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Allow postgres_fdw to ship extension funcs/operators for remote execution.

The user can whitelist specified extension(s) in the foreign server's
options, whereupon we will treat immutable functions and operators of those
extensions as candidates to be sent for remote execution.

Whitelisting an extension in this way basically promises that the extension
exists on the remote server and behaves compatibly with the local instance.
We have no way to prove that formally, so we have to rely on the user to
get it right.  But this seems like something that people can usually get
right in practice.

We might in future allow functions and operators to be whitelisted
individually, but extension granularity is a very convenient special case,
so it got done first.

The patch as-committed lacks any regression tests, which is unfortunate,
but introducing dependencies on other extensions for testing purposes
would break "make installcheck" scenarios, which is worse.  I have some
ideas about klugy ways around that, but it seems like material for a
separate patch.  For the moment, leave the problem open.

Paul Ramsey, hacked up a bit more by me
This commit is contained in:
Tom Lane
2015-11-03 18:42:02 -05:00
parent ee44cb7566
commit d894941663
9 changed files with 427 additions and 91 deletions

View File

@ -50,40 +50,6 @@ PG_MODULE_MAGIC;
/* If no remote estimates, assume a sort costs 20% extra */
#define DEFAULT_FDW_SORT_MULTIPLIER 1.2
/*
* FDW-specific planner information kept in RelOptInfo.fdw_private for a
* foreign table. This information is collected by postgresGetForeignRelSize.
*/
typedef struct PgFdwRelationInfo
{
/* baserestrictinfo clauses, broken down into safe and unsafe subsets. */
List *remote_conds;
List *local_conds;
/* Bitmap of attr numbers we need to fetch from the remote server. */
Bitmapset *attrs_used;
/* Cost and selectivity of local_conds. */
QualCost local_conds_cost;
Selectivity local_conds_sel;
/* Estimated size and cost for a scan with baserestrictinfo quals. */
double rows;
int width;
Cost startup_cost;
Cost total_cost;
/* Options extracted from catalogs. */
bool use_remote_estimate;
Cost fdw_startup_cost;
Cost fdw_tuple_cost;
/* Cached catalog information. */
ForeignTable *table;
ForeignServer *server;
UserMapping *user; /* only set in use_remote_estimate mode */
} PgFdwRelationInfo;
/*
* Indexes of FDW-private information stored in fdw_private lists.
*
@ -409,6 +375,7 @@ postgresGetForeignRelSize(PlannerInfo *root,
fpinfo->use_remote_estimate = false;
fpinfo->fdw_startup_cost = DEFAULT_FDW_STARTUP_COST;
fpinfo->fdw_tuple_cost = DEFAULT_FDW_TUPLE_COST;
fpinfo->shippable_extensions = NIL;
foreach(lc, fpinfo->server->options)
{
@ -420,6 +387,9 @@ postgresGetForeignRelSize(PlannerInfo *root,
fpinfo->fdw_startup_cost = strtod(defGetString(def), NULL);
else if (strcmp(def->defname, "fdw_tuple_cost") == 0)
fpinfo->fdw_tuple_cost = strtod(defGetString(def), NULL);
else if (strcmp(def->defname, "extensions") == 0)
fpinfo->shippable_extensions =
ExtractExtensionList(defGetString(def), false);
}
foreach(lc, fpinfo->table->options)
{