diff options
Diffstat (limited to 'src/include/nodes/pathnodes.h')
| -rw-r--r-- | src/include/nodes/pathnodes.h | 26 |
1 files changed, 10 insertions, 16 deletions
diff --git a/src/include/nodes/pathnodes.h b/src/include/nodes/pathnodes.h index 616ec3b3dbf..a008ae07da5 100644 --- a/src/include/nodes/pathnodes.h +++ b/src/include/nodes/pathnodes.h @@ -1185,26 +1185,20 @@ typedef struct IndexPath * conditions is done by a planner support function attached to the * indexclause's top-level function or operator. * - * If indexquals is NIL, it means that rinfo->clause is directly usable as - * an indexqual. Otherwise indexquals contains one or more directly-usable - * indexqual conditions extracted from the given clause. The 'lossy' flag - * indicates whether the indexquals are semantically equivalent to the - * original clause, or form a weaker condition. - * - * Currently, entries in indexquals are RestrictInfos, but they could perhaps - * be bare clauses instead; the only advantage of making them RestrictInfos - * is the possibility of caching cost and selectivity information across - * multiple uses, and it's not clear that that's really worth the price of - * constructing RestrictInfos for them. Note however that the extended-stats - * machinery won't do anything with non-RestrictInfo clauses, so that would - * have to be fixed. + * indexquals is a list of RestrictInfos for the directly-usable index + * conditions associated with this IndexClause. In the simplest case + * it's a one-element list whose member is iclause->rinfo. Otherwise, + * it contains one or more directly-usable indexqual conditions extracted + * from the given clause. The 'lossy' flag indicates whether the + * indexquals are semantically equivalent to the original clause, or + * represent a weaker condition. * * Normally, indexcol is the index of the single index column the clause * works on, and indexcols is NIL. But if the clause is a RowCompareExpr, * indexcol is the index of the leading column, and indexcols is a list of * all the affected columns. (Note that indexcols matches up with the - * columns of the actual indexable RowCompareExpr, which might be in - * indexquals rather than rinfo.) + * columns of the actual indexable RowCompareExpr in indexquals, which + * might be different from the original in rinfo.) * * An IndexPath's IndexClause list is required to be ordered by index * column, i.e. the indexcol values must form a nondecreasing sequence. @@ -1214,7 +1208,7 @@ typedef struct IndexClause { NodeTag type; struct RestrictInfo *rinfo; /* original restriction or join clause */ - List *indexquals; /* indexqual(s) derived from it, or NIL */ + List *indexquals; /* indexqual(s) derived from it */ bool lossy; /* are indexquals a lossy version of clause? */ AttrNumber indexcol; /* index column the clause uses (zero-based) */ List *indexcols; /* multiple index columns, if RowCompare */ |