diff options
Diffstat (limited to 'src/include/nodes/parsenodes.h')
| -rw-r--r-- | src/include/nodes/parsenodes.h | 50 |
1 files changed, 34 insertions, 16 deletions
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h index 8ac9e3d7647..1556bf38693 100644 --- a/src/include/nodes/parsenodes.h +++ b/src/include/nodes/parsenodes.h @@ -6,7 +6,7 @@ * * Copyright (c) 1994, Regents of the University of California * - * $Id: parsenodes.h,v 1.83 1999/10/03 23:55:36 tgl Exp $ + * $Id: parsenodes.h,v 1.84 1999/10/07 04:23:17 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -45,7 +45,7 @@ typedef struct Query bool isBinary; /* binary portal? */ bool isTemp; /* is 'into' a temp table? */ bool unionall; /* union without unique sort */ - bool hasAggs; /* has aggregates in target list */ + bool hasAggs; /* has aggregates in tlist or havingQual */ bool hasSubLinks; /* has subquery SubLink */ List *rtable; /* list of range table entries */ @@ -968,30 +968,48 @@ typedef struct TargetEntry NodeTag type; Resdom *resdom; /* fjoin overload this to be a list?? */ Fjoin *fjoin; - Node *expr; /* can be a list too */ + Node *expr; } TargetEntry; -/* +/*-------------------- * RangeTblEntry - - * used in range tables. Some of the following are only used in one of + * A range table is a List of RangeTblEntry nodes. + * + * Some of the following are only used in one of * the parsing, optimizing, execution stages. * - * inFromCl marks those range variables that are listed in the from clause. - * In SQL, the targetlist can only refer to range variables listed in the - * from clause but POSTQUEL allows you to refer to tables not specified, in - * which case a range table entry will be generated. We use POSTQUEL - * semantics which is more powerful. However, we need SQL semantics in - * some cases (eg. when expanding a '*') + * inFromCl marks those range variables that are listed in the FROM clause. + * In SQL, the query can only refer to range variables listed in the + * FROM clause, but POSTQUEL allows you to refer to tables not listed, + * in which case a range table entry will be generated. We still support + * this POSTQUEL feature, although there is some doubt whether it's + * convenient or merely confusing. The flag is needed since an + * implicitly-added RTE shouldn't change the namespace for unqualified + * column names processed later, and it also shouldn't affect the + * expansion of '*'. + * + * inJoinSet marks those range variables that the planner should join + * over even if they aren't explicitly referred to in the query. For + * example, "SELECT COUNT(1) FROM tx" should produce the number of rows + * in tx. A more subtle example uses a POSTQUEL implicit RTE: + * SELECT COUNT(1) FROM tx WHERE TRUE OR (tx.f1 = ty.f2) + * Here we should get the product of the sizes of tx and ty. However, + * the query optimizer can simplify the WHERE clause to "TRUE", so + * ty will no longer be referred to explicitly; without a flag forcing + * it to be included in the join, we will get the wrong answer. So, + * a POSTQUEL implicit RTE must be marked inJoinSet but not inFromCl. + *-------------------- */ typedef struct RangeTblEntry { NodeTag type; char *relname; /* real name of the relation */ - char *refname; /* the reference name (specified in the - * from clause) */ - Oid relid; - bool inh; /* inheritance? */ - bool inFromCl; /* comes from From Clause */ + char *refname; /* the reference name (as specified in the + * FROM clause) */ + Oid relid; /* OID of the relation */ + bool inh; /* inheritance requested? */ + bool inFromCl; /* present in FROM clause */ + bool inJoinSet; /* planner must include this rel */ bool skipAcl; /* skip ACL check in executor */ } RangeTblEntry; |