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mariadb/sql/sql_cte.cc
Yuchen Pei d06b6de305
 Merge branch '10.5' into 10.6
2024-01-11 12:59:22 +11:00

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/*
Copyright (c) 2016, 2017 MariaDB
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; version 2 of the License.
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., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
#include "mariadb.h"
#include "sql_class.h"
#include "sql_lex.h"
#include "sql_cte.h"
#include "sql_view.h" // for make_valid_column_names
#include "sql_parse.h"
#include "sql_select.h"
#include "sql_show.h" // append_definer, append_identifier
/**
@brief
Add a new element to this with clause
@param elem The with element to add to this with clause
@details
The method adds the with element 'elem' to the elements
in this with clause. The method reports an error if
the number of the added element exceeds the value
of the constant max_number_of_elements_in_with_clause.
@retval
true if an error is reported
false otherwise
*/
bool With_clause::add_with_element(With_element *elem)
{
if (with_list.elements == max_number_of_elements_in_with_clause)
{
my_error(ER_TOO_MANY_DEFINITIONS_IN_WITH_CLAUSE, MYF(0));
return true;
}
elem->owner= this;
elem->number= with_list.elements;
elem->spec->with_element= elem;
with_list.link_in_list(elem, &elem->next);
return false;
}
void st_select_lex_unit::set_with_clause(With_clause *with_cl)
{
with_clause= with_cl;
if (with_clause)
with_clause->set_owner(this);
}
/**
@brief
Check dependencies between tables defined in a list of with clauses
@param
with_clauses_list Pointer to the first clause in the list
@details
For each with clause from the given list the procedure finds all
dependencies between tables defined in the clause by calling the
method With_clause::checked_dependencies.
Additionally, based on the info collected by this method the procedure
finds anchors for each recursive definition and moves them at the head
of the definition.
@retval
false on success
true on failure
*/
bool LEX::check_dependencies_in_with_clauses()
{
for (With_clause *with_clause= with_clauses_list;
with_clause;
with_clause= with_clause->next_with_clause)
{
if (with_clause->check_dependencies())
return true;
if (with_clause->check_anchors())
return true;
with_clause->move_anchors_ahead();
}
return false;
}
/**
@brief
Resolve table references to CTE from a sub-chain of table references
@param tables Points to the beginning of the sub-chain
@param tables_last Points to the address with the sub-chain barrier
@param excl_spec Ignore the definition with this spec
@details
The method resolves tables references to CTE from the chain of
table references specified by the parameters 'tables' and 'tables_last'.
It resolves the references against the CTE definition occurred in a query
or the specification of a CTE whose parsing tree is represented by
this LEX structure. The method is always called right after the process
of parsing the query or of the specification of a CTE has been finished,
thus the chain of table references used in the parsed fragment has been
already built. It is assumed that parameters of the method specify a
a sub-chain of this chain.
If a table reference can be potentially a table reference to a CTE and it
has not been resolved yet then the method tries to find the definition
of the CTE against which the reference can be resolved. If it succeeds
it sets the field TABLE_LIST::with to point to the found definition.
It also sets the field TABLE_LIST::derived to point to the specification
of the found CTE and sets TABLE::db.str to empty_c_string. This will
allow to handle this table reference like a reference to a derived handle.
If another table reference has been already resolved against this CTE
and this CTE is not recursive then a clone of the CTE specification is
constructed using the function With_element::clone_parsed_spec() and
TABLE_LIST::derived is set to point to this clone rather than to the
original specification.
If the method does not find a matched CTE definition in the parsed fragment
then in the case when the flag this->only_cte_resolution is set to true
it just moves to the resolution of the next table reference from the
specified sub-chain while in the case when this->only_cte_resolution is set
to false the method additionally sets an mdl request for this table
reference.
@notes
The flag this->only_cte_resolution is set to true in the cases when
the failure to resolve a table reference as a CTE reference within
the fragment associated with this LEX structure does not imply that
this table reference cannot be resolved as such at all.
@retval false On success: no errors reported, no memory allocations failed
@retval true Otherwise
*/
bool LEX::resolve_references_to_cte(TABLE_LIST *tables,
TABLE_LIST **tables_last,
st_select_lex_unit *excl_spec)
{
With_element *with_elem= 0;
for (TABLE_LIST *tbl= tables; tbl != *tables_last; tbl= tbl->next_global)
{
if (tbl->derived)
continue;
if (!tbl->db.str && !tbl->with)
tbl->with= tbl->select_lex->find_table_def_in_with_clauses(tbl,
excl_spec);
if (!tbl->with) // no CTE matches table reference tbl
{
if (only_cte_resolution)
continue;
if (!tbl->db.str) // no database specified in table reference tbl
{
if (!thd->db.str) // no default database is set
{
my_message(ER_NO_DB_ERROR, ER(ER_NO_DB_ERROR), MYF(0));
return true;
}
if (copy_db_to(&tbl->db))
return true;
if (!(tbl->table_options & TL_OPTION_ALIAS))
MDL_REQUEST_INIT(&tbl->mdl_request, MDL_key::TABLE,
tbl->db.str, tbl->table_name.str,
tbl->mdl_type, MDL_TRANSACTION);
tbl->mdl_request.set_type((tbl->lock_type >= TL_WRITE_ALLOW_WRITE) ?
MDL_SHARED_WRITE : MDL_SHARED_READ);
}
continue;
}
with_elem= tbl->with;
if (tbl->is_recursive_with_table() &&
!tbl->is_with_table_recursive_reference())
{
tbl->with->rec_outer_references++;
while ((with_elem= with_elem->get_next_mutually_recursive()) !=
tbl->with)
with_elem->rec_outer_references++;
}
if (!with_elem->is_used_in_query || with_elem->is_recursive)
{
tbl->derived= with_elem->spec;
if (tbl->derived != tbl->select_lex->master_unit() &&
!with_elem->is_recursive &&
!tbl->is_with_table_recursive_reference())
{
tbl->derived->move_as_slave(tbl->select_lex);
}
with_elem->is_used_in_query= true;
}
else
{
if (!(tbl->derived= tbl->with->clone_parsed_spec(thd->lex, tbl)))
return true;
}
tbl->db.str= empty_c_string;
tbl->db.length= 0;
tbl->schema_table= 0;
if (tbl->derived)
{
tbl->derived->first_select()->set_linkage(DERIVED_TABLE_TYPE);
tbl->select_lex->add_statistics(tbl->derived);
}
if (tbl->with->is_recursive && tbl->is_with_table_recursive_reference())
continue;
with_elem->inc_references();
}
return false;
}
/**
@brief
Find out dependencies between CTEs, resolve references to them
@details
The function can be called in two modes. With this->with_cte_resolution
set to false the function only finds out all dependencies between CTEs
used in a query expression with a WITH clause whose parsing has been
just finished. Based on these dependencies recursive CTEs are detected.
If this->with_cte_resolution is set to true the function additionally
resolves all references to CTE occurred in this query expression.
@retval
true on failure
false on success
*/
bool
LEX::check_cte_dependencies_and_resolve_references()
{
if (check_dependencies_in_with_clauses())
return true;
if (!with_cte_resolution)
return false;
if (resolve_references_to_cte(query_tables, query_tables_last, NULL))
return true;
return false;
}
/**
@brief
Check dependencies between tables defined in this with clause
@details
The method performs the following for this with clause:
- checks that there are no definitions of the tables with the same name
- for each table T defined in this with clause looks for the tables
from the same with clause that are used in the query that specifies T
and set the dependencies of T on these tables in a bitmap.
- builds the transitive closure of the above direct dependencies
to find out all recursive definitions.
@retval
true if an error is reported
false otherwise
*/
bool With_clause::check_dependencies()
{
if (dependencies_are_checked)
return false;
/*
Look for for definitions with the same query name.
When found report an error and return true immediately.
For each table T defined in this with clause look for all other tables
from the same with clause that are used in the specification of T.
For each such table set the dependency bit in the dependency map of
the with element for T.
*/
for (With_element *with_elem= with_list.first;
with_elem;
with_elem= with_elem->next)
{
for (With_element *elem= with_list.first;
elem != with_elem;
elem= elem->next)
{
if (lex_string_cmp(system_charset_info, with_elem->get_name(),
elem->get_name()) == 0)
{
my_error(ER_DUP_QUERY_NAME, MYF(0),
with_elem->get_name_str());
return true;
}
}
if (with_elem->check_dependencies_in_spec())
return true;
}
/* Build the transitive closure of the direct dependencies found above */
for (With_element *with_elem= with_list.first;
with_elem;
with_elem= with_elem->next)
with_elem->derived_dep_map= with_elem->base_dep_map;
for (With_element *with_elem= with_list.first;
with_elem;
with_elem= with_elem->next)
{
table_map with_elem_map= with_elem->get_elem_map();
for (With_element *elem= with_list.first; elem; elem= elem->next)
{
if (elem->derived_dep_map & with_elem_map)
elem->derived_dep_map |= with_elem->derived_dep_map;
}
}
/*
Mark those elements where tables are defined with direct or indirect
recursion.
*/
for (With_element *with_elem= with_list.first;
with_elem;
with_elem= with_elem->next)
{
if (with_elem->derived_dep_map & with_elem->get_elem_map())
with_elem->is_recursive= true;
}
dependencies_are_checked= true;
return false;
}
/*
This structure describes an element of the stack of embedded units.
The stack is used when looking for a definition of a table in
with clauses. The definition can be found only in the scopes
of the with clauses attached to the units from the stack.
The with clauses are looked through from starting from the top
element of the stack.
*/
struct st_unit_ctxt_elem
{
st_unit_ctxt_elem *prev; // the previous element of the stack
st_select_lex_unit *unit;
};
/**
@brief
Find the dependencies of this element on its siblings in its specification
@details
For each table reference ref(T) from the FROM list of every select sl
immediately contained in the specification query of this element this
method searches for the definition of T in the the with clause which
this element belongs to. If such definition is found then the dependency
on it is set in sl->with_dep and in this->base_dep_map.
*/
bool With_element::check_dependencies_in_spec()
{
for (st_select_lex *sl= spec->first_select(); sl; sl= sl->next_select())
{
if (owner->with_recursive)
{
st_unit_ctxt_elem ctxt0= {NULL, owner->owner};
st_unit_ctxt_elem ctxt1= {&ctxt0, spec};
check_dependencies_in_select(sl, &ctxt1, false, &sl->with_dep);
}
else
{
st_unit_ctxt_elem ctxt= {NULL, spec};
check_dependencies_in_select(sl, &ctxt, false, &sl->with_dep);
}
base_dep_map|= sl->with_dep;
}
return false;
}
/**
@brief
Search for the definition of a table among the elements of this with clause
@param table The reference to the table that is looked for
@param barrier The barrier with element for the search
@param excl_spec Ignore the definition with this spec
@details
The function looks through the elements of this with clause trying to find
the definition of the given table. When it encounters the element with
the same query name as the table's name it returns this element. If no
such definitions are found the function returns NULL.
@retval
found with element if the search succeeded
NULL - otherwise
*/
With_element *With_clause::find_table_def(TABLE_LIST *table,
With_element *barrier,
st_select_lex_unit *excl_spec)
{
for (With_element *with_elem= with_list.first;
with_elem != barrier;
with_elem= with_elem->next)
{
if (excl_spec && with_elem->spec == excl_spec)
continue;
if (my_strcasecmp(system_charset_info, with_elem->get_name_str(),
table->table_name.str) == 0 &&
!table->is_fqtn)
{
table->set_derived();
with_elem->referenced= true;
return with_elem;
}
}
return NULL;
}
/**
@brief
Search for the definition of a table in with clauses
@param tbl The reference to the table that is looked for
@param ctxt The context describing in what with clauses of the upper
levels the table has to be searched for.
@details
The function looks for the definition of the table tbl in the definitions
of the with clauses from the upper levels specified by the parameter ctxt.
When it encounters the element with the same query name as the table's name
it returns this element. If no such definitions are found the function
returns NULL.
@retval
found with element if the search succeeded
NULL - otherwise
*/
With_element *find_table_def_in_with_clauses(TABLE_LIST *tbl,
st_unit_ctxt_elem *ctxt)
{
With_element *found= 0;
st_select_lex_unit *top_unit= 0;
for (st_unit_ctxt_elem *unit_ctxt_elem= ctxt;
unit_ctxt_elem;
unit_ctxt_elem= unit_ctxt_elem->prev)
{
st_select_lex_unit *unit= unit_ctxt_elem->unit;
With_clause *with_clause= unit->with_clause;
if (with_clause)
{
/*
If the reference to tbl that has to be resolved belongs to
the FROM clause of a descendant of top_unit->with_element
and this with element belongs to with_clause then this
element must be used as the barrier for the search in the
the list of CTEs from with_clause unless the clause contains
RECURSIVE.
*/
With_element *barrier= 0;
if (top_unit && !with_clause->with_recursive &&
top_unit->with_element &&
top_unit->with_element->get_owner() == with_clause)
barrier= top_unit->with_element;
found= with_clause->find_table_def(tbl, barrier, NULL);
if (found)
break;
}
top_unit= unit;
}
return found;
}
/**
@brief
Find the dependencies of this element on its siblings in a select
@param sl The select where to look for the dependencies
@param ctxt The structure specifying the scope of the definitions
of the with elements of the upper levels
@param in_sbq if true mark dependencies found in subqueries in
this->sq_dep_map
@param dep_map IN/OUT The bit where to mark the found dependencies
@details
For each table reference ref(T) from the FROM list of the select sl
the method searches in with clauses for the definition of the table T.
If the found definition belongs to the same with clause as this with
element then the method set dependency on T in the in/out parameter
dep_map, add if required - in this->sq_dep_map.
The parameter ctxt describes the proper context for the search
of the definition of T.
*/
void With_element::check_dependencies_in_select(st_select_lex *sl,
st_unit_ctxt_elem *ctxt,
bool in_subq,
table_map *dep_map)
{
bool is_spec_select= sl->get_with_element() == this;
for (TABLE_LIST *tbl= sl->table_list.first; tbl; tbl= tbl->next_local)
{
if (tbl->with || tbl->derived || tbl->nested_join)
continue;
tbl->with_internal_reference_map= 0;
/*
Look first for the definition of tbl in the with clause to which
this with element belongs. If such definition is not found there
look in the with clauses of the upper levels via the context
chain of embedding with elements.
If the definition of tbl is found somewhere in with clauses
then tbl->with is set to point to this definition.
*/
if (is_spec_select)
{
With_clause *with_clause= sl->master_unit()->with_clause;
if (with_clause)
tbl->with= with_clause->find_table_def(tbl, NULL, NULL);
if (!tbl->with)
tbl->with= owner->find_table_def(tbl,
owner->with_recursive ? NULL : this,
NULL);
}
if (!tbl->with)
tbl->with= find_table_def_in_with_clauses(tbl, ctxt);
if (tbl->with && tbl->with->owner== this->owner)
{
/*
The found definition T of tbl belongs to the same
with clause as this with element. In this case:
- set the dependence on T in the bitmap dep_map
- set tbl->with_internal_reference_map with
the bitmap for this definition
- set the dependence on T in the bitmap this->sq_dep_map
if needed
*/
*dep_map|= tbl->with->get_elem_map();
tbl->with_internal_reference_map= get_elem_map();
if (in_subq)
sq_dep_map|= tbl->with->get_elem_map();
else
top_level_dep_map|= tbl->with->get_elem_map();
}
}
/* Now look for the dependencies in the subqueries of sl */
st_select_lex_unit *inner_unit= sl->first_inner_unit();
for (; inner_unit; inner_unit= inner_unit->next_unit())
{
check_dependencies_in_unit(inner_unit, ctxt, in_subq, dep_map);
}
}
/**
@brief
Find a recursive reference to this with element in subqueries of a select
@param sel The select in whose subqueries the reference
to be looked for
@details
The function looks for a recursive reference to this with element in
subqueries of select sl. When the first such reference is found
it is returned as the result.
The function assumes that the identification of all CTE references
has been performed earlier.
@retval
Pointer to the found recursive reference if the search succeeded
NULL - otherwise
*/
TABLE_LIST *With_element::find_first_sq_rec_ref_in_select(st_select_lex *sel)
{
TABLE_LIST *rec_ref= NULL;
st_select_lex_unit *inner_unit= sel->first_inner_unit();
for (; inner_unit; inner_unit= inner_unit->next_unit())
{
st_select_lex *sl= inner_unit->first_select();
for (; sl; sl= sl->next_select())
{
for (TABLE_LIST *tbl= sl->table_list.first; tbl; tbl= tbl->next_local)
{
if (tbl->derived || tbl->nested_join)
continue;
if (tbl->with && tbl->with->owner== this->owner &&
(tbl->with_internal_reference_map & mutually_recursive))
{
rec_ref= tbl;
return rec_ref;
}
}
if ((rec_ref= find_first_sq_rec_ref_in_select(sl)))
return rec_ref;
}
}
return 0;
}
/**
@brief
Find the dependencies of this element on its siblings in a unit
@param unit The unit where to look for the dependencies
@param ctxt The structure specifying the scope of the definitions
of the with elements of the upper levels
@param in_sbq if true mark dependencies found in subqueries in
this->sq_dep_map
@param dep_map IN/OUT The bit where to mark the found dependencies
@details
This method searches in the unit 'unit' for the the references in FROM
lists of all selects contained in this unit and in the with clause
attached to this unit that refer to definitions of tables from the
same with clause as this element.
If such definitions are found then the dependencies on them are
set in the in/out parameter dep_map and optionally in this->sq_dep_map.
The parameter ctxt describes the proper context for the search.
*/
void With_element::check_dependencies_in_unit(st_select_lex_unit *unit,
st_unit_ctxt_elem *ctxt,
bool in_subq,
table_map *dep_map)
{
st_unit_ctxt_elem unit_ctxt_elem= {ctxt, unit};
if (unit->with_clause)
{
(void) unit->with_clause->check_dependencies();
check_dependencies_in_with_clause(unit->with_clause, &unit_ctxt_elem,
in_subq, dep_map);
}
in_subq |= unit->item != NULL;
st_select_lex *sl= unit->first_select();
for (; sl; sl= sl->next_select())
{
check_dependencies_in_select(sl, &unit_ctxt_elem, in_subq, dep_map);
}
if ((sl= unit->fake_select_lex))
check_dependencies_in_select(sl, &unit_ctxt_elem, in_subq, dep_map);
}
/**
@brief
Find the dependencies of this element on its siblings in a with clause
@param witt_clause The with clause where to look for the dependencies
@param ctxt The structure specifying the scope of the definitions
of the with elements of the upper levels
@param in_sbq if true mark dependencies found in subqueries in
this->sq_dep_map
@param dep_map IN/OUT The bit where to mark the found dependencies
@details
This method searches in the with_clause for the the references in FROM
lists of all selects contained in the specifications of the with elements
from this with_clause that refer to definitions of tables from the
same with clause as this element.
If such definitions are found then the dependencies on them are
set in the in/out parameter dep_map and optionally in this->sq_dep_map.
The parameter ctxt describes the proper context for the search.
*/
void
With_element::check_dependencies_in_with_clause(With_clause *with_clause,
st_unit_ctxt_elem *ctxt,
bool in_subq,
table_map *dep_map)
{
for (With_element *with_elem= with_clause->with_list.first;
with_elem;
with_elem= with_elem->next)
{
check_dependencies_in_unit(with_elem->spec, ctxt, in_subq, dep_map);
}
}
/**
@brief
Find mutually recursive with elements and check that they have ancors
@details
This method performs the following:
- for each recursive with element finds all mutually recursive with it
- links each group of mutually recursive with elements into a ring chain
- checks that every group of mutually recursive with elements contains
at least one anchor
- checks that after removing any with element with anchor the remaining
with elements mutually recursive with the removed one are not recursive
anymore
@retval
true if an error is reported
false otherwise
*/
bool With_clause::check_anchors()
{
for (With_element *with_elem= with_list.first;
with_elem;
with_elem= with_elem->next)
{
if (!with_elem->is_recursive)
continue;
/*
It with_elem is recursive with element find all elements mutually recursive
with it (any recursive element is mutually recursive with itself). Mark all
these elements in the bitmap->mutually_recursive. Also link all these
elements into a ring chain.
*/
if (!with_elem->next_mutually_recursive)
{
With_element *last_mutually_recursive= with_elem;
table_map with_elem_dep= with_elem->derived_dep_map;
table_map with_elem_map= with_elem->get_elem_map();
for (With_element *elem= with_elem; elem; elem= elem->next)
{
if (!elem->is_recursive)
continue;
if (elem == with_elem ||
((elem->derived_dep_map & with_elem_map) &&
(with_elem_dep & elem->get_elem_map())))
{
elem->next_mutually_recursive= with_elem;
last_mutually_recursive->next_mutually_recursive= elem;
last_mutually_recursive= elem;
with_elem->mutually_recursive|= elem->get_elem_map();
}
}
for (With_element *elem= with_elem->next_mutually_recursive;
elem != with_elem;
elem= elem->next_mutually_recursive)
elem->mutually_recursive= with_elem->mutually_recursive;
}
/*
For each select from the specification of 'with_elem' check whether
it is an anchor i.e. does not depend on any with elements mutually
recursive with 'with_elem".
*/
for (st_select_lex *sl= with_elem->spec->first_select();
sl;
sl= sl->next_select())
{
if (with_elem->is_anchor(sl))
{
with_elem->with_anchor= true;
break;
}
}
}
/*
Check that for any group of mutually recursive with elements
- there is at least one anchor
- after removing any with element with anchor the remaining with elements
mutually recursive with the removed one are not recursive anymore
*/
for (With_element *with_elem= with_list.first;
with_elem;
with_elem= with_elem->next)
{
if (!with_elem->is_recursive)
continue;
if (!with_elem->with_anchor)
{
/*
Check that the other with elements mutually recursive with 'with_elem'
contain at least one anchor.
*/
With_element *elem= with_elem;
while ((elem= elem->get_next_mutually_recursive()) != with_elem)
{
if (elem->with_anchor)
break;
}
if (elem == with_elem)
{
my_error(ER_RECURSIVE_WITHOUT_ANCHORS, MYF(0),
with_elem->get_name_str());
return true;
}
}
else
{
/* 'with_elem' is a with element with an anchor */
With_element *elem= with_elem;
/*
For the other with elements mutually recursive with 'with_elem'
set dependency bits between those elements in the field work_dep_map
and build transitive closure of these dependencies
*/
while ((elem= elem->get_next_mutually_recursive()) != with_elem)
elem->work_dep_map= elem->base_dep_map & elem->mutually_recursive;
elem= with_elem;
while ((elem= elem->get_next_mutually_recursive()) != with_elem)
{
table_map elem_map= elem->get_elem_map();
With_element *el= with_elem;
while ((el= el->get_next_mutually_recursive()) != with_elem)
{
if (el->work_dep_map & elem_map)
el->work_dep_map|= elem->work_dep_map;
}
}
/* If the transitive closure displays any cycle report an arror */
elem= with_elem;
while ((elem= elem->get_next_mutually_recursive()) != with_elem)
{
if (elem->work_dep_map & elem->get_elem_map())
{
my_error(ER_UNACCEPTABLE_MUTUAL_RECURSION, MYF(0),
with_elem->get_name_str());
return true;
}
}
}
}
return false;
}
/**
@brief
Move anchors at the beginning of the specifications for with elements
@details
This method moves anchors at the beginning of the specifications for
all recursive with elements.
*/
void With_clause::move_anchors_ahead()
{
for (With_element *with_elem= with_list.first;
with_elem;
with_elem= with_elem->next)
{
if (with_elem->is_recursive)
with_elem->move_anchors_ahead();
}
}
/**
@brief
Move anchors at the beginning of the specification of this with element
@details
If the specification of this with element contains anchors the method
moves them at the very beginning of the specification.
Additionally for the other selects of the specification if none of them
contains a recursive reference to this with element or a mutually recursive
one the method looks for the first such reference in the first recursive
select and set a pointer to it in this->sq_rec_ref.
*/
void With_element::move_anchors_ahead()
{
st_select_lex *next_sl;
st_select_lex *new_pos= spec->first_select();
new_pos->set_linkage(UNION_TYPE);
for (st_select_lex *sl= new_pos; sl; sl= next_sl)
{
next_sl= sl->next_select();
if (is_anchor(sl))
{
sl->move_node(new_pos);
if (new_pos == spec->first_select())
{
enum sub_select_type type= new_pos->get_linkage();
new_pos->set_linkage(sl->get_linkage());
sl->set_linkage(type);
new_pos->with_all_modifier= sl->with_all_modifier;
sl->with_all_modifier= false;
}
new_pos= sl->next_select();
}
else if (!sq_rec_ref && no_rec_ref_on_top_level())
{
sq_rec_ref= find_first_sq_rec_ref_in_select(sl);
DBUG_ASSERT(sq_rec_ref != NULL);
}
}
first_recursive= new_pos;
spec->first_select()->set_linkage(DERIVED_TABLE_TYPE);
}
/**
@brief
Perform context analysis for all unreferenced tables defined in with clause
@param thd The context of the statement containing this with clause
@details
For each unreferenced table T defined in this with clause the method
calls the method With_element::prepare_unreferenced that performs
context analysis of the element with the definition of T.
@retval
false If context analysis does not report any error
true Otherwise
*/
bool With_clause::prepare_unreferenced_elements(THD *thd)
{
for (With_element *with_elem= with_list.first;
with_elem;
with_elem= with_elem->next)
{
if ((with_elem->is_hanging_recursive() || !with_elem->is_referenced()) &&
with_elem->prepare_unreferenced(thd))
return true;
}
return false;
}
/**
@brief
Save the specification of the given with table as a string
@param thd The context of the statement containing this with element
@param spec_start The beginning of the specification in the input string
@param spec_end The end of the specification in the input string
@param spec_offset The offset of the specification in the input string
@details
The method creates for a string copy of the specification used in this
element. The method is called when the element is parsed. The copy may be
used to create clones of the specification whenever they are needed.
@retval
false on success
true on failure
*/
bool With_element::set_unparsed_spec(THD *thd,
const char *spec_start,
const char *spec_end,
my_ptrdiff_t spec_offset)
{
stmt_prepare_mode= thd->m_parser_state->m_lip.stmt_prepare_mode;
unparsed_spec.length= spec_end - spec_start;
if (stmt_prepare_mode || !thd->lex->sphead)
unparsed_spec.str= spec_start;
else
unparsed_spec.str= thd->strmake(spec_start, unparsed_spec.length);
unparsed_spec_offset= spec_offset;
if (!unparsed_spec.str)
{
my_error(ER_OUTOFMEMORY, MYF(ME_FATAL),
static_cast<int>(unparsed_spec.length));
return true;
}
return false;
}
/**
@brief
Create a clone of the specification for the given with table
@param old_lex The LEX structure created for the query or CTE specification
where this With_element is defined
@param with_table The reference to the table defined in this element for which
the clone is created.
@details
The method creates a clone of the specification used in this element.
The clone is created for the given reference to the table defined by
this element.
The clone is created when the string with the specification saved in
unparsed_spec is fed into the parser as an input string. The parsing
this string a unit object representing the specification is built.
A chain of all table references occurred in the specification is also
formed.
The method includes the new unit and its sub-unit into hierarchy of
the units of the main query. I also insert the constructed chain of the
table references into the chain of all table references of the main query.
The method resolves all references to CTE in the clone.
@note
Clones is created only for not first references to tables defined in
the with clause. They are necessary for merged specifications because
the optimizer handles any such specification as independent on the others.
When a table defined in the with clause is materialized in a temporary table
one could do without specification clones. However in this case they
are created as well, because currently different table references to a
the same temporary table cannot share the same definition structure.
@retval
pointer to the built clone if succeeds
NULL - otherwise
*/
st_select_lex_unit *With_element::clone_parsed_spec(LEX *old_lex,
TABLE_LIST *with_table)
{
THD *thd= old_lex->thd;
LEX *lex;
st_select_lex_unit *res= NULL;
if (!(lex= (LEX*) new(thd->mem_root) st_lex_local))
return res;
thd->lex= lex;
bool parse_status= false;
st_select_lex *with_select;
st_select_lex *last_clone_select;
char save_end= unparsed_spec.str[unparsed_spec.length];
((char*) &unparsed_spec.str[unparsed_spec.length])[0]= '\0';
lex_start(thd);
lex->clone_spec_offset= unparsed_spec_offset;
lex->with_cte_resolution= true;
/*
There's no need to add SPs/SFs referenced in the clone to the global
list of the SPs/SFs used in the query as they were added when the first
reference to the cloned CTE was parsed. Yet the recursive call of the
parser must to know that they were already included into the list.
*/
lex->sroutines= old_lex->sroutines;
lex->sroutines_list_own_last= old_lex->sroutines_list_own_last;
lex->sroutines_list_own_elements= old_lex->sroutines_list_own_elements;
/*
The specification of a CTE is to be parsed as a regular query.
At the very end of the parsing query the function
check_cte_dependencies_and_resolve_references() will be called.
It will check the dependencies between CTEs that are defined
within the query and will resolve CTE references in this query.
If a table reference is not resolved as a CTE reference within
this query it still can be resolved as a reference to a CTE defined
in the same clause as the CTE whose specification is to be parsed
or defined in an embedding CTE definition.
Example:
with
cte1 as ( ... ),
cte2 as ([WITH ...] select ... from cte1 ...)
select ... from cte2 as r, ..., cte2 as s ...
Here the specification of cte2 has be cloned for table reference
with alias s1. The specification contains a reference to cte1
that is defined outside this specification. If the reference to
cte1 cannot be resolved within the specification of cte2 it's
not necessarily has to be a reference to a non-CTE table. That's
why the flag lex->only_cte_resolution has to be set to true
before parsing of the specification of cte2 invoked by this
function starts. Otherwise an mdl_lock would be requested for s
and this would not be correct.
*/
lex->only_cte_resolution= true;
lex->stmt_lex= old_lex->stmt_lex ? old_lex->stmt_lex : old_lex;
parse_status= thd->sql_parser(old_lex, lex,
(char*) unparsed_spec.str,
(unsigned int)unparsed_spec.length,
stmt_prepare_mode);
((char*) &unparsed_spec.str[unparsed_spec.length])[0]= save_end;
with_select= lex->unit.first_select();
if (parse_status)
goto err;
/*
The unit of the specification that just has been parsed is included
as a slave of the select that contained in its from list the table
reference for which the unit has been created.
*/
lex->unit.include_down(with_table->select_lex);
lex->unit.set_slave(with_select);
lex->unit.cloned_from= spec;
/*
Now all references to the CTE defined outside of the cloned specification
has to be resolved. Additionally if old_lex->only_cte_resolution == false
for the table references that has not been resolved requests for mdl_locks
has to be set.
*/
lex->only_cte_resolution= old_lex->only_cte_resolution;
if (lex->resolve_references_to_cte(lex->query_tables,
lex->query_tables_last,
spec))
{
res= NULL;
goto err;
}
/*
The global chain of TABLE_LIST objects created for the specification that
just has been parsed is added to such chain that contains the reference
to the CTE whose specification is parsed right after the TABLE_LIST object
created for the reference.
*/
if (lex->query_tables)
{
head->tables_pos.set_start_pos(&with_table->next_global);
head->tables_pos.set_end_pos(lex->query_tables_last);
TABLE_LIST *next_tbl= with_table->next_global;
if (next_tbl)
{
*(lex->query_tables->prev_global= next_tbl->prev_global)=
lex->query_tables;
*(next_tbl->prev_global= lex->query_tables_last)= next_tbl;
}
else
{
*(lex->query_tables->prev_global= old_lex->query_tables_last)=
lex->query_tables;
old_lex->query_tables_last= lex->query_tables_last;
}
}
old_lex->sroutines_list_own_last= lex->sroutines_list_own_last;
old_lex->sroutines_list_own_elements= lex->sroutines_list_own_elements;
res= &lex->unit;
res->with_element= this;
last_clone_select= lex->all_selects_list;
while (last_clone_select->next_select_in_list())
last_clone_select= last_clone_select->next_select_in_list();
old_lex->all_selects_list=
(st_select_lex*) (lex->all_selects_list->
insert_chain_before(
(st_select_lex_node **) &(old_lex->all_selects_list),
last_clone_select));
lex->sphead= NULL; // in order not to delete lex->sphead
lex_end(lex);
err:
thd->lex= old_lex;
return res;
}
/**
@brief
Rename columns of the unit derived from the spec of this with element
@param thd The context of the statement containing the with element
@param unit The specification of the with element or its clone
@details
The method assumes that the parameter unit is either specification itself
of this with element or a clone of this specification. The looks through
the column list in this with element. It reports an error if the cardinality
of this list differs from the cardinality of select lists in 'unit'.
Otherwise it renames the columns of the first select list and sets the flag
unit->column_list_is_processed to true preventing renaming columns for the
second time.
@retval
true if an error was reported
false otherwise
*/
bool
With_element::process_columns_of_derived_unit(THD *thd,
st_select_lex_unit *unit)
{
if (unit->columns_are_renamed)
return false;
st_select_lex *select= unit->first_select();
if (column_list.elements) // The column list is optional
{
List_iterator_fast<Item> it(select->item_list);
List_iterator_fast<Lex_ident_sys> nm(column_list);
Item *item;
LEX_CSTRING *name;
if (column_list.elements != select->item_list.elements)
{
my_error(ER_WITH_COL_WRONG_LIST, MYF(0));
return true;
}
Query_arena *arena, backup;
arena= thd->activate_stmt_arena_if_needed(&backup);
/* Rename the columns of the first select in the unit */
while ((item= it++, name= nm++))
{
lex_string_set(&item->name, name->str);
item->base_flags|= item_base_t::IS_EXPLICIT_NAME;
}
if (arena)
thd->restore_active_arena(arena, &backup);
}
else
make_valid_column_names(thd, select->item_list);
if (cycle_list)
{
List_iterator_fast<Item> it(select->item_list);
List_iterator_fast<Lex_ident_sys> nm(*cycle_list);
List_iterator_fast<Lex_ident_sys> nm_check(*cycle_list);
DBUG_ASSERT(cycle_list->elements != 0);
while (LEX_CSTRING *name= nm++)
{
Item *item;
/*
Check for uniqueness of each element in the cycle list:
It's sufficient to check that there is no duplicate of 'name'
among the elements that precede it.
*/
LEX_CSTRING *check;
nm_check.rewind();
while ((check= nm_check++) && check != name)
{
if (check->length == name->length &&
strncmp(check->str, name->str, name->length) == 0)
{
my_error(ER_DUP_FIELDNAME, MYF(0), check->str);
return true;
}
}
/* Check that 'name' is the name of a column of the processed CTE */
while ((item= it++) &&
(item->name.length != name->length ||
strncmp(item->name.str, name->str, name->length) != 0));
if (item == NULL)
{
my_error(ER_BAD_FIELD_ERROR, MYF(0), name->str, "CYCLE clause");
return true;
}
item->base_flags|= item_base_t::IS_IN_WITH_CYCLE;
}
}
unit->columns_are_renamed= true;
return false;
}
/**
@brief
Perform context analysis the definition of an unreferenced table
@param thd The context of the statement containing this with element
@details
The method assumes that this with element contains the definition
of a table that is not used anywhere. In this case one has to check
that context conditions are met.
@retval
true if an error was reported
false otherwise
*/
bool With_element::prepare_unreferenced(THD *thd)
{
bool rc= false;
st_select_lex *first_sl= spec->first_select();
/* Prevent name resolution for field references out of with elements */
for (st_select_lex *sl= first_sl;
sl;
sl= sl->next_select())
sl->context.outer_context= 0;
uint8 save_context_analysys_only= thd->lex->context_analysis_only;
thd->lex->context_analysis_only|= CONTEXT_ANALYSIS_ONLY_DERIVED;
if (!spec->prepared &&
(spec->prepare(spec->derived, 0, 0) ||
process_columns_of_derived_unit(thd, spec) ||
check_duplicate_names(thd, first_sl->item_list, 1)))
rc= true;
thd->lex->context_analysis_only= save_context_analysys_only;
return rc;
}
bool With_element::is_anchor(st_select_lex *sel)
{
return !(mutually_recursive & sel->with_dep);
}
/**
@brief
Search for the definition of the given table referred in this select node
@param table reference to the table whose definition is searched for
@param excl_spec ignore the definition with this spec
@details
The method looks for the definition of the table whose reference is occurred
in the FROM list of this select node. First it searches for it in the
with clause attached to the unit this select node belongs to. If such a
definition is not found then the embedding units are looked through.
@retval
pointer to the found definition if the search has been successful
NULL - otherwise
*/
With_element *st_select_lex::find_table_def_in_with_clauses(TABLE_LIST *table,
st_select_lex_unit *excl_spec)
{
With_element *found= NULL;
With_clause *containing_with_clause= NULL;
st_select_lex_unit *master_unit;
st_select_lex *outer_sl;
for (st_select_lex *sl= this; sl; sl= outer_sl)
{
/*
If sl->master_unit() is the spec of a with element then the search for
a definition was already done by With_element::check_dependencies_in_spec
and it was unsuccesful. Yet for units cloned from the spec it has not
been done yet.
*/
With_clause *attached_with_clause= sl->get_with_clause();
if (attached_with_clause &&
attached_with_clause != containing_with_clause &&
(found= attached_with_clause->find_table_def(table, NULL, excl_spec)))
break;
master_unit= sl->master_unit();
outer_sl= master_unit->outer_select();
With_element *with_elem= sl->get_with_element();
if (with_elem)
{
containing_with_clause= with_elem->get_owner();
With_element *barrier= containing_with_clause->with_recursive ?
NULL : with_elem;
if ((found= containing_with_clause->find_table_def(table, barrier,
excl_spec)))
break;
if (outer_sl && !outer_sl->get_with_element())
break;
}
/* Do not look for the table's definition beyond the scope of the view */
if (master_unit->is_view)
break;
}
return found;
}
bool TABLE_LIST::is_recursive_with_table()
{
return with && with->is_recursive;
}
/*
A reference to a with table T is recursive if it occurs somewhere
in the query specifying T or in the query specifying one of the tables
mutually recursive with T.
*/
bool TABLE_LIST::is_with_table_recursive_reference()
{
return (with_internal_reference_map &&
(with->get_mutually_recursive() & with_internal_reference_map));
}
/*
Specifications of with tables with recursive table references
in non-mergeable derived tables are not allowed in this
implementation.
*/
/*
We say that the specification of a with table T is restricted
if all below is true.
1. Any immediate select of the specification contains at most one
recursive table reference taking into account table references
from mergeable derived tables.
2. Any recursive table reference is not an inner operand of an
outer join operation used in an immediate select of the
specification.
3. Any immediate select from the specification of T does not
contain aggregate functions.
4. The specification of T does not contain recursive table references.
If the specification of T is not restricted we call the corresponding
with element unrestricted.
The SQL standards allows only with elements with restricted specification.
By default we comply with the standards here.
Yet we allow unrestricted specification if the status variable
'standards_compliant_cte' set to 'off'(0).
*/
/**
@brief
Check if this select makes the including specification unrestricted
@param
only_standards_compliant true if the system variable
'standards_compliant_cte' is set to 'on'
@details
This method checks whether the conditions 1-4 (see the comment above)
are satisfied for this select. If not then mark this element as
unrestricted and report an error if 'only_standards_compliant' is true.
@retval
true if an error is reported
false otherwise
*/
bool st_select_lex::check_unrestricted_recursive(bool only_standard_compliant)
{
With_element *with_elem= get_with_element();
if (!with_elem ||!with_elem->is_recursive)
{
/*
If this select is not from the specifiocation of a with elememt or
if this not a recursive with element then there is nothing to check.
*/
return false;
}
/* Check conditions 1-2 for restricted specification*/
table_map unrestricted= 0;
table_map encountered= 0;
if (with_elem->check_unrestricted_recursive(this,
unrestricted,
encountered))
return true;
with_elem->get_owner()->add_unrestricted(unrestricted);
/* Check conditions 3-4 for restricted specification*/
if ((with_sum_func && !with_elem->is_anchor(this)) ||
(with_elem->contains_sq_with_recursive_reference()))
with_elem->get_owner()->add_unrestricted(
with_elem->get_mutually_recursive());
/* Report an error on unrestricted specification if this is required */
if (only_standard_compliant && with_elem->is_unrestricted())
{
my_error(ER_NOT_STANDARD_COMPLIANT_RECURSIVE,
MYF(0), with_elem->get_name_str());
return true;
}
return false;
}
/**
@brief
Check if a select from the spec of this with element is partially restricted
@param
sel select from the specification of this element where to check
whether conditions 1-2 are satisfied
unrestricted IN/OUT bitmap where to mark unrestricted specs
encountered IN/OUT bitmap where to mark encountered recursive references
@details
This method checks whether the conditions 1-2 (see the comment above)
are satisfied for the select sel.
This method is called recursively for derived tables.
@retval
true if an error is reported
false otherwise
*/
bool With_element::check_unrestricted_recursive(st_select_lex *sel,
table_map &unrestricted,
table_map &encountered)
{
/* Check conditions 1 for restricted specification*/
List_iterator<TABLE_LIST> ti(sel->leaf_tables);
TABLE_LIST *tbl;
while ((tbl= ti++))
{
st_select_lex_unit *unit= tbl->get_unit();
if (unit)
{
if(!tbl->is_with_table())
{
if (check_unrestricted_recursive(unit->first_select(),
unrestricted,
encountered))
return true;
}
if (!(tbl->is_recursive_with_table() && unit->with_element->owner == owner))
continue;
With_element *with_elem= unit->with_element;
if (encountered & with_elem->get_elem_map())
unrestricted|= with_elem->mutually_recursive;
else if (with_elem ==this)
encountered|= with_elem->get_elem_map();
}
}
for (With_element *with_elem= owner->with_list.first;
with_elem;
with_elem= with_elem->next)
{
if (!with_elem->is_recursive && (unrestricted & with_elem->get_elem_map()))
continue;
if (encountered & with_elem->get_elem_map())
{
uint cnt= 0;
table_map encountered_mr= encountered & with_elem->mutually_recursive;
for (table_map map= encountered_mr >> with_elem->number;
map != 0;
map>>= 1)
{
if (map & 1)
{
if (cnt)
{
unrestricted|= with_elem->mutually_recursive;
break;
}
else
cnt++;
}
}
}
}
/* Check conditions 2 for restricted specification*/
ti.rewind();
while ((tbl= ti++))
{
if (!tbl->is_with_table_recursive_reference())
continue;
for (TABLE_LIST *tab= tbl; tab; tab= tab->embedding)
{
if (tab->outer_join & (JOIN_TYPE_LEFT | JOIN_TYPE_RIGHT))
{
unrestricted|= mutually_recursive;
break;
}
}
}
return false;
}
/**
@brief
Check subqueries with recursive table references from FROM list of this select
@details
For each recursive table reference from the FROM list of this select
this method checks:
- whether this reference is within a materialized derived table and
if so it report an error
- whether this reference is within a subquery and if so it set a flag
in this subquery that disallows some optimization strategies for
this subquery.
@retval
true if an error is reported
false otherwise
*/
bool st_select_lex::check_subqueries_with_recursive_references()
{
List_iterator<TABLE_LIST> ti(leaf_tables);
TABLE_LIST *tbl;
while ((tbl= ti++))
{
if (!(tbl->is_with_table_recursive_reference()))
continue;
With_element *rec_elem= tbl->with;
st_select_lex_unit *sl_master;
for (st_select_lex *sl= this; sl; sl= sl_master->outer_select())
{
sl_master= sl->master_unit();
if (sl_master->with_element &&
sl_master->with_element->get_owner() == rec_elem->get_owner())
break;
sl->uncacheable|= UNCACHEABLE_DEPENDENT;
sl_master->uncacheable|= UNCACHEABLE_DEPENDENT;
if (sl_master->derived)
sl_master->derived->register_as_derived_with_rec_ref(rec_elem);
if (sl_master->item)
{
Item_subselect *subq= (Item_subselect *) (sl_master->item);
subq->register_as_with_rec_ref(rec_elem);
}
}
}
return false;
}
/**
@brief
Print this with clause
@param thd Thread handle
@param str Where to print to
@param query_type The mode of printing
@details
The method prints a string representation of this clause in the
string str. The parameter query_type specifies the mode of printing.
*/
void With_clause::print(THD *thd, String *str, enum_query_type query_type)
{
/*
Any with clause contains just definitions of CTE tables.
No data expansion is applied to these definitions.
*/
query_type= (enum_query_type) (query_type | QT_NO_DATA_EXPANSION);
str->append(STRING_WITH_LEN("with "));
if (with_recursive)
str->append(STRING_WITH_LEN("recursive "));
for (With_element *with_elem= with_list.first;
with_elem;
with_elem= with_elem->next)
{
if (with_elem != with_list.first)
str->append(STRING_WITH_LEN(", "));
with_elem->print(thd, str, query_type);
}
}
static void list_strlex_print(THD *thd, String *str, List<Lex_ident_sys> *list)
{
List_iterator_fast<Lex_ident_sys> li(*list);
bool first= TRUE;
while(Lex_ident_sys *col_name= li++)
{
if (first)
first= FALSE;
else
str->append(',');
append_identifier(thd, str, col_name);
}
}
/**
@brief
Print this with element
@param thd Thread handle
@param str Where to print to
@param query_type The mode of printing
@details
The method prints a string representation of this with element in the
string str. The parameter query_type specifies the mode of printing.
*/
void With_element::print(THD *thd, String *str, enum_query_type query_type)
{
str->append(get_name());
if (column_list.elements)
{
List_iterator_fast<Lex_ident_sys> li(column_list);
str->append('(');
list_strlex_print(thd, str, &column_list);
str->append(')');
}
str->append(STRING_WITH_LEN(" as ("));
spec->print(str, query_type);
str->append(')');
if (cycle_list)
{
DBUG_ASSERT(cycle_list->elements != 0);
str->append(STRING_WITH_LEN(" CYCLE "));
list_strlex_print(thd, str, cycle_list);
str->append(STRING_WITH_LEN(" RESTRICT "));
}
}
bool With_element::instantiate_tmp_tables()
{
List_iterator_fast<TABLE_LIST> li(rec_result->rec_table_refs);
TABLE_LIST *rec_tbl;
while ((rec_tbl= li++))
{
TABLE *rec_table= rec_tbl->table;
if (!rec_table->is_created() &&
instantiate_tmp_table(rec_table,
rec_table->s->key_info,
rec_result->tmp_table_param.start_recinfo,
&rec_result->tmp_table_param.recinfo,
0))
return true;
rec_table->file->extra(HA_EXTRA_WRITE_CACHE);
rec_table->file->extra(HA_EXTRA_IGNORE_DUP_KEY);
}
return false;
}
void With_element::set_cycle_list(List<Lex_ident_sys> *cycle_list_arg)
{
cycle_list= cycle_list_arg;
/*
If a CTE table with columns c1,...,cn is defined with a cycle
clause CYCLE(ci1,...,cik) then no two rows r1 and r2 from the
table shall have r1.ci1=r2.ci1 && ... && r1.cik=r2.cik.
If a cycle clause is used in the specification of a CTE then
each UNION ALL at the top level of the specification is interpreted
as a UNION DISTINCT over the cycle columns.
*/
for (st_select_lex *sl= spec->first_select(); sl; sl= sl->next_select())
{
spec->union_distinct= sl;
if (sl != spec->first_select())
{
sl->distinct= TRUE;
sl->with_all_modifier= FALSE;
}
}
}
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