database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-11-16 15:02:33 +03:00
Code Activity

Rearrange the implementation of index-only scans.

Browse Source 
This commit changes index-only scans so that data is read directly from the
index tuple without first generating a faux heap tuple.  The only immediate
benefit is that indexes on system columns (such as OID) can be used in
index-only scans, but this is necessary infrastructure if we are ever to
support index-only scans on expression indexes.  The executor is now ready
for that, though the planner still needs substantial work to recognize
the possibility.

To do this, Vars in index-only plan nodes have to refer to index columns
not heap columns.  I introduced a new special varno, INDEX_VAR, to mark
such Vars to avoid confusion.  (In passing, this commit renames the two
existing special varnos to OUTER_VAR and INNER_VAR.)  This allows
ruleutils.c to handle them with logic similar to what we use for subplan
reference Vars.

Since index-only scans are now fundamentally different from regular
indexscans so far as their expression subtrees are concerned, I also chose
to change them to have their own plan node type (and hence, their own
executor source file).
This commit is contained in:
Tom Lane
2011-10-11 14:20:06 -04:00
parent fa351d5a0d
commit a0185461dd
34 changed files with 1312 additions and 419 deletions
Download Patch File Download Diff File Expand all files Collapse all files

16
src/include/nodes/primnodes.h
View File

@@ -118,15 +118,19 @@ typedef struct Expr
* Note: during parsing/planning, varnoold/varoattno are always just copies
* of varno/varattno. At the tail end of planning, Var nodes appearing in
* upper-level plan nodes are reassigned to point to the outputs of their
* subplans; for example, in a join node varno becomes INNER or OUTER and
* varattno becomes the index of the proper element of that subplan's target
* list. But varnoold/varoattno continue to hold the original values.
* subplans; for example, in a join node varno becomes INNER_VAR or OUTER_VAR
* and varattno becomes the index of the proper element of that subplan's
* target list. But varnoold/varoattno continue to hold the original values.
* The code doesn't really need varnoold/varoattno, but they are very useful
* for debugging and interpreting completed plans, so we keep them around.
*/
#define INNER 65000
#define OUTER 65001
#define INNER_VAR 65000 /* reference to inner subplan */
#define OUTER_VAR 65001 /* reference to outer subplan */
#define INDEX_VAR 65002 /* reference to index column */
#define IS_SPECIAL_VARNO(varno) ((varno) >= INNER_VAR)
/* Symbols for the indexes of the special RTE entries in rules */
#define PRS2_OLD_VARNO 1
#define PRS2_NEW_VARNO 2
@@ -134,7 +138,7 @@ typedef struct Var
{
Expr xpr;
Index varno; /* index of this var's relation in the range
* table (could also be INNER or OUTER) */
* table, or INNER_VAR/OUTER_VAR/INDEX_VAR */
AttrNumber varattno; /* attribute number of this var, or zero for
* all */
Oid vartype; /* pg_type OID for the type of this var */