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/*-------------------------------------------------------------------------
*
* prepkeyset.c
* Special preperation for keyset queries.
*
* Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "optimizer/planmain.h"
/*
* Node_Copy
* a macro to simplify calling of copyObject on the specified field
*/
#define Node_Copy(from, newnode, field) newnode->field = copyObject(from->field)
bool _use_keyset_query_optimizer = FALSE;
#ifdef ENABLE_KEY_SET_QUERY
static int inspectOpNode(Expr *expr);
static int inspectAndNode(Expr *expr);
static int inspectOrNode(Expr *expr);
static int TotalExpr;
/**********************************************************************
* This routine transforms query trees with the following form:
* SELECT a,b, ... FROM one_table WHERE
* (v1 = const1 AND v2 = const2 [ vn = constn ]) OR
* (v1 = const3 AND v2 = const4 [ vn = constn ]) OR
* (v1 = const5 AND v2 = const6 [ vn = constn ]) OR
* ...
* [(v1 = constn AND v2 = constn [ vn = constn ])]
*
* into
*
* SELECT a,b, ... FROM one_table WHERE
* (v1 = const1 AND v2 = const2 [ vn = constn ]) UNION
* SELECT a,b, ... FROM one_table WHERE
* (v1 = const3 AND v2 = const4 [ vn = constn ]) UNION
* SELECT a,b, ... FROM one_table WHERE
* (v1 = const5 AND v2 = const6 [ vn = constn ]) UNION
* ...
* SELECT a,b, ... FROM one_table WHERE
* [(v1 = constn AND v2 = constn [ vn = constn ])]
*
*
* To qualify for transformation the query must not be a sub select,
* a HAVING, or a GROUP BY. It must be a single table and have KSQO
* set to 'on'.
*
* The primary use of this transformation is to avoid the exponrntial
* memory consumption of cnfify() and to make use of index access
* methods.
*
* daveh@insightdist.com 1998-08-31
*
* May want to also prune out duplicate terms.
**********************************************************************/
void
transformKeySetQuery(Query *origNode)
{
/* Qualify as a key set query candidate */
if (_use_keyset_query_optimizer == FALSE ||
origNode->groupClause ||
origNode->havingQual ||
origNode->hasAggs ||
origNode->utilityStmt ||
origNode->unionClause ||
origNode->unionall ||
origNode->hasSubLinks ||
origNode->commandType != CMD_SELECT)
return;
/* Qualify single table query */
if (length(origNode->rtable) != 1)
return;
/* Sorry about the global, not worth passing around */
/* 9 expressions seems like a good number. More than 9 */
/* and it starts to slow down quite a bit */
TotalExpr = 0;
/*************************/
/* Qualify where clause */
/*************************/
if (!inspectOrNode((Expr *) origNode->jointree->quals) || TotalExpr < 9)
return;
/* Copy essential elements into a union node */
while (((Expr *) origNode->jointree->quals)->opType == OR_EXPR)
{
Query *unionNode = makeNode(Query);
List *qualargs = ((Expr *) origNode->jointree->quals)->args;
unionNode->commandType = origNode->commandType;
unionNode->resultRelation = origNode->resultRelation;
unionNode->isPortal = origNode->isPortal;
unionNode->isBinary = origNode->isBinary;
Node_Copy(origNode, unionNode, distinctClause);
Node_Copy(origNode, unionNode, sortClause);
Node_Copy(origNode, unionNode, rtable);
origNode->jointree->quals = NULL; /* avoid unnecessary
* copying */
Node_Copy(origNode, unionNode, jointree);
Node_Copy(origNode, unionNode, targetList);
/* Pull up Expr = */
unionNode->jointree->quals = lsecond(qualargs);
/* Pull up balance of tree */
origNode->jointree->quals = lfirst(qualargs);
origNode->unionClause = lappend(origNode->unionClause, unionNode);
}
return;
}
static int
/**********************************************************************
* Checks for 1 or more OR terms w/ 1 or more AND terms.
* AND terms must be equal in size.
* Returns the number of each AND term.
**********************************************************************/
inspectOrNode(Expr *expr)
{
int rc;
Expr *firstExpr,
*secondExpr;
if (!(expr && nodeTag(expr) == T_Expr && expr->opType == OR_EXPR))
return 0;
firstExpr = lfirst(expr->args);
secondExpr = lsecond(expr->args);
if (nodeTag(firstExpr) != T_Expr || nodeTag(secondExpr) != T_Expr)
return 0;
if (firstExpr->opType == OR_EXPR && secondExpr->opType == AND_EXPR)
{
if ((rc = inspectOrNode(firstExpr)) == 0)
return 0;
return (rc == inspectAndNode(secondExpr)) ? rc : 0;
}
else if (firstExpr->opType == AND_EXPR && secondExpr->opType == AND_EXPR)
{
if ((rc = inspectAndNode(firstExpr)) == 0)
return 0;
return (rc == inspectAndNode(secondExpr)) ? rc : 0;
}
return 0;
}
static int
/**********************************************************************
* Check for one or more AND terms. Each sub-term must be a T_Const
* T_Var expression.
* Returns the number of AND terms.
**********************************************************************/
inspectAndNode(Expr *expr)
{
int rc;
Expr *firstExpr,
*secondExpr;
if (!(expr && nodeTag(expr) == T_Expr && expr->opType == AND_EXPR))
return 0;
firstExpr = lfirst(expr->args);
secondExpr = lsecond(expr->args);
if (nodeTag(firstExpr) != T_Expr || nodeTag(secondExpr) != T_Expr)
return 0;
if (firstExpr->opType == AND_EXPR &&
secondExpr->opType == OP_EXPR && inspectOpNode(secondExpr))
{
rc = inspectAndNode(firstExpr);
return ((rc) ? (rc + 1) : 0); /* Add up the AND nodes */
}
else if (firstExpr->opType == OP_EXPR && inspectOpNode(firstExpr) &&
secondExpr->opType == OP_EXPR && inspectOpNode(secondExpr))
return 1;
return 0;
}
static int
/******************************************************************
* Return TRUE if T_Var = T_Const, else FALSE
* Actually it does not test for =. Need to do this!
******************************************************************/
inspectOpNode(Expr *expr)
{
Expr *firstExpr,
*secondExpr;
if (nodeTag(expr) != T_Expr || expr->opType != OP_EXPR)
return FALSE;
TotalExpr++;
firstExpr = lfirst(expr->args);
secondExpr = lsecond(expr->args);
return (firstExpr && secondExpr && nodeTag(firstExpr) == T_Var && nodeTag(secondExpr) == T_Const);
}
#endif /* ENABLE_KEY_SET_QUERY */
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