+++ /dev/null
-/*-------------------------------------------------------------------------
- *
- * prepkeyset.c
- * Special preparation for keyset queries (KSQO).
- *
- * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
- * Portions Copyright (c) 1994, Regents of the University of California
- *
- *-------------------------------------------------------------------------
- */
-
-/* THIS FILE WAS USED FOR KSQO, WHICH IS DISABLED NOW. bjm 2002-06-15 */
-
-#include "postgres.h"
-#include "optimizer/planmain.h"
-
-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 exponential
- * 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.
- *
- * XXX: this code is currently not compiled because it has not been
- * updated to work with the re-implementation of UNION/INTERSECT/EXCEPT
- * in PostgreSQL 7.1. However, it is of questionable value in any
- * case, because it changes the semantics of the original query:
- * UNION will add an implicit SELECT DISTINCT, which might change
- * the results that are returned.
- **********************************************************************/
-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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