/table.h:
  Moved column usage bitmaps from handler to TABLE
  Added to TABLE_SHARE all_set and column_bitmap_size
  Added to TABLE merge_keys, bitmap_init_values, def_read_set, def_write_set, tmp_set, read_set and write_set.
  Declared all new table column bitmap functions
  Added TABLE functions column_bitmaps_set(), column_bitmaps_set_no_signal(), use_all_columns() and default_column_bitmaps()
  Added functions: tmp_use_all_columns() and tmp_restore_column_map() to temporarly switch column bitmaps
  Added functions: dbug_tmp_use_all_columns() and dbug_tmp_restore_column_map() to temporarly switch column bitmaps to avoid asserts in Field::store() and Field::val().
sql/tztime.cc:
  Mark all columns as used for timezone tables
storage/archive/ha_archive.cc:
  Update to new handler interface
storage/archive/ha_archive.h:
  Update to new handler interface
storage/blackhole/ha_blackhole.cc:
  Update to new handler interface
storage/blackhole/ha_blackhole.h:
  Update to new handler interface
  removed not needed flag HA_DUPP_POS
storage/csv/ha_tina.cc:
  Update to new handler interface
storage/csv/ha_tina.h:
  Update to new handler interface
storage/example/ha_example.cc:
  Update to new handler interface
storage/example/ha_example.h:
  Update to new handler interface
storage/heap/hp_extra.c:
  Added heap_reset() (Required by new handler interface)
storage/heap/hp_test2.c:
  Use heap_reset()
storage/myisam/ft_boolean_search.c:
  Fixed compiler warning
storage/myisam/mi_extra.c:
  Added mi_reset() (Required by new handler interface)
storage/myisam/mi_search.c:
  Fixed DBUG_PRINT messages to use 0x%lx instead of %lx
storage/myisam/mi_test2.c:
  Use mi_reset()
storage/myisam/myisampack.c:
  Use mi_reset()
storage/myisammrg/myrg_extra.c:
  Added myrg_reset() (Required by new handler interface)
unittest/mysys/base64.t.c:
  Include my_global.h
  Don't include implictely include file 'stdlib.h'
2006-06-04 18:52:22 +03:00

884 lines
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/* Copyright (C) 2000-2003 MySQL AB
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
/*
Optimising of MIN(), MAX() and COUNT(*) queries without 'group by' clause
by replacing the aggregate expression with a constant.
Given a table with a compound key on columns (a,b,c), the following
types of queries are optimised (assuming the table handler supports
the required methods)
SELECT COUNT(*) FROM t1[,t2,t3,...]
SELECT MIN(b) FROM t1 WHERE a=const
SELECT MAX(c) FROM t1 WHERE a=const AND b=const
SELECT MAX(b) FROM t1 WHERE a=const AND b<const
SELECT MIN(b) FROM t1 WHERE a=const AND b>const
SELECT MIN(b) FROM t1 WHERE a=const AND b BETWEEN const AND const
SELECT MAX(b) FROM t1 WHERE a=const AND b BETWEEN const AND const
Instead of '<' one can use '<=', '>', '>=' and '=' as well.
Instead of 'a=const' the condition 'a IS NULL' can be used.
If all selected fields are replaced then we will also remove all
involved tables and return the answer without any join. Thus, the
following query will be replaced with a row of two constants:
SELECT MAX(b), MIN(d) FROM t1,t2
WHERE a=const AND b<const AND d>const
(assuming a index for column d of table t2 is defined)
*/
#include "mysql_priv.h"
#include "sql_select.h"
static bool find_key_for_maxmin(bool max_fl, TABLE_REF *ref, Field* field,
COND *cond, uint *range_fl,
uint *key_prefix_length);
static int reckey_in_range(bool max_fl, TABLE_REF *ref, Field* field,
COND *cond, uint range_fl, uint prefix_len);
static int maxmin_in_range(bool max_fl, Field* field, COND *cond);
/*
Get exact count of rows in all tables
SYNOPSIS
get_exact_records()
tables List of tables
NOTES
When this is called, we know all table handlers supports HA_HAS_RECORDS
or HA_STATS_RECORDS_IS_EXACT
RETURN
ULONGLONG_MAX Error: Could not calculate number of rows
# Multiplication of number of rows in all tables
*/
static ulonglong get_exact_record_count(TABLE_LIST *tables)
{
ulonglong count= 1;
for (TABLE_LIST *tl= tables; tl; tl= tl->next_leaf)
{
ha_rows tmp= tl->table->file->records();
if ((tmp == HA_POS_ERROR))
return ULONGLONG_MAX;
count*= tmp;
}
return count;
}
/*
Substitutes constants for some COUNT(), MIN() and MAX() functions.
SYNOPSIS
opt_sum_query()
tables list of leaves of join table tree
all_fields All fields to be returned
conds WHERE clause
NOTE:
This function is only called for queries with sum functions and no
GROUP BY part.
RETURN VALUES
0 No errors
1 if all items were resolved
-1 on impossible conditions
OR an error number from my_base.h HA_ERR_... if a deadlock or a lock
wait timeout happens, for example
*/
int opt_sum_query(TABLE_LIST *tables, List<Item> &all_fields,COND *conds)
{
List_iterator_fast<Item> it(all_fields);
int const_result= 1;
bool recalc_const_item= 0;
ulonglong count= 1;
bool is_exact_count= TRUE, maybe_exact_count= TRUE;
table_map removed_tables= 0, outer_tables= 0, used_tables= 0;
table_map where_tables= 0;
Item *item;
int error;
if (conds)
where_tables= conds->used_tables();
/*
Analyze outer join dependencies, and, if possible, compute the number
of returned rows.
*/
for (TABLE_LIST *tl= tables; tl; tl= tl->next_leaf)
{
TABLE_LIST *embedded;
for (embedded= tl ; embedded; embedded= embedded->embedding)
{
if (embedded->on_expr)
break;
}
if (embedded)
/* Don't replace expression on a table that is part of an outer join */
{
outer_tables|= tl->table->map;
/*
We can't optimise LEFT JOIN in cases where the WHERE condition
restricts the table that is used, like in:
SELECT MAX(t1.a) FROM t1 LEFT JOIN t2 join-condition
WHERE t2.field IS NULL;
*/
if (tl->table->map & where_tables)
return 0;
}
else
used_tables|= tl->table->map;
/*
If the storage manager of 'tl' gives exact row count as part of
statistics (cheap), compute the total number of rows. If there are
no outer table dependencies, this count may be used as the real count.
Schema tables are filled after this function is invoked, so we can't
get row count
*/
if (!(tl->table->file->ha_table_flags() & HA_STATS_RECORDS_IS_EXACT) ||
tl->schema_table)
{
maybe_exact_count&= test(!tl->schema_table &&
(tl->table->file->ha_table_flags() &
HA_HAS_RECORDS));
is_exact_count= FALSE;
count= 1; // ensure count != 0
}
else
{
tl->table->file->info(HA_STATUS_VARIABLE | HA_STATUS_NO_LOCK);
count*= tl->table->file->stats.records;
}
}
/*
Iterate through all items in the SELECT clause and replace
COUNT(), MIN() and MAX() with constants (if possible).
*/
while ((item= it++))
{
if (item->type() == Item::SUM_FUNC_ITEM)
{
Item_sum *item_sum= (((Item_sum*) item));
switch (item_sum->sum_func()) {
case Item_sum::COUNT_FUNC:
/*
If the expr in COUNT(expr) can never be null we can change this
to the number of rows in the tables if this number is exact and
there are no outer joins.
*/
if (!conds && !((Item_sum_count*) item)->args[0]->maybe_null &&
!outer_tables && maybe_exact_count)
{
if (!is_exact_count)
{
if ((count= get_exact_record_count(tables)) == ULONGLONG_MAX)
{
/* Error from handler in counting rows. Don't optimize count() */
const_result= 0;
continue;
}
is_exact_count= 1; // count is now exact
}
((Item_sum_count*) item)->make_const((longlong) count);
recalc_const_item= 1;
}
else
const_result= 0;
break;
case Item_sum::MIN_FUNC:
{
/*
If MIN(expr) is the first part of a key or if all previous
parts of the key is found in the COND, then we can use
indexes to find the key.
*/
Item *expr=item_sum->args[0];
if (expr->real_item()->type() == Item::FIELD_ITEM)
{
byte key_buff[MAX_KEY_LENGTH];
TABLE_REF ref;
uint range_fl, prefix_len;
ref.key_buff= key_buff;
Item_field *item_field= (Item_field*) (expr->real_item());
TABLE *table= item_field->field->table;
/*
Look for a partial key that can be used for optimization.
If we succeed, ref.key_length will contain the length of
this key, while prefix_len will contain the length of
the beginning of this key without field used in MIN().
Type of range for the key part for this field will be
returned in range_fl.
*/
if ((outer_tables & table->map) ||
!find_key_for_maxmin(0, &ref, item_field->field, conds,
&range_fl, &prefix_len))
{
const_result= 0;
break;
}
error= table->file->ha_index_init((uint) ref.key, 1);
if (!ref.key_length)
error= table->file->index_first(table->record[0]);
else
error= table->file->index_read(table->record[0],key_buff,
ref.key_length,
range_fl & NEAR_MIN ?
HA_READ_AFTER_KEY :
HA_READ_KEY_OR_NEXT);
if (!error && reckey_in_range(0, &ref, item_field->field,
conds, range_fl, prefix_len))
error= HA_ERR_KEY_NOT_FOUND;
if (table->key_read)
{
table->key_read= 0;
table->file->extra(HA_EXTRA_NO_KEYREAD);
}
table->file->ha_index_end();
if (error)
{
if (error == HA_ERR_KEY_NOT_FOUND || error == HA_ERR_END_OF_FILE)
return -1; // No rows matching WHERE
/* HA_ERR_LOCK_DEADLOCK or some other error */
table->file->print_error(error, MYF(0));
return(error);
}
removed_tables|= table->map;
}
else if (!expr->const_item() || !is_exact_count)
{
/*
The optimization is not applicable in both cases:
(a) 'expr' is a non-constant expression. Then we can't
replace 'expr' by a constant.
(b) 'expr' is a costant. According to ANSI, MIN/MAX must return
NULL if the query does not return any rows. Thus, if we are not
able to determine if the query returns any rows, we can't apply
the optimization and replace MIN/MAX with a constant.
*/
const_result= 0;
break;
}
if (!count)
{
/* If count == 0, then we know that is_exact_count == TRUE. */
((Item_sum_min*) item_sum)->clear(); /* Set to NULL. */
}
else
((Item_sum_min*) item_sum)->reset(); /* Set to the constant value. */
((Item_sum_min*) item_sum)->make_const();
recalc_const_item= 1;
break;
}
case Item_sum::MAX_FUNC:
{
/*
If MAX(expr) is the first part of a key or if all previous
parts of the key is found in the COND, then we can use
indexes to find the key.
*/
Item *expr=item_sum->args[0];
if (expr->real_item()->type() == Item::FIELD_ITEM)
{
byte key_buff[MAX_KEY_LENGTH];
TABLE_REF ref;
uint range_fl, prefix_len;
ref.key_buff= key_buff;
Item_field *item_field= (Item_field*) (expr->real_item());
TABLE *table= item_field->field->table;
/*
Look for a partial key that can be used for optimization.
If we succeed, ref.key_length will contain the length of
this key, while prefix_len will contain the length of
the beginning of this key without field used in MAX().
Type of range for the key part for this field will be
returned in range_fl.
*/
if ((outer_tables & table->map) ||
!find_key_for_maxmin(1, &ref, item_field->field, conds,
&range_fl, &prefix_len))
{
const_result= 0;
break;
}
error= table->file->ha_index_init((uint) ref.key, 1);
if (!ref.key_length)
error= table->file->index_last(table->record[0]);
else
error= table->file->index_read(table->record[0], key_buff,
ref.key_length,
range_fl & NEAR_MAX ?
HA_READ_BEFORE_KEY :
HA_READ_PREFIX_LAST_OR_PREV);
if (!error && reckey_in_range(1, &ref, item_field->field,
conds, range_fl, prefix_len))
error= HA_ERR_KEY_NOT_FOUND;
if (table->key_read)
{
table->key_read=0;
table->file->extra(HA_EXTRA_NO_KEYREAD);
}
table->file->ha_index_end();
if (error)
{
if (error == HA_ERR_KEY_NOT_FOUND || error == HA_ERR_END_OF_FILE)
return -1; // No rows matching WHERE
/* HA_ERR_LOCK_DEADLOCK or some other error */
table->file->print_error(error, MYF(0));
return(error);
}
removed_tables|= table->map;
}
else if (!expr->const_item() || !is_exact_count)
{
/*
The optimization is not applicable in both cases:
(a) 'expr' is a non-constant expression. Then we can't
replace 'expr' by a constant.
(b) 'expr' is a costant. According to ANSI, MIN/MAX must return
NULL if the query does not return any rows. Thus, if we are not
able to determine if the query returns any rows, we can't apply
the optimization and replace MIN/MAX with a constant.
*/
const_result= 0;
break;
}
if (!count)
{
/* If count != 1, then we know that is_exact_count == TRUE. */
((Item_sum_max*) item_sum)->clear(); /* Set to NULL. */
}
else
((Item_sum_max*) item_sum)->reset(); /* Set to the constant value. */
((Item_sum_max*) item_sum)->make_const();
recalc_const_item= 1;
break;
}
default:
const_result= 0;
break;
}
}
else if (const_result)
{
if (recalc_const_item)
item->update_used_tables();
if (!item->const_item())
const_result= 0;
}
}
/*
If we have a where clause, we can only ignore searching in the
tables if MIN/MAX optimisation replaced all used tables
We do not use replaced values in case of:
SELECT MIN(key) FROM table_1, empty_table
removed_tables is != 0 if we have used MIN() or MAX().
*/
if (removed_tables && used_tables != removed_tables)
const_result= 0; // We didn't remove all tables
return const_result;
}
/*
Test if the predicate compares a field with constants
SYNOPSIS
simple_pred()
func_item Predicate item
args out: Here we store the field followed by constants
inv_order out: Is set to 1 if the predicate is of the form
'const op field'
RETURN
0 func_item is a simple predicate: a field is compared with
constants
1 Otherwise
*/
bool simple_pred(Item_func *func_item, Item **args, bool *inv_order)
{
Item *item;
*inv_order= 0;
switch (func_item->argument_count()) {
case 0:
/* MULT_EQUAL_FUNC */
{
Item_equal *item_equal= (Item_equal *) func_item;
Item_equal_iterator it(*item_equal);
args[0]= it++;
if (it++)
return 0;
if (!(args[1]= item_equal->get_const()))
return 0;
}
break;
case 1:
/* field IS NULL */
item= func_item->arguments()[0];
if (item->type() != Item::FIELD_ITEM)
return 0;
args[0]= item;
break;
case 2:
/* 'field op const' or 'const op field' */
item= func_item->arguments()[0];
if (item->type() == Item::FIELD_ITEM)
{
args[0]= item;
item= func_item->arguments()[1];
if (!item->const_item())
return 0;
args[1]= item;
}
else if (item->const_item())
{
args[1]= item;
item= func_item->arguments()[1];
if (item->type() != Item::FIELD_ITEM)
return 0;
args[0]= item;
*inv_order= 1;
}
else
return 0;
break;
case 3:
/* field BETWEEN const AND const */
item= func_item->arguments()[0];
if (item->type() == Item::FIELD_ITEM)
{
args[0]= item;
for (int i= 1 ; i <= 2; i++)
{
item= func_item->arguments()[i];
if (!item->const_item())
return 0;
args[i]= item;
}
}
else
return 0;
}
return 1;
}
/*
Check whether a condition matches a key to get {MAX|MIN}(field):
SYNOPSIS
matching_cond()
max_fl in: Set to 1 if we are optimising MAX()
ref in/out: Reference to the structure we store the key value
keyinfo in Reference to the key info
field_part in: Pointer to the key part for the field
cond in WHERE condition
key_part_used in/out: Map of matchings parts
range_fl in/out: Says whether including key will be used
prefix_len out: Length of common key part for the range
where MAX/MIN is searched for
DESCRIPTION
For the index specified by the keyinfo parameter, index that
contains field as its component (field_part), the function
checks whether the condition cond is a conjunction and all its
conjuncts referring to the columns of the same table as column
field are one of the following forms:
- f_i= const_i or const_i= f_i or f_i is null,
where f_i is part of the index
- field {<|<=|>=|>|=} const or const {<|<=|>=|>|=} field
- field between const1 and const2
RETURN
0 Index can't be used.
1 We can use index to get MIN/MAX value
*/
static bool matching_cond(bool max_fl, TABLE_REF *ref, KEY *keyinfo,
KEY_PART_INFO *field_part, COND *cond,
key_part_map *key_part_used, uint *range_fl,
uint *prefix_len)
{
if (!cond)
return 1;
Field *field= field_part->field;
if (!(cond->used_tables() & field->table->map))
{
/* Condition doesn't restrict the used table */
return 1;
}
if (cond->type() == Item::COND_ITEM)
{
if (((Item_cond*) cond)->functype() == Item_func::COND_OR_FUNC)
return 0;
/* AND */
List_iterator_fast<Item> li(*((Item_cond*) cond)->argument_list());
Item *item;
while ((item= li++))
{
if (!matching_cond(max_fl, ref, keyinfo, field_part, item,
key_part_used, range_fl, prefix_len))
return 0;
}
return 1;
}
if (cond->type() != Item::FUNC_ITEM)
return 0; // Not operator, can't optimize
bool eq_type= 0; // =, <=> or IS NULL
bool noeq_type= 0; // < or >
bool less_fl= 0; // < or <=
bool is_null= 0;
bool between= 0;
switch (((Item_func*) cond)->functype()) {
case Item_func::ISNULL_FUNC:
is_null= 1; /* fall through */
case Item_func::EQ_FUNC:
case Item_func::EQUAL_FUNC:
eq_type= 1;
break;
case Item_func::LT_FUNC:
noeq_type= 1; /* fall through */
case Item_func::LE_FUNC:
less_fl= 1;
break;
case Item_func::GT_FUNC:
noeq_type= 1; /* fall through */
case Item_func::GE_FUNC:
break;
case Item_func::BETWEEN:
between= 1;
break;
case Item_func::MULT_EQUAL_FUNC:
eq_type= 1;
break;
default:
return 0; // Can't optimize function
}
Item *args[3];
bool inv;
/* Test if this is a comparison of a field and constant */
if (!simple_pred((Item_func*) cond, args, &inv))
return 0;
if (inv && !eq_type)
less_fl= 1-less_fl; // Convert '<' -> '>' (etc)
/* Check if field is part of the tested partial key */
byte *key_ptr= ref->key_buff;
KEY_PART_INFO *part;
for (part= keyinfo->key_part;
;
key_ptr+= part++->store_length)
{
if (part > field_part)
return 0; // Field is beyond the tested parts
if (part->field->eq(((Item_field*) args[0])->field))
break; // Found a part od the key for the field
}
bool is_field_part= part == field_part;
if (!(is_field_part || eq_type))
return 0;
key_part_map org_key_part_used= *key_part_used;
if (eq_type || between || max_fl == less_fl)
{
uint length= (key_ptr-ref->key_buff)+part->store_length;
if (ref->key_length < length)
/* Ultimately ref->key_length will contain the length of the search key */
ref->key_length= length;
if (!*prefix_len && part+1 == field_part)
*prefix_len= length;
if (is_field_part && eq_type)
*prefix_len= ref->key_length;
*key_part_used|= (key_part_map) 1 << (part - keyinfo->key_part);
}
if (org_key_part_used != *key_part_used ||
(is_field_part &&
(between || eq_type || max_fl == less_fl) && !cond->val_int()))
{
/*
It's the first predicate for this part or a predicate of the
following form that moves upper/lower bounds for max/min values:
- field BETWEEN const AND const
- field = const
- field {<|<=} const, when searching for MAX
- field {>|>=} const, when searching for MIN
*/
if (is_null)
{
part->field->set_null();
*key_ptr= (byte) 1;
}
else
{
store_val_in_field(part->field, args[between && max_fl ? 2 : 1]);
if (part->null_bit)
*key_ptr++= (byte) test(part->field->is_null());
part->field->get_key_image((char*) key_ptr, part->length, Field::itRAW);
}
if (is_field_part)
{
if (between || eq_type)
*range_fl&= ~(NO_MAX_RANGE | NO_MIN_RANGE);
else
{
*range_fl&= ~(max_fl ? NO_MAX_RANGE : NO_MIN_RANGE);
if (noeq_type)
*range_fl|= (max_fl ? NEAR_MAX : NEAR_MIN);
else
*range_fl&= ~(max_fl ? NEAR_MAX : NEAR_MIN);
}
}
}
else if (eq_type)
{
if (!is_null && !cond->val_int() ||
is_null && !test(part->field->is_null()))
return 0; // Impossible test
}
else if (is_field_part)
*range_fl&= ~(max_fl ? NO_MIN_RANGE : NO_MAX_RANGE);
return 1;
}
/*
Check whether we can get value for {max|min}(field) by using a key.
SYNOPSIS
find_key_for_maxmin()
max_fl in: 0 for MIN(field) / 1 for MAX(field)
ref in/out Reference to the structure we store the key value
field in: Field used inside MIN() / MAX()
cond in: WHERE condition
range_fl out: Bit flags for how to search if key is ok
prefix_len out: Length of prefix for the search range
DESCRIPTION
If where condition is not a conjunction of 0 or more conjuct the
function returns false, otherwise it checks whether there is an
index including field as its k-th component/part such that:
1. for each previous component f_i there is one and only one conjunct
of the form: f_i= const_i or const_i= f_i or f_i is null
2. references to field occur only in conjucts of the form:
field {<|<=|>=|>|=} const or const {<|<=|>=|>|=} field or
field BETWEEN const1 AND const2
3. all references to the columns from the same table as column field
occur only in conjucts mentioned above.
If such an index exists the function through the ref parameter
returns the key value to find max/min for the field using the index,
the length of first (k-1) components of the key and flags saying
how to apply the key for the search max/min value.
(if we have a condition field = const, prefix_len contains the length
of the whole search key)
NOTE
This function may set table->key_read to 1, which must be reset after
index is used! (This can only happen when function returns 1)
RETURN
0 Index can not be used to optimize MIN(field)/MAX(field)
1 Can use key to optimize MIN()/MAX()
In this case ref, range_fl and prefix_len are updated
*/
static bool find_key_for_maxmin(bool max_fl, TABLE_REF *ref,
Field* field, COND *cond,
uint *range_fl, uint *prefix_len)
{
if (!(field->flags & PART_KEY_FLAG))
return 0; // Not key field
TABLE *table= field->table;
uint idx= 0;
KEY *keyinfo,*keyinfo_end;
for (keyinfo= table->key_info, keyinfo_end= keyinfo+table->s->keys ;
keyinfo != keyinfo_end;
keyinfo++,idx++)
{
KEY_PART_INFO *part,*part_end;
key_part_map key_part_to_use= 0;
uint jdx= 0;
*prefix_len= 0;
for (part= keyinfo->key_part, part_end= part+keyinfo->key_parts ;
part != part_end ;
part++, jdx++, key_part_to_use= (key_part_to_use << 1) | 1)
{
if (!(table->file->index_flags(idx, jdx, 0) & HA_READ_ORDER))
return 0;
if (field->eq(part->field))
{
ref->key= idx;
ref->key_length= 0;
key_part_map key_part_used= 0;
*range_fl= NO_MIN_RANGE | NO_MAX_RANGE;
if (matching_cond(max_fl, ref, keyinfo, part, cond,
&key_part_used, range_fl, prefix_len) &&
!(key_part_to_use & ~key_part_used))
{
if (!max_fl && key_part_used == key_part_to_use && part->null_bit)
{
/*
SELECT MIN(key_part2) FROM t1 WHERE key_part1=const
If key_part2 may be NULL, then we want to find the first row
that is not null
*/
ref->key_buff[ref->key_length]= 1;
ref->key_length+= part->store_length;
*range_fl&= ~NO_MIN_RANGE;
*range_fl|= NEAR_MIN; // > NULL
}
/*
The following test is false when the key in the key tree is
converted (for example to upper case)
*/
if (field->part_of_key.is_set(idx))
{
table->key_read= 1;
table->file->extra(HA_EXTRA_KEYREAD);
}
return 1;
}
}
}
}
return 0;
}
/*
Check whether found key is in range specified by conditions
SYNOPSIS
reckey_in_range()
max_fl in: 0 for MIN(field) / 1 for MAX(field)
ref in: Reference to the key value and info
field in: Field used the MIN/MAX expression
cond in: WHERE condition
range_fl in: Says whether there is a condition to to be checked
prefix_len in: Length of the constant part of the key
RETURN
0 ok
1 WHERE was not true for the found row
*/
static int reckey_in_range(bool max_fl, TABLE_REF *ref, Field* field,
COND *cond, uint range_fl, uint prefix_len)
{
if (key_cmp_if_same(field->table, ref->key_buff, ref->key, prefix_len))
return 1;
if (!cond || (range_fl & (max_fl ? NO_MIN_RANGE : NO_MAX_RANGE)))
return 0;
return maxmin_in_range(max_fl, field, cond);
}
/*
Check whether {MAX|MIN}(field) is in range specified by conditions
SYNOPSIS
maxmin_in_range()
max_fl in: 0 for MIN(field) / 1 for MAX(field)
field in: Field used the MIN/MAX expression
cond in: WHERE condition
RETURN
0 ok
1 WHERE was not true for the found row
*/
static int maxmin_in_range(bool max_fl, Field* field, COND *cond)
{
/* If AND/OR condition */
if (cond->type() == Item::COND_ITEM)
{
List_iterator_fast<Item> li(*((Item_cond*) cond)->argument_list());
Item *item;
while ((item= li++))
{
if (maxmin_in_range(max_fl, field, item))
return 1;
}
return 0;
}
if (cond->used_tables() != field->table->map)
return 0;
bool less_fl= 0;
switch (((Item_func*) cond)->functype()) {
case Item_func::BETWEEN:
return cond->val_int() == 0; // Return 1 if WHERE is false
case Item_func::LT_FUNC:
case Item_func::LE_FUNC:
less_fl= 1;
case Item_func::GT_FUNC:
case Item_func::GE_FUNC:
{
Item *item= ((Item_func*) cond)->arguments()[1];
/* In case of 'const op item' we have to swap the operator */
if (!item->const_item())
less_fl= 1-less_fl;
/*
We only have to check the expression if we are using an expression like
SELECT MAX(b) FROM t1 WHERE a=const AND b>const
not for
SELECT MAX(b) FROM t1 WHERE a=const AND b<const
*/
if (max_fl != less_fl)
return cond->val_int() == 0; // Return 1 if WHERE is false
return 0;
}
case Item_func::EQ_FUNC:
case Item_func::EQUAL_FUNC:
break;
default: // Keep compiler happy
DBUG_ASSERT(1); // Impossible
break;
}
return 0;
}
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