Allow generalized expression syntax for partition bounds

Previously, only literals were allowed.  This change allows general
expressions, including functions calls, which are evaluated at the
time the DDL command is executed.

Besides offering some more functionality, it simplifies the parser
structures and removes some inconsistencies in how the literals were
handled.

Author: Kyotaro Horiguchi, Tom Lane, Amit Langote
Reviewed-by: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
Discussion: https://www.postgresql.org/message-id/flat/9f88b5e0-6da2-5227-20d0-0d7012beaa1c@lab.ntt.co.jp/

Author: petere

doc/src/sgml/ref/alter_table.sgml

@@ -86,9 +86,9 @@ ALTER TABLE [ IF EXISTS ] <replaceable class="parameter">name</replaceable>
 
 <phrase>and <replaceable class="parameter">partition_bound_spec</replaceable> is:</phrase>
 
-IN ( { <replaceable class="parameter">numeric_literal</replaceable> | <replaceable class="parameter">string_literal</replaceable> | TRUE | FALSE | NULL } [, ...] ) |
-FROM ( { <replaceable class="parameter">numeric_literal</replaceable> | <replaceable class="parameter">string_literal</replaceable> | TRUE | FALSE | MINVALUE | MAXVALUE } [, ...] )
-  TO ( { <replaceable class="parameter">numeric_literal</replaceable> | <replaceable class="parameter">string_literal</replaceable> | TRUE | FALSE | MINVALUE | MAXVALUE } [, ...] ) |
+IN ( <replaceable class="parameter">partition_bound_expr</replaceable> [, ...] ) |
+FROM ( { <replaceable class="parameter">partition_bound_expr</replaceable> | MINVALUE | MAXVALUE } [, ...] )
+  TO ( { <replaceable class="parameter">partition_bound_expr</replaceable> | MINVALUE | MAXVALUE } [, ...] ) |
 WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REMAINDER <replaceable class="parameter">numeric_literal</replaceable> )
 
 <phrase>and <replaceable class="parameter">column_constraint</replaceable> is:</phrase>

doc/src/sgml/ref/create_table.sgml

@@ -87,9 +87,9 @@ class="parameter">referential_action</replaceable> ] [ ON UPDATE <replaceable cl
 
 <phrase>and <replaceable class="parameter">partition_bound_spec</replaceable> is:</phrase>
 
-IN ( { <replaceable class="parameter">numeric_literal</replaceable> | <replaceable class="parameter">string_literal</replaceable> | TRUE | FALSE | NULL } [, ...] ) |
-FROM ( { <replaceable class="parameter">numeric_literal</replaceable> | <replaceable class="parameter">string_literal</replaceable> | TRUE | FALSE | MINVALUE | MAXVALUE } [, ...] )
-  TO ( { <replaceable class="parameter">numeric_literal</replaceable> | <replaceable class="parameter">string_literal</replaceable> | TRUE | FALSE | MINVALUE | MAXVALUE } [, ...] ) |
+IN ( <replaceable class="parameter">partition_bound_expr</replaceable> [, ...] ) |
+FROM ( { <replaceable class="parameter">partition_bound_expr</replaceable> | MINVALUE | MAXVALUE } [, ...] )
+  TO ( { <replaceable class="parameter">partition_bound_expr</replaceable> | MINVALUE | MAXVALUE } [, ...] ) |
 WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REMAINDER <replaceable class="parameter">numeric_literal</replaceable> )
 
 <phrase><replaceable class="parameter">index_parameters</replaceable> in <literal>UNIQUE</literal>, <literal>PRIMARY KEY</literal>, and <literal>EXCLUDE</literal> constraints are:</phrase>
@@ -413,12 +413,13 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
      </para>
 
      <para>
-      Each of the values specified in
-      the <replaceable class="parameter">partition_bound_spec</replaceable> is
-      a literal, <literal>NULL</literal>, <literal>MINVALUE</literal>, or
-      <literal>MAXVALUE</literal>.  Each literal value must be either a
-      numeric constant that is coercible to the corresponding partition key
-      column's type, or a string literal that is valid input for that type.
+      <replaceable class="parameter">partition_bound_expr</replaceable> is
+      any variable-free expression (subqueries, window functions, aggregate
+      functions, and set-returning functions are not allowed).  Its data type
+      must match the data type of the corresponding partition key column.
+      The expression is evaluated once at table creation time, so it can
+      even contain volatile expressions such as
+      <literal><function>CURRENT_TIMESTAMP</function></literal>.
      </para>
 
      <para>

src/backend/commands/tablecmds.c

@@ -830,6 +830,7 @@ DefineRelation(CreateStmt *stmt, char relkind, Oid ownerId,
 					defaultPartOid;
 		Relation	parent,
 					defaultRel = NULL;
+		RangeTblEntry *rte;
 
 		/* Already have strong enough lock on the parent */
 		parent = table_open(parentId, NoLock);
@@ -872,6 +873,14 @@ DefineRelation(CreateStmt *stmt, char relkind, Oid ownerId,
 		pstate = make_parsestate(NULL);
 		pstate->p_sourcetext = queryString;
 
+		/*
+		 * Add an RTE containing this relation, so that transformExpr called
+		 * on partition bound expressions is able to report errors using a
+		 * proper context.
+		 */
+		rte = addRangeTableEntryForRelation(pstate, rel, AccessShareLock,
+											NULL, false, false);
+		addRTEtoQuery(pstate, rte, false, true, true);
 		bound = transformPartitionBound(pstate, parent, stmt->partbound);
 
 		/*

src/backend/optimizer/util/clauses.c

@@ -150,8 +150,6 @@ static Node *substitute_actual_parameters(Node *expr, int nargs, List *args,
 static Node *substitute_actual_parameters_mutator(Node *node,
 									 substitute_actual_parameters_context *context);
 static void sql_inline_error_callback(void *arg);
-static Expr *evaluate_expr(Expr *expr, Oid result_type, int32 result_typmod,
-			  Oid result_collation);
 static Query *substitute_actual_srf_parameters(Query *expr,
 								 int nargs, List *args);
 static Node *substitute_actual_srf_parameters_mutator(Node *node,
@@ -5045,7 +5043,7 @@ sql_inline_error_callback(void *arg)
  * We use the executor's routine ExecEvalExpr() to avoid duplication of
  * code and ensure we get the same result as the executor would get.
  */
-static Expr *
+Expr *
 evaluate_expr(Expr *expr, Oid result_type, int32 result_typmod,
 			  Oid result_collation)
 {

src/backend/parser/gram.y

@@ -581,8 +581,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <partelem>	part_elem
 %type <list>		part_params
 %type <partboundspec> PartitionBoundSpec
-%type <node>		partbound_datum PartitionRangeDatum
-%type <list>		hash_partbound partbound_datum_list range_datum_list
+%type <list>		hash_partbound
 %type <defelt>		hash_partbound_elem
 
 /*
@@ -2731,7 +2730,7 @@ PartitionBoundSpec:
 				}
 
 			/* a LIST partition */
-			| FOR VALUES IN_P '(' partbound_datum_list ')'
+			| FOR VALUES IN_P '(' expr_list ')'
 				{
 					PartitionBoundSpec *n = makeNode(PartitionBoundSpec);
 
@@ -2744,7 +2743,7 @@ PartitionBoundSpec:
 				}
 
 			/* a RANGE partition */
-			| FOR VALUES FROM '(' range_datum_list ')' TO '(' range_datum_list ')'
+			| FOR VALUES FROM '(' expr_list ')' TO '(' expr_list ')'
 				{
 					PartitionBoundSpec *n = makeNode(PartitionBoundSpec);
 
@@ -2787,59 +2786,6 @@ hash_partbound:
 			}
 		;
 
-partbound_datum:
-			Sconst			{ $$ = makeStringConst($1, @1); }
-			| NumericOnly	{ $$ = makeAConst($1, @1); }
-			| TRUE_P		{ $$ = makeStringConst(pstrdup("true"), @1); }
-			| FALSE_P		{ $$ = makeStringConst(pstrdup("false"), @1); }
-			| NULL_P		{ $$ = makeNullAConst(@1); }
-		;
-
-partbound_datum_list:
-			partbound_datum						{ $$ = list_make1($1); }
-			| partbound_datum_list ',' partbound_datum
-												{ $$ = lappend($1, $3); }
-		;
-
-range_datum_list:
-			PartitionRangeDatum					{ $$ = list_make1($1); }
-			| range_datum_list ',' PartitionRangeDatum
-												{ $$ = lappend($1, $3); }
-		;
-
-PartitionRangeDatum:
-			MINVALUE
-				{
-					PartitionRangeDatum *n = makeNode(PartitionRangeDatum);
-
-					n->kind = PARTITION_RANGE_DATUM_MINVALUE;
-					n->value = NULL;
-					n->location = @1;
-
-					$$ = (Node *) n;
-				}
-			| MAXVALUE
-				{
-					PartitionRangeDatum *n = makeNode(PartitionRangeDatum);
-
-					n->kind = PARTITION_RANGE_DATUM_MAXVALUE;
-					n->value = NULL;
-					n->location = @1;
-
-					$$ = (Node *) n;
-				}
-			| partbound_datum
-				{
-					PartitionRangeDatum *n = makeNode(PartitionRangeDatum);
-
-					n->kind = PARTITION_RANGE_DATUM_VALUE;
-					n->value = $1;
-					n->location = @1;
-
-					$$ = (Node *) n;
-				}
-		;
-
 /*****************************************************************************
  *
  *	ALTER TYPE

src/backend/parser/parse_agg.c

@@ -506,6 +506,13 @@ check_agglevels_and_constraints(ParseState *pstate, Node *expr)
 			else
 				err = _("grouping operations are not allowed in trigger WHEN conditions");
 
+			break;
+		case EXPR_KIND_PARTITION_BOUND:
+			if (isAgg)
+				err = _("aggregate functions are not allowed in partition bound");
+			else
+				err = _("grouping operations are not allowed in partition bound");
+
 			break;
 		case EXPR_KIND_PARTITION_EXPRESSION:
 			if (isAgg)
@@ -904,6 +911,9 @@ transformWindowFuncCall(ParseState *pstate, WindowFunc *wfunc,
 		case EXPR_KIND_TRIGGER_WHEN:
 			err = _("window functions are not allowed in trigger WHEN conditions");
 			break;
+		case EXPR_KIND_PARTITION_BOUND:
+			err = _("window functions are not allowed in partition bound");
+			break;
 		case EXPR_KIND_PARTITION_EXPRESSION:
 			err = _("window functions are not allowed in partition key expressions");
 			break;

src/backend/parser/parse_expr.c

@@ -1843,6 +1843,9 @@ transformSubLink(ParseState *pstate, SubLink *sublink)
 		case EXPR_KIND_TRIGGER_WHEN:
 			err = _("cannot use subquery in trigger WHEN condition");
 			break;
+		case EXPR_KIND_PARTITION_BOUND:
+			err = _("cannot use subquery in partition bound");
+			break;
 		case EXPR_KIND_PARTITION_EXPRESSION:
 			err = _("cannot use subquery in partition key expression");
 			break;
@@ -3474,6 +3477,8 @@ ParseExprKindName(ParseExprKind exprKind)
 			return "EXECUTE";
 		case EXPR_KIND_TRIGGER_WHEN:
 			return "WHEN";
+		case EXPR_KIND_PARTITION_BOUND:
+			return "partition bound";
 		case EXPR_KIND_PARTITION_EXPRESSION:
 			return "PARTITION BY";
 		case EXPR_KIND_CALL_ARGUMENT:

src/backend/parser/parse_func.c

@@ -2364,6 +2364,9 @@ check_srf_call_placement(ParseState *pstate, Node *last_srf, int location)
 		case EXPR_KIND_TRIGGER_WHEN:
 			err = _("set-returning functions are not allowed in trigger WHEN conditions");
 			break;
+		case EXPR_KIND_PARTITION_BOUND:
+			err = _("set-returning functions are not allowed in partition bound");
+			break;
 		case EXPR_KIND_PARTITION_EXPRESSION:
 			err = _("set-returning functions are not allowed in partition key expressions");
 			break;