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Commit04942bf

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Remove rewriteTargetListIU's expansion of view targetlists in UPDATE.
Commit2ec993a, which added triggers on views, modified the rewriterto add dummy entries like "SET x = x" for all columns that weren'tactually being updated by the user in any UPDATE directed at a view.That was needed at the time to produce a complete "NEW" row to passto the trigger. Later it was found to cause problems for ordinaryupdatable views, so commitcab5dc5 restricted it to happen only fortrigger-updatable views. But in the wake of commit86dc900, wereally don't need it at all. nodeModifyTable.c populates the trigger"OLD" row from the whole-row variable that is generated for the view,and then it computes the "NEW" row using that old row and the UPDATEtargetlist. So there is no need for the UPDATE tlist to have dummyentries, any more than it needs them for regular tables or othertypes of views.(The comments for rewriteTargetListIU suggest that we must do thisfor correct expansion of NEW references in rules, but I now thinkthat that was just lazy comment editing in2ec993a. If we didn'tneed it for rules on views before there were triggers, we don't needit after that.)This essentially propagates86dc900's decision that we don't needdummy column updates into the view case. Aside from making thedifferent cases more uniform and hence possibly forestalling futurebugs, it ought to save a little bit of rewriter/planner effort.Discussion:https://postgr.es/m/2181213.1619397634@sss.pgh.pa.us
1 parent79a5928 commit04942bf

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1 file changed

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‎src/backend/rewrite/rewriteHandler.c

Lines changed: 4 additions & 38 deletions
Original file line numberDiff line numberDiff line change
@@ -679,30 +679,19 @@ adjustJoinTreeList(Query *parsetree, bool removert, int rt_index)
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* and UPDATE, replace explicit DEFAULT specifications with column default
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* expressions.
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*
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* 2. For an UPDATE on a trigger-updatable view, add tlist entries for any
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* unassigned-to attributes, assigning them their old values. These will
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* later get expanded to the output values of the view. This is only needed
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* for trigger-updatable views, for which the view remains the result relation
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* of the query; without it, we would not have a complete "new tuple" to pass
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* to triggers. For auto-updatable views we must not do this, since it might
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* add assignments to non-updatable view columns. For rule-updatable views it
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* is unnecessary extra work, since the query will be rewritten with a
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* different result relation which will be processed when we recurse via
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* RewriteQuery.
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*
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* 3. Merge multiple entries for the same target attribute, or declare error
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* 2. Merge multiple entries for the same target attribute, or declare error
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* if we can't. Multiple entries are only allowed for INSERT/UPDATE of
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* portions of an array or record field, for example
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*UPDATE table SET foo[2] = 42, foo[4] = 43;
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* We can merge such operations into a single assignment op. Essentially,
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* the expression we want to produce in this case is like
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*foo = array_set_element(array_set_element(foo, 2, 42), 4, 43)
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*
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*4. Sort the tlist into standard order: non-junk fields in order by resno,
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*3. Sort the tlist into standard order: non-junk fields in order by resno,
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* then junk fields (these in no particular order).
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*
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* We must do items 1,2,3 before firing rewrite rules, else rewritten
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* references to NEW.foo will produce wrong or incomplete results. Item4
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* We must do items 1 and 2 before firing rewrite rules, else rewritten
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* references to NEW.foo will produce wrong or incomplete results. Item3
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* is not needed for rewriting, but it is helpful for the planner, and we
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* can do it essentially for free while handling the other items.
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*
@@ -984,29 +973,6 @@ rewriteTargetListIU(List *targetList,
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false);
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}
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/*
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* For an UPDATE on a trigger-updatable view, provide a dummy entry
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* whenever there is no explicit assignment.
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*/
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if (new_tle==NULL&&commandType==CMD_UPDATE&&
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target_relation->rd_rel->relkind==RELKIND_VIEW&&
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view_has_instead_trigger(target_relation,CMD_UPDATE))
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{
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Node*new_expr;
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new_expr= (Node*)makeVar(result_rti,
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attrno,
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att_tup->atttypid,
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att_tup->atttypmod,
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att_tup->attcollation,
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0);
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new_tle=makeTargetEntry((Expr*)new_expr,
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attrno,
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pstrdup(NameStr(att_tup->attname)),
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false);
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}
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if (new_tle)
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new_tlist=lappend(new_tlist,new_tle);
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}

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