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author | Yasuo Honda <yasuo.honda@gmail.com> | 2014-11-04 04:44:01 +0900 |
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committer | Yasuo Honda <yasuo.honda@gmail.com> | 2015-06-19 23:02:58 +0000 |
commit | 0e1427e917a4e47dce9f02ad9309600073622c73 (patch) | |
tree | aa87b1860def6939c47cb46b236105f8b8c42bc2 /lib/arel/visitors | |
parent | 8d04c28b619212f99e6ce534f75ebda59bb200a1 (diff) | |
download | rails-0e1427e917a4e47dce9f02ad9309600073622c73.tar.gz rails-0e1427e917a4e47dce9f02ad9309600073622c73.tar.bz2 rails-0e1427e917a4e47dce9f02ad9309600073622c73.zip |
Create Arel::Visitors::Oracle12 to provide better top-N query
to support `FETCH FIRST n ROWS` and `OFFSET` for Oracle 12c database
Diffstat (limited to 'lib/arel/visitors')
-rw-r--r-- | lib/arel/visitors/oracle12.rb | 53 |
1 files changed, 53 insertions, 0 deletions
diff --git a/lib/arel/visitors/oracle12.rb b/lib/arel/visitors/oracle12.rb new file mode 100644 index 0000000000..4a42343c9b --- /dev/null +++ b/lib/arel/visitors/oracle12.rb @@ -0,0 +1,53 @@ +module Arel + module Visitors + class Oracle12 < Arel::Visitors::ToSql + private + + def visit_Arel_Nodes_SelectStatement o, collector + # Oracle does not allow LIMIT clause with select for update + if o.limit && o.lock + o = o.dup + o.limit = [] + end + + super + end + + def visit_Arel_Nodes_SelectOptions o, collector + collector = maybe_visit o.offset, collector + collector = maybe_visit o.limit, collector + collector = maybe_visit o.lock, collector + end + + def visit_Arel_Nodes_Limit o, collector + collector << "FETCH FIRST " + collector = visit o.expr, collector + collector << " ROWS ONLY" + end + + def visit_Arel_Nodes_Offset o, collector + collector << "OFFSET " + visit o.expr, collector + collector << " ROWS" + end + + def visit_Arel_Nodes_Except o, collector + collector << "( " + collector = infix_value o, collector, " MINUS " + collector << " )" + end + + def visit_Arel_Nodes_UpdateStatement o, collector + # Oracle does not allow ORDER BY/LIMIT in UPDATEs. + if o.orders.any? && o.limit.nil? + # However, there is no harm in silently eating the ORDER BY clause if no LIMIT has been provided, + # otherwise let the user deal with the error + o = o.dup + o.orders = [] + end + + super + end + end + end +end |