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  • Committer: Prafulla Tekawade
  • Date: 2010-07-18 03:36:32 UTC
  • mto: (1662.1.4 rollup)
  • mto: This revision was merged to the branch mainline in revision 1664.
  • Revision ID: prafulla_t@users.sourceforge.net-20100718033632-p7q6qtgliqbhe38p
Fix for Bug 592444

There were two problems:
o. In greedy_search optimizer method, best_extension_by_limited search
   maintains join embedding(nestedness) of tables added so far, so that 
   correct(valid)  join order is selected
   These are requirements from nested outer join executioner.
   The problem was, embedding_map was not correctly updated when a table 
   is added to optimal plan outside best_extension_by_limited search, 
   by greedy_search method. We need to update join->cur_embedding_map
   correctly here so that execution plan for other tables get
   generated.
   Invoked checked_interleaving_with_nj from greedy_search on the
   best_table selected. Fixed its prototype to take only one JoinTab
   This is same as mysql 5.1 source tree.
o. The other problem was, join->cur_embedding_map was not restored correctly
   when a table is added to the optimal plan to reflect the current embedding 
   map. 
   Taken good documented method restore_prev_nj_state which restores 
   cur_embedding_map from mysql 5.1 source tree and modified it for drizzled 
   code.

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Lines of Context:
drizzled/plugin/query_rewrite.cc
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#include <algorithm>
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#include <vector>
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using namespace std;
 
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namespace drizzled
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{
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namespace plugin
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{
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std::vector<plugin::QueryRewriter *> all_rewriters;
 
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vector<plugin::QueryRewriter *> all_rewriters;
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bool QueryRewriter::addPlugin(QueryRewriter *in_rewriter)
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{
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  if (in_rewriter != NULL)
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  {
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    all_rewriters.erase(std::find(all_rewriters.begin(),
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                                  all_rewriters.end(),
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                                  in_rewriter));
 
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    all_rewriters.erase(find(all_rewriters.begin(),
 
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                             all_rewriters.end(),
 
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                             in_rewriter));
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  }
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}
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 * This is the QueryRewriter::rewrite entry point.
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 * This gets called from within the Drizzle kernel.
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 */
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void QueryRewriter::rewriteQuery(const std::string &schema, std::string &to_rewrite)
 
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void QueryRewriter::rewriteQuery(const string &schema, string &to_rewrite)
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{
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  for (std::vector<plugin::QueryRewriter *>::iterator iter= all_rewriters.begin();
 
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  for (vector<plugin::QueryRewriter *>::iterator iter= all_rewriters.begin();
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       iter != all_rewriters.end();
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       ++iter)
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  {