greenplumn foreign 源码
greenplumn foreign 代码
文件路径：/src/backend/foreign/foreign.c
/*-------------------------------------------------------------------------
*
* foreign.c
* support for foreign-data wrappers, servers and user mappings.
*
* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
*
* IDENTIFICATION
* src/backend/foreign/foreign.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/htup_details.h"
#include "access/reloptions.h"
#include "catalog/pg_foreign_data_wrapper.h"
#include "catalog/pg_foreign_server.h"
#include "catalog/pg_foreign_table.h"
#include "catalog/pg_user_mapping.h"
#include "cdb/cdbutil.h"
#include "commands/defrem.h"
#include "foreign/fdwapi.h"
#include "foreign/foreign.h"
#include "lib/stringinfo.h"
#include "miscadmin.h"
#include "utils/builtins.h"
#include "utils/memutils.h"
#include "utils/rel.h"
#include "utils/syscache.h"
extern Datum pg_options_to_table(PG_FUNCTION_ARGS);
extern Datum postgresql_fdw_validator(PG_FUNCTION_ARGS);
/* Get and separate out the mpp_execute option. */
char
SeparateOutMppExecute(List **options)
{
ListCell *lc = NULL;
ListCell *prev = NULL;
char *mpp_execute = NULL;
char exec_location = FTEXECLOCATION_NOT_DEFINED;
foreach(lc, *options)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "mpp_execute") == 0)
{
mpp_execute = defGetString(def);
if (pg_strcasecmp(mpp_execute, "any") == 0)
exec_location = FTEXECLOCATION_ANY;
else if (pg_strcasecmp(mpp_execute, "master") == 0)
exec_location = FTEXECLOCATION_COORDINATOR;
else if (pg_strcasecmp(mpp_execute, "coordinator") == 0)
exec_location = FTEXECLOCATION_COORDINATOR;
else if (pg_strcasecmp(mpp_execute, "all segments") == 0)
exec_location = FTEXECLOCATION_ALL_SEGMENTS;
else
{
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("\"%s\" is not a valid mpp_execute value",
mpp_execute)));
}
*options = list_delete_cell(*options, lc, prev);
break;
}
prev = lc;
}
return exec_location;
}
/* Get and separate out the num_segments option */
int32
SeparateOutNumSegments(List **options)
{
ListCell *lc = NULL;
ListCell *prev = NULL;
char *num_segments_str = NULL;
int32 num_segments = 0;
foreach(lc, *options)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "num_segments") == 0)
{
num_segments_str = defGetString(def);
num_segments = pg_atoi(num_segments_str, sizeof(int32), 0);
if (num_segments <= 0)
{
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("\"%d\" is not a valid num_segments value",
num_segments)));
}
*options = list_delete_cell(*options, lc, prev);
break;
}
prev = lc;
}
return num_segments;
}
/*
* GetForeignDataWrapper - look up the foreign-data wrapper by OID.
*/
ForeignDataWrapper *
GetForeignDataWrapper(Oid fdwid)
{
return GetForeignDataWrapperExtended(fdwid, 0);
}
/*
* GetForeignDataWrapperExtended - look up the foreign-data wrapper
* by OID. If flags uses FDW_MISSING_OK, return NULL if the object cannot
* be found instead of raising an error.
*/
ForeignDataWrapper *
GetForeignDataWrapperExtended(Oid fdwid, bits16 flags)
{
Form_pg_foreign_data_wrapper fdwform;
ForeignDataWrapper *fdw;
Datum datum;
HeapTuple tp;
bool isnull;
tp = SearchSysCache1(FOREIGNDATAWRAPPEROID, ObjectIdGetDatum(fdwid));
if (!HeapTupleIsValid(tp))
{
if ((flags & FDW_MISSING_OK) == 0)
elog(ERROR, "cache lookup failed for foreign-data wrapper %u", fdwid);
return NULL;
}
fdwform = (Form_pg_foreign_data_wrapper) GETSTRUCT(tp);
fdw = (ForeignDataWrapper *) palloc(sizeof(ForeignDataWrapper));
fdw->fdwid = fdwid;
fdw->owner = fdwform->fdwowner;
fdw->fdwname = pstrdup(NameStr(fdwform->fdwname));
fdw->fdwhandler = fdwform->fdwhandler;
fdw->fdwvalidator = fdwform->fdwvalidator;
/* Extract the fdwoptions */
datum = SysCacheGetAttr(FOREIGNDATAWRAPPEROID,
tp,
Anum_pg_foreign_data_wrapper_fdwoptions,
&isnull);
if (isnull)
fdw->options = NIL;
else
fdw->options = untransformRelOptions(datum);
fdw->exec_location = SeparateOutMppExecute(&fdw->options);
if (fdw->exec_location == FTEXECLOCATION_NOT_DEFINED)
fdw->exec_location = FTEXECLOCATION_COORDINATOR;
ReleaseSysCache(tp);
return fdw;
}
/*
* GetForeignDataWrapperByName - look up the foreign-data wrapper
* definition by name.
*/
ForeignDataWrapper *
GetForeignDataWrapperByName(const char *fdwname, bool missing_ok)
{
Oid fdwId = get_foreign_data_wrapper_oid(fdwname, missing_ok);
if (!OidIsValid(fdwId))
return NULL;
return GetForeignDataWrapper(fdwId);
}
/*
* GetForeignServer - look up the foreign server definition.
*/
ForeignServer *
GetForeignServer(Oid serverid)
{
return GetForeignServerExtended(serverid, 0);
}
/*
* GetForeignServerExtended - look up the foreign server definition. If
* flags uses FSV_MISSING_OK, return NULL if the object cannot be found
* instead of raising an error.
*/
ForeignServer *
GetForeignServerExtended(Oid serverid, bits16 flags)
{
Form_pg_foreign_server serverform;
ForeignServer *server;
HeapTuple tp;
Datum datum;
bool isnull;
tp = SearchSysCache1(FOREIGNSERVEROID, ObjectIdGetDatum(serverid));
if (!HeapTupleIsValid(tp))
{
if ((flags & FSV_MISSING_OK) == 0)
elog(ERROR, "cache lookup failed for foreign server %u", serverid);
return NULL;
}
serverform = (Form_pg_foreign_server) GETSTRUCT(tp);
server = (ForeignServer *) palloc(sizeof(ForeignServer));
server->serverid = serverid;
server->servername = pstrdup(NameStr(serverform->srvname));
server->owner = serverform->srvowner;
server->fdwid = serverform->srvfdw;
/* Extract server type */
datum = SysCacheGetAttr(FOREIGNSERVEROID,
tp,
Anum_pg_foreign_server_srvtype,
&isnull);
server->servertype = isnull ? NULL : TextDatumGetCString(datum);
/* Extract server version */
datum = SysCacheGetAttr(FOREIGNSERVEROID,
tp,
Anum_pg_foreign_server_srvversion,
&isnull);
server->serverversion = isnull ? NULL : TextDatumGetCString(datum);
/* Extract the srvoptions */
datum = SysCacheGetAttr(FOREIGNSERVEROID,
tp,
Anum_pg_foreign_server_srvoptions,
&isnull);
if (isnull)
server->options = NIL;
else
server->options = untransformRelOptions(datum);
server->exec_location = SeparateOutMppExecute(&server->options);
if (server->exec_location == FTEXECLOCATION_NOT_DEFINED)
{
ForeignDataWrapper *fdw = GetForeignDataWrapper(server->fdwid);
server->exec_location = fdw->exec_location;
}
server->num_segments = SeparateOutNumSegments(&server->options);
if (server->num_segments <= 0)
{
server->num_segments = getgpsegmentCount();
}
ReleaseSysCache(tp);
return server;
}
/*
* GetForeignServerByName - look up the foreign server definition by name.
*/
ForeignServer *
GetForeignServerByName(const char *srvname, bool missing_ok)
{
Oid serverid = get_foreign_server_oid(srvname, missing_ok);
if (!OidIsValid(serverid))
return NULL;
return GetForeignServer(serverid);
}
/*
* GetUserMapping - look up the user mapping.
*
* If no mapping is found for the supplied user, we also look for
* PUBLIC mappings (userid == InvalidOid).
*/
UserMapping *
GetUserMapping(Oid userid, Oid serverid)
{
Datum datum;
HeapTuple tp;
bool isnull;
UserMapping *um;
tp = SearchSysCache2(USERMAPPINGUSERSERVER,
ObjectIdGetDatum(userid),
ObjectIdGetDatum(serverid));
if (!HeapTupleIsValid(tp))
{
/* Not found for the specific user -- try PUBLIC */
tp = SearchSysCache2(USERMAPPINGUSERSERVER,
ObjectIdGetDatum(InvalidOid),
ObjectIdGetDatum(serverid));
}
if (!HeapTupleIsValid(tp))
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_OBJECT),
errmsg("user mapping not found for \"%s\"",
MappingUserName(userid))));
um = (UserMapping *) palloc(sizeof(UserMapping));
um->umid = ((Form_pg_user_mapping) GETSTRUCT(tp))->oid;
um->userid = userid;
um->serverid = serverid;
/* Extract the umoptions */
datum = SysCacheGetAttr(USERMAPPINGUSERSERVER,
tp,
Anum_pg_user_mapping_umoptions,
&isnull);
if (isnull)
um->options = NIL;
else
um->options = untransformRelOptions(datum);
ReleaseSysCache(tp);
return um;
}
/*
* GetForeignTable - look up the foreign table definition by relation oid.
*/
ForeignTable *
GetForeignTable(Oid relid)
{
Form_pg_foreign_table tableform;
ForeignTable *ft;
HeapTuple tp;
Datum datum;
bool isnull;
tp = SearchSysCache1(FOREIGNTABLEREL, ObjectIdGetDatum(relid));
if (!HeapTupleIsValid(tp))
elog(ERROR, "cache lookup failed for foreign table %u", relid);
tableform = (Form_pg_foreign_table) GETSTRUCT(tp);
ft = (ForeignTable *) palloc(sizeof(ForeignTable));
ft->relid = relid;
ft->serverid = tableform->ftserver;
/* Extract the ftoptions */
datum = SysCacheGetAttr(FOREIGNTABLEREL,
tp,
Anum_pg_foreign_table_ftoptions,
&isnull);
if (isnull)
ft->options = NIL;
else
ft->options = untransformRelOptions(datum);
ft->exec_location = SeparateOutMppExecute(&ft->options);
if (ft->exec_location == FTEXECLOCATION_NOT_DEFINED)
{
ForeignServer *server = GetForeignServer(ft->serverid);
ft->exec_location = server->exec_location;
}
ReleaseSysCache(tp);
return ft;
}
/*
* Is the given table a GPDB external table, rather than a normal foreign
* table?
*/
bool
rel_is_external_table(Oid relid)
{
Form_pg_foreign_table tableform;
HeapTuple tp;
bool result;
tp = SearchSysCache1(FOREIGNTABLEREL, ObjectIdGetDatum(relid));
if (!HeapTupleIsValid(tp))
return false;
tableform = (Form_pg_foreign_table) GETSTRUCT(tp);
result = (tableform->ftserver == get_foreign_server_oid(GP_EXTTABLE_SERVER_NAME, false));
ReleaseSysCache(tp);
return result;
}
/*
* GetForeignColumnOptions - Get attfdwoptions of given relation/attnum
* as list of DefElem.
*/
List *
GetForeignColumnOptions(Oid relid, AttrNumber attnum)
{
List *options;
HeapTuple tp;
Datum datum;
bool isnull;
tp = SearchSysCache2(ATTNUM,
ObjectIdGetDatum(relid),
Int16GetDatum(attnum));
if (!HeapTupleIsValid(tp))
elog(ERROR, "cache lookup failed for attribute %d of relation %u",
attnum, relid);
datum = SysCacheGetAttr(ATTNUM,
tp,
Anum_pg_attribute_attfdwoptions,
&isnull);
if (isnull)
options = NIL;
else
options = untransformRelOptions(datum);
ReleaseSysCache(tp);
return options;
}
/*
* GetFdwRoutine - call the specified foreign-data wrapper handler routine
* to get its FdwRoutine struct.
*/
FdwRoutine *
GetFdwRoutine(Oid fdwhandler)
{
Datum datum;
FdwRoutine *routine;
datum = OidFunctionCall0(fdwhandler);
routine = (FdwRoutine *) DatumGetPointer(datum);
if (routine == NULL || !IsA(routine, FdwRoutine))
elog(ERROR, "foreign-data wrapper handler function %u did not return an FdwRoutine struct",
fdwhandler);
return routine;
}
/*
* GetForeignServerIdByRelId - look up the foreign server
* for the given foreign table, and return its OID.
*/
Oid
GetForeignServerIdByRelId(Oid relid)
{
HeapTuple tp;
Form_pg_foreign_table tableform;
Oid serverid;
tp = SearchSysCache1(FOREIGNTABLEREL, ObjectIdGetDatum(relid));
if (!HeapTupleIsValid(tp))
elog(ERROR, "cache lookup failed for foreign table %u", relid);
tableform = (Form_pg_foreign_table) GETSTRUCT(tp);
serverid = tableform->ftserver;
ReleaseSysCache(tp);
return serverid;
}
/*
* GetFdwRoutineByServerId - look up the handler of the foreign-data wrapper
* for the given foreign server, and retrieve its FdwRoutine struct.
*/
FdwRoutine *
GetFdwRoutineByServerId(Oid serverid)
{
HeapTuple tp;
Form_pg_foreign_data_wrapper fdwform;
Form_pg_foreign_server serverform;
Oid fdwid;
Oid fdwhandler;
/* Get foreign-data wrapper OID for the server. */
tp = SearchSysCache1(FOREIGNSERVEROID, ObjectIdGetDatum(serverid));
if (!HeapTupleIsValid(tp))
elog(ERROR, "cache lookup failed for foreign server %u", serverid);
serverform = (Form_pg_foreign_server) GETSTRUCT(tp);
fdwid = serverform->srvfdw;
ReleaseSysCache(tp);
/* Get handler function OID for the FDW. */
tp = SearchSysCache1(FOREIGNDATAWRAPPEROID, ObjectIdGetDatum(fdwid));
if (!HeapTupleIsValid(tp))
elog(ERROR, "cache lookup failed for foreign-data wrapper %u", fdwid);
fdwform = (Form_pg_foreign_data_wrapper) GETSTRUCT(tp);
fdwhandler = fdwform->fdwhandler;
/* Complain if FDW has been set to NO HANDLER. */
if (!OidIsValid(fdwhandler))
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("foreign-data wrapper \"%s\" has no handler",
NameStr(fdwform->fdwname))));
ReleaseSysCache(tp);
/* And finally, call the handler function. */
return GetFdwRoutine(fdwhandler);
}
/*
* GetFdwRoutineByRelId - look up the handler of the foreign-data wrapper
* for the given foreign table, and retrieve its FdwRoutine struct.
*/
FdwRoutine *
GetFdwRoutineByRelId(Oid relid)
{
Oid serverid;
/* Get server OID for the foreign table. */
serverid = GetForeignServerIdByRelId(relid);
/* Now retrieve server's FdwRoutine struct. */
return GetFdwRoutineByServerId(serverid);
}
/*
* GetFdwRoutineForRelation - look up the handler of the foreign-data wrapper
* for the given foreign table, and retrieve its FdwRoutine struct.
*
* This function is preferred over GetFdwRoutineByRelId because it caches
* the data in the relcache entry, saving a number of catalog lookups.
*
* If makecopy is true then the returned data is freshly palloc'd in the
* caller's memory context. Otherwise, it's a pointer to the relcache data,
* which will be lost in any relcache reset --- so don't rely on it long.
*/
FdwRoutine *
GetFdwRoutineForRelation(Relation relation, bool makecopy)
{
FdwRoutine *fdwroutine;
FdwRoutine *cfdwroutine;
if (relation->rd_fdwroutine == NULL)
{
/* Get the info by consulting the catalogs and the FDW code */
fdwroutine = GetFdwRoutineByRelId(RelationGetRelid(relation));
/* Save the data for later reuse in CacheMemoryContext */
cfdwroutine = (FdwRoutine *) MemoryContextAlloc(CacheMemoryContext,
sizeof(FdwRoutine));
memcpy(cfdwroutine, fdwroutine, sizeof(FdwRoutine));
relation->rd_fdwroutine = cfdwroutine;
/* Give back the locally palloc'd copy regardless of makecopy */
return fdwroutine;
}
/* We have valid cached data --- does the caller want a copy? */
if (makecopy)
{
fdwroutine = (FdwRoutine *) palloc(sizeof(FdwRoutine));
memcpy(fdwroutine, relation->rd_fdwroutine, sizeof(FdwRoutine));
return fdwroutine;
}
/* Only a short-lived reference is needed, so just hand back cached copy */
return relation->rd_fdwroutine;
}
/*
* IsImportableForeignTable - filter table names for IMPORT FOREIGN SCHEMA
*
* Returns true if given table name should be imported according to the
* statement's import filter options.
*/
bool
IsImportableForeignTable(const char *tablename,
ImportForeignSchemaStmt *stmt)
{
ListCell *lc;
switch (stmt->list_type)
{
case FDW_IMPORT_SCHEMA_ALL:
return true;
case FDW_IMPORT_SCHEMA_LIMIT_TO:
foreach(lc, stmt->table_list)
{
RangeVar *rv = (RangeVar *) lfirst(lc);
if (strcmp(tablename, rv->relname) == 0)
return true;
}
return false;
case FDW_IMPORT_SCHEMA_EXCEPT:
foreach(lc, stmt->table_list)
{
RangeVar *rv = (RangeVar *) lfirst(lc);
if (strcmp(tablename, rv->relname) == 0)
return false;
}
return true;
}
return false; /* shouldn't get here */
}
/*
* deflist_to_tuplestore - Helper function to convert DefElem list to
* tuplestore usable in SRF.
*/
static void
deflist_to_tuplestore(ReturnSetInfo *rsinfo, List *options)
{
ListCell *cell;
TupleDesc tupdesc;
Tuplestorestate *tupstore;
Datum values[2];
bool nulls[2];
MemoryContext per_query_ctx;
MemoryContext oldcontext;
/* check to see if caller supports us returning a tuplestore */
if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("set-valued function called in context that cannot accept a set")));
if (!(rsinfo->allowedModes & SFRM_Materialize) ||
rsinfo->expectedDesc == NULL)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("materialize mode required, but it is not allowed in this context")));
per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
oldcontext = MemoryContextSwitchTo(per_query_ctx);
/*
* Now prepare the result set.
*/
tupdesc = CreateTupleDescCopy(rsinfo->expectedDesc);
tupstore = tuplestore_begin_heap(true, false, work_mem);
rsinfo->returnMode = SFRM_Materialize;
rsinfo->setResult = tupstore;
rsinfo->setDesc = tupdesc;
foreach(cell, options)
{
DefElem *def = lfirst(cell);
values[0] = CStringGetTextDatum(def->defname);
nulls[0] = false;
if (def->arg)
{
values[1] = CStringGetTextDatum(((Value *) (def->arg))->val.str);
nulls[1] = false;
}
else
{
values[1] = (Datum) 0;
nulls[1] = true;
}
tuplestore_putvalues(tupstore, tupdesc, values, nulls);
}
/* clean up and return the tuplestore */
tuplestore_donestoring(tupstore);
MemoryContextSwitchTo(oldcontext);
}
/*
* Convert options array to name/value table. Useful for information
* schema and pg_dump.
*/
Datum
pg_options_to_table(PG_FUNCTION_ARGS)
{
Datum array = PG_GETARG_DATUM(0);
deflist_to_tuplestore((ReturnSetInfo *) fcinfo->resultinfo,
untransformRelOptions(array));
return (Datum) 0;
}
/*
* Describes the valid options for postgresql FDW, server, and user mapping.
*/
struct ConnectionOption
{
const char *optname;
Oid optcontext; /* Oid of catalog in which option may appear */
};
/*
* Copied from fe-connect.c PQconninfoOptions.
*
* The list is small - don't bother with bsearch if it stays so.
*/
static const struct ConnectionOption libpq_conninfo_options[] = {
{"authtype", ForeignServerRelationId},
{"service", ForeignServerRelationId},
{"user", UserMappingRelationId},
{"password", UserMappingRelationId},
{"connect_timeout", ForeignServerRelationId},
{"dbname", ForeignServerRelationId},
{"host", ForeignServerRelationId},
{"hostaddr", ForeignServerRelationId},
{"port", ForeignServerRelationId},
{"tty", ForeignServerRelationId},
{"options", ForeignServerRelationId},
{"requiressl", ForeignServerRelationId},
{"sslmode", ForeignServerRelationId},
{"gsslib", ForeignServerRelationId},
{NULL, InvalidOid}
};
/*
* Check if the provided option is one of libpq conninfo options.
* context is the Oid of the catalog the option came from, or 0 if we
* don't care.
*/
static bool
is_conninfo_option(const char *option, Oid context)
{
const struct ConnectionOption *opt;
for (opt = libpq_conninfo_options; opt->optname; opt++)
if (context == opt->optcontext && strcmp(opt->optname, option) == 0)
return true;
return false;
}
/*
* Validate the generic option given to SERVER or USER MAPPING.
* Raise an ERROR if the option or its value is considered invalid.
*
* Valid server options are all libpq conninfo options except
* user and password -- these may only appear in USER MAPPING options.
*
* Caution: this function is deprecated, and is now meant only for testing
* purposes, because the list of options it knows about doesn't necessarily
* square with those known to whichever libpq instance you might be using.
* Inquire of libpq itself, instead.
*/
Datum
postgresql_fdw_validator(PG_FUNCTION_ARGS)
{
List *options_list = untransformRelOptions(PG_GETARG_DATUM(0));
Oid catalog = PG_GETARG_OID(1);
ListCell *cell;
foreach(cell, options_list)
{
DefElem *def = lfirst(cell);
if (!is_conninfo_option(def->defname, catalog))
{
const struct ConnectionOption *opt;
StringInfoData buf;
/*
* Unknown option specified, complain about it. Provide a hint
* with list of valid options for the object.
*/
initStringInfo(&buf);
for (opt = libpq_conninfo_options; opt->optname; opt++)
if (catalog == opt->optcontext)
appendStringInfo(&buf, "%s%s", (buf.len > 0) ? ", " : "",
opt->optname);
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("invalid option \"%s\"", def->defname),
errhint("Valid options in this context are: %s",
buf.data)));
PG_RETURN_BOOL(false);
}
}
PG_RETURN_BOOL(true);
}
/*
* get_foreign_data_wrapper_oid - given a FDW name, look up the OID
*
* If missing_ok is false, throw an error if name not found. If true, just
* return InvalidOid.
*/
Oid
get_foreign_data_wrapper_oid(const char *fdwname, bool missing_ok)
{
Oid oid;
oid = GetSysCacheOid1(FOREIGNDATAWRAPPERNAME,
Anum_pg_foreign_data_wrapper_oid,
CStringGetDatum(fdwname));
if (!OidIsValid(oid) && !missing_ok)
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_OBJECT),
errmsg("foreign-data wrapper \"%s\" does not exist",
fdwname)));
return oid;
}
/*
* get_foreign_server_oid - given a server name, look up the OID
*
* If missing_ok is false, throw an error if name not found. If true, just
* return InvalidOid.
*/
Oid
get_foreign_server_oid(const char *servername, bool missing_ok)
{
Oid oid;
oid = GetSysCacheOid1(FOREIGNSERVERNAME, Anum_pg_foreign_server_oid,
CStringGetDatum(servername));
if (!OidIsValid(oid) && !missing_ok)
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_OBJECT),
errmsg("server \"%s\" does not exist", servername)));
return oid;
}
/*
* Get a copy of an existing local path for a given join relation.
*
* This function is usually helpful to obtain an alternate local path for EPQ
* checks.
*
* Right now, this function only supports unparameterized foreign joins, so we
* only search for unparameterized path in the given list of paths. Since we
* are searching for a path which can be used to construct an alternative local
* plan for a foreign join, we look for only MergeJoin, HashJoin or NestLoop
* paths.
*
* If the inner or outer subpath of the chosen path is a ForeignScan, we
* replace it with its outer subpath. For this reason, and also because the
* planner might free the original path later, the path returned by this
* function is a shallow copy of the original. There's no need to copy
* the substructure, so we don't.
*
* Since the plan created using this path will presumably only be used to
* execute EPQ checks, efficiency of the path is not a concern. But since the
* path list in RelOptInfo is anyway sorted by total cost we are likely to
* choose the most efficient path, which is all for the best.
*/
Path *
GetExistingLocalJoinPath(RelOptInfo *joinrel)
{
ListCell *lc;
Assert(IS_JOIN_REL(joinrel));
foreach(lc, joinrel->pathlist)
{
Path *path = (Path *) lfirst(lc);
JoinPath *joinpath = NULL;
/* Skip parameterized paths. */
if (path->param_info != NULL)
continue;
switch (path->pathtype)
{
case T_HashJoin:
{
HashPath *hash_path = makeNode(HashPath);
memcpy(hash_path, path, sizeof(HashPath));
joinpath = (JoinPath *) hash_path;
}
break;
case T_NestLoop:
{
NestPath *nest_path = makeNode(NestPath);
memcpy(nest_path, path, sizeof(NestPath));
joinpath = (JoinPath *) nest_path;
}
break;
case T_MergeJoin:
{
MergePath *merge_path = makeNode(MergePath);
memcpy(merge_path, path, sizeof(MergePath));
joinpath = (JoinPath *) merge_path;
}
break;
default:
/*
* Just skip anything else. We don't know if corresponding
* plan would build the output row from whole-row references
* of base relations and execute the EPQ checks.
*/
break;
}
/* This path isn't good for us, check next. */
if (!joinpath)
continue;
/*
* If either inner or outer path is a ForeignPath corresponding to a
* pushed down join, replace it with the fdw_outerpath, so that we
* maintain path for EPQ checks built entirely of local join
* strategies.
*/
if (IsA(joinpath->outerjoinpath, ForeignPath))
{
ForeignPath *foreign_path;
foreign_path = (ForeignPath *) joinpath->outerjoinpath;
if (IS_JOIN_REL(foreign_path->path.parent))
joinpath->outerjoinpath = foreign_path->fdw_outerpath;
}
if (IsA(joinpath->innerjoinpath, ForeignPath))
{
ForeignPath *foreign_path;
foreign_path = (ForeignPath *) joinpath->innerjoinpath;
if (IS_JOIN_REL(foreign_path->path.parent))
joinpath->innerjoinpath = foreign_path->fdw_outerpath;
}
return (Path *) joinpath;
}
return NULL;
}
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