diff options
Diffstat (limited to 'src/backend/optimizer/README')
| -rw-r--r-- | src/backend/optimizer/README | 10 |
1 files changed, 4 insertions, 6 deletions
diff --git a/src/backend/optimizer/README b/src/backend/optimizer/README index 3c2fd32d520..b19f6118ff1 100644 --- a/src/backend/optimizer/README +++ b/src/backend/optimizer/README @@ -75,11 +75,10 @@ way. All the Paths made for a given relation are placed in its RelOptInfo.pathlist. (Actually, we discard Paths that are obviously inferior alternatives before they ever get into the pathlist --- what ends up in the pathlist is the cheapest way of generating each potentially -useful sort ordering of the relation.) Also create RelOptInfo.joininfo -nodes that list all the join clauses that involve this relation. For -example, the WHERE clause "tab1.col1 = tab2.col1" generates a JoinInfo -for tab1 listing tab2 as an unjoined relation, and also one for tab2 -showing tab1 as an unjoined relation. +useful sort ordering of the relation.) Also create a RelOptInfo.joininfo +list including all the join clauses that involve this relation. For +example, the WHERE clause "tab1.col1 = tab2.col1" generates entries in +both tab1 and tab2's joininfo lists. If we have only a single base relation in the query, we are done. Otherwise we have to figure out how to join the base relations into a @@ -252,7 +251,6 @@ RelOptInfo - a relation or joined relations RestrictInfo - WHERE clauses, like "x = 3" or "y = z" (note the same structure is used for restriction and join clauses) - JoinInfo - join clauses associated with a particular pair of relations Path - every way to generate a RelOptInfo(sequential,index,joins) SeqScan - a plain Path node with pathtype = T_SeqScan |