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Allow contrib/file_fdw to read from a program, like COPY FROM PROGRAM.

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This patch just exposes COPY's FROM PROGRAM option in contrib/file_fdw.
There don't seem to be any security issues with that that are any worse
than what already exist with file_fdw and COPY; as in the existing cases,
only superusers are allowed to control what gets executed.

A regression test case might be nice here, but choosing a 100% portable
command to run is hard.  (We haven't got a test for COPY FROM PROGRAM
itself, either.)

Corey Huinker and Adam Gomaa, reviewed by Amit Langote

Discussion: <CADkLM=dGDGmaEiZ=UDepzumWg-CVn7r8MHPjr2NArj8S3TsROQ@mail.gmail.com>
pull/17/head
Tom Lane 9 years ago
parent 728a3e73e9
commit 8e91e12bc3
3 changed files with 137 additions and 66 deletions
Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL
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  1. 131
      contrib/file_fdw/file_fdw.c
  2. 6
      contrib/file_fdw/output/file_fdw.source
  3. 66
      doc/src/sgml/file-fdw.sgml

131
contrib/file_fdw/file_fdw.c
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@ -1,7 +1,7 @@
/*-------------------------------------------------------------------------
*
* file_fdw.c
* foreign-data wrapper for server-side flat files.
* foreign-data wrapper for server-side flat files (or programs).
*
* Copyright (c) 2010-2016, PostgreSQL Global Development Group
*
@ -57,8 +57,9 @@ struct FileFdwOption
* fileGetOptions(), which currently doesn't bother to look at user mappings.
*/
static const struct FileFdwOption valid_options[] = {
/* File options */
/* Data source options */
{"filename", ForeignTableRelationId},
{"program", ForeignTableRelationId},
/* Format options */
/* oids option is not supported */
@ -85,10 +86,12 @@ static const struct FileFdwOption valid_options[] = {
*/
typedef struct FileFdwPlanState
{
char *filename; /* file to read */
List *options; /* merged COPY options, excluding filename */
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 rows in file */
double ntuples; /* estimate of number of data rows */
} FileFdwPlanState;
/*
@ -96,9 +99,11 @@ typedef struct FileFdwPlanState
*/
typedef struct FileFdwExecutionState
{
char *filename; /* file to read */
List *options; /* merged COPY options, excluding filename */
CopyState cstate; /* state of reading file */
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;
/*
@ -139,7 +144,9 @@ static bool fileIsForeignScanParallelSafe(PlannerInfo *root, RelOptInfo *rel,
*/
static bool is_valid_option(const char *option, Oid context);
static void fileGetOptions(Oid foreigntableid,
char **filename, List **other_options);
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,
@ -196,16 +203,16 @@ file_fdw_validator(PG_FUNCTION_ARGS)
/*
* 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.
* This is because we don't want non-superusers 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 at any
* options level other than foreign table --- otherwise there'd still be a
* security hole.
* 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 (catalog == ForeignTableRelationId && !superuser())
ereport(ERROR,
@ -247,11 +254,11 @@ file_fdw_validator(PG_FUNCTION_ARGS)
}
/*
* Separate out filename and column-specific options, since
* Separate out filename, program, and column-specific options, since
* ProcessCopyOptions won't accept them.
*/
if (strcmp(def->defname, "filename") == 0)
if (strcmp(def->defname, "filename") == 0 ||
strcmp(def->defname, "program") == 0)
{
if (filename)
ereport(ERROR,
@ -296,12 +303,13 @@ file_fdw_validator(PG_FUNCTION_ARGS)
ProcessCopyOptions(NULL, NULL, true, other_options);
/*
* Filename option is required for file_fdw foreign tables.
* 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("filename is required for file_fdw foreign tables")));
errmsg("either filename or program is required for file_fdw foreign tables")));
PG_RETURN_VOID();
}
@ -326,12 +334,12 @@ is_valid_option(const char *option, Oid context)
/*
* 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.
* 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, List **other_options)
char **filename, bool *is_program, List **other_options)
{
ForeignTable *table;
ForeignServer *server;
@ -359,9 +367,11 @@ fileGetOptions(Oid foreigntableid,
options = list_concat(options, get_file_fdw_attribute_options(foreigntableid));
/*
* Separate out the filename.
* Separate out the filename or program option (we assume there is only
* one).
*/
*filename = NULL;
*is_program = false;
prev = NULL;
foreach(lc, options)
{
@ -373,15 +383,22 @@ fileGetOptions(Oid foreigntableid,
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 a filename was included in the
* options, but check again, just in case.
* 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, "filename is required for file_fdw foreign tables");
elog(ERROR, "either filename or program is required for file_fdw foreign tables");
*other_options = options;
}
@ -475,12 +492,15 @@ fileGetForeignRelSize(PlannerInfo *root,
FileFdwPlanState *fdw_private;
/*
* Fetch options. We only need filename at this point, but we might as
* well get everything and not need to re-fetch it later in planning.
* 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->options);
&fdw_private->filename,
&fdw_private->is_program,
&fdw_private->options);
baserel->fdw_private = (void *) fdw_private;
/* Estimate relation size */
@ -583,20 +603,25 @@ static void
fileExplainForeignScan(ForeignScanState *node, ExplainState *es)
{
char *filename;
bool is_program;
List *options;
/* Fetch options --- we only need filename at this point */
/* Fetch options --- we only need filename and is_program at this point */
fileGetOptions(RelationGetRelid(node->ss.ss_currentRelation),
&filename, &options);
&filename, &is_program, &options);
ExplainPropertyText("Foreign File", filename, es);
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 (stat(filename, &stat_buf) == 0)
if (!is_program &&
stat(filename, &stat_buf) == 0)
ExplainPropertyLong("Foreign File Size", (long) stat_buf.st_size,
es);
}
@ -611,6 +636,7 @@ fileBeginForeignScan(ForeignScanState *node, int eflags)
{
ForeignScan *plan = (ForeignScan *) node->ss.ps.plan;
char *filename;
bool is_program;
List *options;
CopyState cstate;
FileFdwExecutionState *festate;
@ -623,7 +649,7 @@ fileBeginForeignScan(ForeignScanState *node, int eflags)
/* Fetch options of foreign table */
fileGetOptions(RelationGetRelid(node->ss.ss_currentRelation),
&filename, &options);
&filename, &is_program, &options);
/* Add any options from the plan (currently only convert_selectively) */
options = list_concat(options, plan->fdw_private);
@ -635,7 +661,7 @@ fileBeginForeignScan(ForeignScanState *node, int eflags)
cstate = BeginCopyFrom(NULL,
node->ss.ss_currentRelation,
filename,
false,
is_program,
NIL,
options);
@ -645,6 +671,7 @@ fileBeginForeignScan(ForeignScanState *node, int eflags)
*/
festate = (FileFdwExecutionState *) palloc(sizeof(FileFdwExecutionState));
festate->filename = filename;
festate->is_program = is_program;
festate->options = options;
festate->cstate = cstate;
@ -709,7 +736,7 @@ fileReScanForeignScan(ForeignScanState *node)
festate->cstate = BeginCopyFrom(NULL,
node->ss.ss_currentRelation,
festate->filename,
false,
festate->is_program,
NIL,
festate->options);
}
@ -738,11 +765,22 @@ fileAnalyzeForeignTable(Relation relation,
BlockNumber *totalpages)
{
char *filename;
bool is_program;
List *options;
struct stat stat_buf;
/* Fetch options of foreign table */
fileGetOptions(RelationGetRelid(relation), &filename, &options);
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
@ -769,8 +807,8 @@ fileAnalyzeForeignTable(Relation relation,
/*
* fileIsForeignScanParallelSafe
* Reading a file in a parallel worker should work just the same as
* reading it in the leader, so mark scans safe.
* 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,
@ -916,9 +954,10 @@ estimate_size(PlannerInfo *root, RelOptInfo *baserel,
/*
* Get size of the file. It might not be there at plan time, though, in
* which case we have to use a default estimate.
* 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 (stat(fdw_private->filename, &stat_buf) < 0)
if (fdw_private->is_program || stat(fdw_private->filename, &stat_buf) < 0)
stat_buf.st_size = 10 * BLCKSZ;
/*
@ -1000,6 +1039,11 @@ estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
* 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;
@ -1036,6 +1080,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
bool *nulls;
bool found;
char *filename;
bool is_program;
List *options;
CopyState cstate;
ErrorContextCallback errcallback;
@ -1050,12 +1095,12 @@ file_acquire_sample_rows(Relation onerel, int elevel,
nulls = (bool *) palloc(tupDesc->natts * sizeof(bool));
/* Fetch options of foreign table */
fileGetOptions(RelationGetRelid(onerel), &filename, &options);
fileGetOptions(RelationGetRelid(onerel), &filename, &is_program, &options);
/*
* Create CopyState from FDW options.
*/
cstate = BeginCopyFrom(NULL, onerel, filename, false, NIL, options);
cstate = BeginCopyFrom(NULL, onerel, filename, is_program, NIL, options);
/*
* Use per-tuple memory context to prevent leak of memory used to read

6
contrib/file_fdw/output/file_fdw.source
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@ -76,7 +76,7 @@ CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'csv', null '
'); -- ERROR
ERROR: COPY null representation cannot use newline or carriage return
CREATE FOREIGN TABLE tbl () SERVER file_server; -- ERROR
ERROR: filename is required for file_fdw foreign tables
ERROR: either filename or program is required for file_fdw foreign tables
CREATE FOREIGN TABLE agg_text (
a int2 CHECK (a >= 0),
b float4
@ -132,7 +132,7 @@ ERROR: invalid option "force_not_null"
HINT: There are no valid options in this context.
CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (force_not_null '*'); -- ERROR
ERROR: invalid option "force_not_null"
HINT: Valid options in this context are: filename, format, header, delimiter, quote, escape, null, encoding
HINT: Valid options in this context are: filename, program, format, header, delimiter, quote, escape, null, encoding
-- force_null is not allowed to be specified at any foreign object level:
ALTER FOREIGN DATA WRAPPER file_fdw OPTIONS (ADD force_null '*'); -- ERROR
ERROR: invalid option "force_null"
@ -145,7 +145,7 @@ ERROR: invalid option "force_null"
HINT: There are no valid options in this context.
CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (force_null '*'); -- ERROR
ERROR: invalid option "force_null"
HINT: Valid options in this context are: filename, format, header, delimiter, quote, escape, null, encoding
HINT: Valid options in this context are: filename, program, format, header, delimiter, quote, escape, null, encoding
-- basic query tests
SELECT * FROM agg_text WHERE b > 10.0 ORDER BY a;
a | b

66
doc/src/sgml/file-fdw.sgml
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@ -10,10 +10,11 @@
<para>
The <filename>file_fdw</> module provides the foreign-data wrapper
<function>file_fdw</function>, which can be used to access data
files in the server's file system. Data files must be in a format
files in the server's file system, or to execute programs on the server
and read their output. The data file or program output must be in a format
that can be read by <command>COPY FROM</command>;
see <xref linkend="sql-copy"> for details.
Access to such data files is currently read-only.
Access to data files is currently read-only.
</para>
<para>
@ -27,7 +28,22 @@
<listitem>
<para>
Specifies the file to be read. Required. Must be an absolute path name.
Specifies the file to be read. Must be an absolute path name.
Either <literal>filename</literal> or <literal>program</literal> must be
specified, but not both.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>program</literal></term>
<listitem>
<para>
Specifies the command to be executed. The standard output of this
command will be read as though <command>COPY FROM PROGRAM</> were used.
Either <literal>program</literal> or <literal>filename</literal> must be
specified, but not both.
</para>
</listitem>
</varlistentry>
@ -37,7 +53,7 @@
<listitem>
<para>
Specifies the file's format,
Specifies the data format,
the same as <command>COPY</>'s <literal>FORMAT</literal> option.
</para>
</listitem>
@ -48,7 +64,7 @@
<listitem>
<para>
Specifies whether the file has a header line,
Specifies whether the data has a header line,
the same as <command>COPY</>'s <literal>HEADER</literal> option.
</para>
</listitem>
@ -59,7 +75,7 @@
<listitem>
<para>
Specifies the file's delimiter character,
Specifies the data delimiter character,
the same as <command>COPY</>'s <literal>DELIMITER</literal> option.
</para>
</listitem>
@ -70,7 +86,7 @@
<listitem>
<para>
Specifies the file's quote character,
Specifies the data quote character,
the same as <command>COPY</>'s <literal>QUOTE</literal> option.
</para>
</listitem>
@ -81,7 +97,7 @@
<listitem>
<para>
Specifies the file's escape character,
Specifies the data escape character,
the same as <command>COPY</>'s <literal>ESCAPE</literal> option.
</para>
</listitem>
@ -92,7 +108,7 @@
<listitem>
<para>
Specifies the file's null string,
Specifies the data null string,
the same as <command>COPY</>'s <literal>NULL</literal> option.
</para>
</listitem>
@ -103,7 +119,7 @@
<listitem>
<para>
Specifies the file's encoding,
Specifies the data encoding,
the same as <command>COPY</>'s <literal>ENCODING</literal> option.
</para>
</listitem>
@ -112,11 +128,11 @@
</variablelist>
<para>
Note that while <command>COPY</> allows options such as OIDS and HEADER
to be specified without a corresponding value, the foreign data wrapper
Note that while <command>COPY</> allows options such as <literal>HEADER</>
to be specified without a corresponding value, the foreign table option
syntax requires a value to be present in all cases. To activate
<command>COPY</> options normally supplied without a value, you can
instead pass the value TRUE.
<command>COPY</> options typically written without a value, you can pass
the value TRUE, since all such options are Booleans.
</para>
<para>
@ -133,7 +149,7 @@
<para>
This is a Boolean option. If true, it specifies that values of the
column should not be matched against the null string (that is, the
file-level <literal>null</literal> option). This has the same effect
table-level <literal>null</literal> option). This has the same effect
as listing the column in <command>COPY</>'s
<literal>FORCE_NOT_NULL</literal> option.
</para>
@ -171,14 +187,24 @@
<para>
Changing table-level options requires superuser privileges, for security
reasons: only a superuser should be able to determine which file is read.
In principle non-superusers could be allowed to change the other options,
but that's not supported at present.
reasons: only a superuser should be able to control which file is read
or which program is run. In principle non-superusers could be allowed to
change the other options, but that's not supported at present.
</para>
<para>
When specifying the <literal>program</> option, keep in mind that the option
string is executed by the shell. If you need to pass any arguments to the
command that come from an untrusted source, you must be careful to strip or
escape any characters that might have special meaning to the shell.
For security reasons, it is best to use a fixed command string, or at least
avoid passing any user input in it.
</para>
<para>
For a foreign table using <literal>file_fdw</>, <command>EXPLAIN</> shows
the name of the file to be read. Unless <literal>COSTS OFF</> is
the name of the file to be read or program to be run.
For a file, unless <literal>COSTS OFF</> is
specified, the file size (in bytes) is shown as well.
</para>
@ -186,7 +212,7 @@
<title id="csvlog-fdw">Create a Foreign Table for PostgreSQL CSV Logs</title>
<para>
One of the obvious uses for the <literal>file_fdw</> is to make
One of the obvious uses for <literal>file_fdw</> is to make
the PostgreSQL activity log available as a table for querying. To
do this, first you must be logging to a CSV file, which here we
will call <literal>pglog.csv</>. First, install <literal>file_fdw</>

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