postgresql/src/backend/parser/analyze.c

/*-------------------------------------------------------------------------
 *
 * analyze.c--
 *	  transform the parse tree into a query tree
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 *  $Id: analyze.c,v 1.98 1999/02/08 14:14:11 wieck Exp $
 *
 *-------------------------------------------------------------------------
 */

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <string.h>

#include "postgres.h"
#include "access/heapam.h"
#include "nodes/makefuncs.h"
#include "nodes/memnodes.h"
#include "nodes/pg_list.h"
#include "parser/analyze.h"
#include "parser/parse_agg.h"
#include "parser/parse_clause.h"
#include "parser/parse_node.h"
#include "parser/parse_relation.h"
#include "parser/parse_target.h"
/***S*I***/
#include "parser/parse_expr.h"
#include "catalog/pg_type.h"
#include "parse.h"

#include "utils/builtins.h"
#include "utils/mcxt.h"

static Query *transformStmt(ParseState *pstate, Node *stmt);
static Query *transformDeleteStmt(ParseState *pstate, DeleteStmt *stmt);
static Query *transformInsertStmt(ParseState *pstate, InsertStmt *stmt);
static Query *transformIndexStmt(ParseState *pstate, IndexStmt *stmt);
static Query *transformExtendStmt(ParseState *pstate, ExtendStmt *stmt);
static Query *transformRuleStmt(ParseState *query, RuleStmt *stmt);
static Query *transformSelectStmt(ParseState *pstate, SelectStmt *stmt);
static Query *transformUpdateStmt(ParseState *pstate, UpdateStmt *stmt);
static Query *transformCursorStmt(ParseState *pstate, SelectStmt *stmt);
static Query *transformCreateStmt(ParseState *pstate, CreateStmt *stmt);

static void		transformForUpdate(Query *qry, List *forUpdate);
void			CheckSelectForUpdate(Query *qry);

List	   *extras_before = NIL;
List	   *extras_after = NIL;

/*
 * parse_analyze -
 *	  analyze a list of parse trees and transform them if necessary.
 *
 * Returns a list of transformed parse trees. Optimizable statements are
 * all transformed to Query while the rest stays the same.
 *
 */
QueryTreeList *
parse_analyze(List *pl, ParseState *parentParseState)
{
	QueryTreeList *result;
	ParseState *pstate;
	Query *parsetree;
	int			i = 0;

	result = malloc(sizeof(QueryTreeList));
	result->len = length(pl);
	result->qtrees = (Query **) malloc(result->len * sizeof(Query *));

	while (pl != NIL)
	{
		pstate = make_parsestate(parentParseState);
		parsetree = transformStmt(pstate, lfirst(pl));
		if (pstate->p_target_relation != NULL)
			heap_close(pstate->p_target_relation);

		if (extras_before != NIL)
		{
			result->len += length(extras_before);
			result->qtrees = (Query **) realloc(result->qtrees, result->len * sizeof(Query *));
			while (extras_before != NIL)
			{
				result->qtrees[i++] = transformStmt(pstate, lfirst(extras_before));
				if (pstate->p_target_relation != NULL)
					heap_close(pstate->p_target_relation);
				extras_before = lnext(extras_before);
			}
		}
		extras_before = NIL;

		result->qtrees[i++] = parsetree;

		if (extras_after != NIL)
		{
			result->len += length(extras_after);
			result->qtrees = (Query **) realloc(result->qtrees, result->len * sizeof(Query *));
			while (extras_after != NIL)
			{
				result->qtrees[i++] = transformStmt(pstate, lfirst(extras_after));
				if (pstate->p_target_relation != NULL)
					heap_close(pstate->p_target_relation);
				extras_after = lnext(extras_after);
			}
		}
		extras_after = NIL;

		pl = lnext(pl);
		pfree(pstate);
	}

	return result;
}

/*
 * transformStmt -
 *	  transform a Parse tree. If it is an optimizable statement, turn it
 *	  into a Query tree.
 */
static Query *
transformStmt(ParseState *pstate, Node *parseTree)
{
	Query	   *result = NULL;

	switch (nodeTag(parseTree))
	{
			/*------------------------
			 *	Non-optimizable statements
			 *------------------------
			 */
		case T_CreateStmt:
			result = transformCreateStmt(pstate, (CreateStmt *) parseTree);
			break;

		case T_IndexStmt:
			result = transformIndexStmt(pstate, (IndexStmt *) parseTree);
			break;

		case T_ExtendStmt:
			result = transformExtendStmt(pstate, (ExtendStmt *) parseTree);
			break;

		case T_RuleStmt:
			result = transformRuleStmt(pstate, (RuleStmt *) parseTree);
			break;

		case T_ViewStmt:
			{
				ViewStmt   *n = (ViewStmt *) parseTree;

				n->query = (Query *) transformStmt(pstate, (Node *) n->query);
				result = makeNode(Query);
				result->commandType = CMD_UTILITY;
				result->utilityStmt = (Node *) n;
			}
			break;

		case T_VacuumStmt:
			{
				MemoryContext oldcontext;

				/*
				 * make sure that this Query is allocated in TopMemory
				 * context because vacuum spans transactions and we don't
				 * want to lose the vacuum Query due to end-of-transaction
				 * free'ing
				 */
				oldcontext = MemoryContextSwitchTo(TopMemoryContext);
				result = makeNode(Query);
				result->commandType = CMD_UTILITY;
				result->utilityStmt = (Node *) parseTree;
				MemoryContextSwitchTo(oldcontext);
				break;

			}
		case T_ExplainStmt:
			{
				ExplainStmt *n = (ExplainStmt *) parseTree;

				result = makeNode(Query);
				result->commandType = CMD_UTILITY;
				n->query = transformStmt(pstate, (Node *) n->query);
				result->utilityStmt = (Node *) parseTree;
			}
			break;

			/*------------------------
			 *	Optimizable statements
			 *------------------------
			 */
		case T_InsertStmt:
			result = transformInsertStmt(pstate, (InsertStmt *) parseTree);
			break;

		case T_DeleteStmt:
			result = transformDeleteStmt(pstate, (DeleteStmt *) parseTree);
			break;

		case T_UpdateStmt:
			result = transformUpdateStmt(pstate, (UpdateStmt *) parseTree);
			break;

		case T_SelectStmt:
			if (!((SelectStmt *) parseTree)->portalname)
			{
				result = transformSelectStmt(pstate, (SelectStmt *) parseTree);
				result->limitOffset = ((SelectStmt *)parseTree)->limitOffset;
				result->limitCount = ((SelectStmt *)parseTree)->limitCount;
			}
			else
				result = transformCursorStmt(pstate, (SelectStmt *) parseTree);
			break;

		default:

			/*
			 * other statments don't require any transformation-- just
			 * return the original parsetree, yea!
			 */
			result = makeNode(Query);
			result->commandType = CMD_UTILITY;
			result->utilityStmt = (Node *) parseTree;
			break;
	}
	return result;
}

/*
 * transformDeleteStmt -
 *	  transforms a Delete Statement
 */
static Query *
transformDeleteStmt(ParseState *pstate, DeleteStmt *stmt)
{
	Query	   *qry = makeNode(Query);

	qry->commandType = CMD_DELETE;

	/* set up a range table */
	makeRangeTable(pstate, stmt->relname, NULL);

	qry->uniqueFlag = NULL;

	/* fix where clause */
	qry->qual = transformWhereClause(pstate, stmt->whereClause);
	qry->hasSubLinks = pstate->p_hasSubLinks;

	qry->rtable = pstate->p_rtable;
	qry->resultRelation = refnameRangeTablePosn(pstate, stmt->relname, NULL);

	qry->hasAggs = pstate->p_hasAggs;
	if (pstate->p_hasAggs)
		parseCheckAggregates(pstate, qry);

	return (Query *) qry;
}

/*
 * transformInsertStmt -
 *	  transform an Insert Statement
 */
static Query *
transformInsertStmt(ParseState *pstate, InsertStmt *stmt)
{
	Query	   *qry = makeNode(Query);	/* make a new query tree */
	List	   *icolumns;

	qry->commandType = CMD_INSERT;
	pstate->p_is_insert = true;

	/* set up a range table */
	makeRangeTable(pstate, stmt->relname, stmt->fromClause);

	qry->uniqueFlag = stmt->unique;

	/* fix the target list */
	icolumns = pstate->p_insert_columns = makeTargetNames(pstate, stmt->cols);

	qry->targetList = transformTargetList(pstate, stmt->targetList);

	/* DEFAULT handling */
	if (length(qry->targetList) < pstate->p_target_relation->rd_att->natts &&
		pstate->p_target_relation->rd_att->constr &&
		pstate->p_target_relation->rd_att->constr->num_defval > 0)
	{
		Form_pg_attribute *att = pstate->p_target_relation->rd_att->attrs;
		AttrDefault *defval = pstate->p_target_relation->rd_att->constr->defval;
		int			ndef = pstate->p_target_relation->rd_att->constr->num_defval;

		/*
		 * if stmt->cols == NIL then makeTargetNames returns list of all attrs.
		 * May have to shorten icolumns list...
		 */
		if (stmt->cols == NIL)
		{
			List	   *extrl;
			int			i = length(qry->targetList);

			foreach(extrl, icolumns)
			{
				/*
				 * decrements first, so if we started with zero items
				 * it will now be negative
				 */
				if (--i <= 0)
					break;
			}
			/*
			 * this an index into the targetList,
			 * so make sure we had one to start...
			 */
			if (i >= 0)
			{
				freeList(lnext(extrl));
				lnext(extrl) = NIL;
			}
			else
			{
				icolumns = NIL;
			}
		}

		while (ndef-- > 0)
		{
			List	   *tl;
			Ident	   *id;
			TargetEntry *te;

			foreach(tl, icolumns)
			{
				id = (Ident *) lfirst(tl);
				if (namestrcmp(&(att[defval[ndef].adnum - 1]->attname), id->name) == 0)
					break;
			}
			if (tl != NIL)		/* something given for this attr */
				continue;

			/*
			 * Nothing given for this attr with DEFAULT expr, so add new
			 * TargetEntry to qry->targetList. Note, that we set resno to
			 * defval[ndef].adnum: it's what
			 * transformTargetList()->make_targetlist_expr() does for
			 * INSERT ... SELECT. But for INSERT ... VALUES
			 * pstate->p_last_resno is used. It doesn't matter for
			 * "normal" using (planner creates proper target list in
			 * preptlist.c), but may break RULEs in some way. It seems
			 * better to create proper target list here...
			 */
			te = makeTargetEntry(makeResdom(defval[ndef].adnum,
								   att[defval[ndef].adnum - 1]->atttypid,
								  att[defval[ndef].adnum - 1]->atttypmod,
			   pstrdup(nameout(&(att[defval[ndef].adnum - 1]->attname))),
											0, 0, 0),
							  (Node *) stringToNode(defval[ndef].adbin));
			qry->targetList = lappend(qry->targetList, te);
		}
	}

	/* fix where clause */
	qry->qual = transformWhereClause(pstate, stmt->whereClause);

	/*
	 * The havingQual has a similar meaning as "qual" in the where
	 * statement. So we can easily use the code from the "where clause"
	 * with some additional traversals done in
	 * .../optimizer/plan/planner.c
	 */
	qry->havingQual = transformWhereClause(pstate, stmt->havingClause);

	qry->hasSubLinks = pstate->p_hasSubLinks;

	/* now the range table will not change */
	qry->rtable = pstate->p_rtable;
	qry->resultRelation = refnameRangeTablePosn(pstate, stmt->relname, NULL);

	qry->groupClause = transformGroupClause(pstate,
											stmt->groupClause,
											qry->targetList);

	/* fix order clause */
	qry->sortClause = transformSortClause(pstate,
										  NIL,
										  NIL,
										  qry->targetList,
										  qry->uniqueFlag);

	qry->hasAggs = pstate->p_hasAggs;
	if (pstate->p_hasAggs)
		parseCheckAggregates(pstate, qry);

	/*
	 * The INSERT INTO ... SELECT ... could have a UNION in child, so
	 * unionClause may be false
,	 */
  	qry->unionall = stmt->unionall;	

 	/***S*I***/
 	/* Just hand through the unionClause and intersectClause. 
 	 * We will handle it in the function Except_Intersect_Rewrite() */
 	qry->unionClause = stmt->unionClause;
 	qry->intersectClause = stmt->intersectClause;	

	/*
	 * If there is a havingQual but there are no aggregates, then there is
	 * something wrong with the query because having must contain
	 * aggregates in its expressions! Otherwise the query could have been
	 * formulated using the where clause.
	 */
	if ((qry->hasAggs == false) && (qry->havingQual != NULL))
	{
		elog(ERROR, "SELECT/HAVING requires aggregates to be valid");
		return (Query *) NIL;
	}

	if (stmt->forUpdate != NULL)
		transformForUpdate(qry, stmt->forUpdate);

	return (Query *) qry;
}

/*
 *	makeTableName()
 *	Create a table name from a list of fields.
 */
static char *
makeTableName(void *elem,...)
{
	va_list		args;

	char	   *name;
	char		buf[NAMEDATALEN + 1];

	buf[0] = '\0';

	va_start(args, elem);

	name = elem;
	while (name != NULL)
	{
		/* not enough room for next part? then return nothing */
		if ((strlen(buf) + strlen(name)) >= (sizeof(buf) - 1))
			return NULL;

		if (strlen(buf) > 0)
			strcat(buf, "_");
		strcat(buf, name);

		name = va_arg(args, void *);
	}

	va_end(args);

	name = palloc(strlen(buf) + 1);
	strcpy(name, buf);

	return name;
}

static char *
CreateIndexName(char *table_name, char *column_name, char *label, List *indices)
{
	int			pass = 0;
	char	   *iname = NULL;
	List	   *ilist;
	IndexStmt  *index;
	char		name2[NAMEDATALEN + 1];

	/* use working storage, since we might be trying several possibilities */
	strcpy(name2, column_name);
	while (iname == NULL)
	{
		iname = makeTableName(table_name, name2, label, NULL);
		/* unable to make a name at all? then quit */
		if (iname == NULL)
			break;

		ilist = indices;
		while (ilist != NIL)
		{
			index = lfirst(ilist);
			if (strcasecmp(iname, index->idxname) == 0)
				break;

			ilist = lnext(ilist);
		}
		/* ran through entire list? then no name conflict found so done */
		if (ilist == NIL)
			break;

		/* the last one conflicted, so try a new name component */
		pfree(iname);
		iname = NULL;
		pass++;
		sprintf(name2, "%s_%d", column_name, (pass + 1));
	}

	return iname;
}

/*
 * transformCreateStmt -
 *	  transforms the "create table" statement
 *	  SQL92 allows constraints to be scattered all over, so thumb through
 *	   the columns and collect all constraints into one place.
 *	  If there are any implied indices (e.g. UNIQUE or PRIMARY KEY)
 *	   then expand those into multiple IndexStmt blocks.
 *	  - thomas 1997-12-02
 */
static Query *
transformCreateStmt(ParseState *pstate, CreateStmt *stmt)
{
	Query	   *q;
	int			have_pkey = FALSE;
	List	   *elements;
	Node	   *element;
	List	   *columns;
	List	   *dlist;
	ColumnDef  *column;
	List	   *constraints,
			   *clist;
	Constraint *constraint;
	List	   *keys;
	Ident	   *key;
	List	   *blist = NIL;
	List	   *ilist = NIL;
	IndexStmt  *index;
	IndexElem  *iparam;

	q = makeNode(Query);
	q->commandType = CMD_UTILITY;

	elements = stmt->tableElts;
	constraints = stmt->constraints;
	columns = NIL;
	dlist = NIL;

	while (elements != NIL)
	{
		element = lfirst(elements);
		switch (nodeTag(element))
		{
			case T_ColumnDef:
				column = (ColumnDef *) element;
				columns = lappend(columns, column);

				if (column->is_sequence)
				{
					char		  *sname;
					char		  *cstring;
					CreateSeqStmt *sequence;

					sname = makeTableName(stmt->relname, column->colname, "seq", NULL);

					constraint = makeNode(Constraint);
					constraint->contype = CONSTR_DEFAULT;
					constraint->name = sname;
					cstring = palloc(9 + strlen(constraint->name) + 2 + 1);
					strcpy(cstring, "nextval('");
					strcat(cstring, constraint->name);
					strcat(cstring, "')");
					constraint->def = cstring;
					constraint->keys = NULL;

					/* The parser only allows PRIMARY KEY as a constraint for the SERIAL type.
					 * So, if there is a constraint of any kind, assume it is that.
					 * If PRIMARY KEY is specified, then don't need to gin up a UNIQUE constraint
					 * since that will be covered already.
					 * - thomas 1998-09-15
					 */
					if (column->constraints != NIL)
					{
						column->constraints = lappend(column->constraints, constraint);
					}
					else
					{
						column->constraints = lcons(constraint, NIL);

						constraint = makeNode(Constraint);
						constraint->contype = CONSTR_UNIQUE;
						constraint->name = makeTableName(stmt->relname, column->colname, "key", NULL);
						column->constraints = lappend(column->constraints, constraint);
					}

					sequence = makeNode(CreateSeqStmt);
					sequence->seqname = pstrdup(sname);
					sequence->options = NIL;

					elog(NOTICE, "CREATE TABLE will create implicit sequence %s for SERIAL column %s.%s",
					  sequence->seqname, stmt->relname, column->colname);

					blist = lcons(sequence, NIL);
				}

				if (column->constraints != NIL)
				{
					clist = column->constraints;
					while (clist != NIL)
					{
						constraint = lfirst(clist);
						switch (constraint->contype)
						{
							case CONSTR_NOTNULL:
								if (column->is_not_null)
									elog(ERROR, "CREATE TABLE/NOT NULL already specified"
										 " for %s.%s", stmt->relname, column->colname);
								column->is_not_null = TRUE;
								break;

							case CONSTR_DEFAULT:
								if (column->defval != NULL)
									elog(ERROR, "CREATE TABLE/DEFAULT multiple values specified"
										 " for %s.%s", stmt->relname, column->colname);
								column->defval = constraint->def;
								break;

							case CONSTR_PRIMARY:
								if (constraint->name == NULL)
									constraint->name = makeTableName(stmt->relname, "pkey", NULL);
								if (constraint->keys == NIL)
									constraint->keys = lappend(constraint->keys, column);
								dlist = lappend(dlist, constraint);
								break;

							case CONSTR_UNIQUE:
								if (constraint->name == NULL)
									constraint->name = makeTableName(stmt->relname, column->colname, "key", NULL);
								if (constraint->keys == NIL)
									constraint->keys = lappend(constraint->keys, column);
								dlist = lappend(dlist, constraint);
								break;

							case CONSTR_CHECK:
								constraints = lappend(constraints, constraint);
								if (constraint->name == NULL)
									constraint->name = makeTableName(stmt->relname, column->colname, NULL);
								break;

							default:
								elog(ERROR, "parser: unrecognized constraint (internal error)", NULL);
								break;
						}
						clist = lnext(clist);
					}
				}
				break;

			case T_Constraint:
				constraint = (Constraint *) element;
				switch (constraint->contype)
				{
					case CONSTR_PRIMARY:
						if (constraint->name == NULL)
							constraint->name = makeTableName(stmt->relname, "pkey", NULL);
						dlist = lappend(dlist, constraint);
						break;

					case CONSTR_UNIQUE:
#if FALSE
						if (constraint->name == NULL)
							constraint->name = makeTableName(stmt->relname, "key", NULL);
#endif
						dlist = lappend(dlist, constraint);
						break;

					case CONSTR_CHECK:
						constraints = lappend(constraints, constraint);
						break;

					case CONSTR_NOTNULL:
					case CONSTR_DEFAULT:
						elog(ERROR, "parser: illegal context for constraint (internal error)", NULL);
						break;
					default:
						elog(ERROR, "parser: unrecognized constraint (internal error)", NULL);
						break;
				}
				break;

			default:
				elog(ERROR, "parser: unrecognized node (internal error)", NULL);
		}

		elements = lnext(elements);
	}

	stmt->tableElts = columns;
	stmt->constraints = constraints;

/* Now run through the "deferred list" to complete the query transformation.
 * For PRIMARY KEYs, mark each column as NOT NULL and create an index.
 * For UNIQUE, create an index as for PRIMARY KEYS, but do not insist on NOT NULL.
 *
 * Note that this code does not currently look for all possible redundant cases
 *	and either ignore or stop with warning. The create might fail later when
 *	names for indices turn out to be redundant, or a user might have specified
 *	extra useless indices which might hurt performance. - thomas 1997-12-08
 */
	while (dlist != NIL)
	{
		constraint = lfirst(dlist);
		if (nodeTag(constraint) != T_Constraint)
			elog(ERROR, "parser: unrecognized deferred node (internal error)", NULL);

		if (constraint->contype == CONSTR_PRIMARY)
		{
			if (have_pkey)
				elog(ERROR, "CREATE TABLE/PRIMARY KEY multiple primary keys"
					 " for table %s are not legal", stmt->relname);
			else
				have_pkey = TRUE;
		}
		else if (constraint->contype != CONSTR_UNIQUE)
			elog(ERROR, "parser: unrecognized deferred constraint (internal error)", NULL);

		index = makeNode(IndexStmt);

		index->unique = TRUE;
		index->primary = (constraint->contype == CONSTR_PRIMARY ? TRUE:FALSE);
		if (constraint->name != NULL)
			index->idxname = constraint->name;
		else if (constraint->contype == CONSTR_PRIMARY)
		{
			if (have_pkey)
				elog(ERROR, "CREATE TABLE/PRIMARY KEY multiple keys for table %s are not legal", stmt->relname);

			have_pkey = TRUE;
			index->idxname = makeTableName(stmt->relname, "pkey", NULL);
		}
		else
			index->idxname = NULL;

		index->relname = stmt->relname;
		index->accessMethod = "btree";
		index->indexParams = NIL;
		index->withClause = NIL;
		index->whereClause = NULL;

		keys = constraint->keys;
		while (keys != NIL)
		{
			key = lfirst(keys);
			columns = stmt->tableElts;
			column = NULL;
			while (columns != NIL)
			{
				column = lfirst(columns);
				if (strcasecmp(column->colname, key->name) == 0)
					break;
				else
					column = NULL;
				columns = lnext(columns);
			}
			if (column == NULL)
				elog(ERROR, "CREATE TABLE column '%s' in key does not exist", key->name);

			if (constraint->contype == CONSTR_PRIMARY)
				column->is_not_null = TRUE;
			iparam = makeNode(IndexElem);
			iparam->name = strcpy(palloc(strlen(column->colname) + 1), column->colname);
			iparam->args = NIL;
			iparam->class = NULL;
			iparam->typename = NULL;
			index->indexParams = lappend(index->indexParams, iparam);

			if (index->idxname == NULL)
				index->idxname = CreateIndexName(stmt->relname, iparam->name, "key", ilist);

			keys = lnext(keys);
		}

		if (index->idxname == NULL)
			elog(ERROR, "CREATE TABLE unable to construct implicit index for table %s"
				 "; name too long", stmt->relname);
		else
			elog(NOTICE, "CREATE TABLE/%s will create implicit index %s for table %s",
				 ((constraint->contype == CONSTR_PRIMARY) ? "PRIMARY KEY" : "UNIQUE"),
				 index->idxname, stmt->relname);

		ilist = lappend(ilist, index);
		dlist = lnext(dlist);
	}

	q->utilityStmt = (Node *) stmt;
	extras_before = blist;
	extras_after = ilist;

	return q;
}

/*
 * transformIndexStmt -
 *	  transforms the qualification of the index statement
 */
static Query *
transformIndexStmt(ParseState *pstate, IndexStmt *stmt)
{
	Query	   *qry;

	qry = makeNode(Query);
	qry->commandType = CMD_UTILITY;

	/* take care of the where clause */
	stmt->whereClause = transformWhereClause(pstate, stmt->whereClause);
	qry->hasSubLinks = pstate->p_hasSubLinks;

	stmt->rangetable = pstate->p_rtable;

	qry->utilityStmt = (Node *) stmt;

	return qry;
}

/*
 * transformExtendStmt -
 *	  transform the qualifications of the Extend Index Statement
 *
 */
static Query *
transformExtendStmt(ParseState *pstate, ExtendStmt *stmt)
{
	Query	   *qry;

	qry = makeNode(Query);
	qry->commandType = CMD_UTILITY;

	/* take care of the where clause */
	stmt->whereClause = transformWhereClause(pstate, stmt->whereClause);
	qry->hasSubLinks = pstate->p_hasSubLinks;

	stmt->rangetable = pstate->p_rtable;

	qry->utilityStmt = (Node *) stmt;
	return qry;
}

/*
 * transformRuleStmt -
 *	  transform a Create Rule Statement. The actions is a list of parse
 *	  trees which is transformed into a list of query trees.
 */
static Query *
transformRuleStmt(ParseState *pstate, RuleStmt *stmt)
{
	Query	   *qry;
	Query	   *action;
	List	   *actions;

	qry = makeNode(Query);
	qry->commandType = CMD_UTILITY;

	/*
	 * 'instead nothing' rules with a qualification need a query a
	 * rangetable so the rewrite handler can add the negated rule
	 * qualification to the original query. We create a query with the new
	 * command type CMD_NOTHING here that is treated special by the
	 * rewrite system.
	 */
	if (stmt->actions == NIL)
	{
		Query	   *nothing_qry = makeNode(Query);

		nothing_qry->commandType = CMD_NOTHING;

		addRangeTableEntry(pstate, stmt->object->relname, "*CURRENT*",
						   FALSE, FALSE);
		addRangeTableEntry(pstate, stmt->object->relname, "*NEW*",
						   FALSE, FALSE);

		nothing_qry->rtable = pstate->p_rtable;

		stmt->actions = lappend(NIL, nothing_qry);
	}

	actions = stmt->actions;

	/*
	 * transform each statment, like parse_analyze()
	 */
	while (actions != NIL)
	{

		/*
		 * NOTE: 'CURRENT' must always have a varno equal to 1 and 'NEW'
		 * equal to 2.
		 */
		addRangeTableEntry(pstate, stmt->object->relname, "*CURRENT*",
						   FALSE, FALSE);
		addRangeTableEntry(pstate, stmt->object->relname, "*NEW*",
						   FALSE, FALSE);

		pstate->p_last_resno = 1;
		pstate->p_is_rule = true;		/* for expand all */
		pstate->p_hasAggs = false;

		action = (Query *) lfirst(actions);
		if (action->commandType != CMD_NOTHING)
			lfirst(actions) = transformStmt(pstate, lfirst(actions));
		actions = lnext(actions);
	}

	/* take care of the where clause */
	stmt->whereClause = transformWhereClause(pstate, stmt->whereClause);
	qry->hasSubLinks = pstate->p_hasSubLinks;

	qry->utilityStmt = (Node *) stmt;
	return qry;
}


/*
 * transformSelectStmt -
 *	  transforms a Select Statement
 *
 */
static Query *
transformSelectStmt(ParseState *pstate, SelectStmt *stmt)
{
	Query	   *qry = makeNode(Query);

	qry->commandType = CMD_SELECT;

	/* set up a range table */
	makeRangeTable(pstate, NULL, stmt->fromClause);

	qry->uniqueFlag = stmt->unique;

	qry->into = stmt->into;
	qry->isTemp = stmt->istemp;
	qry->isPortal = FALSE;

	qry->targetList = transformTargetList(pstate, stmt->targetList);

	qry->qual = transformWhereClause(pstate, stmt->whereClause);

	/*
	 * The havingQual has a similar meaning as "qual" in the where
	 * statement. So we can easily use the code from the "where clause"
	 * with some additional traversals done in optimizer/plan/planner.c
	 */
	qry->havingQual = transformWhereClause(pstate, stmt->havingClause);

	qry->hasSubLinks = pstate->p_hasSubLinks;

	qry->sortClause = transformSortClause(pstate,
										  stmt->sortClause,
										  NIL,
										  qry->targetList,
										  qry->uniqueFlag);

	qry->groupClause = transformGroupClause(pstate,
											stmt->groupClause,
											qry->targetList);
	qry->rtable = pstate->p_rtable;

	qry->hasAggs = pstate->p_hasAggs;
	if (pstate->p_hasAggs)
		parseCheckAggregates(pstate, qry);

	/*
	 * The INSERT INTO ... SELECT ... could have a UNION in child, so
	 * unionClause may be false
	 */
	qry->unionall = stmt->unionall;

 	/***S*I***/
 	/* Just hand through the unionClause and intersectClause. 
 	 * We will handle it in the function Except_Intersect_Rewrite() */
 	qry->unionClause = stmt->unionClause;
 	qry->intersectClause = stmt->intersectClause;

	/*
	 * If there is a havingQual but there are no aggregates, then there is
	 * something wrong with the query because having must contain
	 * aggregates in its expressions! Otherwise the query could have been
	 * formulated using the where clause.
	 */
	if ((qry->hasAggs == false) && (qry->havingQual != NULL))
	{
		elog(ERROR, "SELECT/HAVING requires aggregates to be valid");
		return (Query *) NIL;
	}

	if (stmt->forUpdate != NULL)
		transformForUpdate(qry, stmt->forUpdate);

	return (Query *) qry;
}

/*
 * transformUpdateStmt -
 *	  transforms an update statement
 *
 */
static Query *
transformUpdateStmt(ParseState *pstate, UpdateStmt *stmt)
{
	Query	   *qry = makeNode(Query);

	qry->commandType = CMD_UPDATE;
	pstate->p_is_update = true;

	/*
	 * the FROM clause is non-standard SQL syntax. We used to be able to
	 * do this with REPLACE in POSTQUEL so we keep the feature.
	 */
	makeRangeTable(pstate, stmt->relname, stmt->fromClause);

	qry->targetList = transformTargetList(pstate, stmt->targetList);

	qry->qual = transformWhereClause(pstate, stmt->whereClause);
	qry->hasSubLinks = pstate->p_hasSubLinks;

	qry->rtable = pstate->p_rtable;

	qry->resultRelation = refnameRangeTablePosn(pstate, stmt->relname, NULL);

	qry->hasAggs = pstate->p_hasAggs;
	if (pstate->p_hasAggs)
		parseCheckAggregates(pstate, qry);

	return (Query *) qry;
}

/*
 * transformCursorStmt -
 *	  transform a Create Cursor Statement
 *
 */
static Query *
transformCursorStmt(ParseState *pstate, SelectStmt *stmt)
{
	Query	   *qry;

	qry = transformSelectStmt(pstate, stmt);

	qry->into = stmt->portalname;
	qry->isTemp = stmt->istemp;
	qry->isPortal = TRUE;
	qry->isBinary = stmt->binary;		/* internal portal */

	return qry;
}

/***S*I***/
/* This function steps through the tree
 * built up by the select_w_o_sort rule
 * and builds a list of all SelectStmt Nodes found
 * The built up list is handed back in **select_list.
 * If one of the SelectStmt Nodes has the 'unionall' flag
 * set to true *unionall_present hands back 'true' */
void 
create_select_list(Node *ptr, List **select_list, bool *unionall_present)
{
  if(IsA(ptr, SelectStmt)) {
    *select_list = lappend(*select_list, ptr);    
    if(((SelectStmt *)ptr)->unionall == TRUE) *unionall_present = TRUE;    
    return;    
  }
  
  /* Recursively call for all arguments. A NOT expr has no lexpr! */
  if (((A_Expr *)ptr)->lexpr != NULL) 
     create_select_list(((A_Expr *)ptr)->lexpr, select_list, unionall_present);
  create_select_list(((A_Expr *)ptr)->rexpr, select_list, unionall_present);
}

/* Changes the A_Expr Nodes to Expr Nodes and exchanges ANDs and ORs.
 * The reason for the exchange is easy: We implement INTERSECTs and EXCEPTs 
 * by rewriting these queries to semantically equivalent queries that use
 * IN and NOT IN subselects. To be able to use all three operations 
 * (UNIONs INTERSECTs and EXCEPTs) in one complex query we have to 
 * translate the queries into Disjunctive Normal Form (DNF). Unfortunately
 * there is no function 'dnfify' but there is a function 'cnfify'
 * which produces DNF when we exchange ANDs and ORs before calling
 * 'cnfify' and exchange them back in the result.
 *
 * If an EXCEPT or INTERSECT is present *intersect_present
 * hands back 'true' */ 
Node *A_Expr_to_Expr(Node *ptr, bool *intersect_present)
{
  Node *result = NULL;
  
  switch(nodeTag(ptr))
    {
    case T_A_Expr:
      {
	A_Expr *a = (A_Expr *)ptr;
	
	switch (a->oper)
	  {
	  case AND:
	    {
	      Expr *expr = makeNode(Expr);
	      Node	   *lexpr = A_Expr_to_Expr(((A_Expr *)ptr)->lexpr, intersect_present);
	      Node	   *rexpr = A_Expr_to_Expr(((A_Expr *)ptr)->rexpr, intersect_present);

	      *intersect_present = TRUE;
	      
	      expr->typeOid = BOOLOID;
	      expr->opType = OR_EXPR;
	      expr->args = makeList(lexpr, rexpr, -1);
	      result = (Node *) expr;
	      break;	      
	    }	  	  
	  case OR:
	    {
	      Expr *expr = makeNode(Expr);
	      Node	   *lexpr = A_Expr_to_Expr(((A_Expr *)ptr)->lexpr, intersect_present);
	      Node	   *rexpr = A_Expr_to_Expr(((A_Expr *)ptr)->rexpr, intersect_present);

	      expr->typeOid = BOOLOID;
	      expr->opType = AND_EXPR;
	      expr->args = makeList(lexpr, rexpr, -1);
	      result = (Node *) expr;
	      break;	      
	    }
	  case NOT:
	    {
	      Expr *expr = makeNode(Expr);
	      Node	   *rexpr = A_Expr_to_Expr(((A_Expr *)ptr)->rexpr, intersect_present);

	      expr->typeOid = BOOLOID;
	      expr->opType = NOT_EXPR;
	      expr->args = makeList(rexpr, -1);
	      result = (Node *) expr;
	      break;	      
	    }
	  }	
	break;	
      }
    default:
      {
	result = ptr;
      }      
    }
  return result;  
}

void
CheckSelectForUpdate(Query *qry)
{
	if (qry->unionClause != NULL)
		elog(ERROR, "SELECT FOR UPDATE is not allowed with UNION/INTERSECT/EXCEPT clause");
	if (qry->uniqueFlag != NULL)
		elog(ERROR, "SELECT FOR UPDATE is not allowed with DISTINCT clause");
	if (qry->groupClause != NULL)
		elog(ERROR, "SELECT FOR UPDATE is not allowed with GROUP BY clause");
	if (qry->hasAggs)
		elog(ERROR, "SELECT FOR UPDATE is not allowed with AGGREGATE");
}

static void
transformForUpdate(Query *qry, List *forUpdate)
{
	List	   *rowMark = NULL;
	RowMark	   *newrm;
	List	   *l;
	Index		i;

	CheckSelectForUpdate(qry);

	if (lfirst(forUpdate) == NULL)		/* all tables */
	{
		i = 1;
		foreach (l, qry->rtable)
		{
			newrm = makeNode(RowMark);
			newrm->rti = i++;
			newrm->info = ROW_MARK_FOR_UPDATE|ROW_ACL_FOR_UPDATE;
			rowMark = lappend(rowMark, newrm);
		}
		qry->rowMark = nconc(qry->rowMark, rowMark);
		return;
	}

	foreach (l, forUpdate)
	{
		List   *l2;
		List   *l3;

		i = 1;
		foreach (l2, qry->rtable)
		{
			if (strcmp(((RangeTblEntry*)lfirst(l2))->refname, lfirst(l)) == 0)
			{
				foreach (l3, rowMark)
				{
					if (((RowMark*)lfirst(l3))->rti == i)	/* duplicate */
						break;
				}
				if (l3 == NULL)
				{
					newrm = makeNode(RowMark);
					newrm->rti = i;
					newrm->info = ROW_MARK_FOR_UPDATE|ROW_ACL_FOR_UPDATE;
					rowMark = lappend(rowMark, newrm);
				}
				break;
			}
			i++;
		}
		if (l2 == NULL)
			elog(ERROR, "FOR UPDATE: relation %s not found in FROM clause", lfirst(l));
	}

	qry->rowMark = rowMark;
	return;
}