diff options
Diffstat (limited to 'src/include/nodes/plannodes.h')
| -rw-r--r-- | src/include/nodes/plannodes.h | 38 |
1 files changed, 30 insertions, 8 deletions
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h index 60467f5276..ababded845 100644 --- a/src/include/nodes/plannodes.h +++ b/src/include/nodes/plannodes.h @@ -285,11 +285,8 @@ typedef Scan SeqScan; * * indexqual has the same form, but the expressions have been commuted if * necessary to put the indexkeys on the left, and the indexkeys are replaced - * by Var nodes identifying the index columns (varattno is the index column - * position, not the base table's column, even though varno is for the base - * table). This is a bit hokey ... would be cleaner to use a special-purpose - * node type that could not be mistaken for a regular Var. But it will do - * for now. + * by Var nodes identifying the index columns (their varno is INDEX_VAR and + * their varattno is the index column number). * * indexorderbyorig is similarly the original form of any ORDER BY expressions * that are being implemented by the index, while indexorderby is modified to @@ -302,8 +299,7 @@ typedef Scan SeqScan; * (Note these fields are used for amcanorderbyop cases, not amcanorder cases.) * * indexorderdir specifies the scan ordering, for indexscans on amcanorder - * indexes (for other indexes it should be "don't care"). indexonly specifies - * an index-only scan, for indexscans on amcanreturn indexes. + * indexes (for other indexes it should be "don't care"). * ---------------- */ typedef struct IndexScan @@ -315,10 +311,36 @@ typedef struct IndexScan List *indexorderby; /* list of index ORDER BY exprs */ List *indexorderbyorig; /* the same in original form */ ScanDirection indexorderdir; /* forward or backward or don't care */ - bool indexonly; /* attempt to skip heap fetches? */ } IndexScan; /* ---------------- + * index-only scan node + * + * IndexOnlyScan is very similar to IndexScan, but it specifies an + * index-only scan, in which the data comes from the index not the heap. + * Because of this, *all* Vars in the plan node's targetlist, qual, and + * index expressions reference index columns and have varno = INDEX_VAR. + * Hence we do not need separate indexqualorig and indexorderbyorig lists, + * since their contents would be equivalent to indexqual and indexorderby. + * + * To help EXPLAIN interpret the index Vars for display, we provide + * indextlist, which represents the contents of the index as a targetlist + * with one TLE per index column. Vars appearing in this list reference + * the base table, and this is the only field in the plan node that may + * contain such Vars. + * ---------------- + */ +typedef struct IndexOnlyScan +{ + Scan scan; + Oid indexid; /* OID of index to scan */ + List *indexqual; /* list of index quals (usually OpExprs) */ + List *indexorderby; /* list of index ORDER BY exprs */ + List *indextlist; /* TargetEntry list describing index's cols */ + ScanDirection indexorderdir; /* forward or backward or don't care */ +} IndexOnlyScan; + +/* ---------------- * bitmap index scan node * * BitmapIndexScan delivers a bitmap of potential tuple locations; |