Re: Re: proposal: schema variables

diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index 9c2957eb546..624858db301 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -361,6 +361,9 @@ typedef struct Const
* of the `paramid' field contain the SubLink's subLinkId, and
* the low-order 16 bits contain the column number. (This type
* of Param is also converted to PARAM_EXEC during planning.)
+ *
+ * PARAM_VARIABLE: The parameter is a reference to a session variable
+ * (paramid holds the variable's OID).
*/
typedef enum ParamKind
{
@@ -368,6 +371,7 @@ typedef enum ParamKind
PARAM_EXEC,
PARAM_SUBLINK,
PARAM_MULTIEXPR,
+ PARAM_VARIABLE,
} ParamKind;

typedef struct Param
@@ -380,6 +384,10 @@ typedef struct Param
int32 paramtypmod pg_node_attr(query_jumble_ignore);
/* OID of collation, or InvalidOid if none */
Oid paramcollid pg_node_attr(query_jumble_ignore);
+ /* OID of session variable if it is used */
+ Oid paramvarid;
+ /* true when param is used like base node of assignment indirection */
+ bool parambasenode;
/* token location, or -1 if unknown */
ParseLoc location;
} Param;

comment should be "(paramvarid holds the variable's OID)"
also
+ /* true when param is used like base node of assignment indirection */
is kind of hard to understand.
param->parambasenode = true;
only happens in transformLetStmt so we can change it to
+ /* true when param is used in part of the LET statement.*/

--- a/src/include/executor/execdesc.h
+++ b/src/include/executor/execdesc.h
@@ -51,6 +51,10 @@ typedef struct QueryDesc
/* This field is set by ExecutePlan */
bool already_executed; /* true if previously executed */

+ /* reference to session variables buffer */
+ int num_session_variables;
+ SessionVariableValue *session_variables;
+
/* This is always set NULL by the core system, but plugins can change it */
struct Instrumentation *totaltime; /* total time spent in ExecutorRun */
} QueryDesc;
QueryDesc->num_session_variables and
QueryDesc->session_variables are never used in 0001 and 0002.
it may be used in later patches,
but at least 0001 and 0002, we don't need to change
struct QueryDesc?

contrib/postgres_fdw/deparse.c
There are some cases of "case T_Param:"
do we need to do something on it?
also on src/backend/nodes/queryjumblefuncs.c, one
appearance of "case T_Param:". (but it seems no need change here)

CREATE VARIABLE v1 AS int;
CREATE VARIABLE v2 AS int;
SELECT pg_stat_statements_reset() IS NOT NULL AS t;
select count(*) from tenk1 where unique1 = v1;
select count(*) from tenk1 where unique1 = v2;

should the last two queries be normalized as one query in pg_stat_statements?
if so, then maybe in typedef struct Param
we need change to:
Oid paramvarid pg_node_attr(query_jumble_ignore);
but then
let v1 = v1+1;
let v1 = v2+1;
will be normalized as one query.