mirror of
https://github.com/postgres/postgres.git
synced 2025-07-11 10:01:57 +03:00
Support index-only scans using the visibility map to avoid heap fetches.
When a btree index contains all columns required by the query, and the visibility map shows that all tuples on a target heap page are visible-to-all, we don't need to fetch that heap page. This patch depends on the previous patches that made the visibility map reliable. There's a fair amount left to do here, notably trying to figure out a less chintzy way of estimating the cost of an index-only scan, but the core functionality seems ready to commit. Robert Haas and Ibrar Ahmed, with some previous work by Heikki Linnakangas.
This commit is contained in:
@ -447,6 +447,7 @@ _outIndexScan(StringInfo str, IndexScan *node)
|
||||
WRITE_NODE_FIELD(indexorderby);
|
||||
WRITE_NODE_FIELD(indexorderbyorig);
|
||||
WRITE_ENUM_FIELD(indexorderdir, ScanDirection);
|
||||
WRITE_BOOL_FIELD(indexonly);
|
||||
}
|
||||
|
||||
static void
|
||||
@ -1500,6 +1501,7 @@ _outIndexPath(StringInfo str, IndexPath *node)
|
||||
WRITE_NODE_FIELD(indexorderbys);
|
||||
WRITE_BOOL_FIELD(isjoininner);
|
||||
WRITE_ENUM_FIELD(indexscandir, ScanDirection);
|
||||
WRITE_BOOL_FIELD(indexonly);
|
||||
WRITE_FLOAT_FIELD(indextotalcost, "%.2f");
|
||||
WRITE_FLOAT_FIELD(indexselectivity, "%.4f");
|
||||
WRITE_FLOAT_FIELD(rows, "%.0f");
|
||||
|
Reference in New Issue
Block a user