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merge

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sql/sql_lex.cc:
  Auto merged
sql/sql_parse.cc:
  Auto merged
sql/sql_update.cc:
  Auto merged
sql/sql_yacc.yy:
  Auto merged
sql/table.cc:
  Auto merged
sql/table.h:
  Auto merged
This commit is contained in:
unknown
2004-10-07 11:36:46 +03:00
parent 61e96be77f 640fefffa7
commit 5b82bc6644
13 changed files with 150 additions and 109 deletions
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52
sql/sql_lex.cc
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@ -1537,11 +1537,17 @@ void st_select_lex::print_limit(THD *thd, String *str)
/*
Check is merging algorithm can be used on this VIEW
Check whether the merging algorithm can be used on this VIEW
SYNOPSIS
st_lex::can_be_merged()
DESCRIPTION
We can apply merge algorithm if it is single SELECT view (we do not
count SELECTs of underlying views) and we have not grpouping, ordering,
HAVING clause, aggregate functions, DISTINCT clause, LIMIT clause and
several underlying tables.
RETURN
FALSE - only temporary table algorithm can be used
TRUE - merge algorithm can be used
@ -1569,12 +1575,18 @@ bool st_lex::can_be_merged()
select_lex.select_limit == HA_POS_ERROR);
}
/*
check if command can use VIEW with MERGE algorithm (for top VIEWs)
SYNOPSIS
st_lex::can_use_merged()
DESCRIPTION
Only listed here commands can use merge algorithm in top level
SELECT_LEX (for subqueries will be used merge algorithm if
st_lex::can_not_use_merged() is not TRUE).
RETURN
FALSE - command can't use merged VIEWs
TRUE - VIEWs with MERGE algorithms can be used
@ -1601,11 +1613,15 @@ bool st_lex::can_use_merged()
}
/*
check if command can't use merged views in any part of command
Check if command can't use merged views in any part of command
SYNOPSIS
st_lex::can_not_use_merged()
DESCRIPTION
Temporary table algorithm will be used on all SELECT levels for queries
listed here (see also st_lex::can_use_merged()).
RETURN
FALSE - command can't use merged VIEWs
TRUE - VIEWs with MERGE algorithms can be used
@ -1673,16 +1689,16 @@ void st_select_lex_unit::set_limit(SELECT_LEX *values,
/*
Unlink first table from global table list and first table from outer select
list (lex->select_lex)
Unlink the first table from the global table list and the first table from
outer select (lex->select_lex) local list
SYNOPSIS
unlink_first_table()
link_to_local Set to 1 if caller should link this table to local
link_to_local Set to 1 if caller should link this table to local list
NOTES
We rely on fact that first table in both list are same or local list
is empty
We assume that first tables in both lists is the same table or the local
list is empty.
RETURN
0 If 'query_tables' == 0
@ -1711,8 +1727,8 @@ TABLE_LIST *st_lex::unlink_first_table(bool *link_to_local)
select_lex.table_list.elements--; //safety
first->next_local= 0;
/*
reorder global list to keep first tables the same in both lists
(if it is need)
Ensure that the global list has the same first table as the local
list.
*/
first_lists_tables_same();
}
@ -1729,11 +1745,12 @@ TABLE_LIST *st_lex::unlink_first_table(bool *link_to_local)
st_lex::first_lists_tables_same()
NOTES
In many cases first table of main SELECT_LEX have special meaning =>
check that it is first table in global list and relink it first in
queries_tables list if it is necessary (we need such relinking only
for queries with subqueries in select list, in this case tables of
subqueries will go to global list first)
In many cases (for example, usual INSERT/DELETE/...) the first table of
main SELECT_LEX have special meaning => check that it is the first table
in global list and re-link to be first in the global list if it is
necessary. We need such re-linking only for queries with sub-queries in
the select list, as only in this case tables of sub-queries will go to
the global list first.
*/
void st_lex::first_lists_tables_same()
@ -1744,14 +1761,15 @@ void st_lex::first_lists_tables_same()
TABLE_LIST *next;
if (query_tables_last == &first_table->next_global)
query_tables_last= first_table->prev_global;
if ((next= *first_table->prev_global= first_table->next_global))
next->prev_global= first_table->prev_global;
/* include in new place */
first_table->next_global= query_tables;
/*
we are sure that above is not 0, because first_table was not
first table in global list => we can do following without check
We are sure that query_tables is not 0, because first_table was not
first table in the global list => we can use
query_tables->prev_global without check of query_tables
*/
query_tables->prev_global= &first_table->next_global;
first_table->prev_global= &query_tables;