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Avoid coercing a whole-row variable that is already coerced.

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Marginal efficiency and beautification hack.  I'm not sure whether
this case ever arises currently, but the pending patch for update
tuple routing will cause it to arise.

Amit Khandekar

Discussion: http://postgr.es/m/CAJ3gD9cazfppe7-wwUbabPcQ4_0SubkiPFD1+0r5_DkVNWo5yg@mail.gmail.com
This commit is contained in:
Robert Haas 2017-10-12 17:10:48 -04:00
parent 60f7c0abef
commit 1c497fa72d
1 changed files with 41 additions and 10 deletions
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51
src/backend/rewrite/rewriteManip.c
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@ -1224,6 +1224,7 @@ typedef struct
/* Target type when converting whole-row vars */
Oid to_rowtype;
bool *found_whole_row; /* output flag */
bool coerced_var; /* var is under ConvertRowTypeExpr */
} map_variable_attnos_context;
static Node *
@ -1267,22 +1268,29 @@ map_variable_attnos_mutator(Node *node,
/* Don't convert unless necessary. */
if (context->to_rowtype != var->vartype)
{
ConvertRowtypeExpr *r;
/* Var itself is converted to the requested type. */
newvar->vartype = context->to_rowtype;
/*
* And a conversion node on top to convert back to the
* original type.
* If this var is already under a ConvertRowtypeExpr,
* we don't have to add another one.
*/
r = makeNode(ConvertRowtypeExpr);
r->arg = (Expr *) newvar;
r->resulttype = var->vartype;
r->convertformat = COERCE_IMPLICIT_CAST;
r->location = -1;
if (!context->coerced_var)
{
ConvertRowtypeExpr *r;
return (Node *) r;
/*
* And a conversion node on top to convert back to
* the original type.
*/
r = makeNode(ConvertRowtypeExpr);
r->arg = (Expr *) newvar;
r->resulttype = var->vartype;
r->convertformat = COERCE_IMPLICIT_CAST;
r->location = -1;
return (Node *) r;
}
}
}
}
@ -1290,6 +1298,28 @@ map_variable_attnos_mutator(Node *node,
}
/* otherwise fall through to copy the var normally */
}
else if (IsA(node, ConvertRowtypeExpr))
{
ConvertRowtypeExpr *r = (ConvertRowtypeExpr *) node;
/*
* If this is coercing a var (which is typical), convert only the var,
* as against adding another ConvertRowtypeExpr over it.
*/
if (IsA(r->arg, Var))
{
ConvertRowtypeExpr *newnode;
newnode = (ConvertRowtypeExpr *) palloc(sizeof(ConvertRowtypeExpr));
*newnode = *r;
context->coerced_var = true;
newnode->arg = (Expr *) map_variable_attnos_mutator((Node *) r->arg, context);
context->coerced_var = false;
return (Node *) newnode;
}
/* Else fall through the expression tree mutator */
}
else if (IsA(node, Query))
{
/* Recurse into RTE subquery or not-yet-planned sublink subquery */
@ -1321,6 +1351,7 @@ map_variable_attnos(Node *node,
context.map_length = map_length;
context.to_rowtype = to_rowtype;
context.found_whole_row = found_whole_row;
context.coerced_var = false;
*found_whole_row = false;