/*-------------------------------------------------------------------------
*
* file_fdw.c
* foreign-data wrapper for server-side flat files.
*
* Copyright (c) 2010-2011, PostgreSQL Global Development Group
*
* IDENTIFICATION
* contrib/file_fdw/file_fdw.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include <sys/stat.h>
#include <unistd.h>
#include "access/reloptions.h"
#include "catalog/pg_foreign_table.h"
#include "commands/copy.h"
#include "commands/defrem.h"
#include "commands/explain.h"
#include "foreign/fdwapi.h"
#include "foreign/foreign.h"
#include "miscadmin.h"
#include "optimizer/cost.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 COPY FROM command.
*
* 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 struct FileFdwOption valid_options[] = {
/* File options */
{ "filename", ForeignTableRelationId },
/* Format options */
/* oids option is not supported */
{ "format", ForeignTableRelationId },
{ "header", ForeignTableRelationId },
{ "delimiter", ForeignTableRelationId },
{ "quote", ForeignTableRelationId },
{ "escape", ForeignTableRelationId },
{ "null", ForeignTableRelationId },
{ "encoding", ForeignTableRelationId },
/*
* force_quote is not supported by file_fdw because it's for COPY TO.
*/
/*
* force_not_null is not supported by file_fdw. It would need a parser
* for list of columns, not to mention a way to check the column list
* against the table.
*/
/* Sentinel */
{ NULL, InvalidOid }
};
/*
* FDW-specific information for ForeignScanState.fdw_state.
*/
typedef struct FileFdwExecutionState
{
char *filename; /* file to read */
List *options; /* merged COPY options, excluding filename */
CopyState cstate; /* state of reading file */
} FileFdwExecutionState;
/*
* SQL functions
*/
extern Datum file_fdw_handler(PG_FUNCTION_ARGS);
extern Datum file_fdw_validator(PG_FUNCTION_ARGS);
PG_FUNCTION_INFO_V1(file_fdw_handler);
PG_FUNCTION_INFO_V1(file_fdw_validator);
/*
* FDW callback routines
*/
static FdwPlan *filePlanForeignScan(Oid foreigntableid,
PlannerInfo *root,
RelOptInfo *baserel);
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);
/*
* Helper functions
*/
static bool is_valid_option(const char *option, Oid context);
static void fileGetOptions(Oid foreigntableid,
char **filename, List **other_options);
static void estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
const char *filename,
Cost *startup_cost, Cost *total_cost);
/*
* 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->PlanForeignScan = filePlanForeignScan;
fdwroutine->ExplainForeignScan = fileExplainForeignScan;
fdwroutine->BeginForeignScan = fileBeginForeignScan;
fdwroutine->IterateForeignScan = fileIterateForeignScan;
fdwroutine->ReScanForeignScan = fileReScanForeignScan;
fdwroutine->EndForeignScan = fileEndForeignScan;
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;
List *other_options = NIL;
ListCell *cell;
/*
* Only superusers are allowed to set options of a file_fdw foreign table.
* This is because the filename is one of those options, and we don't
* want non-superusers to be able to determine which file gets read.
*
* 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 at
* any options level other than foreign table --- otherwise there'd
* still be a security hole.
*/
if (catalog == ForeignTableRelationId && !superuser())
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
errmsg("only superuser can change options of a file_fdw foreign table")));
/*
* 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))
{
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),
errhint("Valid options in this context are: %s",
buf.data)));
}
/* Separate out filename, since ProcessCopyOptions won't allow it */
if (strcmp(def->defname, "filename") == 0)
{
if (filename)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("conflicting or redundant options")));
filename = defGetString(def);
}
else
other_options = lappend(other_options, def);
}
/*
* Now apply the core COPY code's validation logic for more checks.
*/
ProcessCopyOptions(NULL, true, other_options);
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)
{
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" from the other options because
* it must not appear in the options list passed to the core COPY code.
*/
static void
fileGetOptions(Oid foreigntableid,
char **filename, 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);
/*
* Separate out the filename.
*/
*filename = NULL;
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;
}
prev = lc;
}
if (*filename == NULL)
ereport(ERROR,
(errcode(ERRCODE_FDW_UNABLE_TO_CREATE_REPLY),
errmsg("filename is required for file_fdw foreign tables")));
*other_options = options;
}
/*
* filePlanForeignScan
* Create a FdwPlan for a scan on the foreign table
*/
static FdwPlan *
filePlanForeignScan(Oid foreigntableid,
PlannerInfo *root,
RelOptInfo *baserel)
{
FdwPlan *fdwplan;
char *filename;
List *options;
/* Fetch options --- we only need filename at this point */
fileGetOptions(foreigntableid, &filename, &options);
/* Construct FdwPlan with cost estimates */
fdwplan = makeNode(FdwPlan);
estimate_costs(root, baserel, filename,
&fdwplan->startup_cost, &fdwplan->total_cost);
fdwplan->fdw_private = NIL; /* not used */
return fdwplan;
}
/*
* fileExplainForeignScan
* Produce extra output for EXPLAIN
*/
static void
fileExplainForeignScan(ForeignScanState *node, ExplainState *es)
{
char *filename;
List *options;
/* Fetch options --- we only need filename at this point */
fileGetOptions(RelationGetRelid(node->ss.ss_currentRelation),
&filename, &options);
ExplainPropertyText("Foreign File", filename, es);
/* Suppress file size if we're not showing cost details */
if (es->costs)
{
struct stat stat_buf;
if (stat(filename, &stat_buf) == 0)
ExplainPropertyLong("Foreign File Size", (long) stat_buf.st_size,
es);
}
}
/*
* fileBeginForeignScan
* Initiate access to the file by creating CopyState
*/
static void
fileBeginForeignScan(ForeignScanState *node, int eflags)
{
char *filename;
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, &options);
/*
* Create CopyState from FDW options. We always acquire all columns,
* so as to match the expected ScanTupleSlot signature.
*/
cstate = BeginCopyFrom(node->ss.ss_currentRelation,
filename,
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->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 errcontext;
/* Set up callback to identify error line number. */
errcontext.callback = CopyFromErrorCallback;
errcontext.arg = (void *) festate->cstate;
errcontext.previous = error_context_stack;
error_context_stack = &errcontext;
/*
* 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,
NULL);
if (found)
ExecStoreVirtualTuple(slot);
/* Remove error callback. */
error_context_stack = errcontext.previous;
return slot;
}
/*
* 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);
}
/*
* fileReScanForeignScan
* Rescan table, possibly with new parameters
*/
static void
fileReScanForeignScan(ForeignScanState *node)
{
FileFdwExecutionState *festate = (FileFdwExecutionState *) node->fdw_state;
EndCopyFrom(festate->cstate);
festate->cstate = BeginCopyFrom(node->ss.ss_currentRelation,
festate->filename,
NIL,
festate->options);
}
/*
* Estimate costs of scanning a foreign table.
*/
static void
estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
const char *filename,
Cost *startup_cost, Cost *total_cost)
{
struct stat stat_buf;
BlockNumber pages;
int tuple_width;
double ntuples;
double nrows;
Cost run_cost = 0;
Cost cpu_per_tuple;
/*
* Get size of the file. It might not be there at plan time, though,
* in which case we have to use a default estimate.
*/
if (stat(filename, &stat_buf) < 0)
stat_buf.st_size = 10 * BLCKSZ;
/*
* Convert size to pages for use in I/O cost estimate below.
*/
pages = (stat_buf.st_size + (BLCKSZ-1)) / BLCKSZ;
if (pages < 1)
pages = 1;
/*
* Estimate the number of tuples in the file. 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.
* FIXME later.
*/
tuple_width = MAXALIGN(baserel->width) + MAXALIGN(sizeof(HeapTupleHeaderData));
ntuples = clamp_row_est((double) stat_buf.st_size / (double) tuple_width);
/*
* Now estimate the number of rows returned by the scan after applying
* the baserestrictinfo quals. This is pretty bogus too, since the
* planner will have no stats about the relation, but it's better than
* nothing.
*/
nrows = ntuples *
clauselist_selectivity(root,
baserel->baserestrictinfo,
0,
JOIN_INNER,
NULL);
nrows = clamp_row_est(nrows);
/* Save the output-rows estimate for the planner */
baserel->rows = nrows;
/*
* Now estimate costs. 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.
*/
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;
}