From d2fdc5ca9f6d5ac76ee39fc6b7db626345a6c84c Mon Sep 17 00:00:00 2001
From: Daniele Varrazzo <daniele.varrazzo@gmail.com>
Date: Thu, 2 Feb 2017 16:02:33 +0000
Subject: [PATCH] Better docs for fast executemany functions.

Issue #502.
---
 lib/extras.py | 46 +++++++++++++++++++++++++++++++---------------
 1 file changed, 31 insertions(+), 15 deletions(-)

diff --git a/lib/extras.py b/lib/extras.py
index 2d264025..1aad3d1d 100644
--- a/lib/extras.py
+++ b/lib/extras.py
@@ -1168,11 +1168,15 @@ def execute_batch(cur, sql, argslist, page_size=100):
     Execute *sql* several times, against all parameters set (sequences or
     mappings) found in *argslist*.
 
-    The function is semantically similar to `~cursor.executemany()`, but has a
-    different implementation: Psycopg will join the statements into fewer
-    multi-statement commands, reducing the number of server roundtrips,
-    resulting in better performances. Every command contains at most
-    *page_size* statements.
+    The function is semantically similar to
+
+    .. parsed-literal::
+
+        *cur*\.\ `~cursor.executemany`\ (\ *sql*\ , *argslist*\ )
+
+    but has a different implementation: Psycopg will join the statements into
+    fewer multi-statement commands, each one containing at most *page_size*
+    statements, resulting in a reduced number of server roundtrips.
 
     """
     for page in _paginate(argslist, page_size=page_size):
@@ -1183,19 +1187,31 @@ def execute_batch(cur, sql, argslist, page_size=100):
 def execute_values(cur, sql, argslist, template=None, page_size=100):
     '''Execute a statement using :sql:`VALUES` with a sequence of parameters.
 
-    *sql* must contain a single ``%s`` placeholder, which will be replaced by a
-    `VALUES list`__.  Every statement will contain at most *page_size* sets of
-    arguments.
+    :param cur: the cursor to use to execute the query.
+
+    :param sql: the query to execute. It must contain a single ``%s``
+        placeholder, which will be replaced by a `VALUES list`__.
+        Example: ``"INSERT INTO mytable (id, f1, f2) VALUES %s"``.
+
+    :param argslist: sequence of sequences or dictionaries with the arguments
+        to send to the query. The type and content must be consistent with
+        *template*.
+
+    :param template: the snippet to merge to every item in *argslist* to
+        compose the query. If *argslist* items are sequences it should contain
+        positional placeholders (e.g. ``"(%s, %s, %s)"``, or ``"(%s, %s, 42)``"
+        if there are constants value...); If *argslist* is items are mapping
+        it should contain named placeholders (e.g. ``"(%(id)s, %(f1)s, 42)"``).
+        If not specified, assume the arguments are sequence and use a simple
+        positional template (i.e.  ``(%s, %s, ...)``), with the number of
+        placeholders sniffed by the first element in *argslist*.
+
+    :param page_size: maximum number of *argslist* items to include in every
+        statement. If there are more items the function will execute more than
+        one statement.
 
     .. __: https://www.postgresql.org/docs/current/static/queries-values.html
 
-    *template* is the part merged to the arguments, so it should be compatible
-    with the content of *argslist* (it should contain the right number of
-    arguments if *argslist* is a sequence of sequences, or compatible names if
-    *argslist* is a sequence of mappings). If not specified, assume the
-    arguments are sequence and use a simple positional template (i.e.
-    ``(%s, %s, ...)``).
-
     While :sql:`INSERT` is an obvious candidate for this function it is
     possible to use it with other statements, for example::