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Commitd50d172

Browse files
author
Etsuro Fujita
committed
postgres_fdw: Perform the (FINAL, NULL) upperrel operations remotely.
The upper-planner pathification allows FDWs to arrange to push downdifferent types of upper-stage operations to the remote side. Thiscommit teaches postgres_fdw to do it for the (FINAL, NULL) upperrel,which is responsible for doing LockRows, LIMIT, and/or ModifyTable.This provides the ability for postgres_fdw to handle SELECT commandsso that it 1) skips the LockRows step (if any) (note that this issafe since it performs early locking) and 2) pushes down the LIMITand/or OFFSET restrictions (if any) to the remote side. This doesn'thandle the INSERT/UPDATE/DELETE cases.Author: Etsuro FujitaReviewed-By: Antonin Houska and Jeff JanesDiscussion:https://postgr.es/m/87pnz1aby9.fsf@news-spur.riddles.org.uk
1 parentaef65db commitd50d172

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7 files changed

+656
-390
lines changed

7 files changed

+656
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lines changed

‎contrib/postgres_fdw/deparse.c‎

Lines changed: 35 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -169,6 +169,7 @@ static void deparseSelectSql(List *tlist, bool is_subquery, List **retrieved_att
169169
staticvoiddeparseLockingClause(deparse_expr_cxt*context);
170170
staticvoidappendOrderByClause(List*pathkeys,boolhas_final_sort,
171171
deparse_expr_cxt*context);
172+
staticvoidappendLimitClause(deparse_expr_cxt*context);
172173
staticvoidappendConditions(List*exprs,deparse_expr_cxt*context);
173174
staticvoiddeparseFromExprForRel(StringInfobuf,PlannerInfo*root,
174175
RelOptInfo*foreignrel,booluse_alias,
@@ -930,7 +931,7 @@ build_tlist_to_deparse(RelOptInfo *foreignrel)
930931
void
931932
deparseSelectStmtForRel(StringInfobuf,PlannerInfo*root,RelOptInfo*rel,
932933
List*tlist,List*remote_conds,List*pathkeys,
933-
boolhas_final_sort,boolis_subquery,
934+
boolhas_final_sort,boolhas_limit,boolis_subquery,
934935
List**retrieved_attrs,List**params_list)
935936
{
936937
deparse_expr_cxtcontext;
@@ -988,6 +989,10 @@ deparseSelectStmtForRel(StringInfo buf, PlannerInfo *root, RelOptInfo *rel,
988989
if (pathkeys)
989990
appendOrderByClause(pathkeys,has_final_sort,&context);
990991

992+
/* Add LIMIT clause if necessary */
993+
if (has_limit)
994+
appendLimitClause(&context);
995+
991996
/* Add any necessary FOR UPDATE/SHARE. */
992997
deparseLockingClause(&context);
993998
}
@@ -1591,7 +1596,8 @@ deparseRangeTblRef(StringInfo buf, PlannerInfo *root, RelOptInfo *foreignrel,
15911596
/* Deparse the subquery representing the relation. */
15921597
appendStringInfoChar(buf,'(');
15931598
deparseSelectStmtForRel(buf,root,foreignrel,NIL,
1594-
fpinfo->remote_conds,NIL, false, true,
1599+
fpinfo->remote_conds,NIL,
1600+
false, false, true,
15951601
&retrieved_attrs,params_list);
15961602
appendStringInfoChar(buf,')');
15971603

@@ -3160,6 +3166,33 @@ appendOrderByClause(List *pathkeys, bool has_final_sort,
31603166
reset_transmission_modes(nestlevel);
31613167
}
31623168

3169+
/*
3170+
* Deparse LIMIT/OFFSET clause.
3171+
*/
3172+
staticvoid
3173+
appendLimitClause(deparse_expr_cxt*context)
3174+
{
3175+
PlannerInfo*root=context->root;
3176+
StringInfobuf=context->buf;
3177+
intnestlevel;
3178+
3179+
/* Make sure any constants in the exprs are printed portably */
3180+
nestlevel=set_transmission_modes();
3181+
3182+
if (root->parse->limitCount)
3183+
{
3184+
appendStringInfoString(buf," LIMIT ");
3185+
deparseExpr((Expr*)root->parse->limitCount,context);
3186+
}
3187+
if (root->parse->limitOffset)
3188+
{
3189+
appendStringInfoString(buf," OFFSET ");
3190+
deparseExpr((Expr*)root->parse->limitOffset,context);
3191+
}
3192+
3193+
reset_transmission_modes(nestlevel);
3194+
}
3195+
31633196
/*
31643197
* appendFunctionName
31653198
*Deparses function name from given function oid.

‎contrib/postgres_fdw/expected/postgres_fdw.out‎

Lines changed: 251 additions & 369 deletions
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