Date: Wed, 9 Dec 2020 14:13:29 -0600
From: Justin Pryzby <pryzby@telsasoft.com>
To: pgsql-hackers@postgresql.org
Cc: Jacob Champion <pchampion@vmware.com>,
	Heikki Linnakangas <hlinnaka@iki.fi>,
	Ashwin Agrawal <aagrawal@pivotal.io>,
	Ashutosh Sharma <ashu.coek88@gmail.com>,
	Andres Freund <andres@anarazel.de>,
	Robert Haas <robertmhaas@gmail.com>,
	Amit Kapila <amit.kapila16@gmail.com>,
	Alvaro Herrera <alvherre@alvh.no-ip.org>
Subject: create table like: ACCESS METHOD
Message-ID: <20201209201328.GT24052@telsasoft.com>
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I thought this was a good idea, but didn't hear back when I raised it before.

Failing to preserve access method is arguably a bug, reminiscent of CREATE
STATISTICS and 5564c1181.  But maybe it's not important to backpatch a fix in
this case, since access methods are still evolving.

https://www.postgresql.org/message-id/20190818193533.GL11185@telsasoft.com
On Sun, Aug 18, 2019 at 02:35:33PM -0500, Justin Pryzby wrote:
>  . What do you think about pg_restore --no-tableam; similar to
>    --no-tablespaces, it would allow restoring a table to a different AM:
>    PGOPTIONS='-c default_table_access_method=zedstore' pg_restore --no-tableam ./pg_dump.dat -d postgres
>    Otherwise, the dump says "SET default_table_access_method=heap", which
>    overrides any value from PGOPTIONS and precludes restoring to new AM.
...
>  . it'd be nice if there was an ALTER TABLE SET ACCESS METHOD, to allow
>    migrating data.  Otherwise I think the alternative is:
>       begin; lock t;
>       CREATE TABLE new_t LIKE (t INCLUDING ALL) USING (zedstore);
>       INSERT INTO new_t SELECT * FROM t;
>       for index; do CREATE INDEX...; done
>       DROP t; RENAME new_t (and all its indices). attach/inherit, etc.
>       commit;
>
>  . Speaking of which, I think LIKE needs a new option for ACCESS METHOD, which
>    is otherwise lost.

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 filename="v1-0001-create-table-like-.-including-ACCESS-METHOD.patch"

From 3df7de7f3f2b15c447534bcd7e05c5be79030404 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Sun, 15 Nov 2020 16:54:53 -0600
Subject: [PATCH v1] create table (like .. including ACCESS METHOD)

---
 doc/src/sgml/ref/create_table.sgml              | 12 +++++++++++-
 src/backend/parser/gram.y                       |  3 ++-
 src/backend/parser/parse_utilcmd.c              |  7 +++++++
 src/include/nodes/parsenodes.h                  | 17 +++++++++--------
 src/test/regress/expected/create_table_like.out |  2 +-
 src/test/regress/sql/create_table_like.sql      |  2 +-
 6 files changed, 31 insertions(+), 12 deletions(-)

diff --git a/doc/src/sgml/ref/create_table.sgml b/doc/src/sgml/ref/create_table.sgml
index 569f4c9da7..cb95177e92 100644
--- a/doc/src/sgml/ref/create_table.sgml
+++ b/doc/src/sgml/ref/create_table.sgml
@@ -87,7 +87,7 @@ class="parameter">referential_action</replaceable> ] [ ON UPDATE <replaceable cl
 
 <phrase>and <replaceable class="parameter">like_option</replaceable> is:</phrase>
 
-{ INCLUDING | EXCLUDING } { COMMENTS | CONSTRAINTS | DEFAULTS | GENERATED | IDENTITY | INDEXES | STATISTICS | STORAGE | ALL }
+{ INCLUDING | EXCLUDING } { ACCESS METHOD | COMMENTS | CONSTRAINTS | DEFAULTS | GENERATED | IDENTITY | INDEXES | STATISTICS | STORAGE | ALL }
 
 <phrase>and <replaceable class="parameter">partition_bound_spec</replaceable> is:</phrase>
 
@@ -593,6 +593,16 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
       available options are:
 
       <variablelist>
+       <varlistentry>
+        <term><literal>INCLUDING ACCESS METHOD</literal></term>
+        <listitem>
+         <para>
+          The table's access method will be copied.  By default, the
+          <literal>default_table_access_method</literal> is used.
+         </para>
+        </listitem>
+       </varlistentry>
+
        <varlistentry>
         <term><literal>INCLUDING COMMENTS</literal></term>
         <listitem>
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 8f341ac006..b32861a04e 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -3651,7 +3651,8 @@ TableLikeOptionList:
 		;
 
 TableLikeOption:
-				COMMENTS			{ $$ = CREATE_TABLE_LIKE_COMMENTS; }
+				ACCESS METHOD			{ $$ = CREATE_TABLE_LIKE_ACCESSMETHOD; }
+				| COMMENTS			{ $$ = CREATE_TABLE_LIKE_COMMENTS; }
 				| CONSTRAINTS		{ $$ = CREATE_TABLE_LIKE_CONSTRAINTS; }
 				| DEFAULTS			{ $$ = CREATE_TABLE_LIKE_DEFAULTS; }
 				| IDENTITY_P		{ $$ = CREATE_TABLE_LIKE_IDENTITY; }
diff --git a/src/backend/parser/parse_utilcmd.c b/src/backend/parser/parse_utilcmd.c
index 89ee990599..3507fd4738 100644
--- a/src/backend/parser/parse_utilcmd.c
+++ b/src/backend/parser/parse_utilcmd.c
@@ -96,6 +96,7 @@ typedef struct
 	bool		ispartitioned;	/* true if table is partitioned */
 	PartitionBoundSpec *partbound;	/* transformed FOR VALUES */
 	bool		ofType;			/* true if statement contains OF typename */
+	char		*accessMethod;	/* table access method */
 } CreateStmtContext;
 
 /* State shared by transformCreateSchemaStmt and its subroutines */
@@ -252,6 +253,7 @@ transformCreateStmt(CreateStmt *stmt, const char *queryString)
 	cxt.ispartitioned = stmt->partspec != NULL;
 	cxt.partbound = stmt->partbound;
 	cxt.ofType = (stmt->ofTypename != NULL);
+	cxt.accessMethod = NULL;
 
 	Assert(!stmt->ofTypename || !stmt->inhRelations);	/* grammar enforces */
 
@@ -345,6 +347,8 @@ transformCreateStmt(CreateStmt *stmt, const char *queryString)
 	 */
 	stmt->tableElts = cxt.columns;
 	stmt->constraints = cxt.ckconstraints;
+	if (cxt.accessMethod != NULL)
+		stmt->accessMethod = cxt.accessMethod;
 
 	result = lappend(cxt.blist, stmt);
 	result = list_concat(result, cxt.alist);
@@ -1118,6 +1122,9 @@ transformTableLikeClause(CreateStmtContext *cxt, TableLikeClause *table_like_cla
 		cxt->likeclauses = lappend(cxt->likeclauses, table_like_clause);
 	}
 
+	if (table_like_clause->options & CREATE_TABLE_LIKE_ACCESSMETHOD)
+		cxt->accessMethod = get_am_name(relation->rd_rel->relam);
+
 	/*
 	 * We may copy extended statistics if requested, since the representation
 	 * of CreateStatsStmt doesn't depend on column numbers.
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 48a79a7657..589fd0cab0 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -677,14 +677,15 @@ typedef struct TableLikeClause
 
 typedef enum TableLikeOption
 {
-	CREATE_TABLE_LIKE_COMMENTS = 1 << 0,
-	CREATE_TABLE_LIKE_CONSTRAINTS = 1 << 1,
-	CREATE_TABLE_LIKE_DEFAULTS = 1 << 2,
-	CREATE_TABLE_LIKE_GENERATED = 1 << 3,
-	CREATE_TABLE_LIKE_IDENTITY = 1 << 4,
-	CREATE_TABLE_LIKE_INDEXES = 1 << 5,
-	CREATE_TABLE_LIKE_STATISTICS = 1 << 6,
-	CREATE_TABLE_LIKE_STORAGE = 1 << 7,
+	CREATE_TABLE_LIKE_ACCESSMETHOD = 1 << 0,
+	CREATE_TABLE_LIKE_COMMENTS = 1 << 1,
+	CREATE_TABLE_LIKE_CONSTRAINTS = 1 << 2,
+	CREATE_TABLE_LIKE_DEFAULTS = 1 << 3,
+	CREATE_TABLE_LIKE_GENERATED = 1 << 4,
+	CREATE_TABLE_LIKE_IDENTITY = 1 << 5,
+	CREATE_TABLE_LIKE_INDEXES = 1 << 6,
+	CREATE_TABLE_LIKE_STATISTICS = 1 << 7,
+	CREATE_TABLE_LIKE_STORAGE = 1 << 8,
 	CREATE_TABLE_LIKE_ALL = PG_INT32_MAX
 } TableLikeOption;
 
diff --git a/src/test/regress/expected/create_table_like.out b/src/test/regress/expected/create_table_like.out
index 10d17be23c..cac3c57c76 100644
--- a/src/test/regress/expected/create_table_like.out
+++ b/src/test/regress/expected/create_table_like.out
@@ -490,7 +490,7 @@ Check constraints:
     "noinh_con_copy_a_check" CHECK (a > 0) NO INHERIT
 
 -- fail, as partitioned tables don't allow NO INHERIT constraints
-CREATE TABLE noinh_con_copy1_parted (LIKE noinh_con_copy INCLUDING ALL)
+CREATE TABLE noinh_con_copy1_parted (LIKE noinh_con_copy INCLUDING ALL EXCLUDING ACCESS METHOD)
   PARTITION BY LIST (a);
 ERROR:  cannot add NO INHERIT constraint to partitioned table "noinh_con_copy1_parted"
 DROP TABLE noinh_con_copy, noinh_con_copy1;
diff --git a/src/test/regress/sql/create_table_like.sql b/src/test/regress/sql/create_table_like.sql
index 06b76f949d..eda9f39078 100644
--- a/src/test/regress/sql/create_table_like.sql
+++ b/src/test/regress/sql/create_table_like.sql
@@ -189,7 +189,7 @@ CREATE TABLE noinh_con_copy1 (LIKE noinh_con_copy INCLUDING CONSTRAINTS);
 \d noinh_con_copy1
 
 -- fail, as partitioned tables don't allow NO INHERIT constraints
-CREATE TABLE noinh_con_copy1_parted (LIKE noinh_con_copy INCLUDING ALL)
+CREATE TABLE noinh_con_copy1_parted (LIKE noinh_con_copy INCLUDING ALL EXCLUDING ACCESS METHOD)
   PARTITION BY LIST (a);
 
 DROP TABLE noinh_con_copy, noinh_con_copy1;
-- 
2.17.0


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