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jdbc_fdw.c
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jdbc_fdw.c
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/*-------------------------------------------------------------------------
*
* jdbc_fdw.c
* Foreign-data wrapper for remote PostgreSQL servers
*
* Portions Copyright (c) 2012-2014, PostgreSQL Global Development Group
*
* Portions Copyright (c) 2021, TOSHIBA CORPORATION
*
* IDENTIFICATION
* contrib/jdbc_fdw/jdbc_fdw.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "jdbc_fdw.h"
#include "access/htup_details.h"
#include "access/sysattr.h"
#include "commands/defrem.h"
#include "commands/explain.h"
#include "commands/vacuum.h"
#include "foreign/fdwapi.h"
#include "funcapi.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/cost.h"
#include "optimizer/appendinfo.h"
#include "optimizer/pathnode.h"
#include "optimizer/paths.h"
#include "optimizer/planmain.h"
#include "optimizer/planner.h"
#include "optimizer/prep.h"
#include "optimizer/restrictinfo.h"
#include "optimizer/tlist.h"
#include "parser/parsetree.h"
#include "utils/builtins.h"
#include "utils/guc.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/elog.h"
#include "executor/spi.h"
#include "storage/ipc.h"
#include "catalog/pg_foreign_server.h"
#include "catalog/pg_foreign_table.h"
#include "catalog/pg_user_mapping.h"
#define Str(arg) #arg
#define StrValue(arg) Str(arg)
#define STR_PKGLIBDIR StrValue(PKG_LIB_DIR)
#define IS_KEY_COLUMN(A) ((strcmp(A->defname, "key") == 0) && \
(strcmp(strVal(A->arg), "true") == 0))
PG_MODULE_MAGIC;
/* Default CPU cost to start up a foreign query. */
#define DEFAULT_FDW_STARTUP_COST 100.0
/* Default CPU cost to process 1 row (above and beyond cpu_tuple_cost). */
#define DEFAULT_FDW_TUPLE_COST 0.01
/*
* Indexes of FDW-private information stored in fdw_private lists.
*
* We store various information in ForeignScan.fdw_private to pass it from
* planner to executor. Currently we store:
*
* 1) SELECT statement text to be sent to the remote server 2) Integer list
* of attribute numbers retrieved by the SELECT
*
* These items are indexed with the enum FdwScanPrivateIndex, so an item can
* be fetched with list_nth(). For example, to get the SELECT statement: sql
* = strVal(list_nth(fdw_private, FdwScanPrivateSelectSql));
*/
enum FdwScanPrivateIndex
{
/* SQL statement to execute remotely (as a String node) */
FdwScanPrivateSelectSql,
/* Integer list of attribute numbers retrieved by the SELECT */
FdwScanPrivateRetrievedAttrs
};
/*
* This enum describes what's kept in the fdw_private list for a ForeignPath.
* We store:
*
* 1) Boolean flag showing if the remote query has the final sort 2) Boolean
* flag showing if the remote query has the LIMIT clause
*/
enum FdwPathPrivateIndex
{
/* has-final-sort flag (as a Boolean node) */
FdwPathPrivateHasFinalSort,
/* has-limit flag (as a Boolean node) */
FdwPathPrivateHasLimit
};
/*
* Similarly, this enum describes what's kept in the fdw_private list for a
* ModifyTable node referencing a jdbc_fdw foreign table. We store:
*
* 1) INSERT/UPDATE/DELETE statement text to be sent to the remote server 2)
* Integer list of target attribute numbers for INSERT/UPDATE (NIL for a
* DELETE) 3) Boolean flag showing if the remote query has a RETURNING clause
* 4) Integer list of attribute numbers retrieved by RETURNING, if any
*/
enum FdwModifyPrivateIndex
{
/* SQL statement to execute remotely (as a String node) */
FdwModifyPrivateUpdateSql,
/* Integer list of target attribute numbers for INSERT/UPDATE */
FdwModifyPrivateTargetAttnums,
/* has-returning flag (as a Boolean node) */
FdwModifyPrivateHasReturning,
/* Integer list of attribute numbers retrieved by RETURNING */
FdwModifyPrivateRetrievedAttrs
};
/*
* Execution state of a foreign scan using jdbc_fdw.
*/
typedef struct jdbcFdwScanState
{
Relation rel; /* relcache entry for the foreign table */
AttInMetadata *attinmeta; /* attribute datatype conversion metadata */
TupleDesc tupdesc; /* tuple descriptor of scan */
/* extracted fdw_private data */
char *query; /* text of SELECT command */
List *retrieved_attrs; /* list of retrieved attribute numbers */
/* for remote query execution */
Jconn *conn; /* connection for the scan */
unsigned int cursor_number; /* quasi-unique ID for my cursor */
bool cursor_exists; /* have we created the cursor? */
int numParams; /* number of parameters passed to query */
FmgrInfo *param_flinfo; /* output conversion functions for them */
List *param_exprs; /* executable expressions for param values */
const char **param_values; /* textual values of query parameters */
/* for storing result tuples */
HeapTuple *tuples; /* array of currently-retrieved tuples */
int num_tuples; /* # of tuples in array */
int next_tuple; /* index of next one to return */
/*
* batch-level state, for optimizing rewinds and avoiding useless fetch
*/
int fetch_ct_2; /* Min(# of fetches done, 2) */
bool eof_reached; /* true if last fetch reached EOF */
/* working memory contexts */
MemoryContext batch_cxt; /* context holding current batch of tuples */
MemoryContext temp_cxt; /* context for per-tuple temporary data */
/* for the execution of the result from java side */
int resultSetID;
} jdbcFdwScanState;
/*
* Execution state of a foreign insert/update/delete operation.
*/
typedef struct jdbcFdwModifyState
{
Relation rel; /* relcache entry for the foreign table */
AttInMetadata *attinmeta; /* attribute datatype conversion metadata */
/* for remote query execution */
Jconn *conn; /* connection for the scan */
bool is_prepared; /* name of prepared statement, if created */
/* extracted fdw_private data */
char *query; /* text of INSERT/UPDATE/DELETE command */
List *target_attrs; /* list of target attribute numbers */
bool has_returning; /* is there a RETURNING clause? */
List *retrieved_attrs; /* attr numbers retrieved by RETURNING */
/* info about parameters for prepared statement */
AttrNumber *junk_idx; /* the attrnumber of the junk column for
* UPDATE and DELETE */
int p_nums; /* number of parameters to transmit */
FmgrInfo *p_flinfo; /* output conversion functions for them */
/* working memory context */
MemoryContext temp_cxt; /* context for per-tuple temporary data */
/* for the execution of the result from java side */
int resultSetID;
} jdbcFdwModifyState;
/*
* Workspace for analyzing a foreign table.
*/
typedef struct jdbcFdwAnalyzeState
{
Relation rel; /* relcache entry for the foreign table */
AttInMetadata *attinmeta; /* attribute datatype conversion metadata */
List *retrieved_attrs; /* attr numbers retrieved by query */
/* collected sample rows */
HeapTuple *rows; /* array of size targrows */
int targrows; /* target # of sample rows */
int numrows; /* # of sample rows collected */
/* for random sampling */
double samplerows; /* # of rows fetched */
double rowstoskip; /* # of rows to skip before next sample */
double rstate; /* random state */
/* working memory contexts */
MemoryContext anl_cxt; /* context for per-analyze lifespan data */
MemoryContext temp_cxt; /* context for per-tuple temporary data */
} jdbcFdwAnalyzeState;
/*
* Identify the attribute where data conversion fails.
*/
typedef struct ConversionLocation
{
Relation rel; /* foreign table's relcache entry */
AttrNumber cur_attno; /* attribute number being processed, or 0 */
} ConversionLocation;
/*
* SQL functions
*/
PG_FUNCTION_INFO_V1(jdbc_fdw_handler);
PG_FUNCTION_INFO_V1(jdbc_fdw_version);
/*
* FDW callback routines
*/
static void jdbcGetForeignRelSize(PlannerInfo *root,
RelOptInfo *baserel,
Oid foreigntableid);
static void jdbcGetForeignPaths(PlannerInfo *root,
RelOptInfo *baserel,
Oid foreigntableid);
static ForeignScan *jdbcGetForeignPlan(PlannerInfo *root,
RelOptInfo *baserel,
Oid foreigntableid,
ForeignPath *best_path,
List *tlist,
List *scan_clauses,
Plan *outer_plan
);
static void jdbcBeginForeignScan(ForeignScanState *node, int eflags);
static TupleTableSlot *jdbcIterateForeignScan(ForeignScanState *node);
static void jdbcReScanForeignScan(ForeignScanState *node);
static void jdbcEndForeignScan(ForeignScanState *node);
static void jdbcAddForeignUpdateTargets(
#if PG_VERSION_NUM >= 140000
PlannerInfo *root,
Index rtindex,
#else
Query *parsetree,
#endif
RangeTblEntry *target_rte,
Relation target_relation);
static List *jdbcPlanForeignModify(PlannerInfo *root,
ModifyTable *plan,
Index resultRelation,
int subplan_index);
static void jdbcBeginForeignModify(ModifyTableState *mtstate,
ResultRelInfo *resultRelInfo,
List *fdw_private,
int subplan_index,
int eflags);
static TupleTableSlot *jdbcExecForeignInsert(EState *estate,
ResultRelInfo *resultRelInfo,
TupleTableSlot *slot,
TupleTableSlot *planSlot);
static TupleTableSlot *jdbcExecForeignUpdate(EState *estate,
ResultRelInfo *resultRelInfo,
TupleTableSlot *slot,
TupleTableSlot *planSlot);
static TupleTableSlot *jdbcExecForeignDelete(EState *estate,
ResultRelInfo *resultRelInfo,
TupleTableSlot *slot,
TupleTableSlot *planSlot);
static void jdbcEndForeignModify(EState *estate,
ResultRelInfo *resultRelInfo);
static int jdbcIsForeignRelUpdatable(Relation rel);
static void jdbcExplainForeignScan(ForeignScanState *node,
ExplainState *es);
static void jdbcExplainForeignModify(ModifyTableState *mtstate,
ResultRelInfo *rinfo,
List *fdw_private,
int subplan_index,
ExplainState *es);
static bool jdbcAnalyzeForeignTable(Relation relation,
AcquireSampleRowsFunc *func,
BlockNumber *totalpages);
static List *jdbcImportForeignSchema(ImportForeignSchemaStmt *stmt,
Oid serverOid);
static void jdbcGetForeignUpperPaths(PlannerInfo *root,
UpperRelationKind stage,
RelOptInfo *input_rel,
RelOptInfo *output_rel
#if (PG_VERSION_NUM >= 110000)
,void *extra
#endif
);
/*
* Helper functions
*/
static void estimate_path_cost_size(PlannerInfo *root,
RelOptInfo *baserel,
List *join_conds,
double *p_rows, int *p_width,
Cost *p_startup_cost,
Cost *p_total_cost,
char *q_char);
static void get_remote_estimate(const char *sql,
Jconn * conn,
double *rows,
int *width,
Cost *startup_cost,
Cost *total_cost);
static void jdbc_close_cursor(Jconn * conn, unsigned int cursor_number);
static void jdbc_prepare_foreign_modify(jdbcFdwModifyState * fmstate);
static bool jdbc_foreign_grouping_ok(PlannerInfo *root, RelOptInfo *grouped_rel);
static void jdbc_add_foreign_grouping_paths(PlannerInfo *root,
RelOptInfo *input_rel,
RelOptInfo *grouped_rel
#if (PG_VERSION_NUM >= 110000)
,GroupPathExtraData *extra
#endif
);
static void jdbc_add_foreign_final_paths(PlannerInfo *root, RelOptInfo *input_rel,
RelOptInfo *final_rel
#if (PG_VERSION_NUM >= 120000)
,FinalPathExtraData *extra
#endif
);
static void jdbc_execute_commands(List *cmd_list);
static void jdbc_bind_junk_column_value(jdbcFdwModifyState * fmstate,
TupleTableSlot *slot,
TupleTableSlot *planSlot,
Oid foreignTableId,
int bindnum);
/*
* Foreign-data wrapper handler function: return a struct with pointers to my
* callback routines.
*/
Datum
jdbc_fdw_handler(PG_FUNCTION_ARGS)
{
FdwRoutine *routine = makeNode(FdwRoutine);
/* Functions for scanning foreign tables */
routine->GetForeignRelSize = jdbcGetForeignRelSize;
routine->GetForeignPaths = jdbcGetForeignPaths;
routine->GetForeignPlan = jdbcGetForeignPlan;
routine->BeginForeignScan = jdbcBeginForeignScan;
routine->IterateForeignScan = jdbcIterateForeignScan;
routine->ReScanForeignScan = jdbcReScanForeignScan;
routine->EndForeignScan = jdbcEndForeignScan;
/* Functions for updating foreign tables */
routine->AddForeignUpdateTargets = jdbcAddForeignUpdateTargets;
routine->PlanForeignModify = jdbcPlanForeignModify;
routine->BeginForeignModify = jdbcBeginForeignModify;
routine->ExecForeignInsert = jdbcExecForeignInsert;
routine->ExecForeignUpdate = jdbcExecForeignUpdate;
routine->ExecForeignDelete = jdbcExecForeignDelete;
routine->EndForeignModify = jdbcEndForeignModify;
routine->IsForeignRelUpdatable = jdbcIsForeignRelUpdatable;
/* Support functions for EXPLAIN */
routine->ExplainForeignScan = jdbcExplainForeignScan;
routine->ExplainForeignModify = jdbcExplainForeignModify;
/* Support functions for ANALYZE */
routine->AnalyzeForeignTable = jdbcAnalyzeForeignTable;
/* support for IMPORT FOREIGN SCHEMA */
routine->ImportForeignSchema = jdbcImportForeignSchema;
/* Support functions for upper relation push-down */
routine->GetForeignUpperPaths = jdbcGetForeignUpperPaths;
PG_RETURN_POINTER(routine);
}
Datum
jdbc_fdw_version(PG_FUNCTION_ARGS)
{
PG_RETURN_INT32(CODE_VERSION);
}
/*
* jdbcGetForeignRelSize Estimate # of rows and width of the result of the
* scan
*
* We should consider the effect of all baserestrictinfo clauses here, but
* not any join clauses.
*/
static void
jdbcGetForeignRelSize(PlannerInfo *root,
RelOptInfo *baserel,
Oid foreigntableid)
{
jdbcFdwRelationInfo *fpinfo;
ListCell *lc;
RangeTblEntry *rte = planner_rt_fetch(baserel->relid, root);
Oid userid = rte->checkAsUser ? rte->checkAsUser : GetUserId();
Jconn *conn;
/* TODO: remove this functionality and support for remote statistics */
ereport(DEBUG3, (errmsg("In jdbcGetForeignRelSize")));
/*
* We use jdbcFdwRelationInfo to pass various information to subsequent
* functions.
*/
fpinfo = (jdbcFdwRelationInfo *) palloc0(sizeof(jdbcFdwRelationInfo));
baserel->fdw_private = (void *) fpinfo;
/* Base foreign tables need to be pushed down always. */
fpinfo->pushdown_safe = true;
/* Look up foreign-table catalog info. */
fpinfo->table = GetForeignTable(foreigntableid);
fpinfo->server = GetForeignServer(fpinfo->table->serverid);
/*
* Extract user-settable option values. Note that per-table setting of
* use_remote_estimate overrides per-server setting.
*/
fpinfo->use_remote_estimate = false;
fpinfo->fdw_startup_cost = DEFAULT_FDW_STARTUP_COST;
fpinfo->fdw_tuple_cost = DEFAULT_FDW_TUPLE_COST;
foreach(lc, fpinfo->server->options)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "use_remote_estimate") == 0)
fpinfo->use_remote_estimate = defGetBoolean(def);
else if (strcmp(def->defname, "fdw_startup_cost") == 0)
(void) parse_real(defGetString(def), &fpinfo->fdw_startup_cost, 0,
NULL);
else if (strcmp(def->defname, "fdw_tuple_cost") == 0)
(void) parse_real(defGetString(def), &fpinfo->fdw_tuple_cost, 0,
NULL);
}
foreach(lc, fpinfo->table->options)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "use_remote_estimate") == 0)
fpinfo->use_remote_estimate = defGetBoolean(def);
}
/*
* If the table or the server is configured to use remote estimates,
* identify which user to do remote access as during planning. This
* should match what ExecCheckRTEPerms() does. If we fail due to lack of
* permissions, the query would have failed at runtime anyway. And use
* user idenfifier for get default indentifier quote from remote server.
*/
fpinfo->user = GetUserMapping(userid, fpinfo->server->serverid);
conn = jdbc_get_connection(fpinfo->server, fpinfo->user, false);
/*
* Identify which baserestrictinfo clauses can be sent to the remote
* server and which can't.
*/
jdbc_classify_conditions(root, baserel, baserel->baserestrictinfo,
&fpinfo->remote_conds, &fpinfo->local_conds);
/*
* Identify which attributes will need to be retrieved from the remote
* server. These include all attrs needed for joins or final output, plus
* all attrs used in the local_conds. (Note: if we end up using a
* parameterized scan, it's possible that some of the join clauses will be
* sent to the remote and thus we wouldn't really need to retrieve the
* columns used in them. Doesn't seem worth detecting that case though.)
*/
fpinfo->attrs_used = NULL;
#if PG_VERSION_NUM >= 90600
pull_varattnos((Node *) baserel->reltarget->exprs, baserel->relid, &fpinfo->attrs_used);
#else
pull_varattnos((Node *) baserel->reltargetlist, baserel->relid,
&fpinfo->attrs_used);
#endif
foreach(lc, fpinfo->local_conds)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
pull_varattnos((Node *) rinfo->clause, baserel->relid,
&fpinfo->attrs_used);
}
/*
* Compute the selectivity and cost of the local_conds, so we don't have
* to do it over again for each path. The best we can do for these
* conditions is to estimate selectivity on the basis of local statistics.
*/
fpinfo->local_conds_sel = clauselist_selectivity(root,
fpinfo->local_conds,
baserel->relid,
JOIN_INNER,
NULL);
cost_qual_eval(&fpinfo->local_conds_cost, fpinfo->local_conds, root);
/*
* If the table or the server is configured to use remote estimates,
* connect to the foreign server and execute EXPLAIN to estimate the
* number of rows selected by the restriction clauses, as well as the
* average row width. Otherwise, estimate using whatever statistics we
* have locally, in a way similar to ordinary tables.
*/
if (fpinfo->use_remote_estimate)
{
/*
* Get cost/size estimates with help of remote server. Save the
* values in fpinfo so we don't need to do it again to generate the
* basic foreign path.
*/
estimate_path_cost_size(root, baserel, NIL,
&fpinfo->rows, &fpinfo->width,
&fpinfo->startup_cost,
&fpinfo->total_cost, conn->q_char);
}
else
{
/*
* If the foreign table has never been ANALYZEd, it will have relpages
* and reltuples equal to zero, which most likely has nothing to do
* with reality. We can't do a whole lot about that if we're not
* allowed to consult the remote server, but we can use a hack similar
* to plancat.c's treatment of empty relations: use a minimum size
* estimate of 10 pages, and divide by the column-datatype-based width
* estimate to get the corresponding number of tuples.
*/
#if PG_VERSION_NUM < 140000
if (baserel->pages == 0 && baserel->tuples == 0)
#else
if (baserel->tuples < 0)
#endif
{
baserel->pages = 10;
baserel->tuples =
(10 * BLCKSZ) / (baserel->reltarget->width + sizeof(HeapTupleHeaderData));
}
/*
* Estimate baserel size as best we can with local statistics.
*/
set_baserel_size_estimates(root, baserel);
/* Fill in basically-bogus cost estimates for use later. */
estimate_path_cost_size(root, baserel, NIL,
&fpinfo->rows, &fpinfo->width,
&fpinfo->startup_cost,
&fpinfo->total_cost, conn->q_char);
}
}
/*
* jdbcGetForeignPaths Create possible scan paths for a scan on the foreign
* table
*/
static void
jdbcGetForeignPaths(PlannerInfo *root,
RelOptInfo *baserel,
Oid foreigntableid)
{
jdbcFdwRelationInfo *fpinfo = (jdbcFdwRelationInfo *) baserel->fdw_private;
ereport(DEBUG3, (errmsg("In jdbcGetForeignPaths")));
/*
* Create simplest ForeignScan path node and add it to baserel. This path
* corresponds to SeqScan path of regular tables (though depending on what
* baserestrict conditions we were able to send to remote, there might
* actually be an indexscan happening there). We already did all the work
* to estimate cost and size of this path.
*/
add_path(baserel, (Path *)
create_foreignscan_path(root, baserel,
#if PG_VERSION_NUM >= 90600
NULL, /* default pathtarget */
#endif
fpinfo->rows,
fpinfo->startup_cost,
fpinfo->total_cost,
NIL, /* no pathkeys */
baserel->lateral_relids,
NULL, /* no extra plan */
NULL)); /* no fdw_private data */
return;
}
/*
* jdbcGetForeignPlan Create ForeignScan plan node which implements selected
* best path
*/
static ForeignScan *
jdbcGetForeignPlan(PlannerInfo *root,
RelOptInfo *baserel,
Oid foreigntableid,
ForeignPath *best_path,
List *tlist,
List *scan_clauses,
Plan *outer_plan
)
{
jdbcFdwRelationInfo *fpinfo = (jdbcFdwRelationInfo *) baserel->fdw_private;
Index scan_relid = baserel->relid;
List *fdw_private;
List *remote_conds = NIL;
List *remote_exprs = NIL;
List *local_exprs = NIL;
List *params_list = NIL;
List *retrieved_attrs;
StringInfoData sql;
ListCell *lc;
int for_update = 0;
List *fdw_scan_tlist = NIL;
List *fdw_recheck_quals = NIL;
bool has_limit = false;
Jconn *conn;
ereport(DEBUG3, (errmsg("In jdbcGetForeignPlan")));
/*
* Get FDW private data created by griddbGetForeignUpperPaths(), if any.
*/
if (best_path->fdw_private)
{
#if PG_VERSION_NUM >= 150000
has_limit = boolVal(list_nth(best_path->fdw_private, FdwPathPrivateHasLimit));
#else
has_limit = intVal(list_nth(best_path->fdw_private, FdwPathPrivateHasLimit));
#endif
}
/*
* Separate the scan_clauses into those that can be executed remotely and
* those that can't. baserestrictinfo clauses that were previously
* determined to be safe or unsafe by jdbc_classify_conditions are shown
* in fpinfo->remote_conds and fpinfo->local_conds. Anything else in the
* scan_clauses list will be a join clause, which we have to check for
* remote-safety.
*
* Note: the join clauses we see here should be the exact same ones
* previously examined by jdbcGetForeignPaths. Possibly it'd be worth
* passing forward the classification work done then, rather than
* repeating it here.
*
* This code must match "extract_actual_clauses(scan_clauses, false)"
* except for the additional decision about remote versus local execution.
* Note however that we only strip the RestrictInfo nodes from the
* local_exprs list, since jdbc_append_where_clause expects a list of
* RestrictInfos.
*/
if ((baserel->reloptkind == RELOPT_BASEREL ||
baserel->reloptkind == RELOPT_OTHER_MEMBER_REL)
)
{
foreach(lc, scan_clauses)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
Assert(IsA(rinfo, RestrictInfo));
/*
* Ignore any pseudoconstants, they're dealt with elsewhere
*/
if (rinfo->pseudoconstant)
continue;
if (list_member_ptr(fpinfo->remote_conds, rinfo))
{
remote_conds = lappend(remote_conds, rinfo);
remote_exprs = lappend(remote_exprs, rinfo->clause);
}
else if (list_member_ptr(fpinfo->local_conds, rinfo))
local_exprs = lappend(local_exprs, rinfo->clause);
else if (jdbc_is_foreign_expr(root, baserel, rinfo->clause))
{
remote_conds = lappend(remote_conds, rinfo);
remote_exprs = lappend(remote_exprs, rinfo->clause);
}
else
local_exprs = lappend(local_exprs, rinfo->clause);
}
/*
* For a base-relation scan, we have to support EPQ recheck, which
* should recheck all the remote quals.
*/
fdw_recheck_quals = remote_exprs;
}
else
{
/*
* Join relation or upper relation - set scan_relid to 0.
*/
scan_relid = 0;
/*
* For a join rel, baserestrictinfo is NIL and we are not considering
* parameterization right now, so there should be no scan_clauses for
* a joinrel or an upper rel either.
*/
Assert(!scan_clauses);
/*
* Instead we get the conditions to apply from the fdw_private
* structure.
*/
remote_exprs = extract_actual_clauses(fpinfo->remote_conds, false);
local_exprs = extract_actual_clauses(fpinfo->local_conds, false);
/*
* We leave fdw_recheck_quals empty in this case, since we never need
* to apply EPQ recheck clauses. In the case of a joinrel, EPQ
* recheck is handled elsewhere --- see GetForeignJoinPaths(). If
* we're planning an upperrel (ie, remote grouping or aggregation)
* then there's no EPQ to do because SELECT FOR UPDATE wouldn't be
* allowed, and indeed we *can't* put the remote clauses into
* fdw_recheck_quals because the unaggregated Vars won't be available
* locally.
*/
/*
* Build the list of columns to be fetched from the foreign server.
*/
fdw_scan_tlist = jdbc_build_tlist_to_deparse(baserel);
/*
* Ensure that the outer plan produces a tuple whose descriptor
* matches our scan tuple slot. Also, remove the local conditions
* from outer plan's quals, lest they be evaluated twice, once by the
* local plan and once by the scan.
*/
if (outer_plan)
{
ListCell *lc;
/*
* Right now, we only consider grouping and aggregation beyond
* joins. Queries involving aggregates or grouping do not require
* EPQ mechanism, hence should not have an outer plan here.
*/
Assert(!IS_UPPER_REL(baserel));
/*
* First, update the plan's qual list if possible. In some cases
* the quals might be enforced below the topmost plan level, in
* which case we'll fail to remove them; it's not worth working
* harder than this.
*/
foreach(lc, local_exprs)
{
Node *qual = lfirst(lc);
outer_plan->qual = list_delete(outer_plan->qual, qual);
/*
* For an inner join the local conditions of foreign scan plan
* can be part of the joinquals as well. (They might also be
* in the mergequals or hashquals, but we can't touch those
* without breaking the plan.)
*/
if (IsA(outer_plan, NestLoop) ||
IsA(outer_plan, MergeJoin) ||
IsA(outer_plan, HashJoin))
{
Join *join_plan = (Join *) outer_plan;
if (join_plan->jointype == JOIN_INNER)
join_plan->joinqual = list_delete(join_plan->joinqual,
qual);
}
}
/*
* Now fix the subplan's tlist --- this might result in inserting
* a Result node atop the plan tree.
*/
outer_plan = change_plan_targetlist(outer_plan, fdw_scan_tlist,
best_path->path.parallel_safe);
}
}
conn = jdbc_get_connection(fpinfo->server, fpinfo->user, false);
/*
* Build the query string to be sent for execution, and identify
* expressions to be sent as parameters.
*/
initStringInfo(&sql);
jdbc_deparse_select_stmt_for_rel(&sql, root, baserel, remote_conds,
best_path->path.pathkeys,
&retrieved_attrs, ¶ms_list, fdw_scan_tlist,
has_limit, false, NIL, NIL, conn->q_char);
ereport(DEBUG3, (errmsg("SQL: %s", sql.data)));
/*
* Add FOR UPDATE/SHARE if appropriate. We apply locking during the
* initial row fetch, rather than later on as is done for local tables.
* The extra roundtrips involved in trying to duplicate the local
* semantics exactly don't seem worthwhile (see also comments for
* RowMarkType).
*
* Note: because we actually run the query as a cursor, this assumes that
* DECLARE CURSOR ... FOR UPDATE is supported, which it isn't before 8.3.
*/
if (baserel->relid == root->parse->resultRelation &&
(root->parse->commandType == CMD_UPDATE ||
root->parse->commandType == CMD_DELETE))
{
/* Relation is UPDATE/DELETE target, so use FOR UPDATE */
for_update = 1;
}
else
{
RowMarkClause *rc = get_parse_rowmark(root->parse, baserel->relid);
if (rc)
{
/*
* Relation is specified as a FOR UPDATE/SHARE target, so handle
* that.
*
* For now, just ignore any [NO] KEY specification, since (a) it's
* not clear what that means for a remote table that we don't have
* complete information about, and (b) it wouldn't work anyway on
* older remote servers. Likewise, we don't worry about NOWAIT.
*/
switch (rc->strength)
{
case LCS_FORKEYSHARE:
case LCS_FORSHARE:
case LCS_FORNOKEYUPDATE:
case LCS_FORUPDATE:
case LCS_NONE:
break;
}
}
}
/*
* Build the fdw_private list that will be available to the executor.
* Items in the list must match enum FdwScanPrivateIndex, above.
*/
fdw_private = list_make3(makeString(sql.data), retrieved_attrs, makeInteger(for_update));
/*
* Create the ForeignScan node from target list, local filtering
* expressions, remote parameter expressions, and FDW private information.
*
* Note that the remote parameter expressions are stored in the fdw_exprs
* field of the finished plan node; we can't keep them in private state
* because then they wouldn't be subject to later planner processing.
*/
return make_foreignscan(tlist,
local_exprs,
scan_relid,
params_list,
fdw_private,
fdw_scan_tlist,
fdw_recheck_quals,
outer_plan
);
}
/*
* Construct a tuple descriptor for the scan tuples handled by a foreign
* join.
*/
static TupleDesc
get_tupdesc_for_join_scan_tuples(ForeignScanState *node)
{
ForeignScan *fsplan = (ForeignScan *) node->ss.ps.plan;
EState *estate = node->ss.ps.state;
TupleDesc tupdesc;
/*
* The core code has already set up a scan tuple slot based on
* fsplan->fdw_scan_tlist, and this slot's tupdesc is mostly good enough,
* but there's one case where it isn't. If we have any whole-row row
* identifier Vars, they may have vartype RECORD, and we need to replace
* that with the associated table's actual composite type. This ensures
* that when we read those ROW() expression values from the remote server,
* we can convert them to a composite type the local server knows.
*/
tupdesc = CreateTupleDescCopy(node->ss.ss_ScanTupleSlot->tts_tupleDescriptor);
for (int i = 0; i < tupdesc->natts; i++)
{
Form_pg_attribute att = TupleDescAttr(tupdesc, i);
Var *var;
RangeTblEntry *rte;
Oid reltype;
/* Nothing to do if it's not a generic RECORD attribute */
if (att->atttypid != RECORDOID || att->atttypmod >= 0)
continue;
/*
* If we can't identify the referenced table, do nothing. This'll
* likely lead to failure later, but perhaps we can muddle through.
*/
var = (Var *) list_nth_node(TargetEntry, fsplan->fdw_scan_tlist,
i)->expr;
if (!IsA(var, Var) || var->varattno != 0)
continue;
rte = list_nth(estate->es_range_table, var->varno - 1);
if (rte->rtekind != RTE_RELATION)
continue;
reltype = get_rel_type_id(rte->relid);
if (!OidIsValid(reltype))
continue;
att->atttypid = reltype;
/* shouldn't need to change anything else */
}
return tupdesc;
}
/*
* jdbcBeginForeignScan Initiate an executor scan of a foreign JDBC SQL
* table.
*/
static void
jdbcBeginForeignScan(ForeignScanState *node, int eflags)
{
ForeignScan *fsplan = (ForeignScan *) node->ss.ps.plan;
EState *estate = node->ss.ps.state;
jdbcFdwScanState *fsstate;
RangeTblEntry *rte;
Oid userid;
ForeignTable *table;
ForeignServer *server;
UserMapping *user;
int numParams;
int i;
ListCell *lc;
int rtindex;
ereport(DEBUG3, (errmsg("In jdbcBeginForeignScan")));
/*
* Do nothing in EXPLAIN (no ANALYZE) case. node->fdw_state stays NULL.
*/
if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
return;
/*
* We'll save private state in node->fdw_state.
*/
fsstate = (jdbcFdwScanState *) palloc0(sizeof(jdbcFdwScanState));
node->fdw_state = (void *) fsstate;
/*
* Identify which user to do the remote access as. This should match what
* ExecCheckRTEPerms() does.
*/
if (fsplan->scan.scanrelid > 0)
rtindex = fsplan->scan.scanrelid;
else
rtindex = bms_next_member(fsplan->fs_relids, -1);
rte = rt_fetch(rtindex, estate->es_range_table);
userid = rte->checkAsUser ? rte->checkAsUser : GetUserId();
/* Get info about foreign table. */
fsstate->rel = node->ss.ss_currentRelation;
/*
* table->options contains the query and/or table specified for the
* foreign table
*/
table = GetForeignTable(rte->relid);
/*
* server-options contains drivername, url, querytimeout, jarfile and
* maxheapsize
*/