greenplumn CQueryMutators 源码
greenplumn CQueryMutators 代码
文件路径：/src/backend/gpopt/translate/CQueryMutators.cpp
//---------------------------------------------------------------------------
// Greenplum Database
// Copyright (C) 2012 EMC Corp.
//
// @filename:
// CQueryMutators.cpp
//
// @doc:
// Implementation of methods used during translating a GPDB Query object into a
// DXL Tree
//
// @test:
//
//---------------------------------------------------------------------------
extern "C" {
#include "postgres.h"
#include "nodes/makefuncs.h"
#include "nodes/parsenodes.h"
#include "nodes/plannodes.h"
#include "optimizer/walkers.h"
}
#include "gpopt/base/CUtils.h"
#include "gpopt/gpdbwrappers.h"
#include "gpopt/mdcache/CMDAccessor.h"
#include "gpopt/mdcache/CMDAccessorUtils.h"
#include "gpopt/translate/CQueryMutators.h"
#include "gpopt/translate/CTranslatorDXLToPlStmt.h"
#include "naucrates/exception.h"
#include "naucrates/md/IMDAggregate.h"
#include "naucrates/md/IMDScalarOp.h"
#include "naucrates/md/IMDTypeBool.h"
using namespace gpdxl;
using namespace gpmd;
//---------------------------------------------------------------------------
// @function:
// CQueryMutators::NeedsProjListNormalization
//
// @doc:
// Is the group by project list flat (contains only aggregates, grouping
// funcs, and grouping columns)
//---------------------------------------------------------------------------
BOOL
CQueryMutators::NeedsProjListNormalization(const Query *query)
{
if (!query->hasAggs && nullptr == query->groupClause &&
nullptr == query->groupingSets)
{
return false;
}
SContextTLWalker context(query->targetList, query->groupClause);
ListCell *lc = nullptr;
ForEach(lc, query->targetList)
{
TargetEntry *target_entry = (TargetEntry *) lfirst(lc);
if (ShouldFallback((Node *) target_entry->expr, &context))
{
// TODO: remove temporary fix (revert exception to assert) to avoid crash during algebrization
GPOS_RAISE(gpdxl::ExmaDXL, gpdxl::ExmiQuery2DXLError,
GPOS_WSZ_LIT("No attribute"));
}
// Normalize when there is an expression that is neither used for grouping
// nor is an aggregate function
if (!IsA(target_entry->expr, Aggref) &&
!IsA(target_entry->expr, GroupingFunc) &&
!CTranslatorUtils::IsGroupingColumn((Node *) target_entry->expr,
query->groupClause,
query->targetList))
{
return true;
}
}
return false;
}
//---------------------------------------------------------------------------
// @function:
// CQueryMutators::ShouldFallback
//
// @doc:
// Fall back when the target list refers to a attribute which algebrizer
// at this point cannot resolve
//---------------------------------------------------------------------------
BOOL
CQueryMutators::ShouldFallback(Node *node, SContextTLWalker *context)
{
if (nullptr == node)
{
return false;
}
if (IsA(node, Const) || IsA(node, Aggref) || IsA(node, GroupingFunc) ||
IsA(node, SubLink))
{
return false;
}
TargetEntry *entry = gpdb::FindFirstMatchingMemberInTargetList(
node, context->m_target_entries);
if (nullptr != entry && CTranslatorUtils::IsGroupingColumn(
(Node *) entry->expr, context->m_group_clause,
context->m_target_entries))
{
return false;
}
if (IsA(node, SubLink))
{
return false;
}
if (IsA(node, Var))
{
Var *var = (Var *) node;
if (0 == var->varlevelsup)
{
// if we reach a Var that was not a grouping column then there is an equivalent column
// which the algebrizer at this point cannot resolve
// example: consider two table r(a,b) and s(c,d) and the following query
// SELECT a from r LEFT JOIN s on (r.a = s.c) group by r.a
// In the query object, generated by the parse, the output columns refer to the output of
// the left outer join while the grouping column refers to the base table column.
// While r.a and a are equivalent, the algebrizer at this point cannot detect this.
// Therefore, we fall back.
return true;
}
return false;
}
return gpdb::WalkExpressionTree(
node, (ExprWalkerFn) CQueryMutators::ShouldFallback, context);
}
//---------------------------------------------------------------------------
// @function:
// CQueryMutators::NormalizeGroupByProjList
//
// @doc:
// Flatten expressions in project list to contain only aggregates, grouping
// funcs and grouping columns
// ORGINAL QUERY:
// SELECT * from r where r.a > (SELECT max(c) + min(d) FROM t where r.b = t.e)
// NEW QUERY:
// SELECT * from r where r.a > (SELECT x1+x2 as x3
// FROM (SELECT max(c) as x2, min(d) as x2
// FROM t where r.b = t.e) t2)
//---------------------------------------------------------------------------
Query *
CQueryMutators::NormalizeGroupByProjList(CMemoryPool *mp,
CMDAccessor *md_accessor,
const Query *query)
{
Query *query_copy = (Query *) gpdb::CopyObject(const_cast<Query *>(query));
if (!NeedsProjListNormalization(query_copy))
{
return query_copy;
}
Query *new_query =
ConvertToDerivedTable(query_copy, false /*should_fix_target_list*/,
true /*should_fix_having_qual*/);
gpdb::GPDBFree(query_copy);
GPOS_ASSERT(1 == gpdb::ListLength(new_query->rtable));
Query *derived_table_query =
(Query *) ((RangeTblEntry *) gpdb::ListNth(new_query->rtable, 0))
->subquery;
SContextGrpbyPlMutator context(mp, md_accessor, derived_table_query,
nullptr);
List *target_list_copy =
(List *) gpdb::CopyObject(derived_table_query->targetList);
ListCell *lc = nullptr;
// first normalize grouping columns
ForEach(lc, target_list_copy)
{
TargetEntry *target_entry = (TargetEntry *) lfirst(lc);
GPOS_ASSERT(nullptr != target_entry);
if (CTranslatorUtils::IsGroupingColumn(
target_entry, derived_table_query->groupClause))
{
target_entry->expr = (Expr *) FixGroupingCols(
(Node *) target_entry->expr, target_entry, &context);
}
}
lc = nullptr;
// normalize remaining project elements
ForEach(lc, target_list_copy)
{
TargetEntry *target_entry = (TargetEntry *) lfirst(lc);
GPOS_ASSERT(nullptr != target_entry);
BOOL is_grouping_col = CTranslatorUtils::IsGroupingColumn(
target_entry, derived_table_query->groupClause);
if (!is_grouping_col)
{
target_entry->expr = (Expr *) RunExtractAggregatesMutator(
(Node *) target_entry->expr, &context);
GPOS_ASSERT(!IsA(target_entry->expr, Aggref) &&
"New target list entry should not contain any Aggrefs");
GPOS_ASSERT(
!IsA(target_entry->expr, GroupingFunc) &&
"New target list entry should not contain any GroupingFuncs");
}
}
derived_table_query->targetList = context.m_lower_table_tlist;
new_query->targetList = target_list_copy;
ReassignSortClause(new_query, derived_table_query);
return new_query;
}
//---------------------------------------------------------------------------
// @function:
// CQueryMutators::RunIncrLevelsUpMutator
//
// @doc:
// Increment any the query levels up of any outer reference by one
//---------------------------------------------------------------------------
Node *
CQueryMutators::RunIncrLevelsUpMutator(Node *node,
SContextIncLevelsupMutator *context)
{
if (nullptr == node)
{
return nullptr;
}
if (IsA(node, Var))
{
Var *var = (Var *) gpdb::CopyObject(node);
// Consider the following use case:
// ORGINAL QUERY:
// SELECT * from r where r.a > (SELECT max(c) + min(d)
// FROM t where r.b = t.e)
// NEW QUERY:
// SELECT * from r where r.a > (SELECT x1+x2 as x3
// FROM (SELECT max(c) as x2, min(d) as x2
// FROM t where r.b = t.e) t2)
//
// In such a scenario, we need increment the levels up for the
// correlation variable r.b in the subquery by 1.
if (var->varlevelsup > context->m_current_query_level)
{
var->varlevelsup++;
return (Node *) var;
}
return (Node *) var;
}
if (IsA(node, TargetEntry) && 0 == context->m_current_query_level &&
!context->m_should_fix_top_level_target_list)
{
return (Node *) gpdb::CopyObject(node);
}
// recurse into query structure
if (IsA(node, Query))
{
context->m_current_query_level++;
Query *query = query_tree_mutator(
(Query *) node,
(MutatorWalkerFn) CQueryMutators::RunIncrLevelsUpMutator, context,
0 // flags
);
context->m_current_query_level--;
return (Node *) query;
}
return expression_tree_mutator(
node, (MutatorWalkerFn) CQueryMutators::RunIncrLevelsUpMutator,
context);
}
//---------------------------------------------------------------------------
// CQueryMutators::RunFixCTELevelsUpWalker
//
// Increment CTE range table reference by one if it refers to
// an ancestor of the original Query node (level 0 in the context)
//---------------------------------------------------------------------------
BOOL
CQueryMutators::RunFixCTELevelsUpWalker(Node *node,
SContextIncLevelsupMutator *context)
{
if (nullptr == node)
{
return false;
}
if (IsA(node, RangeTblEntry))
{
RangeTblEntry *rte = (RangeTblEntry *) node;
if (RTE_CTE == rte->rtekind &&
rte->ctelevelsup >= context->m_current_query_level)
{
// fix the levels up for CTE range table entry when needed
// the walker in GPDB does not walk range table entries of type CTE
rte->ctelevelsup++;
}
// always return false, as we want to continue fixing up RTEs
return false;
}
// recurse into query structure, incrementing the query level
if (IsA(node, Query))
{
context->m_current_query_level++;
BOOL result = query_tree_walker(
(Query *) node,
(ExprWalkerFn) CQueryMutators::RunFixCTELevelsUpWalker, context,
QTW_EXAMINE_RTES_BEFORE // flags - visit RTEs
);
context->m_current_query_level--;
return result;
}
if (IsA(node, TargetEntry) &&
!context->m_should_fix_top_level_target_list &&
0 == context->m_current_query_level)
{
// skip the top-level target list, if requested
return false;
}
return expression_tree_walker(
node, (ExprWalkerFn) CQueryMutators::RunFixCTELevelsUpWalker, context);
}
//---------------------------------------------------------------------------
// @function:
// CQueryMutators::RunGroupingColMutator
//
// @doc:
// Mutate the grouping columns, fix levels up when necessary
//
//---------------------------------------------------------------------------
Node *
CQueryMutators::RunGroupingColMutator(Node *node,
SContextGrpbyPlMutator *context)
{
if (nullptr == node)
{
return nullptr;
}
if (IsA(node, Const))
{
return (Node *) gpdb::CopyObject(node);
}
if (IsA(node, Var))
{
Var *var_copy = (Var *) gpdb::CopyObject(node);
if (var_copy->varlevelsup > context->m_current_query_level)
{
var_copy->varlevelsup++;
}
return (Node *) var_copy;
}
if (IsA(node, Aggref))
{
// merely fix the arguments of an aggregate
Aggref *old_aggref = (Aggref *) node;
Aggref *aggref = FlatCopyAggref(old_aggref);
aggref->agglevelsup = old_aggref->agglevelsup;
List *new_args = NIL;
ListCell *lc = nullptr;
BOOL is_agg = context->m_is_mutating_agg_arg;
context->m_is_mutating_agg_arg = true;
ForEach(lc, old_aggref->args)
{
Node *arg = (Node *) gpdb::CopyObject((Node *) lfirst(lc));
GPOS_ASSERT(nullptr != arg);
// traverse each argument and fix levels up when needed
new_args = gpdb::LAppend(
new_args,
gpdb::MutateQueryOrExpressionTree(
arg,
(MutatorWalkerFn) CQueryMutators::RunGroupingColMutator,
(void *) context,
0 // flags -- mutate into cte-lists
));
}
context->m_is_mutating_agg_arg = is_agg;
aggref->args = new_args;
return (Node *) aggref;
}
if (IsA(node, GroupingFunc))
{
// FIXME: we do not fix levelsup for GroupingFunc here, the translator
// will fall back later when it detects levelsup > 0. We need to do
// similar things as AggRef here when ORCA adds support for GroupingFunc
// with outer refs
return (Node *) gpdb::CopyObject(node);
}
if (IsA(node, SubLink))
{
SubLink *old_sublink = (SubLink *) node;
SubLink *new_sublink = MakeNode(SubLink);
new_sublink->subLinkType = old_sublink->subLinkType;
new_sublink->location = old_sublink->location;
new_sublink->operName =
(List *) gpdb::CopyObject(old_sublink->operName);
new_sublink->testexpr = gpdb::MutateQueryOrExpressionTree(
old_sublink->testexpr,
(MutatorWalkerFn) CQueryMutators::RunGroupingColMutator,
(void *) context,
0 // flags -- mutate into cte-lists
);
context->m_current_query_level++;
GPOS_ASSERT(IsA(old_sublink->subselect, Query));
new_sublink->subselect = gpdb::MutateQueryOrExpressionTree(
old_sublink->subselect,
(MutatorWalkerFn) CQueryMutators::RunGroupingColMutator, context,
0 // flags -- mutate into cte-lists
);
context->m_current_query_level--;
return (Node *) new_sublink;
}
if (IsA(node, CommonTableExpr))
{
CommonTableExpr *cte = (CommonTableExpr *) gpdb::CopyObject(node);
context->m_current_query_level++;
GPOS_ASSERT(IsA(cte->ctequery, Query));
cte->ctequery = gpdb::MutateQueryOrExpressionTree(
cte->ctequery,
(MutatorWalkerFn) CQueryMutators::RunGroupingColMutator,
(void *) context,
0 // flags --- mutate into cte-lists
);
context->m_current_query_level--;
return (Node *) cte;
}
// recurse into query structure
if (IsA(node, Query))
{
Query *query = gpdb::MutateQueryTree(
(Query *) node,
(MutatorWalkerFn) CQueryMutators::RunGroupingColMutator, context,
1 // flag -- do not mutate range table entries
);
// fix the outer reference in derived table entries
List *rtable = query->rtable;
ListCell *lc = nullptr;
ForEach(lc, rtable)
{
RangeTblEntry *rte = (RangeTblEntry *) lfirst(lc);
if (RTE_SUBQUERY == rte->rtekind)
{
Query *subquery = rte->subquery;
// since we did not walk inside derived tables
context->m_current_query_level++;
rte->subquery =
(Query *) RunGroupingColMutator((Node *) subquery, context);
context->m_current_query_level--;
gpdb::GPDBFree(subquery);
}
}
return (Node *) query;
}
return gpdb::MutateExpressionTree(
node, (MutatorWalkerFn) CQueryMutators::RunGroupingColMutator, context);
}
//---------------------------------------------------------------------------
// @function:
// CQueryMutators::FixGroupingCols
//
// @doc:
// Mutate the grouping columns, fix levels up when necessary
//---------------------------------------------------------------------------
Node *
CQueryMutators::FixGroupingCols(Node *node, TargetEntry *orginal_target_entry,
SContextGrpbyPlMutator *context)
{
GPOS_ASSERT(nullptr != node);
ULONG arity = gpdb::ListLength(context->m_lower_table_tlist) + 1;
// fix any outer references in the grouping column expression
Node *expr = (Node *) RunGroupingColMutator(node, context);
CHAR *name = CQueryMutators::GetTargetEntryColName(orginal_target_entry,
context->m_query);
TargetEntry *new_target_entry = gpdb::MakeTargetEntry(
(Expr *) expr, (AttrNumber) arity, name, false /*resjunk */);
new_target_entry->ressortgroupref = orginal_target_entry->ressortgroupref;
new_target_entry->resjunk = false;
context->m_lower_table_tlist =
gpdb::LAppend(context->m_lower_table_tlist, new_target_entry);
Var *new_var = gpdb::MakeVar(
1, // varno
(AttrNumber) arity, gpdb::ExprType((Node *) orginal_target_entry->expr),
gpdb::ExprTypeMod((Node *) orginal_target_entry->expr),
0 // query levelsup
);
return (Node *) new_var;
}
//---------------------------------------------------------------------------
// @function:
// CQueryMutators::GetTargetEntryForAggExpr
//
// @doc:
// Return a target entry for an aggregate expression
//---------------------------------------------------------------------------
TargetEntry *
CQueryMutators::GetTargetEntryForAggExpr(CMemoryPool *mp,
CMDAccessor *md_accessor, Node *node,
ULONG attno)
{
GPOS_ASSERT(IsA(node, Aggref) || IsA(node, GroupingFunc));
// get the function/aggregate name
CHAR *name = nullptr;
if (IsA(node, GroupingFunc))
{
name = CTranslatorUtils::CreateMultiByteCharStringFromWCString(
GPOS_WSZ_LIT("grouping"));
}
else
{
Aggref *aggref = (Aggref *) node;
CMDIdGPDB *agg_mdid = GPOS_NEW(mp) CMDIdGPDB(aggref->aggfnoid);
const IMDAggregate *md_agg = md_accessor->RetrieveAgg(agg_mdid);
agg_mdid->Release();
const CWStringConst *str = md_agg->Mdname().GetMDName();
name = CTranslatorUtils::CreateMultiByteCharStringFromWCString(
str->GetBuffer());
}
GPOS_ASSERT(nullptr != name);
return gpdb::MakeTargetEntry((Expr *) node, (AttrNumber) attno, name,
false);
}
// Traverse the entire tree under an arbitrarily complex project element (node)
// to extract all aggregate functions out into the derived query's target list
//
// This mutator should be called after creating a derived query (a subquery in
// the FROM clause), on each element in the old query's target list or qual to
// update any AggRef, GroupingFunc & Var to refer to the output from the derived
// query.
//
// See comments below & in the callers for specific use cases.
Node *
CQueryMutators::RunExtractAggregatesMutator(Node *node,
SContextGrpbyPlMutator *context)
{
if (nullptr == node)
{
return nullptr;
}
if (IsA(node, Const))
{
return (Node *) gpdb::CopyObject(node);
}
if (IsA(node, Aggref))
{
Aggref *old_aggref = (Aggref *) node;
// If the agglevelsup matches the current query level, this Aggref only
// uses vars from the top level query. This needs to be moved to the
// derived query, and the entire AggRef replaced with a Var referencing the
// derived table's target list.
if (old_aggref->agglevelsup == context->m_current_query_level)
{
Aggref *new_aggref = FlatCopyAggref(old_aggref);
BOOL is_agg_old = context->m_is_mutating_agg_arg;
ULONG agg_levels_up = context->m_agg_levels_up;
context->m_is_mutating_agg_arg = true;
context->m_agg_levels_up = old_aggref->agglevelsup;
List *new_args = NIL;
ListCell *lc = nullptr;
ForEach(lc, old_aggref->args)
{
Node *arg = (Node *) lfirst(lc);
GPOS_ASSERT(nullptr != arg);
// traverse each argument and fix levels up when needed
new_args = gpdb::LAppend(
new_args,
gpdb::MutateQueryOrExpressionTree(
arg, (MutatorWalkerFn) RunExtractAggregatesMutator,
(void *) context,
0 // mutate into cte-lists
));
}
new_aggref->args = new_args;
context->m_is_mutating_agg_arg = is_agg_old;
context->m_agg_levels_up = agg_levels_up;
// create a new entry in the derived table and return its corresponding var
return (Node *) MakeVarInDerivedTable((Node *) new_aggref, context);
}
}
if (0 == context->m_current_query_level)
{
if (IsA(node, Var) && context->m_is_mutating_agg_arg)
{
// This mutator may be run on a nested query object with aggregates on
// outer references. It pulls out any aggregates and moves it into the
// derived query (which is subquery), in effect, increasing the levels up
// any Var in the aggregate must now reference
//
// e.g SELECT (SELECT sum(o.o) + 1 FROM i GRP BY i.i) FROM o;
// becomes SELECT (SELECT x + 1 FROM (SELECT sum(o.o) GRP BY i.i)) FROM o;
// which means Var::varlevelup must be increased for o.o
return (Node *) IncrLevelsUpIfOuterRef((Var *) node);
}
if (IsA(node, GroupingFunc))
{
// create a new entry in the derived table and return its corresponding var
Node *node_copy = (Node *) gpdb::CopyObject(node);
return (Node *) MakeVarInDerivedTable(node_copy, context);
}
if (!context->m_is_mutating_agg_arg)
{
// check if an entry already exists, if so no need for duplicate
Node *found_node = FindNodeInGroupByTargetList(node, context);
if (nullptr != found_node)
{
return found_node;
}
}
}
if (IsA(node, Var))
{
Var *var = (Var *) gpdb::CopyObject(node);
// Handle other top-level outer references in the project element.
if (var->varlevelsup == context->m_current_query_level)
{
if (var->varlevelsup == context->m_agg_levels_up)
{
// If Var references the top level query inside an Aggref that also
// references top level query, the Aggref is moved to the derived query
// (see comments in Aggref if-case above). Thus, these Var references
// are brought up to the top-query level.
// e.g:
// explain select (select sum(foo.a) from jazz) from foo group by a, b;
// is transformed into
// select (select fnew.sum_t from jazz)
// from (select foo.a, foo.b, sum(foo.a) sum_t
// from foo group by foo.a, foo.b) fnew;
//
// Note the foo.a var which is in sum() in a subquery must now become a
// var referencing the current query level.
var->varlevelsup = 0;
return (Node *) var;
}
// Skip vars inside Aggrefs, since they have already been fixed when they
// were moved into the derived query in ConvertToDerivedTable(), and thus,
// the relative varno, varattno & varlevelsup should still be valid.
// e.g:
// SELECT foo.b+1, avg(( SELECT bar.f FROM bar
// WHERE bar.d = foo.b)) AS t
// FROM foo GROUP BY foo.b;
// is transformed into
// SELECT fnew.b+1, fnew.avg_t
// FROM (SELECT foo.b,`avg(( SELECT bar.f FROM bar
// WHERE bar.d = foo.b)) AS t
// FROM foo) fnew;
//
// Note the foo.b outerref in subquery inside the avg() aggregation.
// Because it is inside the aggregation, it was pushed down along with
// the aggregate function, and thus does not need to be fixed.
if (context->m_is_mutating_agg_arg)
{
return (Node *) var;
}
// For other top-level references, correct their varno & varattno, since
// they now must refer to the target list of the derived query - whose
// target list may be different from the original query.
// Set varlevelsup to 0 temporarily while searching in the target list
var->varlevelsup = 0;
TargetEntry *found_tle = gpdb::FindFirstMatchingMemberInTargetList(
(Node *) var, context->m_lower_table_tlist);
if (nullptr == found_tle)
{
// Consider two table r(a,b) and s(c,d) and the following query
// SELECT 1 from r LEFT JOIN s on (r.a = s.c) group by r.a having count(*) > a
// The having clause refers to the output of the left outer join while the
// grouping column refers to the base table column.
// While r.a and a are equivalent, the algebrizer at this point cannot detect this.
// Therefore, found_target_entry will be NULL and we fall back.
// TODO: Oct 14 2013, remove temporary fix (revert exception to assert) to avoid crash during algebrization
GPOS_RAISE(gpdxl::ExmaDXL, gpdxl::ExmiQuery2DXLError,
GPOS_WSZ_LIT("No attribute"));
return nullptr;
}
var->varno =
1; // derived query is the only table in FROM expression
var->varattno = found_tle->resno;
var->varlevelsup =
context->m_current_query_level; // reset varlevels up
found_tle->resjunk = false;
return (Node *) var;
}
return (Node *) var;
}
if (IsA(node, CommonTableExpr))
{
CommonTableExpr *cte = (CommonTableExpr *) gpdb::CopyObject(node);
context->m_current_query_level++;
GPOS_ASSERT(IsA(cte->ctequery, Query));
cte->ctequery = gpdb::MutateQueryOrExpressionTree(
cte->ctequery, (MutatorWalkerFn) RunExtractAggregatesMutator,
(void *) context,
0 // mutate into cte-lists
);
context->m_current_query_level--;
return (Node *) cte;
}
if (IsA(node, SubLink))
{
SubLink *old_sublink = (SubLink *) node;
SubLink *new_sublink = MakeNode(SubLink);
new_sublink->subLinkType = old_sublink->subLinkType;
new_sublink->location = old_sublink->location;
new_sublink->operName =
(List *) gpdb::CopyObject(old_sublink->operName);
new_sublink->testexpr = gpdb::MutateQueryOrExpressionTree(
old_sublink->testexpr,
(MutatorWalkerFn) RunExtractAggregatesMutator, (void *) context,
0 // mutate into cte-lists
);
context->m_current_query_level++;
GPOS_ASSERT(IsA(old_sublink->subselect, Query));
new_sublink->subselect = gpdb::MutateQueryOrExpressionTree(
old_sublink->subselect,
(MutatorWalkerFn) RunExtractAggregatesMutator, (void *) context,
0 // mutate into cte-lists
);
context->m_current_query_level--;
return (Node *) new_sublink;
}
return gpdb::MutateExpressionTree(
node, (MutatorWalkerFn) RunExtractAggregatesMutator, context);
}
// Create a new entry in the derived table and return its corresponding var
Var *
CQueryMutators::MakeVarInDerivedTable(Node *node,
SContextGrpbyPlMutator *context)
{
GPOS_ASSERT(nullptr != node);
GPOS_ASSERT(nullptr != context);
GPOS_ASSERT(IsA(node, Aggref) || IsA(node, Var) || IsA(node, GroupingFunc));
// Append a new target entry for the node to the derived target list ...
const ULONG attno = gpdb::ListLength(context->m_lower_table_tlist) + 1;
TargetEntry *tle = nullptr;
if (IsA(node, Aggref) || IsA(node, GroupingFunc))
{
tle = GetTargetEntryForAggExpr(context->m_mp, context->m_mda, node,
attno);
}
else if (IsA(node, Var))
{
tle = gpdb::MakeTargetEntry((Expr *) node, (AttrNumber) attno, nullptr,
false);
}
context->m_lower_table_tlist =
gpdb::LAppend(context->m_lower_table_tlist, tle);
// ... and return a Var referring to it in its stead
// NB: Since the new tle is appended at the top query level, Var::varlevelsup
// should equal the current nested level. This will take care of any outer references
// to the original tlist.
Var *new_var =
gpdb::MakeVar(1 /* varno */, attno, gpdb::ExprType((Node *) node),
gpdb::ExprTypeMod((Node *) node),
context->m_current_query_level /* varlevelsup */);
return new_var;
}
// Check if a matching entry already exists in the list of target
// entries, if yes return its corresponding var, otherwise return NULL
Node *
CQueryMutators::FindNodeInGroupByTargetList(Node *node,
SContextGrpbyPlMutator *context)
{
GPOS_ASSERT(nullptr != node);
GPOS_ASSERT(nullptr != context);
TargetEntry *found_tle = gpdb::FindFirstMatchingMemberInTargetList(
node, context->m_lower_table_tlist);
if (nullptr != found_tle)
{
gpdb::GPDBFree(node);
// NB: Var::varlevelsup is set to the current query level since the created
// Var must reference the group by targetlist at the top level.
Var *new_var =
gpdb::MakeVar(1 /* varno */, found_tle->resno,
gpdb::ExprType((Node *) found_tle->expr),
gpdb::ExprTypeMod((Node *) found_tle->expr),
context->m_current_query_level /* varlevelsup */);
found_tle->resjunk = false;
return (Node *) new_var;
}
return nullptr;
}
//---------------------------------------------------------------------------
// @function:
// CQueryMutators::FlatCopyAggref
//
// @doc:
// Make a copy of the aggref (minus the arguments)
//---------------------------------------------------------------------------
Aggref *
CQueryMutators::FlatCopyAggref(Aggref *old_aggref)
{
Aggref *new_aggref = MakeNode(Aggref);
*new_aggref = *old_aggref;
new_aggref->agglevelsup = 0;
// This is not strictly necessary: we seem to ALWAYS assgin to args from
// the callers
// Explicitly setting this both to be safe and to be clear that we are
// intentionally NOT copying the args
new_aggref->args = NIL;
return new_aggref;
}
// Increment the levels up of outer references
Var *
CQueryMutators::IncrLevelsUpIfOuterRef(Var *var)
{
GPOS_ASSERT(nullptr != var);
Var *var_copy = (Var *) gpdb::CopyObject(var);
if (0 != var_copy->varlevelsup)
{
var_copy->varlevelsup++;
}
return var_copy;
}
//---------------------------------------------------------------------------
// @function:
// CQueryMutators::NormalizeHaving
//
// @doc:
// Pull up having qual into a select and fix correlated references
// to the top-level query
//---------------------------------------------------------------------------
Query *
CQueryMutators::NormalizeHaving(CMemoryPool *mp, CMDAccessor *md_accessor,
const Query *query)
{
Query *query_copy = (Query *) gpdb::CopyObject(const_cast<Query *>(query));
if (nullptr == query->havingQual)
{
return query_copy;
}
Query *new_query =
ConvertToDerivedTable(query_copy, true /*should_fix_target_list*/,
false /*should_fix_having_qual*/);
gpdb::GPDBFree(query_copy);
RangeTblEntry *rte =
((RangeTblEntry *) gpdb::ListNth(new_query->rtable, 0));
Query *derived_table_query = (Query *) rte->subquery;
// Add all necessary target list entries of subquery
// into the target list of the RTE as well as the new top most query
ListCell *lc = nullptr;
ULONG num_target_entries = 1;
ForEach(lc, derived_table_query->targetList)
{
TargetEntry *target_entry = (TargetEntry *) lfirst(lc);
GPOS_ASSERT(nullptr != target_entry);
// Add to the target lists:
// (1) All grouping / sorting columns even if they do not appear in the subquery output (resjunked)
// (2) All non-resjunked target list entries
if (CTranslatorUtils::IsGroupingColumn(
target_entry, derived_table_query->groupClause) ||
CTranslatorUtils::IsSortingColumn(
target_entry, derived_table_query->sortClause) ||
!target_entry->resjunk)
{
TargetEntry *new_target_entry =
MakeTopLevelTargetEntry(target_entry, num_target_entries);
new_query->targetList =
gpdb::LAppend(new_query->targetList, new_target_entry);
// Ensure that such target entries is not suppressed in the target list of the RTE
// and has a name
target_entry->resname =
GetTargetEntryColName(target_entry, derived_table_query);
target_entry->resjunk = false;
new_target_entry->ressortgroupref = target_entry->ressortgroupref;
num_target_entries++;
}
}
SContextGrpbyPlMutator context(mp, md_accessor, derived_table_query,
derived_table_query->targetList);
// fix outer references in the qual
new_query->jointree->quals =
RunExtractAggregatesMutator(derived_table_query->havingQual, &context);
derived_table_query->havingQual = nullptr;
ReassignSortClause(new_query, rte->subquery);
if (!rte->subquery->hasAggs && NIL == rte->subquery->groupClause &&
NIL == rte->subquery->groupingSets)
{
// if the derived table has no grouping columns or aggregates then the
// subquery is equivalent to select XXXX FROM CONST-TABLE
// (where XXXX is the original subquery's target list)
Query *new_subquery = MakeNode(Query);
new_subquery->commandType = CMD_SELECT;
new_subquery->targetList = NIL;
new_subquery->hasAggs = false;
new_subquery->hasWindowFuncs = false;
new_subquery->hasSubLinks = false;
ListCell *lc = nullptr;
ForEach(lc, rte->subquery->targetList)
{
TargetEntry *target_entry = (TargetEntry *) lfirst(lc);
GPOS_ASSERT(nullptr != target_entry);
GPOS_ASSERT(!target_entry->resjunk);
new_subquery->targetList =
gpdb::LAppend(new_subquery->targetList,
(TargetEntry *) gpdb::CopyObject(target_entry));
}
gpdb::GPDBFree(rte->subquery);
rte->subquery = new_subquery;
rte->subquery->jointree = MakeNode(FromExpr);
rte->subquery->groupClause = NIL;
rte->subquery->groupingSets = NIL;
rte->subquery->sortClause = NIL;
rte->subquery->windowClause = NIL;
}
return new_query;
}
//---------------------------------------------------------------------------
// @function:
// CQueryMutators::NormalizeQuery
//
// @doc:
// Normalize queries with having and group by clauses
//---------------------------------------------------------------------------
Query *
CQueryMutators::NormalizeQuery(CMemoryPool *mp, CMDAccessor *md_accessor,
const Query *query, ULONG query_level)
{
// flatten join alias vars defined at the current level of the query
Query *pqueryResolveJoinVarReferences =
gpdb::FlattenJoinAliasVar(const_cast<Query *>(query), query_level);
// eliminate distinct clause
Query *pqueryEliminateDistinct =
CQueryMutators::EliminateDistinctClause(pqueryResolveJoinVarReferences);
GPOS_ASSERT(nullptr == pqueryEliminateDistinct->distinctClause);
gpdb::GPDBFree(pqueryResolveJoinVarReferences);
// normalize window operator's project list
Query *pqueryWindowPlNormalized = CQueryMutators::NormalizeWindowProjList(
mp, md_accessor, pqueryEliminateDistinct);
gpdb::GPDBFree(pqueryEliminateDistinct);
// pull-up having quals into a select
Query *pqueryHavingNormalized = CQueryMutators::NormalizeHaving(
mp, md_accessor, pqueryWindowPlNormalized);
GPOS_ASSERT(nullptr == pqueryHavingNormalized->havingQual);
gpdb::GPDBFree(pqueryWindowPlNormalized);
// normalize the group by project list
Query *new_query = CQueryMutators::NormalizeGroupByProjList(
mp, md_accessor, pqueryHavingNormalized);
gpdb::GPDBFree(pqueryHavingNormalized);
return new_query;
}
//---------------------------------------------------------------------------
// @function:
// CQueryMutators::GetTargetEntry
//
// @doc:
// Given an Target list entry in the derived table, create a new
// TargetEntry to be added to the top level query. This function allocates
// memory
//---------------------------------------------------------------------------
TargetEntry *
CQueryMutators::MakeTopLevelTargetEntry(TargetEntry *old_target_entry,
ULONG attno)
{
Var *new_var = gpdb::MakeVar(
1, (AttrNumber) attno, gpdb::ExprType((Node *) old_target_entry->expr),
gpdb::ExprTypeMod((Node *) old_target_entry->expr),
0 // query levelsup
);
TargetEntry *new_target_entry = gpdb::MakeTargetEntry(
(Expr *) new_var, (AttrNumber) attno, old_target_entry->resname,
old_target_entry->resjunk);
return new_target_entry;
}
//---------------------------------------------------------------------------
// @function:
// CQueryMutators::GetTargetEntryColName
//
// @doc:
// Return the column name of the target list entry
//---------------------------------------------------------------------------
CHAR *
CQueryMutators::GetTargetEntryColName(TargetEntry *target_entry, Query *query)
{
if (nullptr != target_entry->resname)
{
return target_entry->resname;
}
// Since a resjunked target list entry will not have a column name create a dummy column name
CWStringConst dummy_colname(GPOS_WSZ_LIT("?column?"));
return CTranslatorUtils::CreateMultiByteCharStringFromWCString(
dummy_colname.GetBuffer());
}
//---------------------------------------------------------------------------
// CQueryMutators::ConvertToDerivedTable
//
// Convert "original_query" into two nested Query structs
// and return the new upper query.
//
// upper_query
// original_query ===> |
// lower_query
//
// - The result lower Query has:
// * The original rtable, join tree, groupClause, WindowClause, etc.,
// with modified varlevelsup and ctelevelsup fields, as needed
// * The original targetList, either modified or unmodified,
// depending on should_fix_target_list
// * The original havingQual, either modified or unmodified,
// depending on should_fix_having_qual
//
// - The result upper Query has:
// * a single RTE, pointing to the lower query
// * the CTE list of the original query
// (CTE levels in original have been fixed up)
// * an empty target list
//
//---------------------------------------------------------------------------
Query *
CQueryMutators::ConvertToDerivedTable(const Query *original_query,
BOOL should_fix_target_list,
BOOL should_fix_having_qual)
{
// Step 1: Make a copy of the original Query, this will become the lower query
Query *query_copy =
(Query *) gpdb::CopyObject(const_cast<Query *>(original_query));
// Step 2: Remove things from the query copy that will go in the new, upper Query object
// or won't be modified
Node *having_qual = nullptr;
if (!should_fix_having_qual)
{
having_qual = query_copy->havingQual;
query_copy->havingQual = nullptr;
}
List *original_cte_list = query_copy->cteList;
query_copy->cteList = NIL;
// intoPolicy, if not null, must be set on the top query, not on the derived table
struct GpPolicy *into_policy = query_copy->intoPolicy;
query_copy->intoPolicy = nullptr;
// Step 3: fix outer references and CTE levels
// increment varlevelsup in the lower query where they point to a Query
// that is an ancestor of the original query
Query *lower_query;
{
SContextIncLevelsupMutator context1(0, should_fix_target_list);
lower_query = gpdb::MutateQueryTree(
query_copy, (MutatorWalkerFn) RunIncrLevelsUpMutator, &context1,
0 // flags
);
}
// fix the CTE levels up -- while the old query is converted into a derived table, its cte list
// is re-assigned to the new top-level query. The references to the ctes listed in the old query
// as well as those listed before the current query level are accordingly adjusted in the new
// derived table.
{
SContextIncLevelsupMutator context2(0 /*starting level */,
should_fix_target_list);
(void) gpdb::WalkQueryOrExpressionTree(
(Node *) lower_query, (ExprWalkerFn) RunFixCTELevelsUpWalker,
&context2, QTW_EXAMINE_RTES_BEFORE);
}
if (nullptr != having_qual)
{
lower_query->havingQual = having_qual;
}
// Step 4: Create a new, single range table entry for the upper query
RangeTblEntry *rte = MakeNode(RangeTblEntry);
rte->rtekind = RTE_SUBQUERY;
rte->subquery = lower_query;
rte->inFromCl = true;
rte->subquery->cteList = NIL;
// create a new range table reference for the new RTE
RangeTblRef *rtref = MakeNode(RangeTblRef);
rtref->rtindex = 1;
// Step 5: Create a new upper query with the new RTE in its from clause
Query *upper_query = MakeNode(Query);
upper_query->cteList = original_cte_list;
upper_query->rtable = gpdb::LAppend(upper_query->rtable, rte);
upper_query->intoPolicy = into_policy;
upper_query->parentStmtType = lower_query->parentStmtType;
lower_query->parentStmtType = PARENTSTMTTYPE_NONE;
FromExpr *fromexpr = MakeNode(FromExpr);
fromexpr->quals = nullptr;
fromexpr->fromlist = gpdb::LAppend(fromexpr->fromlist, rtref);
upper_query->jointree = fromexpr;
upper_query->commandType = CMD_SELECT;
GPOS_ASSERT(1 == gpdb::ListLength(upper_query->rtable));
GPOS_ASSERT(false == upper_query->hasWindowFuncs);
return upper_query;
}
//---------------------------------------------------------------------------
// @function:
// CQueryMutators::EliminateDistinctClause
//
// @doc:
// Eliminate distinct columns by translating it into a grouping columns
//---------------------------------------------------------------------------
Query *
CQueryMutators::EliminateDistinctClause(const Query *query)
{
if (0 == gpdb::ListLength(query->distinctClause))
{
return (Query *) gpdb::CopyObject(const_cast<Query *>(query));
}
// create a derived table out of the previous query
Query *new_query =
ConvertToDerivedTable(query, true /*should_fix_target_list*/,
true /*should_fix_having_qual*/);
GPOS_ASSERT(1 == gpdb::ListLength(new_query->rtable));
Query *derived_table_query =
(Query *) ((RangeTblEntry *) gpdb::ListNth(new_query->rtable, 0))
->subquery;
ReassignSortClause(new_query, derived_table_query);
new_query->targetList = NIL;
List *target_entries = derived_table_query->targetList;
ListCell *lc = nullptr;
// build the project list of the new top-level query
ForEach(lc, target_entries)
{
ULONG resno = gpdb::ListLength(new_query->targetList) + 1;
TargetEntry *target_entry = (TargetEntry *) lfirst(lc);
GPOS_ASSERT(nullptr != target_entry);
if (!target_entry->resjunk)
{
// create a new target entry that points to the corresponding entry in the derived table
Var *new_var =
gpdb::MakeVar(1, target_entry->resno,
gpdb::ExprType((Node *) target_entry->expr),
gpdb::ExprTypeMod((Node *) target_entry->expr),
0 // query levels up
);
TargetEntry *new_target_entry =
gpdb::MakeTargetEntry((Expr *) new_var, (AttrNumber) resno,
target_entry->resname, false);
new_target_entry->ressortgroupref = target_entry->ressortgroupref;
new_query->targetList =
gpdb::LAppend(new_query->targetList, new_target_entry);
}
if (0 < target_entry->ressortgroupref &&
!CTranslatorUtils::IsGroupingColumn(
target_entry, derived_table_query->groupClause) &&
!CTranslatorUtils::IsReferencedInWindowSpec(
target_entry, derived_table_query->windowClause))
{
// initialize the ressortgroupref of target entries not used in the grouping clause
target_entry->ressortgroupref = 0;
}
}
if (gpdb::ListLength(new_query->targetList) !=
gpdb::ListLength(query->distinctClause))
{
GPOS_RAISE(
gpdxl::ExmaDXL, gpdxl::ExmiQuery2DXLUnsupportedFeature,
GPOS_WSZ_LIT(
"DISTINCT operation on a subset of target list columns"));
}
ListCell *pl = nullptr;
ForEach(pl, query->distinctClause)
{
SortGroupClause *sort_group_clause = (SortGroupClause *) lfirst(pl);
GPOS_ASSERT(nullptr != sort_group_clause);
SortGroupClause *new_sort_group_clause = MakeNode(SortGroupClause);
new_sort_group_clause->tleSortGroupRef =
sort_group_clause->tleSortGroupRef;
new_sort_group_clause->eqop = sort_group_clause->eqop;
new_sort_group_clause->sortop = sort_group_clause->sortop;
new_sort_group_clause->nulls_first = sort_group_clause->nulls_first;
new_query->groupClause =
gpdb::LAppend(new_query->groupClause, new_sort_group_clause);
}
new_query->distinctClause = NIL;
derived_table_query->distinctClause = NIL;
return new_query;
}
//---------------------------------------------------------------------------
// CQueryMutators::NeedsProjListWindowNormalization
//
// Check whether the window operator's project list only contains
// window functions, vars, or expressions used in the window specification.
// Examples of queries that will be normalized:
// select rank() over(...) -1
// select rank() over(order by a), a+b
// select (SQ), rank over(...)
// Some of these, e.g. the second one, may not strictly need normalization.
//---------------------------------------------------------------------------
BOOL
CQueryMutators::NeedsProjListWindowNormalization(const Query *query)
{
if (!query->hasWindowFuncs)
{
return false;
}
ListCell *lc = nullptr;
ForEach(lc, query->targetList)
{
TargetEntry *target_entry = (TargetEntry *) lfirst(lc);
if (!CTranslatorUtils::IsReferencedInWindowSpec(target_entry,
query->windowClause) &&
!IsA(target_entry->expr, WindowFunc) &&
!IsA(target_entry->expr, Var))
{
// computed columns in the target list that is not
// used in the order by or partition by of the window specification(s)
return true;
}
}
return false;
}
//---------------------------------------------------------------------------
// CQueryMutators::NormalizeWindowProjList
//
// Flatten expressions in project list to contain only window functions,
// columns (vars) and columns (vars) used in the window specifications.
// This is a restriction in Orca and DXL, that we don't support a mix of
// window functions and general expressions in a target list.
//
// ORGINAL QUERY:
// SELECT row_number() over() + rank() over(partition by a+b order by a-b) from foo
//
// NEW QUERY:
// SELECT rn+rk from (SELECT row_number() over() as rn, rank() over(partition by a+b order by a-b) as rk FROM foo) foo_new
//---------------------------------------------------------------------------
Query *
CQueryMutators::NormalizeWindowProjList(CMemoryPool *mp,
CMDAccessor *md_accessor,
const Query *original_query)
{
Query *query_copy =
(Query *) gpdb::CopyObject(const_cast<Query *>(original_query));
if (!NeedsProjListWindowNormalization(original_query))
{
return query_copy;
}
// we assume here that we have already performed the transformGroupedWindows()
// transformation, which separates GROUP BY from window functions
GPOS_ASSERT(nullptr == original_query->distinctClause);
GPOS_ASSERT(nullptr == original_query->groupClause);
GPOS_ASSERT(nullptr == original_query->groupingSets);
// we do not fix target list of the derived table since we will be mutating it below
// to ensure that it does not have window functions
Query *upper_query =
ConvertToDerivedTable(query_copy, false /*should_fix_target_list*/,
true /*should_fix_having_qual*/);
gpdb::GPDBFree(query_copy);
GPOS_ASSERT(1 == gpdb::ListLength(upper_query->rtable));
Query *lower_query =
(Query *) ((RangeTblEntry *) gpdb::ListNth(upper_query->rtable, 0))
->subquery;
SContextGrpbyPlMutator projlist_context(mp, md_accessor, lower_query,
nullptr);
ListCell *lc = nullptr;
List *target_entries = lower_query->targetList;
ForEach(lc, target_entries)
{
// If this target entry is referenced in a window spec, is a var or is a window function,
// add it to the lower target list. Adjust the outer refs to ancestors of the orginal
// query by adding one to the varlevelsup. Add a var to the upper target list to refer
// to it.
//
// Any other target entries, add them to the upper target list, and ensure that any vars
// they reference in the current scope are produced by the lower query and are adjusted
// to refer to the new, single RTE of the upper query.
TargetEntry *target_entry = (TargetEntry *) lfirst(lc);
const ULONG ulResNoNew = gpdb::ListLength(upper_query->targetList) + 1;
if (CTranslatorUtils::IsReferencedInWindowSpec(
target_entry, original_query->windowClause))
{
// This entry is used in a window spec. Since this clause refers to its argument by
// ressortgroupref, the target entry must be preserved in the lower target list,
// so insert the entire Expr of the TargetEntry into the lower target list, using the
// same ressortgroupref and also preserving the resjunk attribute.
SContextIncLevelsupMutator level_context(
0, true /* should_fix_top_level_target_list */);
TargetEntry *lower_target_entry =
(TargetEntry *) gpdb::MutateExpressionTree(
(Node *) target_entry,
(MutatorWalkerFn) RunIncrLevelsUpMutator, &level_context);
lower_target_entry->resno =
gpdb::ListLength(projlist_context.m_lower_table_tlist) + 1;
projlist_context.m_lower_table_tlist = gpdb::LAppend(
projlist_context.m_lower_table_tlist, lower_target_entry);
BOOL is_sorting_col = CTranslatorUtils::IsSortingColumn(
target_entry, original_query->sortClause);
if (!target_entry->resjunk || is_sorting_col)
{
// the target list entry is present in the query output or it is used in the ORDER BY,
// so also add it to the target list of the new upper Query
Var *new_var = gpdb::MakeVar(
1, lower_target_entry->resno,
gpdb::ExprType((Node *) target_entry->expr),
gpdb::ExprTypeMod((Node *) target_entry->expr),
0 // query levels up
);
TargetEntry *upper_target_entry = gpdb::MakeTargetEntry(
(Expr *) new_var, ulResNoNew, target_entry->resname,
target_entry->resjunk);
if (is_sorting_col)
{
// This target list entry is referenced in the ORDER BY as well, evaluated in the upper
// query. Set the ressortgroupref, keeping the same number as in the original query.
upper_target_entry->ressortgroupref =
lower_target_entry->ressortgroupref;
}
// Set target list entry of the derived table to be non-resjunked, since we need it in the upper
lower_target_entry->resjunk = false;
upper_query->targetList =
gpdb::LAppend(upper_query->targetList, upper_target_entry);
}
}
else
{
// push any window functions in the target entry into the lower target list
// and also add any needed vars to the lower target list
target_entry->resno = ulResNoNew;
TargetEntry *upper_target_entry =
(TargetEntry *) gpdb::MutateExpressionTree(
(Node *) target_entry,
(MutatorWalkerFn) RunWindowProjListMutator,
&projlist_context);
upper_query->targetList =
gpdb::LAppend(upper_query->targetList, upper_target_entry);
}
}
// once we finish the above loop, the context has accumulated all the needed vars,
// window spec expressions and window functions for the lower targer list
lower_query->targetList = projlist_context.m_lower_table_tlist;
GPOS_ASSERT(gpdb::ListLength(upper_query->targetList) <=
gpdb::ListLength(original_query->targetList));
ReassignSortClause(upper_query, lower_query);
return upper_query;
}
//---------------------------------------------------------------------------
// @function:
// CQueryMutators::RunWindowProjListMutator
//
// @doc:
// Traverse the project list of extract all window functions in an
// arbitrarily complex project element
//---------------------------------------------------------------------------
Node *
CQueryMutators::RunWindowProjListMutator(Node *node,
SContextGrpbyPlMutator *context)
{
if (nullptr == node)
{
return nullptr;
}
const ULONG resno = gpdb::ListLength(context->m_lower_table_tlist) + 1;
if (IsA(node, WindowFunc) && 0 == context->m_current_query_level)
{
// This is a window function that needs to be executed in the lower Query.
// Insert window function as a new TargetEntry into the lower target list
// (requires incrementing varlevelsup on its arguments).
// Create a var that refers to the newly created lower TargetEntry and return
// that, to be used instead of the window function in the upper TargetEntry.
// make a copy of the tree and increment varlevelsup, using a different mutator
SContextIncLevelsupMutator levelsUpContext(
context->m_current_query_level,
true /* should_fix_top_level_target_list */);
WindowFunc *window_func = (WindowFunc *) expression_tree_mutator(
node, (MutatorWalkerFn) RunIncrLevelsUpMutator, &levelsUpContext);
GPOS_ASSERT(IsA(window_func, WindowFunc));
// get the function name and create a new target entry for window_func
CMDIdGPDB *mdid_func =
GPOS_NEW(context->m_mp) CMDIdGPDB(window_func->winfnoid);
const CWStringConst *str =
CMDAccessorUtils::PstrWindowFuncName(context->m_mda, mdid_func);
mdid_func->Release();
TargetEntry *target_entry = gpdb::MakeTargetEntry(
(Expr *) window_func, (AttrNumber) resno,
CTranslatorUtils::CreateMultiByteCharStringFromWCString(
str->GetBuffer()),
false /* resjunk */
);
context->m_lower_table_tlist =
gpdb::LAppend(context->m_lower_table_tlist, target_entry);
// return a variable referring to the lower table's corresponding target entry,
// to be used somewhere in the upper query's target list
Var *new_var = gpdb::MakeVar(
1, // derived query which is now the only table in FROM expression
(AttrNumber) resno, gpdb::ExprType(node), gpdb::ExprTypeMod(node),
0 // query levelsup
);
return (Node *) new_var;
}
if (IsA(node, Var) &&
((Var *) node)->varlevelsup == context->m_current_query_level)
{
// This is a Var referencing the original query scope. It now needs to reference
// the new upper query scope.
// Since the rtable of the upper Query is different from that of the original
// Query, calculate the new varno (always 1) and varattno to use.
Var *var = (Var *) gpdb::CopyObject(node);
// Set varlevelsup to 0 temporarily while searching in the target list
var->varlevelsup = 0;
TargetEntry *found_tle = gpdb::FindFirstMatchingMemberInTargetList(
(Node *) var, context->m_lower_table_tlist);
if (nullptr == found_tle)
{
// this var is not yet provided by the lower target list, so
// create a new TargetEntry for it
Node *var_copy = (Node *) gpdb::CopyObject(var);
return (Node *) MakeVarInDerivedTable(var_copy, context);
}
var->varno = 1; // derived query is the only table in FROM expression
var->varattno = found_tle->resno;
var->varlevelsup =
context->m_current_query_level; // reset varlevels up
found_tle->resjunk = false;
return (Node *) var;
}
if (IsA(node, Query))
{
// recurse into Query nodes
context->m_current_query_level++;
Query *result = query_tree_mutator(
(Query *) node, (MutatorWalkerFn) RunWindowProjListMutator, context,
0);
context->m_current_query_level--;
return (Node *) result;
}
return expression_tree_mutator(
node, (MutatorWalkerFn) CQueryMutators::RunWindowProjListMutator,
context);
}
//---------------------------------------------------------------------------
// @function:
// CQueryMutators::ReassignSortClause
//
// @doc:
// Reassign the sorting clause from the derived table to the new top-level query
//---------------------------------------------------------------------------
void
CQueryMutators::ReassignSortClause(Query *top_level_query,
Query *derived_table_query)
{
top_level_query->sortClause = derived_table_query->sortClause;
top_level_query->limitOffset = derived_table_query->limitOffset;
top_level_query->limitCount = derived_table_query->limitCount;
derived_table_query->sortClause = nullptr;
derived_table_query->limitOffset = nullptr;
derived_table_query->limitCount = nullptr;
}
// EOF
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