Hi,
On Mon, Jan 31, 2022 at 10:05:44PM +0100, Pavel Stehule wrote:
>
> I don't feel good about forcing an alias. relname doesn't ensure
> uniqueness. You can have two views with the same name from different
> schemas. Moreover this field is necessary only when a deparsed query is
> printed, not always.
Yes I agree.
> Isn't possible to compute the correct subquery alias in print time when it
> is missing?
Actually I think that the current code already does everything to generate
unique refnames, it's just that they don't get printed for a query after view
expansions. I modified the patch to simply make sure that an alias is
displayed when it's a subquery and the output using a custom pg_get_query_def
is like that:
# select pg_get_query_def('select * from nsp1.v1');
pg_get_query_def
-------------------------------
SELECT nb +
FROM ( SELECT 1 AS nb) v1;+
(1 row)
# select pg_get_query_def('select * from nsp1.v1, nsp2.v1');
pg_get_query_def
-------------------------------
SELECT v1.nb, +
v1_1.nb +
FROM ( SELECT 1 AS nb) v1,+
( SELECT 1 AS nb) v1_1; +
(1 row)
>From 093cc350c09b3e0a458822da7f541ca602af4ef6 Mon Sep 17 00:00:00 2001
From: Julien Rouhaud <[email protected]>
Date: Sun, 27 Jun 2021 11:39:47 +0800
Subject: [PATCH v3] Add pg_get_query_def() to deparse and print a rewritten
SQL statement.
---
src/backend/utils/adt/ruleutils.c | 75 +++++++++++++++++++++++++++++
src/include/catalog/pg_proc.dat | 3 ++
src/test/regress/expected/rules.out | 26 ++++++++++
src/test/regress/sql/rules.sql | 3 ++
4 files changed, 107 insertions(+)
diff --git a/src/backend/utils/adt/ruleutils.c
b/src/backend/utils/adt/ruleutils.c
index 039b1d2b95..1186438757 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -49,6 +49,8 @@
#include "nodes/nodeFuncs.h"
#include "nodes/pathnodes.h"
#include "optimizer/optimizer.h"
+#include "parser/analyze.h"
+#include "parser/parse_node.h"
#include "parser/parse_agg.h"
#include "parser/parse_func.h"
#include "parser/parse_node.h"
@@ -58,6 +60,7 @@
#include "rewrite/rewriteHandler.h"
#include "rewrite/rewriteManip.h"
#include "rewrite/rewriteSupport.h"
+#include "tcop/tcopprot.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
@@ -493,6 +496,68 @@ static void get_reloptions(StringInfo buf, Datum
reloptions);
#define only_marker(rte) ((rte)->inh ? "" : "ONLY ")
+/* return the query as postgres will rewrite */
+Datum
+pg_get_query_def(PG_FUNCTION_ARGS)
+{
+ char *sql = TextDatumGetCString(PG_GETARG_TEXT_PP(0));
+ List *parsetree_list;
+ List *querytree_list;
+ RawStmt *parsetree;
+ Query *query;
+ bool snapshot_set = false;
+ StringInfoData buf;
+ StringInfoData res;
+ ListCell *lc;
+
+ parsetree_list = pg_parse_query(sql);
+
+ /* only support one statement at a time */
+ if (list_length(parsetree_list) != 1)
+ ereport(ERROR,
+ (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ errmsg("a single statement should be
provided")));
+
+ initStringInfo(&res);
+
+ parsetree = linitial_node(RawStmt, parsetree_list);
+
+ /*
+ * Set up a snapshot if parse analysis/planning will need one.
+ */
+ if (analyze_requires_snapshot(parsetree))
+ {
+ PushActiveSnapshot(GetTransactionSnapshot());
+ snapshot_set = true;
+ }
+
+ querytree_list = pg_analyze_and_rewrite(parsetree, sql,
+ NULL, 0, NULL);
+
+ /* Done with the snapshot used for parsing/planning */
+ if (snapshot_set)
+ PopActiveSnapshot();
+
+ foreach(lc, querytree_list)
+ {
+ query = (Query *) lfirst(lc);
+ initStringInfo(&buf);
+
+ if (query->utilityStmt)
+ appendStringInfo(&res, "%s;\n", sql);
+ else
+ {
+ get_query_def(query, &buf, NIL, NULL,
+ PRETTYFLAG_INDENT,
+ WRAP_COLUMN_DEFAULT, 0);
+
+ appendStringInfo(&res, "%s;\n", buf.data);
+ }
+ }
+ pfree(buf.data);
+
+ PG_RETURN_TEXT_P(string_to_text(res.data));
+}
/* ----------
* pg_get_ruledef - Do it all and return a text
@@ -10989,6 +11054,16 @@ get_from_clause_item(Node *jtnode, Query *query,
deparse_context *context)
if (strcmp(refname, rte->ctename) != 0)
printalias = true;
}
+ else if (rte->rtekind == RTE_SUBQUERY)
+ {
+ /*
+ * For a subquery RTE, always print alias. A
user-specified query
+ * should only be valid if an alias is provided, but
our view
+ * expansion doesn't generate aliases, so a rewritten
query might
+ * not be valid SQL.
+ */
+ printalias = true;
+ }
if (printalias)
appendStringInfo(buf, " %s", quote_identifier(refname));
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 0859dc81ca..a2e5de7967 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -3704,6 +3704,9 @@
proargtypes => 'oid oid', prosrc => 'oidge' },
# System-view support functions
+{ oid => '9246', descr => 'show a query as rewritten',
+ proname => 'pg_get_query_def', provolatile => 'v', prorettype => 'text',
+ proargtypes => 'text', prosrc => 'pg_get_query_def' },
{ oid => '1573', descr => 'source text of a rule',
proname => 'pg_get_ruledef', provolatile => 's', prorettype => 'text',
proargtypes => 'oid', prosrc => 'pg_get_ruledef' },
diff --git a/src/test/regress/expected/rules.out
b/src/test/regress/expected/rules.out
index d652f7b5fb..8a17936a05 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -3120,6 +3120,32 @@ select pg_get_viewdef('shoe'::regclass,0) as prettier;
WHERE sh.slunit = un.un_name;
(1 row)
+-- test pg_get_query_def()
+SELECT pg_get_query_def('SELECT * FROM shoe') as def;
+ def
+--------------------------------------------------------
+ SELECT shoename, +
+ sh_avail, +
+ slcolor, +
+ slminlen, +
+ slminlen_cm, +
+ slmaxlen, +
+ slmaxlen_cm, +
+ slunit +
+ FROM ( SELECT sh.shoename, +
+ sh.sh_avail, +
+ sh.slcolor, +
+ sh.slminlen, +
+ (sh.slminlen * un.un_fact) AS slminlen_cm,+
+ sh.slmaxlen, +
+ (sh.slmaxlen * un.un_fact) AS slmaxlen_cm,+
+ sh.slunit +
+ FROM shoe_data sh, +
+ unit un +
+ WHERE (sh.slunit = un.un_name)) shoe; +
+
+(1 row)
+
--
-- check multi-row VALUES in rules
--
diff --git a/src/test/regress/sql/rules.sql b/src/test/regress/sql/rules.sql
index b732833e63..a10377fcc5 100644
--- a/src/test/regress/sql/rules.sql
+++ b/src/test/regress/sql/rules.sql
@@ -1012,6 +1012,9 @@ select pg_get_viewdef('shoe'::regclass) as unpretty;
select pg_get_viewdef('shoe'::regclass,true) as pretty;
select pg_get_viewdef('shoe'::regclass,0) as prettier;
+-- test pg_get_query_def()
+SELECT pg_get_query_def('SELECT * FROM shoe') as def;
+
--
-- check multi-row VALUES in rules
--
--
2.35.0
