Something that has been bothering me in PL/Python for a long time is the
non-object-oriented way in which plans are prepared and executed:
plan = plpy.prepare(...)
res = plpy.execute(plan, ...)
where plpy.execute() takes either a plan or a query string.
I think a better style would be
plan = plpy.prepare(...)
res = plan.execute(...)
so that the "plan" is more like a statement handle that one finds in
other APIs.
This ended up being very easy to implement, so I'm proposing to allow
this new syntax as an alternative.
I came across this again as I was developing the background sessions API
for PL/Python. So I'm also wondering here which style people prefer so
I can implement it there.
--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
From 9dccf70110d9d5818318c651c2662f2b8f86b2bc Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <pete...@gmx.net>
Date: Sat, 25 Feb 2017 08:42:25 -0500
Subject: [PATCH] PL/Python: Add cursor and execute methods to plan object
Instead of
plan = plpy.prepare(...)
res = plpy.execute(plan, ...)
you can now write
plan = plpy.prepare(...)
res = plan.execute(...)
or even
res = plpy.prepare(...).execute(...)
and similarly for the cursor() method.
This is more in object oriented style, and makes the hybrid nature of
the existing execute() function less confusing.
---
doc/src/sgml/plpython.sgml | 14 ++++++++++++--
src/pl/plpython/expected/plpython_spi.out | 19 ++++++++++++++++---
src/pl/plpython/plpy_cursorobject.c | 3 +--
src/pl/plpython/plpy_cursorobject.h | 1 +
src/pl/plpython/plpy_planobject.c | 31 +++++++++++++++++++++++++++++++
src/pl/plpython/plpy_spi.c | 3 +--
src/pl/plpython/plpy_spi.h | 1 +
src/pl/plpython/sql/plpython_spi.sql | 18 ++++++++++++++++--
8 files changed, 79 insertions(+), 11 deletions(-)
diff --git a/doc/src/sgml/plpython.sgml b/doc/src/sgml/plpython.sgml
index 46397781be..6888ce1ae3 100644
--- a/doc/src/sgml/plpython.sgml
+++ b/doc/src/sgml/plpython.sgml
@@ -1048,6 +1048,14 @@ <title>Database Access Functions</title>
</para>
<para>
+ Alternatively, you can call the <function>execute</function> method on
+ the plan object:
+<programlisting>
+rv = plan.execute(["name"], 5)
+</programlisting>
+ </para>
+
+ <para>
Query parameters and result row fields are converted between PostgreSQL
and Python data types as described in <xref linkend="plpython-data">.
</para>
@@ -1082,7 +1090,9 @@ <title>Database Access Functions</title>
as <literal>plpy.execute</literal> (except for the row limit) and returns
a cursor object, which allows you to process large result sets in smaller
chunks. As with <literal>plpy.execute</literal>, either a query string
- or a plan object along with a list of arguments can be used.
+ or a plan object along with a list of arguments can be used, or
+ the <function>cursor</function> function can be called as a method of
+ the plan object.
</para>
<para>
@@ -1126,7 +1136,7 @@ <title>Database Access Functions</title>
CREATE FUNCTION count_odd_prepared() RETURNS integer AS $$
odd = 0
plan = plpy.prepare("select num from largetable where num % $1 <> 0", ["integer"])
-rows = list(plpy.cursor(plan, [2]))
+rows = list(plpy.cursor(plan, [2])) # or: = list(plan.cursor([2]))
return len(rows)
$$ LANGUAGE plpythonu;
diff --git a/src/pl/plpython/expected/plpython_spi.out b/src/pl/plpython/expected/plpython_spi.out
index 0d78ca1de4..e54dca9e2e 100644
--- a/src/pl/plpython/expected/plpython_spi.out
+++ b/src/pl/plpython/expected/plpython_spi.out
@@ -31,6 +31,19 @@ except Exception, ex:
return None
'
LANGUAGE plpythonu;
+CREATE FUNCTION spi_prepared_plan_test_two(a text) RETURNS text
+ AS
+'if "myplan" not in SD:
+ q = "SELECT count(*) FROM users WHERE lname = $1"
+ SD["myplan"] = plpy.prepare(q, [ "text" ])
+try:
+ rv = SD["myplan"].execute([a])
+ return "there are " + str(rv[0]["count"]) + " " + str(a) + "s"
+except Exception, ex:
+ plpy.error(str(ex))
+return None
+'
+ LANGUAGE plpythonu;
CREATE FUNCTION spi_prepared_plan_test_nested(a text) RETURNS text
AS
'if "myplan" not in SD:
@@ -80,8 +93,8 @@ select spi_prepared_plan_test_one('doe');
there are 3 does
(1 row)
-select spi_prepared_plan_test_one('smith');
- spi_prepared_plan_test_one
+select spi_prepared_plan_test_two('smith');
+ spi_prepared_plan_test_two
----------------------------
there are 1 smiths
(1 row)
@@ -372,7 +385,7 @@ plan = plpy.prepare(
["text"])
for row in plpy.cursor(plan, ["w"]):
yield row['fname']
-for row in plpy.cursor(plan, ["j"]):
+for row in plan.cursor(["j"]):
yield row['fname']
$$ LANGUAGE plpythonu;
CREATE FUNCTION cursor_plan_wrong_args() RETURNS SETOF text AS $$
diff --git a/src/pl/plpython/plpy_cursorobject.c b/src/pl/plpython/plpy_cursorobject.c
index 7bb8992148..18e689f141 100644
--- a/src/pl/plpython/plpy_cursorobject.c
+++ b/src/pl/plpython/plpy_cursorobject.c
@@ -25,7 +25,6 @@
static PyObject *PLy_cursor_query(const char *query);
-static PyObject *PLy_cursor_plan(PyObject *ob, PyObject *args);
static void PLy_cursor_dealloc(PyObject *arg);
static PyObject *PLy_cursor_iternext(PyObject *self);
static PyObject *PLy_cursor_fetch(PyObject *self, PyObject *args);
@@ -160,7 +159,7 @@ PLy_cursor_query(const char *query)
return (PyObject *) cursor;
}
-static PyObject *
+PyObject *
PLy_cursor_plan(PyObject *ob, PyObject *args)
{
PLyCursorObject *cursor;
diff --git a/src/pl/plpython/plpy_cursorobject.h b/src/pl/plpython/plpy_cursorobject.h
index c73033c486..ef23865dd2 100644
--- a/src/pl/plpython/plpy_cursorobject.h
+++ b/src/pl/plpython/plpy_cursorobject.h
@@ -19,5 +19,6 @@ typedef struct PLyCursorObject
extern void PLy_cursor_init_type(void);
extern PyObject *PLy_cursor(PyObject *self, PyObject *args);
+extern PyObject *PLy_cursor_plan(PyObject *ob, PyObject *args);
#endif /* PLPY_CURSOROBJECT_H */
diff --git a/src/pl/plpython/plpy_planobject.c b/src/pl/plpython/plpy_planobject.c
index 16c39a05dd..390b4e90d4 100644
--- a/src/pl/plpython/plpy_planobject.c
+++ b/src/pl/plpython/plpy_planobject.c
@@ -10,11 +10,15 @@
#include "plpy_planobject.h"
+#include "plpy_cursorobject.h"
#include "plpy_elog.h"
+#include "plpy_spi.h"
#include "utils/memutils.h"
static void PLy_plan_dealloc(PyObject *arg);
+static PyObject *PLy_plan_cursor(PyObject *self, PyObject *args);
+static PyObject *PLy_plan_execute(PyObject *self, PyObject *args);
static PyObject *PLy_plan_status(PyObject *self, PyObject *args);
static char PLy_plan_doc[] = {
@@ -22,6 +26,8 @@ static char PLy_plan_doc[] = {
};
static PyMethodDef PLy_plan_methods[] = {
+ {"cursor", PLy_plan_cursor, METH_VARARGS, NULL},
+ {"execute", PLy_plan_execute, METH_VARARGS, NULL},
{"status", PLy_plan_status, METH_VARARGS, NULL},
{NULL, NULL, 0, NULL}
};
@@ -112,6 +118,31 @@ PLy_plan_dealloc(PyObject *arg)
static PyObject *
+PLy_plan_cursor(PyObject *self, PyObject *args)
+{
+ PyObject *planargs = NULL;
+
+ if (!PyArg_ParseTuple(args, "|O", &planargs))
+ return NULL;
+
+ return PLy_cursor_plan(self, planargs);
+}
+
+
+static PyObject *
+PLy_plan_execute(PyObject *self, PyObject *args)
+{
+ PyObject *list = NULL;
+ long limit = 0;
+
+ if (!PyArg_ParseTuple(args, "|Ol", &list, &limit))
+ return NULL;
+
+ return PLy_spi_execute_plan(self, list, limit);
+}
+
+
+static PyObject *
PLy_plan_status(PyObject *self, PyObject *args)
{
if (PyArg_ParseTuple(args, ":status"))
diff --git a/src/pl/plpython/plpy_spi.c b/src/pl/plpython/plpy_spi.c
index 07ab6a087e..c6856ccbac 100644
--- a/src/pl/plpython/plpy_spi.c
+++ b/src/pl/plpython/plpy_spi.c
@@ -30,7 +30,6 @@
static PyObject *PLy_spi_execute_query(char *query, long limit);
-static PyObject *PLy_spi_execute_plan(PyObject *ob, PyObject *list, long limit);
static PyObject *PLy_spi_execute_fetch_result(SPITupleTable *tuptable,
uint64 rows, int status);
static void PLy_spi_exception_set(PyObject *excclass, ErrorData *edata);
@@ -193,7 +192,7 @@ PLy_spi_execute(PyObject *self, PyObject *args)
return NULL;
}
-static PyObject *
+PyObject *
PLy_spi_execute_plan(PyObject *ob, PyObject *list, long limit)
{
volatile int nargs;
diff --git a/src/pl/plpython/plpy_spi.h b/src/pl/plpython/plpy_spi.h
index b0427947ef..817a7584e7 100644
--- a/src/pl/plpython/plpy_spi.h
+++ b/src/pl/plpython/plpy_spi.h
@@ -10,6 +10,7 @@
extern PyObject *PLy_spi_prepare(PyObject *self, PyObject *args);
extern PyObject *PLy_spi_execute(PyObject *self, PyObject *args);
+extern PyObject *PLy_spi_execute_plan(PyObject *ob, PyObject *list, long limit);
typedef struct PLyExceptionEntry
{
diff --git a/src/pl/plpython/sql/plpython_spi.sql b/src/pl/plpython/sql/plpython_spi.sql
index 7427de824b..fcf049cb66 100644
--- a/src/pl/plpython/sql/plpython_spi.sql
+++ b/src/pl/plpython/sql/plpython_spi.sql
@@ -37,6 +37,20 @@ CREATE FUNCTION spi_prepared_plan_test_one(a text) RETURNS text
'
LANGUAGE plpythonu;
+CREATE FUNCTION spi_prepared_plan_test_two(a text) RETURNS text
+ AS
+'if "myplan" not in SD:
+ q = "SELECT count(*) FROM users WHERE lname = $1"
+ SD["myplan"] = plpy.prepare(q, [ "text" ])
+try:
+ rv = SD["myplan"].execute([a])
+ return "there are " + str(rv[0]["count"]) + " " + str(a) + "s"
+except Exception, ex:
+ plpy.error(str(ex))
+return None
+'
+ LANGUAGE plpythonu;
+
CREATE FUNCTION spi_prepared_plan_test_nested(a text) RETURNS text
AS
'if "myplan" not in SD:
@@ -79,7 +93,7 @@ CREATE FUNCTION spi_recursive_sum(a int) RETURNS int
--
select nested_call_one('pass this along');
select spi_prepared_plan_test_one('doe');
-select spi_prepared_plan_test_one('smith');
+select spi_prepared_plan_test_two('smith');
select spi_prepared_plan_test_nested('smith');
SELECT join_sequences(sequences) FROM sequences;
@@ -275,7 +289,7 @@ CREATE FUNCTION cursor_plan() RETURNS SETOF text AS $$
["text"])
for row in plpy.cursor(plan, ["w"]):
yield row['fname']
-for row in plpy.cursor(plan, ["j"]):
+for row in plan.cursor(["j"]):
yield row['fname']
$$ LANGUAGE plpythonu;
--
2.11.1
--
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