Implement a psql command "\ef" to edit the definition of a function.

In support of that, create a backend function pg_get_functiondef().
The psql command is functional but maybe a bit rough around the edges...

Abhijit Menon-Sen

doc/src/sgml/func.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.443 2008/07/21 04:47:00 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.444 2008/09/06 00:01:21 tgl Exp $ -->
 
  <chapter id="functions">
   <title>Functions and Operators</title>
@@ -11562,6 +11562,10 @@ SELECT pg_type_is_visible('myschema.widget'::regtype);
     <primary>pg_get_ruledef</primary>
    </indexterm>
 
+   <indexterm>
+    <primary>pg_get_functiondef</primary>
+   </indexterm>
+
    <indexterm>
     <primary>pg_get_function_arguments</primary>
    </indexterm>
@@ -11643,6 +11647,11 @@ SELECT pg_type_is_visible('myschema.widget'::regtype);
        <entry>decompile internal form of an expression, assuming that any Vars
        in it refer to the relation indicated by the second parameter</entry>
       </row>
+      <row>
+       <entry><literal><function>pg_get_functiondef</function>(<parameter>func_oid</parameter>)</literal></entry>
+       <entry><type>text</type></entry>
+       <entry>get definition of a function</entry>
+      </row>
       <row>
        <entry><literal><function>pg_get_function_arguments</function>(<parameter>func_oid</parameter>)</literal></entry>
        <entry><type>text</type></entry>
@@ -11756,6 +11765,8 @@ SELECT pg_type_is_visible('myschema.widget'::regtype);
   </para>
 
   <para>
+   <function>pg_get_functiondef</> returns a complete
+   <command>CREATE OR REPLACE FUNCTION</> statement for a function.
    <function>pg_get_function_arguments</function> returns the argument list
    of a function, in the form it would need to appear in within
    <command>CREATE FUNCTION</>.

doc/src/sgml/ref/psql-ref.sgml

 <!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/psql-ref.sgml,v 1.209 2008/07/03 03:37:16 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/psql-ref.sgml,v 1.210 2008/09/06 00:01:21 tgl Exp $
 PostgreSQL documentation
 -->
 
@@ -1195,6 +1195,29 @@ testdb=&gt;
       </varlistentry>
 
 
+      <varlistentry>
+        <term><literal>\ef <replaceable class="parameter">function_description</replaceable> </literal></term>
+
+        <listitem>
+        <para>
+         This command fetches and edits the definition of the named function,
+         in the form of a <command>CREATE OR REPLACE FUNCTION</> command.
+         Editing is done in the same way as for <literal>\e</>.
+         After the editor exits, the updated command waits in the query buffer;
+         type semicolon or <literal>\g</> to send it, or <literal>\r</>
+         to cancel.
+        </para>
+
+        <para>
+         The target function can be specified by name alone, or by name
+         and arguments, for example <literal>foo(integer, text)</>.
+         The argument types must be given if there is more
+         than one function of the same name.
+        </para>
+        </listitem>
+      </varlistentry>
+
+
       <varlistentry>
         <term><literal>\echo <replaceable class="parameter">text</replaceable> [ ... ]</literal></term>
         <listitem>

src/bin/psql/command.c

@@ -3,7 +3,7 @@
  *
  * Copyright (c) 2000-2008, PostgreSQL Global Development Group
  *
- * $PostgreSQL: pgsql/src/bin/psql/command.c,v 1.193 2008/08/16 00:16:56 momjian Exp $
+ * $PostgreSQL: pgsql/src/bin/psql/command.c,v 1.194 2008/09/06 00:01:24 tgl Exp $
  */
 #include "postgres_fe.h"
 #include "command.h"
@@ -56,9 +56,12 @@
 static backslashResult exec_command(const char *cmd,
 			 PsqlScanState scan_state,
 			 PQExpBuffer query_buf);
-static bool do_edit(const char *filename_arg, PQExpBuffer query_buf);
+static bool do_edit(const char *filename_arg, PQExpBuffer query_buf,
+					bool *edited);
 static bool do_connect(char *dbname, char *user, char *host, char *port);
 static bool do_shell(const char *command);
+static bool lookup_function_oid(PGconn *conn, const char *desc, Oid *foid);
+static bool get_create_function_cmd(PGconn *conn, Oid oid, PQExpBuffer buf);
 
 #ifdef USE_SSL
 static void printSSLInfo(void);
@@ -444,11 +447,64 @@ exec_command(const char *cmd,
 			expand_tilde(&fname);
 			if (fname)
 				canonicalize_path(fname);
-			status = do_edit(fname, query_buf) ? PSQL_CMD_NEWEDIT : PSQL_CMD_ERROR;
+			if (do_edit(fname, query_buf, NULL))
+				status = PSQL_CMD_NEWEDIT;
+			else
+				status = PSQL_CMD_ERROR;
 			free(fname);
 		}
 	}
 
+	/*
+	 * \ef -- edit the named function in $EDITOR.
+	 */
+	else if (strcmp(cmd, "ef") == 0)
+	{
+		char   *func;
+		Oid		foid;
+
+		func = psql_scan_slash_option(scan_state, OT_WHOLE_LINE, NULL, true);
+		if (!func)
+		{
+			psql_error("no function name specified\n");
+			status = PSQL_CMD_ERROR;
+		}
+		else if (!lookup_function_oid(pset.db, func, &foid))
+		{
+			psql_error(PQerrorMessage(pset.db));
+			status = PSQL_CMD_ERROR;
+		}
+		else if (!query_buf)
+		{
+			psql_error("no query buffer\n");
+			status = PSQL_CMD_ERROR;
+		}
+		else if (!get_create_function_cmd(pset.db, foid, query_buf))
+		{
+			psql_error(PQerrorMessage(pset.db));
+			status = PSQL_CMD_ERROR;
+		}
+		else
+		{
+			bool edited = false;
+
+			if (!do_edit(0, query_buf, &edited))
+			{
+				status = PSQL_CMD_ERROR;
+			}
+			else if (!edited)
+			{
+				printf("No changes\n");
+			}
+			else
+			{
+				status = PSQL_CMD_NEWEDIT;
+			}
+		}
+		if (func)
+			free(func);
+	}
+
 	/* \echo and \qecho */
 	else if (strcmp(cmd, "echo") == 0 || strcmp(cmd, "qecho") == 0)
 	{
@@ -1410,7 +1466,7 @@ editFile(const char *fname)
 
 /* call this one */
 static bool
-do_edit(const char *filename_arg, PQExpBuffer query_buf)
+do_edit(const char *filename_arg, PQExpBuffer query_buf, bool *edited)
 {
 	char		fnametmp[MAXPGPATH];
 	FILE	   *stream = NULL;
@@ -1532,10 +1588,13 @@ do_edit(const char *filename_arg, PQExpBuffer query_buf)
 				psql_error("%s: %s\n", fname, strerror(errno));
 				error = true;
 			}
+			else if (edited)
+			{
+				*edited = true;
+			}
 
 			fclose(stream);
 		}
-
 	}
 
 	/* remove temp file */
@@ -1912,3 +1971,66 @@ do_shell(const char *command)
 	}
 	return true;
 }
+
+/*
+ * This function takes a function description, e.g. "x" or "x(int)", and
+ * issues a query on the given connection to retrieve the function's OID
+ * using a cast to regproc or regprocedure (as appropriate). The result,
+ * if there is one, is returned at *foid.  Note that we'll fail if the
+ * function doesn't exist OR if there are multiple matching candidates
+ * OR if there's something syntactically wrong with the function description;
+ * unfortunately it can be hard to tell the difference.
+ */
+static bool
+lookup_function_oid(PGconn *conn, const char *desc, Oid *foid)
+{
+	bool		result = true;
+	PQExpBuffer query;
+	PGresult *res;
+
+	query = createPQExpBuffer();
+	printfPQExpBuffer(query, "SELECT ");
+	appendStringLiteralConn(query, desc, conn);
+	appendPQExpBuffer(query, "::pg_catalog.%s::pg_catalog.oid",
+					  strchr(desc, '(') ? "regprocedure" : "regproc");
+
+	res = PQexec(conn, query->data);
+	if (PQresultStatus(res) == PGRES_TUPLES_OK && PQntuples(res) == 1)
+		*foid = atooid(PQgetvalue(res, 0, 0));
+	else
+		result = false;
+
+	PQclear(res);
+	destroyPQExpBuffer(query);
+
+	return result;
+}
+
+/*
+ * Fetches the "CREATE OR REPLACE FUNCTION ..." command that describes the
+ * function with the given OID.  If successful, the result is stored in buf.
+ */
+static bool
+get_create_function_cmd(PGconn *conn, Oid oid, PQExpBuffer buf)
+{
+	bool		result = true;
+	PQExpBuffer query;
+	PGresult *res;
+
+	query = createPQExpBuffer();
+	printfPQExpBuffer(query, "SELECT pg_catalog.pg_get_functiondef(%u)", oid);
+
+	res = PQexec(conn, query->data);
+	if (PQresultStatus(res) == PGRES_TUPLES_OK && PQntuples(res) == 1)
+	{
+		resetPQExpBuffer(buf);
+		appendPQExpBufferStr(buf, PQgetvalue(res, 0, 0));
+	}
+	else
+		result = false;
+
+	PQclear(res);
+	destroyPQExpBuffer(query);
+
+	return result;
+}

src/include/catalog/catversion.h

@@ -37,7 +37,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.482 2008/09/01 20:42:45 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.483 2008/09/06 00:01:24 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	200808311
+#define CATALOG_VERSION_NO	200809051
 
 #endif

src/include/catalog/pg_proc.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/catalog/pg_proc.h,v 1.512 2008/08/25 11:18:43 mha Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/pg_proc.h,v 1.513 2008/09/06 00:01:24 tgl Exp $
  *
  * NOTES
  *	  The script catalog/genbki.sh reads this file and generates .bki
@@ -2292,6 +2292,8 @@ DATA(insert OID = 1716 (  pg_get_expr		   PGNSP PGUID 12 1 0 0 f f t f s 2 25 "2
 DESCR("deparse an encoded expression");
 DATA(insert OID = 1665 (  pg_get_serial_sequence	PGNSP PGUID 12 1 0 0 f f t f s 2 25 "25 25" _null_ _null_ _null_	pg_get_serial_sequence _null_ _null_ _null_ ));
 DESCR("name of sequence for a serial column");
+DATA(insert OID = 2098 (  pg_get_functiondef	PGNSP PGUID 12 1 0 0 f f t f s 1 25 "26" _null_ _null_ _null_	pg_get_functiondef _null_ _null_ _null_ ));
+DESCR("definition of a function");
 DATA(insert OID = 2162 (  pg_get_function_arguments	   PGNSP PGUID 12 1 0 0 f f t f s 1 25 "26" _null_ _null_ _null_	pg_get_function_arguments _null_ _null_ _null_ ));
 DESCR("argument list of a function");
 DATA(insert OID = 2165 (  pg_get_function_result	   PGNSP PGUID 12 1 0 0 f f t f s 1 25 "26" _null_ _null_ _null_	pg_get_function_result _null_ _null_ _null_ ));

src/include/utils/builtins.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/utils/builtins.h,v 1.319 2008/07/18 03:32:53 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/utils/builtins.h,v 1.320 2008/09/06 00:01:25 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -551,6 +551,7 @@ extern Datum pg_get_expr(PG_FUNCTION_ARGS);
 extern Datum pg_get_expr_ext(PG_FUNCTION_ARGS);
 extern Datum pg_get_userbyid(PG_FUNCTION_ARGS);
 extern Datum pg_get_serial_sequence(PG_FUNCTION_ARGS);
+extern Datum pg_get_functiondef(PG_FUNCTION_ARGS);
 extern Datum pg_get_function_arguments(PG_FUNCTION_ARGS);
 extern Datum pg_get_function_result(PG_FUNCTION_ARGS);
 extern char *deparse_expression(Node *expr, List *dpcontext,