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537 lines
14 KiB
C
537 lines
14 KiB
C
/*-------------------------------------------------------------------------
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*
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* file_fdw.c
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* foreign-data wrapper for server-side flat files.
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*
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* Copyright (c) 2010-2011, PostgreSQL Global Development Group
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*
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* IDENTIFICATION
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* contrib/file_fdw/file_fdw.c
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include <sys/stat.h>
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#include <unistd.h>
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#include "access/reloptions.h"
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#include "catalog/pg_foreign_table.h"
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#include "commands/copy.h"
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#include "commands/defrem.h"
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#include "commands/explain.h"
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#include "foreign/fdwapi.h"
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#include "foreign/foreign.h"
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#include "miscadmin.h"
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#include "optimizer/cost.h"
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PG_MODULE_MAGIC;
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/*
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* Describes the valid options for objects that use this wrapper.
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*/
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struct FileFdwOption
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{
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const char *optname;
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Oid optcontext; /* Oid of catalog in which option may appear */
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};
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/*
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* Valid options for file_fdw.
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* These options are based on the options for COPY FROM command.
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*
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* Note: If you are adding new option for user mapping, you need to modify
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* fileGetOptions(), which currently doesn't bother to look at user mappings.
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*/
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static struct FileFdwOption valid_options[] = {
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/* File options */
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{"filename", ForeignTableRelationId},
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/* Format options */
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/* oids option is not supported */
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{"format", ForeignTableRelationId},
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{"header", ForeignTableRelationId},
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{"delimiter", ForeignTableRelationId},
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{"quote", ForeignTableRelationId},
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{"escape", ForeignTableRelationId},
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{"null", ForeignTableRelationId},
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{"encoding", ForeignTableRelationId},
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/*
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* force_quote is not supported by file_fdw because it's for COPY TO.
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*/
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/*
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* force_not_null is not supported by file_fdw. It would need a parser
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* for list of columns, not to mention a way to check the column list
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* against the table.
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*/
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/* Sentinel */
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{NULL, InvalidOid}
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};
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/*
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* FDW-specific information for ForeignScanState.fdw_state.
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*/
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typedef struct FileFdwExecutionState
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{
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char *filename; /* file to read */
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List *options; /* merged COPY options, excluding filename */
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CopyState cstate; /* state of reading file */
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} FileFdwExecutionState;
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/*
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* SQL functions
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*/
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extern Datum file_fdw_handler(PG_FUNCTION_ARGS);
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extern Datum file_fdw_validator(PG_FUNCTION_ARGS);
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PG_FUNCTION_INFO_V1(file_fdw_handler);
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PG_FUNCTION_INFO_V1(file_fdw_validator);
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/*
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* FDW callback routines
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*/
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static FdwPlan *filePlanForeignScan(Oid foreigntableid,
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PlannerInfo *root,
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RelOptInfo *baserel);
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static void fileExplainForeignScan(ForeignScanState *node, ExplainState *es);
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static void fileBeginForeignScan(ForeignScanState *node, int eflags);
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static TupleTableSlot *fileIterateForeignScan(ForeignScanState *node);
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static void fileReScanForeignScan(ForeignScanState *node);
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static void fileEndForeignScan(ForeignScanState *node);
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/*
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* Helper functions
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*/
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static bool is_valid_option(const char *option, Oid context);
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static void fileGetOptions(Oid foreigntableid,
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char **filename, List **other_options);
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static void estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
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const char *filename,
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Cost *startup_cost, Cost *total_cost);
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/*
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* Foreign-data wrapper handler function: return a struct with pointers
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* to my callback routines.
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*/
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Datum
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file_fdw_handler(PG_FUNCTION_ARGS)
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{
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FdwRoutine *fdwroutine = makeNode(FdwRoutine);
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fdwroutine->PlanForeignScan = filePlanForeignScan;
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fdwroutine->ExplainForeignScan = fileExplainForeignScan;
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fdwroutine->BeginForeignScan = fileBeginForeignScan;
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fdwroutine->IterateForeignScan = fileIterateForeignScan;
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fdwroutine->ReScanForeignScan = fileReScanForeignScan;
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fdwroutine->EndForeignScan = fileEndForeignScan;
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PG_RETURN_POINTER(fdwroutine);
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}
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/*
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* Validate the generic options given to a FOREIGN DATA WRAPPER, SERVER,
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* USER MAPPING or FOREIGN TABLE that uses file_fdw.
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*
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* Raise an ERROR if the option or its value is considered invalid.
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*/
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Datum
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file_fdw_validator(PG_FUNCTION_ARGS)
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{
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List *options_list = untransformRelOptions(PG_GETARG_DATUM(0));
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Oid catalog = PG_GETARG_OID(1);
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char *filename = NULL;
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List *other_options = NIL;
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ListCell *cell;
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/*
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* Only superusers are allowed to set options of a file_fdw foreign table.
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* This is because the filename is one of those options, and we don't want
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* non-superusers to be able to determine which file gets read.
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*
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* Putting this sort of permissions check in a validator is a bit of a
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* crock, but there doesn't seem to be any other place that can enforce
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* the check more cleanly.
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*
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* Note that the valid_options[] array disallows setting filename at any
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* options level other than foreign table --- otherwise there'd still be a
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* security hole.
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*/
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if (catalog == ForeignTableRelationId && !superuser())
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ereport(ERROR,
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(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
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errmsg("only superuser can change options of a file_fdw foreign table")));
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/*
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* Check that only options supported by file_fdw, and allowed for the
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* current object type, are given.
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*/
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foreach(cell, options_list)
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{
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DefElem *def = (DefElem *) lfirst(cell);
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if (!is_valid_option(def->defname, catalog))
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{
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struct FileFdwOption *opt;
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StringInfoData buf;
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/*
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* Unknown option specified, complain about it. Provide a hint
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* with list of valid options for the object.
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*/
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initStringInfo(&buf);
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for (opt = valid_options; opt->optname; opt++)
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{
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if (catalog == opt->optcontext)
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appendStringInfo(&buf, "%s%s", (buf.len > 0) ? ", " : "",
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opt->optname);
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}
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ereport(ERROR,
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(errcode(ERRCODE_FDW_INVALID_OPTION_NAME),
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errmsg("invalid option \"%s\"", def->defname),
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errhint("Valid options in this context are: %s",
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buf.data)));
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}
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/* Separate out filename, since ProcessCopyOptions won't allow it */
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if (strcmp(def->defname, "filename") == 0)
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{
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if (filename)
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ereport(ERROR,
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(errcode(ERRCODE_SYNTAX_ERROR),
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errmsg("conflicting or redundant options")));
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filename = defGetString(def);
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}
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else
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other_options = lappend(other_options, def);
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}
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/*
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* Now apply the core COPY code's validation logic for more checks.
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*/
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ProcessCopyOptions(NULL, true, other_options);
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PG_RETURN_VOID();
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}
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/*
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* Check if the provided option is one of the valid options.
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* context is the Oid of the catalog holding the object the option is for.
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*/
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static bool
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is_valid_option(const char *option, Oid context)
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{
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struct FileFdwOption *opt;
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for (opt = valid_options; opt->optname; opt++)
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{
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if (context == opt->optcontext && strcmp(opt->optname, option) == 0)
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return true;
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}
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return false;
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}
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/*
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* Fetch the options for a file_fdw foreign table.
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*
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* We have to separate out "filename" from the other options because
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* it must not appear in the options list passed to the core COPY code.
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*/
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static void
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fileGetOptions(Oid foreigntableid,
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char **filename, List **other_options)
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{
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ForeignTable *table;
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ForeignServer *server;
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ForeignDataWrapper *wrapper;
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List *options;
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ListCell *lc,
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*prev;
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/*
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* Extract options from FDW objects. We ignore user mappings because
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* file_fdw doesn't have any options that can be specified there.
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*
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* (XXX Actually, given the current contents of valid_options[], there's
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* no point in examining anything except the foreign table's own options.
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* Simplify?)
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*/
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table = GetForeignTable(foreigntableid);
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server = GetForeignServer(table->serverid);
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wrapper = GetForeignDataWrapper(server->fdwid);
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options = NIL;
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options = list_concat(options, wrapper->options);
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options = list_concat(options, server->options);
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options = list_concat(options, table->options);
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/*
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* Separate out the filename.
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*/
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*filename = NULL;
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prev = NULL;
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foreach(lc, options)
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{
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DefElem *def = (DefElem *) lfirst(lc);
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if (strcmp(def->defname, "filename") == 0)
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{
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*filename = defGetString(def);
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options = list_delete_cell(options, lc, prev);
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break;
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}
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prev = lc;
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}
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if (*filename == NULL)
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ereport(ERROR,
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(errcode(ERRCODE_FDW_UNABLE_TO_CREATE_REPLY),
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errmsg("filename is required for file_fdw foreign tables")));
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*other_options = options;
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}
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/*
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* filePlanForeignScan
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* Create a FdwPlan for a scan on the foreign table
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*/
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static FdwPlan *
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filePlanForeignScan(Oid foreigntableid,
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PlannerInfo *root,
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RelOptInfo *baserel)
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{
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FdwPlan *fdwplan;
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char *filename;
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List *options;
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/* Fetch options --- we only need filename at this point */
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fileGetOptions(foreigntableid, &filename, &options);
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/* Construct FdwPlan with cost estimates */
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fdwplan = makeNode(FdwPlan);
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estimate_costs(root, baserel, filename,
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&fdwplan->startup_cost, &fdwplan->total_cost);
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fdwplan->fdw_private = NIL; /* not used */
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return fdwplan;
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}
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/*
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* fileExplainForeignScan
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* Produce extra output for EXPLAIN
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*/
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static void
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fileExplainForeignScan(ForeignScanState *node, ExplainState *es)
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{
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char *filename;
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List *options;
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/* Fetch options --- we only need filename at this point */
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fileGetOptions(RelationGetRelid(node->ss.ss_currentRelation),
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&filename, &options);
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ExplainPropertyText("Foreign File", filename, es);
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/* Suppress file size if we're not showing cost details */
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if (es->costs)
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{
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struct stat stat_buf;
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if (stat(filename, &stat_buf) == 0)
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ExplainPropertyLong("Foreign File Size", (long) stat_buf.st_size,
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es);
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}
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}
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/*
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* fileBeginForeignScan
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* Initiate access to the file by creating CopyState
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*/
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static void
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fileBeginForeignScan(ForeignScanState *node, int eflags)
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{
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char *filename;
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List *options;
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CopyState cstate;
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FileFdwExecutionState *festate;
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/*
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* Do nothing in EXPLAIN (no ANALYZE) case. node->fdw_state stays NULL.
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*/
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if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
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return;
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/* Fetch options of foreign table */
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fileGetOptions(RelationGetRelid(node->ss.ss_currentRelation),
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&filename, &options);
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/*
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* Create CopyState from FDW options. We always acquire all columns, so
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* as to match the expected ScanTupleSlot signature.
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*/
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cstate = BeginCopyFrom(node->ss.ss_currentRelation,
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filename,
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NIL,
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options);
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/*
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* Save state in node->fdw_state. We must save enough information to call
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* BeginCopyFrom() again.
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*/
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festate = (FileFdwExecutionState *) palloc(sizeof(FileFdwExecutionState));
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festate->filename = filename;
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festate->options = options;
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festate->cstate = cstate;
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node->fdw_state = (void *) festate;
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}
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/*
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* fileIterateForeignScan
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* Read next record from the data file and store it into the
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* ScanTupleSlot as a virtual tuple
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*/
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static TupleTableSlot *
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fileIterateForeignScan(ForeignScanState *node)
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{
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FileFdwExecutionState *festate = (FileFdwExecutionState *) node->fdw_state;
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TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
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bool found;
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ErrorContextCallback errcontext;
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/* Set up callback to identify error line number. */
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errcontext.callback = CopyFromErrorCallback;
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errcontext.arg = (void *) festate->cstate;
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errcontext.previous = error_context_stack;
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error_context_stack = &errcontext;
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/*
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* The protocol for loading a virtual tuple into a slot is first
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* ExecClearTuple, then fill the values/isnull arrays, then
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* ExecStoreVirtualTuple. If we don't find another row in the file, we
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* just skip the last step, leaving the slot empty as required.
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*
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* We can pass ExprContext = NULL because we read all columns from the
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* file, so no need to evaluate default expressions.
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*
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* We can also pass tupleOid = NULL because we don't allow oids for
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* foreign tables.
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*/
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ExecClearTuple(slot);
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found = NextCopyFrom(festate->cstate, NULL,
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slot->tts_values, slot->tts_isnull,
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NULL);
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if (found)
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ExecStoreVirtualTuple(slot);
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/* Remove error callback. */
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error_context_stack = errcontext.previous;
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return slot;
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}
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/*
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* fileEndForeignScan
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* Finish scanning foreign table and dispose objects used for this scan
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*/
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static void
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fileEndForeignScan(ForeignScanState *node)
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{
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FileFdwExecutionState *festate = (FileFdwExecutionState *) node->fdw_state;
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/* if festate is NULL, we are in EXPLAIN; nothing to do */
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if (festate)
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EndCopyFrom(festate->cstate);
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}
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/*
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* fileReScanForeignScan
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* Rescan table, possibly with new parameters
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*/
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static void
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fileReScanForeignScan(ForeignScanState *node)
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{
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FileFdwExecutionState *festate = (FileFdwExecutionState *) node->fdw_state;
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EndCopyFrom(festate->cstate);
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festate->cstate = BeginCopyFrom(node->ss.ss_currentRelation,
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festate->filename,
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NIL,
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festate->options);
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}
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/*
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* Estimate costs of scanning a foreign table.
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*/
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static void
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estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
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const char *filename,
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Cost *startup_cost, Cost *total_cost)
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{
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struct stat stat_buf;
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BlockNumber pages;
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int tuple_width;
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double ntuples;
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double nrows;
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Cost run_cost = 0;
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Cost cpu_per_tuple;
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/*
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* Get size of the file. It might not be there at plan time, though, in
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* which case we have to use a default estimate.
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*/
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if (stat(filename, &stat_buf) < 0)
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stat_buf.st_size = 10 * BLCKSZ;
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/*
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* Convert size to pages for use in I/O cost estimate below.
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*/
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pages = (stat_buf.st_size + (BLCKSZ - 1)) / BLCKSZ;
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if (pages < 1)
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pages = 1;
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/*
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* Estimate the number of tuples in the file. We back into this estimate
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* using the planner's idea of the relation width; which is bogus if not
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* all columns are being read, not to mention that the text representation
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* of a row probably isn't the same size as its internal representation.
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* FIXME later.
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*/
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tuple_width = MAXALIGN(baserel->width) + MAXALIGN(sizeof(HeapTupleHeaderData));
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ntuples = clamp_row_est((double) stat_buf.st_size / (double) tuple_width);
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/*
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* Now estimate the number of rows returned by the scan after applying the
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* baserestrictinfo quals. This is pretty bogus too, since the planner
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* will have no stats about the relation, but it's better than nothing.
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*/
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nrows = ntuples *
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clauselist_selectivity(root,
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baserel->baserestrictinfo,
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0,
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JOIN_INNER,
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NULL);
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nrows = clamp_row_est(nrows);
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/* Save the output-rows estimate for the planner */
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baserel->rows = nrows;
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/*
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* Now estimate costs. We estimate costs almost the same way as
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* cost_seqscan(), thus assuming that I/O costs are equivalent to a
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* regular table file of the same size. However, we take per-tuple CPU
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* costs as 10x of a seqscan, to account for the cost of parsing records.
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*/
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run_cost += seq_page_cost * pages;
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*startup_cost = baserel->baserestrictcost.startup;
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cpu_per_tuple = cpu_tuple_cost * 10 + baserel->baserestrictcost.per_tuple;
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run_cost += cpu_per_tuple * ntuples;
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*total_cost = *startup_cost + run_cost;
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}
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