This is useful as a way for extensions to process COPY TO rows in the
way they see fit (say auditing, analytics, backend, etc.) without the
need to invoke an external process running as the OS user running the
backend through PROGRAM that requires superuser rights. COPY FROM
already provides a similar callback for logical replication. For COPY
TO, the callback is triggered when we are ready to send a row in
CopySendEndOfRow(), which is the same code path as when sending a row
to a frontend or a pipe/file.
A small test module, test_copy_callbacks, is added to provide some
coverage for this facility.
Author: Bilva Sanaba, Nathan Bossart
Discussion: https://postgr.es/m/
253C21D1-FCEB-41D9-A2AF-
E6517015B7D7@amazon.com
cstate = BeginCopyTo(pstate, rel, query, relid,
stmt->filename, stmt->is_program,
- stmt->attlist, stmt->options);
+ NULL, stmt->attlist, stmt->options);
*processed = DoCopyTo(cstate); /* copy from database to file */
EndCopyTo(cstate);
}
{
COPY_FILE, /* to file (or a piped program) */
COPY_FRONTEND, /* to frontend */
+ COPY_CALLBACK /* to callback function */
} CopyDest;
/*
List *attnumlist; /* integer list of attnums to copy */
char *filename; /* filename, or NULL for STDOUT */
bool is_program; /* is 'filename' a program to popen? */
+ copy_data_dest_cb data_dest_cb; /* function for writing data */
CopyFormatOptions opts;
Node *whereClause; /* WHERE condition (or NULL) */
/* Dump the accumulated row as one CopyData message */
(void) pq_putmessage('d', fe_msgbuf->data, fe_msgbuf->len);
break;
+ case COPY_CALLBACK:
+ cstate->data_dest_cb(fe_msgbuf->data, fe_msgbuf->len);
+ break;
}
/* Update the progress */
/*
* Setup CopyToState to read tuples from a table or a query for COPY TO.
+ *
+ * 'rel': Relation to be copied
+ * 'raw_query': Query whose results are to be copied
+ * 'queryRelId': OID of base relation to convert to a query (for RLS)
+ * 'filename': Name of server-local file to write, NULL for STDOUT
+ * 'is_program': true if 'filename' is program to execute
+ * 'data_dest_cb': Callback that processes the output data
+ * 'attnamelist': List of char *, columns to include. NIL selects all cols.
+ * 'options': List of DefElem. See copy_opt_item in gram.y for selections.
+ *
+ * Returns a CopyToState, to be passed to DoCopyTo() and related functions.
*/
CopyToState
BeginCopyTo(ParseState *pstate,
Oid queryRelId,
const char *filename,
bool is_program,
+ copy_data_dest_cb data_dest_cb,
List *attnamelist,
List *options)
{
CopyToState cstate;
- bool pipe = (filename == NULL);
+ bool pipe = (filename == NULL && data_dest_cb == NULL);
TupleDesc tupDesc;
int num_phys_attrs;
MemoryContext oldcontext;
cstate->copy_dest = COPY_FILE; /* default */
- if (pipe)
+ if (data_dest_cb)
+ {
+ progress_vals[1] = PROGRESS_COPY_TYPE_CALLBACK;
+ cstate->copy_dest = COPY_CALLBACK;
+ cstate->data_dest_cb = data_dest_cb;
+ }
+ else if (pipe)
{
progress_vals[1] = PROGRESS_COPY_TYPE_PIPE;
/*
* Copy from relation or query TO file.
+ *
+ * Returns the number of rows processed.
*/
uint64
DoCopyTo(CopyToState cstate)
{
- bool pipe = (cstate->filename == NULL);
+ bool pipe = (cstate->filename == NULL && cstate->data_dest_cb == NULL);
bool fe_copy = (pipe && whereToSendOutput == DestRemote);
TupleDesc tupDesc;
int num_phys_attrs;
typedef struct CopyToStateData *CopyToState;
typedef int (*copy_data_source_cb) (void *outbuf, int minread, int maxread);
+typedef void (*copy_data_dest_cb) (void *data, int len);
extern void DoCopy(ParseState *pstate, const CopyStmt *stmt,
int stmt_location, int stmt_len,
*/
extern CopyToState BeginCopyTo(ParseState *pstate, Relation rel, RawStmt *raw_query,
Oid queryRelId, const char *filename, bool is_program,
- List *attnamelist, List *options);
+ copy_data_dest_cb data_dest_cb, List *attnamelist, List *options);
extern void EndCopyTo(CopyToState cstate);
extern uint64 DoCopyTo(CopyToState cstate);
extern List *CopyGetAttnums(TupleDesc tupDesc, Relation rel,
snapshot_too_old \
spgist_name_ops \
test_bloomfilter \
+ test_copy_callbacks \
test_ddl_deparse \
test_extensions \
test_ginpostinglist \
subdir('spgist_name_ops')
subdir('ssl_passphrase_callback')
subdir('test_bloomfilter')
+subdir('test_copy_callbacks')
subdir('test_ddl_deparse')
subdir('test_extensions')
subdir('test_ginpostinglist')
--- /dev/null
+# Generated subdirectories
+/log/
+/results/
+/tmp_check/
--- /dev/null
+# src/test/modules/test_copy_callbacks/Makefile
+
+MODULE_big = test_copy_callbacks
+OBJS = \
+ $(WIN32RES) \
+ test_copy_callbacks.o
+PGFILEDESC = "test_copy_callbacks - test COPY callbacks"
+
+EXTENSION = test_copy_callbacks
+DATA = test_copy_callbacks--1.0.sql
+
+REGRESS = test_copy_callbacks
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = src/test/modules/test_copy_callbacks
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
--- /dev/null
+CREATE EXTENSION test_copy_callbacks;
+CREATE TABLE public.test (a INT, b INT, c INT);
+INSERT INTO public.test VALUES (1, 2, 3), (12, 34, 56), (123, 456, 789);
+SELECT test_copy_to_callback('public.test'::pg_catalog.regclass);
+NOTICE: COPY TO callback called with data "1 2 3" and length 5
+NOTICE: COPY TO callback called with data "12 34 56" and length 8
+NOTICE: COPY TO callback called with data "123 456 789" and length 11
+NOTICE: COPY TO callback has processed 3 rows
+ test_copy_to_callback
+-----------------------
+
+(1 row)
+
--- /dev/null
+# FIXME: prevent install during main install, but not during test :/
+
+test_copy_callbacks_sources = files(
+ 'test_copy_callbacks.c',
+)
+
+if host_system == 'windows'
+ test_copy_callbacks_sources += rc_lib_gen.process(win32ver_rc, extra_args: [
+ '--NAME', 'test_copy_callbacks',
+ '--FILEDESC', 'test_copy_callbacks - test COPY callbacks',])
+endif
+
+test_copy_callbacks = shared_module('test_copy_callbacks',
+ test_copy_callbacks_sources,
+ kwargs: pg_mod_args,
+)
+testprep_targets += test_copy_callbacks
+
+install_data(
+ 'test_copy_callbacks.control',
+ 'test_copy_callbacks--1.0.sql',
+ kwargs: contrib_data_args,
+)
+
+tests += {
+ 'name': 'test_copy_callbacks',
+ 'sd': meson.current_source_dir(),
+ 'bd': meson.current_build_dir(),
+ 'regress': {
+ 'sql': [
+ 'test_copy_callbacks',
+ ],
+ },
+}
--- /dev/null
+CREATE EXTENSION test_copy_callbacks;
+CREATE TABLE public.test (a INT, b INT, c INT);
+INSERT INTO public.test VALUES (1, 2, 3), (12, 34, 56), (123, 456, 789);
+SELECT test_copy_to_callback('public.test'::pg_catalog.regclass);
--- /dev/null
+/* src/test/modules/test_copy_callbacks/test_copy_callbacks--1.0.sql */
+
+-- complain if script is sourced in psql, rather than via CREATE EXTENSION
+\echo Use "CREATE EXTENSION test_copy_callbacks" to load this file. \quit
+
+CREATE FUNCTION test_copy_to_callback(pg_catalog.regclass)
+ RETURNS pg_catalog.void
+ AS 'MODULE_PATHNAME' LANGUAGE C;
--- /dev/null
+/*--------------------------------------------------------------------------
+ *
+ * test_copy_callbacks.c
+ * Code for testing COPY callbacks.
+ *
+ * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ * src/test/modules/test_copy_callbacks/test_copy_callbacks.c
+ *
+ * -------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/table.h"
+#include "commands/copy.h"
+#include "fmgr.h"
+#include "utils/rel.h"
+
+PG_MODULE_MAGIC;
+
+static void
+to_cb(void *data, int len)
+{
+ ereport(NOTICE,
+ (errmsg("COPY TO callback called with data \"%s\" and length %d",
+ (char *) data, len)));
+}
+
+PG_FUNCTION_INFO_V1(test_copy_to_callback);
+Datum
+test_copy_to_callback(PG_FUNCTION_ARGS)
+{
+ Relation rel = table_open(PG_GETARG_OID(0), AccessShareLock);
+ CopyToState cstate;
+ int64 processed;
+
+ cstate = BeginCopyTo(NULL, rel, NULL, RelationGetRelid(rel), NULL, NULL,
+ to_cb, NIL, NIL);
+ processed = DoCopyTo(cstate);
+ EndCopyTo(cstate);
+
+ ereport(NOTICE, (errmsg("COPY TO callback has processed %lld rows",
+ (long long) processed)));
+
+ table_close(rel, NoLock);
+
+ PG_RETURN_VOID();
+}
--- /dev/null
+comment = 'Test code for COPY callbacks'
+default_version = '1.0'
+module_pathname = '$libdir/test_copy_callbacks'
+relocatable = true
config_var_value
contain_aggs_of_level_context
convert_testexpr_context
+copy_data_dest_cb
copy_data_source_cb
core_YYSTYPE
core_yy_extra_type
projects / users / rhaas / postgres.git / commitdiff