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Merge Resdom nodes into TargetEntry nodes to simplify code and save a
few palloc's. I also chose to eliminate the restype and restypmod fields entirely, since they are redundant with information stored in the node's contained expression; re-examining the expression at need seems simpler and more reliable than trying to keep restype/restypmod up to date. initdb forced due to change in contents of stored rules.
This commit is contained in:
Tom Lane
@@ -10,7 +10,7 @@
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* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $PostgreSQL: pgsql/src/include/nodes/primnodes.h,v 1.106 2004/12/31 22:03:34 pgsql Exp $
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* $PostgreSQL: pgsql/src/include/nodes/primnodes.h,v 1.107 2005/04/06 16:34:07 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@@ -27,72 +27,6 @@
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* ----------------------------------------------------------------
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*/
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/*--------------------
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* Resdom (Result Domain)
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*
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* Notes:
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*
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* In a SELECT's targetlist, resno should always be equal to the item's
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* ordinal position (counting from 1). However, in an INSERT or UPDATE
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* targetlist, resno represents the attribute number of the destination
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* column for the item; so there may be missing or out-of-order resnos.
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* It is even legal to have duplicated resnos; consider
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* UPDATE table SET arraycol[1] = ..., arraycol[2] = ..., ...
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* The two meanings come together in the executor, because the planner
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* transforms INSERT/UPDATE tlists into a normalized form with exactly
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* one entry for each column of the destination table. Before that's
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* happened, however, it is risky to assume that resno == position.
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* Generally get_tle_by_resno() should be used rather than list_nth()
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* to fetch tlist entries by resno, and only in SELECT should you assume
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* that resno is a unique identifier.
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*
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* resname is required to represent the correct column name in non-resjunk
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* entries of top-level SELECT targetlists, since it will be used as the
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* column title sent to the frontend. In most other contexts it is only
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* a debugging aid, and may be wrong or even NULL. (In particular, it may
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* be wrong in a tlist from a stored rule, if the referenced column has been
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* renamed by ALTER TABLE since the rule was made. Also, the planner tends
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* to store NULL rather than look up a valid name for tlist entries in
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* non-toplevel plan nodes.) In resjunk entries, resname should be either
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* a specific system-generated name (such as "ctid") or NULL; anything else
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* risks confusing ExecGetJunkAttribute!
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*
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* ressortgroupref is used in the representation of ORDER BY and
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* GROUP BY items. Targetlist entries with ressortgroupref=0 are not
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* sort/group items. If ressortgroupref>0, then this item is an ORDER BY or
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* GROUP BY value. No two entries in a targetlist may have the same nonzero
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* ressortgroupref --- but there is no particular meaning to the nonzero
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* values, except as tags. (For example, one must not assume that lower
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* ressortgroupref means a more significant sort key.) The order of the
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* associated SortClause or GroupClause lists determine the semantics.
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*
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* resorigtbl/resorigcol identify the source of the column, if it is a
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* simple reference to a column of a base table (or view). If it is not
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* a simple reference, these fields are zeroes.
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*
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* If resjunk is true then the column is a working column (such as a sort key)
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* that should be removed from the final output of the query. Resjunk columns
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* must have resnos that cannot duplicate any regular column's resno. Also
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* note that there are places that assume resjunk columns come after non-junk
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* columns.
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*--------------------
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*/
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typedef struct Resdom
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{
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NodeTag type;
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AttrNumber resno; /* attribute number (see notes above) */
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Oid restype; /* type of the value */
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int32 restypmod; /* type-specific modifier of the value */
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char *resname; /* name of the column (could be NULL) */
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Index ressortgroupref;/* nonzero if referenced by a sort/group
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* clause */
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Oid resorigtbl; /* OID of column's source table */
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AttrNumber resorigcol; /* column's number in source table */
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bool resjunk; /* set to true to eliminate the attribute
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* from final target list */
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} Resdom;
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/*
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* Alias -
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* specifies an alias for a range variable; the alias might also
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@@ -822,7 +756,7 @@ typedef struct SetToDefault
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int32 typeMod; /* typemod for substituted value */
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} SetToDefault;
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/*
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/*--------------------
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* TargetEntry -
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* a target entry (used in query target lists)
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*
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@@ -831,14 +765,63 @@ typedef struct SetToDefault
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* very many places it's convenient to process a whole query targetlist as a
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* single expression tree.
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*
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* The separation between TargetEntry and Resdom is historical. One of these
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* days, Resdom should probably get folded into TargetEntry.
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* In a SELECT's targetlist, resno should always be equal to the item's
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* ordinal position (counting from 1). However, in an INSERT or UPDATE
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* targetlist, resno represents the attribute number of the destination
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* column for the item; so there may be missing or out-of-order resnos.
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* It is even legal to have duplicated resnos; consider
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* UPDATE table SET arraycol[1] = ..., arraycol[2] = ..., ...
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* The two meanings come together in the executor, because the planner
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* transforms INSERT/UPDATE tlists into a normalized form with exactly
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* one entry for each column of the destination table. Before that's
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* happened, however, it is risky to assume that resno == position.
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* Generally get_tle_by_resno() should be used rather than list_nth()
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* to fetch tlist entries by resno, and only in SELECT should you assume
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* that resno is a unique identifier.
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*
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* resname is required to represent the correct column name in non-resjunk
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* entries of top-level SELECT targetlists, since it will be used as the
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* column title sent to the frontend. In most other contexts it is only
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* a debugging aid, and may be wrong or even NULL. (In particular, it may
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* be wrong in a tlist from a stored rule, if the referenced column has been
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* renamed by ALTER TABLE since the rule was made. Also, the planner tends
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* to store NULL rather than look up a valid name for tlist entries in
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* non-toplevel plan nodes.) In resjunk entries, resname should be either
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* a specific system-generated name (such as "ctid") or NULL; anything else
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* risks confusing ExecGetJunkAttribute!
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*
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* ressortgroupref is used in the representation of ORDER BY and
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* GROUP BY items. Targetlist entries with ressortgroupref=0 are not
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* sort/group items. If ressortgroupref>0, then this item is an ORDER BY or
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* GROUP BY value. No two entries in a targetlist may have the same nonzero
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* ressortgroupref --- but there is no particular meaning to the nonzero
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* values, except as tags. (For example, one must not assume that lower
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* ressortgroupref means a more significant sort key.) The order of the
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* associated SortClause or GroupClause lists determine the semantics.
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*
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* resorigtbl/resorigcol identify the source of the column, if it is a
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* simple reference to a column of a base table (or view). If it is not
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* a simple reference, these fields are zeroes.
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*
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* If resjunk is true then the column is a working column (such as a sort key)
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* that should be removed from the final output of the query. Resjunk columns
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* must have resnos that cannot duplicate any regular column's resno. Also
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* note that there are places that assume resjunk columns come after non-junk
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* columns.
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*--------------------
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*/
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typedef struct TargetEntry
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{
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Expr xpr;
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Resdom *resdom; /* descriptor for targetlist item */
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Expr *expr; /* expression to evaluate */
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AttrNumber resno; /* attribute number (see notes above) */
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char *resname; /* name of the column (could be NULL) */
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Index ressortgroupref;/* nonzero if referenced by a sort/group
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* clause */
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Oid resorigtbl; /* OID of column's source table */
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AttrNumber resorigcol; /* column's number in source table */
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bool resjunk; /* set to true to eliminate the attribute
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* from final target list */
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} TargetEntry;
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