greenplumn file_fdw 源码
greenplumn file_fdw 代码
文件路径：/contrib/file_fdw/file_fdw.c
/*-------------------------------------------------------------------------
*
* file_fdw.c
* foreign-data wrapper for server-side flat files (or programs).
*
* Copyright (c) 2010-2019, PostgreSQL Global Development Group
*
* IDENTIFICATION
* contrib/file_fdw/file_fdw.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include <sys/stat.h>
#include <unistd.h>
#include "access/htup_details.h"
#include "access/reloptions.h"
#include "access/sysattr.h"
#include "access/table.h"
#include "catalog/pg_authid.h"
#include "catalog/pg_foreign_table.h"
#include "commands/copy.h"
#include "commands/defrem.h"
#include "commands/explain.h"
#include "commands/vacuum.h"
#include "foreign/fdwapi.h"
#include "foreign/foreign.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "optimizer/cost.h"
#include "optimizer/optimizer.h"
#include "optimizer/pathnode.h"
#include "optimizer/planmain.h"
#include "optimizer/restrictinfo.h"
#include "utils/memutils.h"
#include "utils/rel.h"
#include "utils/sampling.h"
PG_MODULE_MAGIC;
/*
* Describes the valid options for objects that use this wrapper.
*/
struct FileFdwOption
{
const char *optname;
Oid optcontext; /* Oid of catalog in which option may appear */
};
/*
* Valid options for file_fdw.
* These options are based on the options for the COPY FROM command.
* But note that force_not_null and force_null are handled as boolean options
* attached to a column, not as table options.
*
* Note: If you are adding new option for user mapping, you need to modify
* fileGetOptions(), which currently doesn't bother to look at user mappings.
*/
static const struct FileFdwOption valid_options[] = {
/* Data source options */
{"filename", ForeignTableRelationId},
{"program", ForeignTableRelationId},
/* Format options */
/* oids option is not supported */
{"format", ForeignTableRelationId},
{"header", ForeignTableRelationId},
{"delimiter", ForeignTableRelationId},
{"quote", ForeignTableRelationId},
{"escape", ForeignTableRelationId},
{"null", ForeignTableRelationId},
{"encoding", ForeignTableRelationId},
{"force_not_null", AttributeRelationId},
{"force_null", AttributeRelationId},
/*
* force_quote is not supported by file_fdw because it's for COPY TO.
*/
/* Sentinel */
{NULL, InvalidOid}
};
/*
* FDW-specific information for RelOptInfo.fdw_private.
*/
typedef struct FileFdwPlanState
{
char *filename; /* file or program to read from */
bool is_program; /* true if filename represents an OS command */
List *options; /* merged COPY options, excluding filename and
* is_program */
BlockNumber pages; /* estimate of file's physical size */
double ntuples; /* estimate of number of data rows */
} FileFdwPlanState;
/*
* FDW-specific information for ForeignScanState.fdw_state.
*/
typedef struct FileFdwExecutionState
{
char *filename; /* file or program to read from */
bool is_program; /* true if filename represents an OS command */
List *options; /* merged COPY options, excluding filename and
* is_program */
CopyState cstate; /* COPY execution state */
} FileFdwExecutionState;
/*
* SQL functions
*/
PG_FUNCTION_INFO_V1(file_fdw_handler);
PG_FUNCTION_INFO_V1(file_fdw_validator);
/*
* FDW callback routines
*/
static void fileGetForeignRelSize(PlannerInfo *root,
RelOptInfo *baserel,
Oid foreigntableid);
static void fileGetForeignPaths(PlannerInfo *root,
RelOptInfo *baserel,
Oid foreigntableid);
static ForeignScan *fileGetForeignPlan(PlannerInfo *root,
RelOptInfo *baserel,
Oid foreigntableid,
ForeignPath *best_path,
List *tlist,
List *scan_clauses,
Plan *outer_plan);
static void fileExplainForeignScan(ForeignScanState *node, ExplainState *es);
static void fileBeginForeignScan(ForeignScanState *node, int eflags);
static TupleTableSlot *fileIterateForeignScan(ForeignScanState *node);
static void fileReScanForeignScan(ForeignScanState *node);
static void fileEndForeignScan(ForeignScanState *node);
static bool fileAnalyzeForeignTable(Relation relation,
AcquireSampleRowsFunc *func,
BlockNumber *totalpages);
static bool fileIsForeignScanParallelSafe(PlannerInfo *root, RelOptInfo *rel,
RangeTblEntry *rte);
/*
* Helper functions
*/
static bool is_valid_option(const char *option, Oid context);
static void fileGetOptions(Oid foreigntableid,
char **filename,
bool *is_program,
List **other_options);
static List *get_file_fdw_attribute_options(Oid relid);
static bool check_selective_binary_conversion(RelOptInfo *baserel,
Oid foreigntableid,
List **columns);
static void estimate_size(PlannerInfo *root, RelOptInfo *baserel,
FileFdwPlanState *fdw_private);
static void estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
FileFdwPlanState *fdw_private,
Cost *startup_cost, Cost *total_cost);
static int file_acquire_sample_rows(Relation onerel, int elevel,
HeapTuple *rows, int targrows,
double *totalrows, double *totaldeadrows);
/*
* Foreign-data wrapper handler function: return a struct with pointers
* to my callback routines.
*/
Datum
file_fdw_handler(PG_FUNCTION_ARGS)
{
FdwRoutine *fdwroutine = makeNode(FdwRoutine);
fdwroutine->GetForeignRelSize = fileGetForeignRelSize;
fdwroutine->GetForeignPaths = fileGetForeignPaths;
fdwroutine->GetForeignPlan = fileGetForeignPlan;
fdwroutine->ExplainForeignScan = fileExplainForeignScan;
fdwroutine->BeginForeignScan = fileBeginForeignScan;
fdwroutine->IterateForeignScan = fileIterateForeignScan;
fdwroutine->ReScanForeignScan = fileReScanForeignScan;
fdwroutine->EndForeignScan = fileEndForeignScan;
fdwroutine->AnalyzeForeignTable = fileAnalyzeForeignTable;
fdwroutine->IsForeignScanParallelSafe = fileIsForeignScanParallelSafe;
PG_RETURN_POINTER(fdwroutine);
}
/*
* Validate the generic options given to a FOREIGN DATA WRAPPER, SERVER,
* USER MAPPING or FOREIGN TABLE that uses file_fdw.
*
* Raise an ERROR if the option or its value is considered invalid.
*/
Datum
file_fdw_validator(PG_FUNCTION_ARGS)
{
List *options_list = untransformRelOptions(PG_GETARG_DATUM(0));
Oid catalog = PG_GETARG_OID(1);
char *filename = NULL;
DefElem *force_not_null = NULL;
DefElem *force_null = NULL;
List *other_options = NIL;
ListCell *cell;
/*
* Check that only options supported by file_fdw, and allowed for the
* current object type, are given.
*/
foreach(cell, options_list)
{
DefElem *def = (DefElem *) lfirst(cell);
if (!is_valid_option(def->defname, catalog))
{
const struct FileFdwOption *opt;
StringInfoData buf;
/*
* Unknown option specified, complain about it. Provide a hint
* with list of valid options for the object.
*/
initStringInfo(&buf);
for (opt = valid_options; opt->optname; opt++)
{
if (catalog == opt->optcontext)
appendStringInfo(&buf, "%s%s", (buf.len > 0) ? ", " : "",
opt->optname);
}
ereport(ERROR,
(errcode(ERRCODE_FDW_INVALID_OPTION_NAME),
errmsg("invalid option \"%s\"", def->defname),
buf.len > 0
? errhint("Valid options in this context are: %s",
buf.data)
: errhint("There are no valid options in this context.")));
}
/*
* Separate out filename, program, and column-specific options, since
* ProcessCopyOptions won't accept them.
*/
if (strcmp(def->defname, "filename") == 0 ||
strcmp(def->defname, "program") == 0)
{
if (filename)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("conflicting or redundant options")));
/*
* Check permissions for changing which file or program is used by
* the file_fdw.
*
* Only members of the role 'pg_read_server_files' are allowed to
* set the 'filename' option of a file_fdw foreign table, while
* only members of the role 'pg_execute_server_program' are
* allowed to set the 'program' option. This is because we don't
* want regular users to be able to control which file gets read
* or which program gets executed.
*
* Putting this sort of permissions check in a validator is a bit
* of a crock, but there doesn't seem to be any other place that
* can enforce the check more cleanly.
*
* Note that the valid_options[] array disallows setting filename
* and program at any options level other than foreign table ---
* otherwise there'd still be a security hole.
*/
if (strcmp(def->defname, "filename") == 0 &&
!is_member_of_role(GetUserId(), DEFAULT_ROLE_READ_SERVER_FILES))
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
errmsg("only superuser or a member of the pg_read_server_files role may specify the filename option of a file_fdw foreign table")));
if (strcmp(def->defname, "program") == 0 &&
!is_member_of_role(GetUserId(), DEFAULT_ROLE_EXECUTE_SERVER_PROGRAM))
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
errmsg("only superuser or a member of the pg_execute_server_program role may specify the program option of a file_fdw foreign table")));
filename = defGetString(def);
}
/*
* force_not_null is a boolean option; after validation we can discard
* it - it will be retrieved later in get_file_fdw_attribute_options()
*/
else if (strcmp(def->defname, "force_not_null") == 0)
{
if (force_not_null)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("conflicting or redundant options"),
errhint("Option \"force_not_null\" supplied more than once for a column.")));
force_not_null = def;
/* Don't care what the value is, as long as it's a legal boolean */
(void) defGetBoolean(def);
}
/* See comments for force_not_null above */
else if (strcmp(def->defname, "force_null") == 0)
{
if (force_null)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("conflicting or redundant options"),
errhint("Option \"force_null\" supplied more than once for a column.")));
force_null = def;
(void) defGetBoolean(def);
}
else
other_options = lappend(other_options, def);
}
/*
* Now apply the core COPY code's validation logic for more checks.
*/
ProcessCopyOptions(NULL, NULL, true, other_options);
/*
* Either filename or program option is required for file_fdw foreign
* tables.
*/
if (catalog == ForeignTableRelationId && filename == NULL)
ereport(ERROR,
(errcode(ERRCODE_FDW_DYNAMIC_PARAMETER_VALUE_NEEDED),
errmsg("either filename or program is required for file_fdw foreign tables")));
PG_RETURN_VOID();
}
/*
* Check if the provided option is one of the valid options.
* context is the Oid of the catalog holding the object the option is for.
*/
static bool
is_valid_option(const char *option, Oid context)
{
const struct FileFdwOption *opt;
for (opt = valid_options; opt->optname; opt++)
{
if (context == opt->optcontext && strcmp(opt->optname, option) == 0)
return true;
}
return false;
}
/*
* Fetch the options for a file_fdw foreign table.
*
* We have to separate out filename/program from the other options because
* those must not appear in the options list passed to the core COPY code.
*/
static void
fileGetOptions(Oid foreigntableid,
char **filename, bool *is_program, List **other_options)
{
ForeignTable *table;
ForeignServer *server;
ForeignDataWrapper *wrapper;
List *options;
ListCell *lc,
*prev;
/*
* Extract options from FDW objects. We ignore user mappings because
* file_fdw doesn't have any options that can be specified there.
*
* (XXX Actually, given the current contents of valid_options[], there's
* no point in examining anything except the foreign table's own options.
* Simplify?)
*/
table = GetForeignTable(foreigntableid);
server = GetForeignServer(table->serverid);
wrapper = GetForeignDataWrapper(server->fdwid);
options = NIL;
options = list_concat(options, wrapper->options);
options = list_concat(options, server->options);
options = list_concat(options, table->options);
options = list_concat(options, get_file_fdw_attribute_options(foreigntableid));
/*
* Separate out the filename or program option (we assume there is only
* one).
*/
*filename = NULL;
*is_program = false;
prev = NULL;
foreach(lc, options)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "filename") == 0)
{
*filename = defGetString(def);
options = list_delete_cell(options, lc, prev);
break;
}
else if (strcmp(def->defname, "program") == 0)
{
*filename = defGetString(def);
*is_program = true;
options = list_delete_cell(options, lc, prev);
break;
}
prev = lc;
}
/*
* The validator should have checked that filename or program was included
* in the options, but check again, just in case.
*/
if (*filename == NULL)
elog(ERROR, "either filename or program is required for file_fdw foreign tables");
if (table->exec_location == FTEXECLOCATION_ALL_SEGMENTS)
{
/*
* pass the on_segment option to COPY, which will replace the required
* placeholder "<SEGID>" in filename
*/
options = list_append_unique(options, makeDefElem("on_segment", (Node *)makeInteger(true), -1));
}
else if (table->exec_location == FTEXECLOCATION_ANY)
{
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("file_fdw does not support mpp_execute option 'any'")));
}
*other_options = options;
}
/*
* Retrieve per-column generic options from pg_attribute and construct a list
* of DefElems representing them.
*
* At the moment we only have "force_not_null", and "force_null",
* which should each be combined into a single DefElem listing all such
* columns, since that's what COPY expects.
*/
static List *
get_file_fdw_attribute_options(Oid relid)
{
Relation rel;
TupleDesc tupleDesc;
AttrNumber natts;
AttrNumber attnum;
List *fnncolumns = NIL;
List *fncolumns = NIL;
List *options = NIL;
rel = table_open(relid, AccessShareLock);
tupleDesc = RelationGetDescr(rel);
natts = tupleDesc->natts;
/* Retrieve FDW options for all user-defined attributes. */
for (attnum = 1; attnum <= natts; attnum++)
{
Form_pg_attribute attr = TupleDescAttr(tupleDesc, attnum - 1);
List *options;
ListCell *lc;
/* Skip dropped attributes. */
if (attr->attisdropped)
continue;
options = GetForeignColumnOptions(relid, attnum);
foreach(lc, options)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "force_not_null") == 0)
{
if (defGetBoolean(def))
{
char *attname = pstrdup(NameStr(attr->attname));
fnncolumns = lappend(fnncolumns, makeString(attname));
}
}
else if (strcmp(def->defname, "force_null") == 0)
{
if (defGetBoolean(def))
{
char *attname = pstrdup(NameStr(attr->attname));
fncolumns = lappend(fncolumns, makeString(attname));
}
}
/* maybe in future handle other options here */
}
}
table_close(rel, AccessShareLock);
/*
* Return DefElem only when some column(s) have force_not_null /
* force_null options set
*/
if (fnncolumns != NIL)
options = lappend(options, makeDefElem("force_not_null", (Node *) fnncolumns, -1));
if (fncolumns != NIL)
options = lappend(options, makeDefElem("force_null", (Node *) fncolumns, -1));
return options;
}
/*
* fileGetForeignRelSize
* Obtain relation size estimates for a foreign table
*/
static void
fileGetForeignRelSize(PlannerInfo *root,
RelOptInfo *baserel,
Oid foreigntableid)
{
FileFdwPlanState *fdw_private;
/*
* Fetch options. We only need filename (or program) at this point, but
* we might as well get everything and not need to re-fetch it later in
* planning.
*/
fdw_private = (FileFdwPlanState *) palloc(sizeof(FileFdwPlanState));
fileGetOptions(foreigntableid,
&fdw_private->filename,
&fdw_private->is_program,
&fdw_private->options);
baserel->fdw_private = (void *) fdw_private;
/* Estimate relation size */
estimate_size(root, baserel, fdw_private);
}
/*
* fileGetForeignPaths
* Create possible access paths for a scan on the foreign table
*
* Currently we don't support any push-down feature, so there is only one
* possible access path, which simply returns all records in the order in
* the data file.
*/
static void
fileGetForeignPaths(PlannerInfo *root,
RelOptInfo *baserel,
Oid foreigntableid)
{
FileFdwPlanState *fdw_private = (FileFdwPlanState *) baserel->fdw_private;
Cost startup_cost;
Cost total_cost;
List *columns;
List *coptions = NIL;
/* Decide whether to selectively perform binary conversion */
if (check_selective_binary_conversion(baserel,
foreigntableid,
&columns))
coptions = list_make1(makeDefElem("convert_selectively",
(Node *) columns, -1));
/* Estimate costs */
estimate_costs(root, baserel, fdw_private,
&startup_cost, &total_cost);
/*
* Create a ForeignPath node and add it as only possible path. We use the
* fdw_private list of the path to carry the convert_selectively option;
* it will be propagated into the fdw_private list of the Plan node.
*
* We don't support pushing join clauses into the quals of this path, but
* it could still have required parameterization due to LATERAL refs in
* its tlist.
*/
add_path(baserel, (Path *)
create_foreignscan_path(root, baserel,
NULL, /* default pathtarget */
baserel->rows,
startup_cost,
total_cost,
NIL, /* no pathkeys */
baserel->lateral_relids,
NULL, /* no extra plan */
coptions));
/*
* If data file was sorted, and we knew it somehow, we could insert
* appropriate pathkeys into the ForeignPath node to tell the planner
* that.
*/
}
/*
* fileGetForeignPlan
* Create a ForeignScan plan node for scanning the foreign table
*/
static ForeignScan *
fileGetForeignPlan(PlannerInfo *root,
RelOptInfo *baserel,
Oid foreigntableid,
ForeignPath *best_path,
List *tlist,
List *scan_clauses,
Plan *outer_plan)
{
Index scan_relid = baserel->relid;
/*
* We have no native ability to evaluate restriction clauses, so we just
* put all the scan_clauses into the plan node's qual list for the
* executor to check. So all we have to do here is strip RestrictInfo
* nodes from the clauses and ignore pseudoconstants (which will be
* handled elsewhere).
*/
scan_clauses = extract_actual_clauses(scan_clauses, false);
/* Create the ForeignScan node */
return make_foreignscan(tlist,
scan_clauses,
scan_relid,
NIL, /* no expressions to evaluate */
best_path->fdw_private,
NIL, /* no custom tlist */
NIL, /* no remote quals */
outer_plan);
}
/*
* fileExplainForeignScan
* Produce extra output for EXPLAIN
*/
static void
fileExplainForeignScan(ForeignScanState *node, ExplainState *es)
{
char *filename;
bool is_program;
List *options;
/* Fetch options --- we only need filename and is_program at this point */
fileGetOptions(RelationGetRelid(node->ss.ss_currentRelation),
&filename, &is_program, &options);
if (is_program)
ExplainPropertyText("Foreign Program", filename, es);
else
ExplainPropertyText("Foreign File", filename, es);
/* Suppress file size if we're not showing cost details */
if (es->costs)
{
struct stat stat_buf;
if (!is_program &&
stat(filename, &stat_buf) == 0)
ExplainPropertyInteger("Foreign File Size", "b",
(int64) stat_buf.st_size, es);
}
}
/*
* fileBeginForeignScan
* Initiate access to the file by creating CopyState
*/
static void
fileBeginForeignScan(ForeignScanState *node, int eflags)
{
ForeignScan *plan = (ForeignScan *) node->ss.ps.plan;
char *filename;
bool is_program;
List *options;
CopyState cstate;
FileFdwExecutionState *festate;
/*
* Do nothing in EXPLAIN (no ANALYZE) case. node->fdw_state stays NULL.
*/
if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
return;
/* Fetch options of foreign table */
fileGetOptions(RelationGetRelid(node->ss.ss_currentRelation),
&filename, &is_program, &options);
/* Add any options from the plan (currently only convert_selectively) */
options = list_concat(options, plan->fdw_private);
/*
* Create CopyState from FDW options. We always acquire all columns, so
* as to match the expected ScanTupleSlot signature.
*/
cstate = BeginCopyFrom(NULL,
node->ss.ss_currentRelation,
filename,
is_program,
NULL,
NULL,
NIL,
options);
/*
* Save state in node->fdw_state. We must save enough information to call
* BeginCopyFrom() again.
*/
festate = (FileFdwExecutionState *) palloc(sizeof(FileFdwExecutionState));
festate->filename = filename;
festate->is_program = is_program;
festate->options = options;
festate->cstate = cstate;
node->fdw_state = (void *) festate;
}
/*
* fileIterateForeignScan
* Read next record from the data file and store it into the
* ScanTupleSlot as a virtual tuple
*/
static TupleTableSlot *
fileIterateForeignScan(ForeignScanState *node)
{
FileFdwExecutionState *festate = (FileFdwExecutionState *) node->fdw_state;
TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
bool found;
ErrorContextCallback errcallback;
/* Set up callback to identify error line number. */
errcallback.callback = CopyFromErrorCallback;
errcallback.arg = (void *) festate->cstate;
errcallback.previous = error_context_stack;
error_context_stack = &errcallback;
/*
* The protocol for loading a virtual tuple into a slot is first
* ExecClearTuple, then fill the values/isnull arrays, then
* ExecStoreVirtualTuple. If we don't find another row in the file, we
* just skip the last step, leaving the slot empty as required.
*
* We can pass ExprContext = NULL because we read all columns from the
* file, so no need to evaluate default expressions.
*
* We can also pass tupleOid = NULL because we don't allow oids for
* foreign tables.
*/
ExecClearTuple(slot);
found = NextCopyFrom(festate->cstate, NULL,
slot->tts_values, slot->tts_isnull);
if (found)
ExecStoreVirtualTuple(slot);
/* Remove error callback. */
error_context_stack = errcallback.previous;
return slot;
}
/*
* fileReScanForeignScan
* Rescan table, possibly with new parameters
*/
static void
fileReScanForeignScan(ForeignScanState *node)
{
FileFdwExecutionState *festate = (FileFdwExecutionState *) node->fdw_state;
EndCopyFrom(festate->cstate);
festate->cstate = BeginCopyFrom(NULL,
node->ss.ss_currentRelation,
festate->filename,
festate->is_program,
NULL,
NULL,
NIL,
festate->options);
}
/*
* fileEndForeignScan
* Finish scanning foreign table and dispose objects used for this scan
*/
static void
fileEndForeignScan(ForeignScanState *node)
{
FileFdwExecutionState *festate = (FileFdwExecutionState *) node->fdw_state;
/* if festate is NULL, we are in EXPLAIN; nothing to do */
if (festate)
EndCopyFrom(festate->cstate);
}
/*
* fileAnalyzeForeignTable
* Test whether analyzing this foreign table is supported
*/
static bool
fileAnalyzeForeignTable(Relation relation,
AcquireSampleRowsFunc *func,
BlockNumber *totalpages)
{
char *filename;
bool is_program;
List *options;
struct stat stat_buf;
/* Fetch options of foreign table */
fileGetOptions(RelationGetRelid(relation), &filename, &is_program, &options);
/*
* If this is a program instead of a file, just return false to skip
* analyzing the table. We could run the program and collect stats on
* whatever it currently returns, but it seems likely that in such cases
* the output would be too volatile for the stats to be useful. Maybe
* there should be an option to enable doing this?
*/
if (is_program)
return false;
/*
* Get size of the file. (XXX if we fail here, would it be better to just
* return false to skip analyzing the table?)
*/
if (stat(filename, &stat_buf) < 0)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not stat file \"%s\": %m",
filename)));
/*
* Convert size to pages. Must return at least 1 so that we can tell
* later on that pg_class.relpages is not default.
*/
*totalpages = (stat_buf.st_size + (BLCKSZ - 1)) / BLCKSZ;
if (*totalpages < 1)
*totalpages = 1;
*func = file_acquire_sample_rows;
return true;
}
/*
* fileIsForeignScanParallelSafe
* Reading a file, or external program, in a parallel worker should work
* just the same as reading it in the leader, so mark scans safe.
*/
static bool
fileIsForeignScanParallelSafe(PlannerInfo *root, RelOptInfo *rel,
RangeTblEntry *rte)
{
return true;
}
/*
* check_selective_binary_conversion
*
* Check to see if it's useful to convert only a subset of the file's columns
* to binary. If so, construct a list of the column names to be converted,
* return that at *columns, and return true. (Note that it's possible to
* determine that no columns need be converted, for instance with a COUNT(*)
* query. So we can't use returning a NIL list to indicate failure.)
*/
static bool
check_selective_binary_conversion(RelOptInfo *baserel,
Oid foreigntableid,
List **columns)
{
ForeignTable *table;
ListCell *lc;
Relation rel;
TupleDesc tupleDesc;
AttrNumber attnum;
Bitmapset *attrs_used = NULL;
bool has_wholerow = false;
int numattrs;
int i;
*columns = NIL; /* default result */
/*
* Check format of the file. If binary format, this is irrelevant.
*/
table = GetForeignTable(foreigntableid);
foreach(lc, table->options)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "format") == 0)
{
char *format = defGetString(def);
if (strcmp(format, "binary") == 0)
return false;
break;
}
}
/* Collect all the attributes needed for joins or final output. */
pull_varattnos((Node *) baserel->reltarget->exprs, baserel->relid,
&attrs_used);
/* Add all the attributes used by restriction clauses. */
foreach(lc, baserel->baserestrictinfo)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
pull_varattnos((Node *) rinfo->clause, baserel->relid,
&attrs_used);
}
/* Convert attribute numbers to column names. */
rel = table_open(foreigntableid, AccessShareLock);
tupleDesc = RelationGetDescr(rel);
while ((attnum = bms_first_member(attrs_used)) >= 0)
{
/* Adjust for system attributes. */
attnum += FirstLowInvalidHeapAttributeNumber;
if (attnum == 0)
{
has_wholerow = true;
break;
}
/* Ignore system attributes. */
if (attnum < 0)
continue;
/* Get user attributes. */
if (attnum > 0)
{
Form_pg_attribute attr = TupleDescAttr(tupleDesc, attnum - 1);
char *attname = NameStr(attr->attname);
/* Skip dropped attributes (probably shouldn't see any here). */
if (attr->attisdropped)
continue;
/*
* Skip generated columns (COPY won't accept them in the column
* list)
*/
if (attr->attgenerated)
continue;
*columns = lappend(*columns, makeString(pstrdup(attname)));
}
}
/* Count non-dropped user attributes while we have the tupdesc. */
numattrs = 0;
for (i = 0; i < tupleDesc->natts; i++)
{
Form_pg_attribute attr = TupleDescAttr(tupleDesc, i);
if (attr->attisdropped)
continue;
numattrs++;
}
table_close(rel, AccessShareLock);
/* If there's a whole-row reference, fail: we need all the columns. */
if (has_wholerow)
{
*columns = NIL;
return false;
}
/* If all the user attributes are needed, fail. */
if (numattrs == list_length(*columns))
{
*columns = NIL;
return false;
}
return true;
}
/*
* Estimate size of a foreign table.
*
* The main result is returned in baserel->rows. We also set
* fdw_private->pages and fdw_private->ntuples for later use in the cost
* calculation.
*/
static void
estimate_size(PlannerInfo *root, RelOptInfo *baserel,
FileFdwPlanState *fdw_private)
{
struct stat stat_buf;
BlockNumber pages;
double ntuples;
double nrows;
/*
* Get size of the file. It might not be there at plan time, though, in
* which case we have to use a default estimate. We also have to fall
* back to the default if using a program as the input.
*/
if (fdw_private->is_program || stat(fdw_private->filename, &stat_buf) < 0)
stat_buf.st_size = 10 * BLCKSZ;
/*
* Convert size to pages for use in I/O cost estimate later.
*/
pages = (stat_buf.st_size + (BLCKSZ - 1)) / BLCKSZ;
if (pages < 1)
pages = 1;
fdw_private->pages = pages;
/*
* Estimate the number of tuples in the file.
*/
if (baserel->pages > 0)
{
/*
* We have # of pages and # of tuples from pg_class (that is, from a
* previous ANALYZE), so compute a tuples-per-page estimate and scale
* that by the current file size.
*/
double density;
density = baserel->tuples / (double) baserel->pages;
ntuples = clamp_row_est(density * (double) pages);
}
else
{
/*
* Otherwise we have to fake it. We back into this estimate using the
* planner's idea of the relation width; which is bogus if not all
* columns are being read, not to mention that the text representation
* of a row probably isn't the same size as its internal
* representation. Possibly we could do something better, but the
* real answer to anyone who complains is "ANALYZE" ...
*/
int tuple_width;
tuple_width = MAXALIGN(baserel->reltarget->width) +
MAXALIGN(SizeofHeapTupleHeader);
ntuples = clamp_row_est((double) stat_buf.st_size /
(double) tuple_width);
}
fdw_private->ntuples = ntuples;
/*
* Now estimate the number of rows returned by the scan after applying the
* baserestrictinfo quals.
*/
nrows = ntuples *
clauselist_selectivity(root,
baserel->baserestrictinfo,
0,
JOIN_INNER,
NULL,
false);
nrows = clamp_row_est(nrows);
/* Save the output-rows estimate for the planner */
baserel->rows = nrows;
}
/*
* Estimate costs of scanning a foreign table.
*
* Results are returned in *startup_cost and *total_cost.
*/
static void
estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
FileFdwPlanState *fdw_private,
Cost *startup_cost, Cost *total_cost)
{
BlockNumber pages = fdw_private->pages;
double ntuples = fdw_private->ntuples;
Cost run_cost = 0;
Cost cpu_per_tuple;
/*
* We estimate costs almost the same way as cost_seqscan(), thus assuming
* that I/O costs are equivalent to a regular table file of the same size.
* However, we take per-tuple CPU costs as 10x of a seqscan, to account
* for the cost of parsing records.
*
* In the case of a program source, this calculation is even more divorced
* from reality, but we have no good alternative; and it's not clear that
* the numbers we produce here matter much anyway, since there's only one
* access path for the rel.
*/
run_cost += seq_page_cost * pages;
*startup_cost = baserel->baserestrictcost.startup;
cpu_per_tuple = cpu_tuple_cost * 10 + baserel->baserestrictcost.per_tuple;
run_cost += cpu_per_tuple * ntuples;
*total_cost = *startup_cost + run_cost;
}
/*
* file_acquire_sample_rows -- acquire a random sample of rows from the table
*
* Selected rows are returned in the caller-allocated array rows[],
* which must have at least targrows entries.
* The actual number of rows selected is returned as the function result.
* We also count the total number of rows in the file and return it into
* *totalrows. Note that *totaldeadrows is always set to 0.
*
* Note that the returned list of rows is not always in order by physical
* position in the file. Therefore, correlation estimates derived later
* may be meaningless, but it's OK because we don't use the estimates
* currently (the planner only pays attention to correlation for indexscans).
*/
static int
file_acquire_sample_rows(Relation onerel, int elevel,
HeapTuple *rows, int targrows,
double *totalrows, double *totaldeadrows)
{
int numrows = 0;
double rowstoskip = -1; /* -1 means not set yet */
ReservoirStateData rstate;
TupleDesc tupDesc;
Datum *values;
bool *nulls;
bool found;
char *filename;
bool is_program;
List *options;
CopyState cstate;
ErrorContextCallback errcallback;
MemoryContext oldcontext = CurrentMemoryContext;
MemoryContext tupcontext;
Assert(onerel);
Assert(targrows > 0);
tupDesc = RelationGetDescr(onerel);
values = (Datum *) palloc(tupDesc->natts * sizeof(Datum));
nulls = (bool *) palloc(tupDesc->natts * sizeof(bool));
/* Fetch options of foreign table */
fileGetOptions(RelationGetRelid(onerel), &filename, &is_program, &options);
/*
* Create CopyState from FDW options.
*/
cstate = BeginCopyFrom(NULL, onerel, filename, is_program, NULL, NULL, NIL,
options);
/*
* Use per-tuple memory context to prevent leak of memory used to read
* rows from the file with Copy routines.
*/
tupcontext = AllocSetContextCreate(CurrentMemoryContext,
"file_fdw temporary context",
ALLOCSET_DEFAULT_SIZES);
/* Prepare for sampling rows */
reservoir_init_selection_state(&rstate, targrows);
/* Set up callback to identify error line number. */
errcallback.callback = CopyFromErrorCallback;
errcallback.arg = (void *) cstate;
errcallback.previous = error_context_stack;
error_context_stack = &errcallback;
*totalrows = 0;
*totaldeadrows = 0;
for (;;)
{
/* Check for user-requested abort or sleep */
vacuum_delay_point();
/* Fetch next row */
MemoryContextReset(tupcontext);
MemoryContextSwitchTo(tupcontext);
found = NextCopyFrom(cstate, NULL, values, nulls);
MemoryContextSwitchTo(oldcontext);
if (!found)
break;
/*
* The first targrows sample rows are simply copied into the
* reservoir. Then we start replacing tuples in the sample until we
* reach the end of the relation. This algorithm is from Jeff Vitter's
* paper (see more info in commands/analyze.c).
*/
if (numrows < targrows)
{
rows[numrows++] = heap_form_tuple(tupDesc, values, nulls);
}
else
{
/*
* t in Vitter's paper is the number of records already processed.
* If we need to compute a new S value, we must use the
* not-yet-incremented value of totalrows as t.
*/
if (rowstoskip < 0)
rowstoskip = reservoir_get_next_S(&rstate, *totalrows, targrows);
if (rowstoskip <= 0)
{
/*
* Found a suitable tuple, so save it, replacing one old tuple
* at random
*/
int k = (int) (targrows * sampler_random_fract(rstate.randstate));
Assert(k >= 0 && k < targrows);
heap_freetuple(rows[k]);
rows[k] = heap_form_tuple(tupDesc, values, nulls);
}
rowstoskip -= 1;
}
*totalrows += 1;
}
/* Remove error callback. */
error_context_stack = errcallback.previous;
/* Clean up. */
MemoryContextDelete(tupcontext);
EndCopyFrom(cstate);
pfree(values);
pfree(nulls);
/*
* Emit some interesting relation info
*/
ereport(elevel,
(errmsg("\"%s\": file contains %.0f rows; "
"%d rows in sample",
RelationGetRelationName(onerel),
*totalrows, numrows)));
return numrows;
}
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