On Mon, Jun 15, 2020 at 04:47:01PM +0900, Michael Paquier wrote:
> On Sun, Jun 14, 2020 at 08:45:17PM -0700, Mark Wong wrote:
> > Sounds good to me. Something more like the attached patch?
>
> That's the idea. I have not gone in details into what you have here,
> but perhaps it would make sense to do a bit more and show how things
> are done in the context of a PL function called in a trigger? Your
> patch removes from the docs a code block that outlined that.
Ah, right. For the moment I've added some empty conditionals for
trigger and event trigger handling.
I've created a new entry in the commitfest app. [1] I'll keep at it. :)
Regards,
Mark
[1] https://commitfest.postgresql.org/29/2678/
--
Mark Wong
2ndQuadrant - PostgreSQL Solutions for the Enterprise
https://www.2ndQuadrant.com/
diff --git a/doc/src/sgml/plhandler.sgml b/doc/src/sgml/plhandler.sgml
index e1b0af7a60..7b2c5624c0 100644
--- a/doc/src/sgml/plhandler.sgml
+++ b/doc/src/sgml/plhandler.sgml
@@ -96,62 +96,12 @@
</para>
<para>
- This is a template for a procedural-language handler written in C:
-<programlisting>
-#include "postgres.h"
-#include "executor/spi.h"
-#include "commands/trigger.h"
-#include "fmgr.h"
-#include "access/heapam.h"
-#include "utils/syscache.h"
-#include "catalog/pg_proc.h"
-#include "catalog/pg_type.h"
-
-PG_MODULE_MAGIC;
-
-PG_FUNCTION_INFO_V1(plsample_call_handler);
-
-Datum
-plsample_call_handler(PG_FUNCTION_ARGS)
-{
- Datum retval;
-
- if (CALLED_AS_TRIGGER(fcinfo))
- {
- /*
- * Called as a trigger function
- */
- TriggerData *trigdata = (TriggerData *) fcinfo->context;
-
- retval = ...
- }
- else
- {
- /*
- * Called as a function
- */
-
- retval = ...
- }
-
- return retval;
-}
-</programlisting>
- Only a few thousand lines of code have to be added instead of the
- dots to complete the call handler.
- </para>
-
- <para>
- After having compiled the handler function into a loadable module
- (see <xref linkend="dfunc"/>), the following commands then
- register the sample procedural language:
-<programlisting>
-CREATE FUNCTION plsample_call_handler() RETURNS language_handler
- AS '<replaceable>filename</replaceable>'
- LANGUAGE C;
-CREATE LANGUAGE plsample
- HANDLER plsample_call_handler;
-</programlisting>
+ A template for a procedural-language handler written as a C extension is
+ provided in <literal>src/test/modules/plsample</literal>. This is a
+ working sample demonstrating one way to create a procedural-language
+ handler, process parameters, and return a value. A few thousand lines of
+ additional code may have to be added to complete a fully functional
+ handler.
</para>
<para>
diff --git a/src/test/modules/Makefile b/src/test/modules/Makefile
index 29de73c060..95144d8d7c 100644
--- a/src/test/modules/Makefile
+++ b/src/test/modules/Makefile
@@ -9,6 +9,7 @@ SUBDIRS = \
commit_ts \
dummy_index_am \
dummy_seclabel \
+ plsample \
snapshot_too_old \
test_bloomfilter \
test_ddl_deparse \
diff --git a/src/test/modules/plsample/Makefile b/src/test/modules/plsample/Makefile
new file mode 100644
index 0000000000..757b47c785
--- /dev/null
+++ b/src/test/modules/plsample/Makefile
@@ -0,0 +1,20 @@
+# src/test/modules/plsample/Makefile
+
+PGFILEDESC = "PL/Sample - procedural language"
+
+REGRESS = create_pl create_func select_func
+
+EXTENSION = plsample
+EXTVERSION = 0.1
+
+MODULE_big = plsample
+
+OBJS = plsample.o
+
+DATA = plsample.control plsample--0.1.sql
+
+plsample.o: plsample.c
+
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
diff --git a/src/test/modules/plsample/README b/src/test/modules/plsample/README
new file mode 100644
index 0000000000..7ee213700b
--- /dev/null
+++ b/src/test/modules/plsample/README
@@ -0,0 +1,3 @@
+plsample is an example procedural-language handler. It is a simple functional
+template that demonstrates some of the things that need to be done in order to
+build a fully functional procedural-language handler.
diff --git a/src/test/modules/plsample/expected/create_func.out b/src/test/modules/plsample/expected/create_func.out
new file mode 100644
index 0000000000..df2b915a97
--- /dev/null
+++ b/src/test/modules/plsample/expected/create_func.out
@@ -0,0 +1,5 @@
+CREATE FUNCTION plsample_func(a1 NUMERIC, a2 TEXT, a3 INTEGER[])
+RETURNS TEXT
+AS $$
+ This is function's source text.
+$$ LANGUAGE plsample;
diff --git a/src/test/modules/plsample/expected/create_pl.out b/src/test/modules/plsample/expected/create_pl.out
new file mode 100644
index 0000000000..5365391284
--- /dev/null
+++ b/src/test/modules/plsample/expected/create_pl.out
@@ -0,0 +1,8 @@
+CREATE FUNCTION plsample_call_handler()
+RETURNS language_handler
+AS '$libdir/plsample'
+LANGUAGE C;
+CREATE LANGUAGE plsample
+HANDLER plsample_call_handler;
+COMMENT ON LANGUAGE plsample
+IS 'PL/Sample procedural language';
diff --git a/src/test/modules/plsample/expected/select_func.out b/src/test/modules/plsample/expected/select_func.out
new file mode 100644
index 0000000000..dc396cbc04
--- /dev/null
+++ b/src/test/modules/plsample/expected/select_func.out
@@ -0,0 +1,8 @@
+SELECT plsample_func(1.23, 'abc', '{4, 5, 6}');
+ plsample_func
+-----------------------------------
+ +
+ This is function's source text.+
+
+(1 row)
+
diff --git a/src/test/modules/plsample/plsample--0.1.sql b/src/test/modules/plsample/plsample--0.1.sql
new file mode 100644
index 0000000000..b429b83ceb
--- /dev/null
+++ b/src/test/modules/plsample/plsample--0.1.sql
@@ -0,0 +1,9 @@
+CREATE FUNCTION plsample_call_handler()
+RETURNS language_handler
+AS 'MODULE_PATHNAME'
+LANGUAGE C;
+
+CREATE LANGUAGE plsample
+HANDLER plsample_call_handler;
+
+COMMENT ON LANGUAGE plsample IS 'PL/Sample procedural language';
diff --git a/src/test/modules/plsample/plsample.c b/src/test/modules/plsample/plsample.c
new file mode 100644
index 0000000000..69f76e6067
--- /dev/null
+++ b/src/test/modules/plsample/plsample.c
@@ -0,0 +1,156 @@
+/*-------------------------------------------------------------------------
+ *
+ * plsample.c
+ * Handler for the PL/Sample procedural language
+ *
+ * Copyright (c) 2020, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ * src/test/modules/plsample.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include <postgres.h>
+#include <fmgr.h>
+#include <funcapi.h>
+#include <access/htup_details.h>
+#include <catalog/pg_proc.h>
+#include <catalog/pg_type.h>
+#include <commands/event_trigger.h>
+#include <commands/trigger.h>
+#include <utils/builtins.h>
+#include <utils/elog.h>
+#include <utils/memutils.h>
+#include <utils/lsyscache.h>
+#include <utils/syscache.h>
+
+MemoryContext TopMemoryContext = NULL;
+
+PG_MODULE_MAGIC;
+
+PG_FUNCTION_INFO_V1(plsample_call_handler);
+
+static Datum plsample_func_handler(PG_FUNCTION_ARGS);
+
+/*
+ * Handle function, procedure, and trigger calls.
+ */
+Datum
+plsample_call_handler(PG_FUNCTION_ARGS)
+{
+ Datum retval = (Datum) 0;
+
+ PG_TRY();
+ {
+ /*
+ * Determine if called as function or trigger and call appropriate
+ * subhandler.
+ */
+ if (CALLED_AS_TRIGGER(fcinfo))
+ {
+ /* TODO: Invoke the trigger handler. */
+ }
+ else if (CALLED_AS_EVENT_TRIGGER(fcinfo))
+ {
+ /* TODO: Invoke the event trigger handler. */
+ }
+ else
+ {
+ /* Invoke the regular function handler. */
+ retval = plsample_func_handler(fcinfo);
+ }
+ }
+ PG_FINALLY();
+ {
+ }
+ PG_END_TRY();
+ return retval;
+}
+
+/* Handler for regular function and stored procedure calls. */
+static Datum
+plsample_func_handler(PG_FUNCTION_ARGS)
+{
+ HeapTuple pl_tuple;
+ Datum ret;
+ char *source;
+ bool isnull;
+
+ int i;
+ FmgrInfo *arg_out_func;
+ Form_pg_type type_struct;
+ HeapTuple type_tuple;
+ Form_pg_proc pl_struct;
+ volatile MemoryContext proc_cxt = NULL;
+ Oid *argtypes;
+ char **argnames;
+ char *argmodes;
+ char *value;
+
+ Form_pg_type pg_type_entry;
+ Oid result_typioparam;
+ FmgrInfo result_in_func;
+
+ /* Fetch the source of the function. */
+
+ pl_tuple = SearchSysCache(PROCOID,
+ ObjectIdGetDatum(fcinfo->flinfo->fn_oid), 0, 0, 0);
+ if (!HeapTupleIsValid(pl_tuple))
+ elog(ERROR, "cache lookup failed for function %u",
+ fcinfo->flinfo->fn_oid);
+ pl_struct = (Form_pg_proc) GETSTRUCT(pl_tuple);
+
+ ret = SysCacheGetAttr(PROCOID, pl_tuple, Anum_pg_proc_prosrc, &isnull);
+ if (isnull)
+ elog(ERROR, "null prosrc");
+ ReleaseSysCache(pl_tuple);
+
+ source = DatumGetCString(DirectFunctionCall1(textout, ret));
+ elog(LOG, "source text:\n%s", source);
+
+ arg_out_func = (FmgrInfo *) palloc0(fcinfo->nargs * sizeof(FmgrInfo));
+ proc_cxt = AllocSetContextCreate(TopMemoryContext,
+ "PL/Sample function", 0, (1 * 1024), (8 * 1024));
+ get_func_arg_info(pl_tuple, &argtypes, &argnames, &argmodes);
+
+ /* Iterate through all of the function arguments. */
+ elog(LOG, "number of arguments : %d", fcinfo->nargs);
+ for (i = 0; i < fcinfo->nargs; i++)
+ {
+ Oid argtype = pl_struct->proargtypes.values[i];
+ type_tuple = SearchSysCache1(TYPEOID, ObjectIdGetDatum(argtype));
+ if (!HeapTupleIsValid(type_tuple))
+ elog(ERROR, "cache lookup failed for type %u", argtype);
+
+ type_struct = (Form_pg_type) GETSTRUCT(type_tuple);
+ fmgr_info_cxt(type_struct->typoutput, &(arg_out_func[i]), proc_cxt);
+ ReleaseSysCache(type_tuple);
+
+ value = OutputFunctionCall(&arg_out_func[i], fcinfo->args[i].value);
+
+ elog(LOG, "argument position: %d; name: %s; value: %s", i, argnames[i],
+ value);
+ }
+
+ /* Fetch the return type of the function. */
+
+ type_tuple = SearchSysCache1(TYPEOID,
+ ObjectIdGetDatum(pl_struct->prorettype));
+ if (!HeapTupleIsValid(type_tuple))
+ elog(ERROR, "cache lookup failed for type %u", pl_struct->prorettype);
+
+ pg_type_entry = (Form_pg_type) GETSTRUCT(type_tuple);
+
+ proc_cxt = AllocSetContextCreate(TopMemoryContext, "PL/Sample function",
+ ALLOCSET_SMALL_SIZES);
+
+ result_typioparam = getTypeIOParam(type_tuple);
+
+ fmgr_info_cxt(pg_type_entry->typinput, &result_in_func, proc_cxt);
+ ReleaseSysCache(type_tuple);
+
+ /* Simply return the function source text. */
+ ret = InputFunctionCall(&result_in_func, source, result_typioparam, -1);
+ PG_RETURN_DATUM(ret);
+}
diff --git a/src/test/modules/plsample/plsample.control b/src/test/modules/plsample/plsample.control
new file mode 100644
index 0000000000..dba58e5abf
--- /dev/null
+++ b/src/test/modules/plsample/plsample.control
@@ -0,0 +1,7 @@
+# plsample extension
+comment = 'PL/Sample'
+default_version = '0.1'
+module_pathname = '$libdir/plsample'
+relocatable = false
+schema = pg_catalog
+superuser = false
diff --git a/src/test/modules/plsample/sql/create_func.sql b/src/test/modules/plsample/sql/create_func.sql
new file mode 100644
index 0000000000..df2b915a97
--- /dev/null
+++ b/src/test/modules/plsample/sql/create_func.sql
@@ -0,0 +1,5 @@
+CREATE FUNCTION plsample_func(a1 NUMERIC, a2 TEXT, a3 INTEGER[])
+RETURNS TEXT
+AS $$
+ This is function's source text.
+$$ LANGUAGE plsample;
diff --git a/src/test/modules/plsample/sql/create_pl.sql b/src/test/modules/plsample/sql/create_pl.sql
new file mode 100644
index 0000000000..c3ace0f1aa
--- /dev/null
+++ b/src/test/modules/plsample/sql/create_pl.sql
@@ -0,0 +1,10 @@
+CREATE FUNCTION plsample_call_handler()
+RETURNS language_handler
+AS '$libdir/plsample'
+LANGUAGE C;
+
+CREATE LANGUAGE plsample
+HANDLER plsample_call_handler;
+
+COMMENT ON LANGUAGE plsample
+IS 'PL/Sample procedural language';
diff --git a/src/test/modules/plsample/sql/select_func.sql b/src/test/modules/plsample/sql/select_func.sql
new file mode 100644
index 0000000000..5ded186984
--- /dev/null
+++ b/src/test/modules/plsample/sql/select_func.sql
@@ -0,0 +1 @@
+SELECT plsample_func(1.23, 'abc', '{4, 5, 6}');
