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Improved the performance of the OCI8 adapter for Oracle #723 [pilx/gj…

…enkins]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@930 5ecf4fe2-1ee6-0310-87b1-e25e094e27de
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1 parent 58bf8f4 commit 1b40f051e7802a0235a777edb29f14230f89e43a @dhh dhh committed Mar 20, 2005
Showing with 16 additions and 11 deletions.
  1. +2 −0 activerecord/CHANGELOG
  2. +14 −11 activerecord/lib/active_record/connection_adapters/oci_adapter.rb
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@@ -1,5 +1,7 @@
*SVN*
+* Improved the performance of the OCI8 adapter for Oracle #723 [pilx/gjenkins]
+
* Added type conversion before saving a record, so string-based values like "10.0" aren't left for the database to convert #820 [dave@cherryville.org]
* Added with additional settings for working with transactional fixtures and pre-loaded test databases #865 [mindel]
@@ -2,15 +2,15 @@
# 1. I had to redefine a method in ActiveRecord to make it possible to implement an autonumbering
# solution for oracle. It's implemented in a way that is intended to not break other adapters.
# 2. Default value support needs a patch to the OCI8 driver, to enable it to read LONG columns.
-# LONG is deprecated, and so may never be properly added to driver.
-# A similar patch is needed for TIMESTAMP.
-# This is dangerous because it may break with newer versions of the driver.
+# The driver-author has said he will add this in a future release.
+# A similar patch is needed for TIMESTAMP. This should be replaced with the 0.2 version of the
+# driver, which will support TIMESTAMP properly.
# 3. Large Object support works by an after_save callback added to the ActiveRecord. This is not
# a problem - you can add other (chained) after_save callbacks.
-# 4. LIMIT and OFFSET work by scrolling through a cursor - no rownum select from select required.
-# It does mean that large OFFSETs will have to scroll through the intervening records. To keep
-# consistency with other adapters I've allowed the LIMIT and OFFSET clauses to be included in
-# the sql string and later extracted them by parsing the string.
+# 4. LIMIT and OFFSET now work using a select from select from select. This pattern enables
+# the middle select to limit downwards as much as possible, before the outermost select
+# limits upwards. The extra rownum column is stripped from the results.
+# See http://asktom.oracle.com/pls/ask/f?p=4950:8:::::F4950_P8_DISPLAYID:127412348064
#
# Do what you want with this code, at your own peril, but if any significant portion of my code
# remains then please acknowledge my contribution.
@@ -118,13 +118,17 @@ def quote(value, column = nil)
end
def select_all(sql, name = nil)
- offset = sql =~ /OFFSET (\d+)$/ ? $1.to_i : -1
+ offset = sql =~ /OFFSET (\d+)$/ ? $1.to_i : 0
sql, limit = $1, $2.to_i if sql =~ /(.*)(?: LIMIT[= ](\d+))(\s*OFFSET \d+)?$/
+ if limit
+ sql = "select * from (select raw_sql_.*, rownum raw_rnum_ from (#{sql}) raw_sql_ where rownum <= #{offset+limit}) where raw_rnum_ > #{offset}"
+ elsif offset > 0
+ sql = "select * from (select raw_sql_.*, rownum raw_rnum_ from (#{sql}) raw_sql_) where raw_rnum_ > #{offset}"
+ end
cursor = log(sql, name, @connection) { @connection.exec sql }
cols = cursor.get_col_names.map { |x| x.downcase }
rows = []
while row = cursor.fetch
- next if cursor.row_count <= offset
hash = Hash.new
cols.each_with_index { |col, i|
hash[col] = case row[i]
@@ -134,10 +138,9 @@ def select_all(sql, name = nil)
(row[i].hour == 0 and row[i].minute == 0 and row[i].second == 0) ?
row[i].to_date : row[i].to_time
else row[i]
- end
+ end unless col == 'raw_rnum_'
}
rows << hash
- break if rows.size == limit
end
rows
ensure

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