10000 Introduce extensible node types. · lisael/postgres@bcac23d · GitHub
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robertmhaasrobertmhaas
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Introduce extensible node types.
An extensible node is always tagged T_Extensible, but the extnodename field identifies it more specifically; it may also include arbitrary private data. Extensible nodes can be copied, tested for equality, serialized, and deserialized, but the core system doesn't know anything about them otherwise. Some extensions may find it useful to include these nodes in fdw_private or custom_private lists in lieu of arm-wrestling their data into a format that the core code can understand. Along the way, so as not to burden the authors of such extensible node types too much, expose the functions for writing serialized tokens, and for serializing and deserializing bitmapsets. KaiGai Kohei, per a design suggested by me. Reviewed by Andres Freund and by me, and further edited by me.
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‎src/backend/nodes/Makefile

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -13,7 +13,7 @@ top_builddir = ../../..
1313
include $(top_builddir)/src/Makefile.global
1414

1515
OBJS = nodeFuncs.o nodes.o list.o bitmapset.o tidbitmap.o \
16-
copyfuncs.o equalfuncs.o makefuncs.o \
16+
copyfuncs.o equalfuncs.o extensible.o makefuncs.o \
1717
outfuncs.o readfuncs.o print.o read.o params.o value.o
1818

1919
include $(top_srcdir)/src/backend/common.mk

‎src/backend/nodes/copyfuncs.c

Lines changed: 29 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -23,6 +23,7 @@
2323
#include "postgres.h"
2424

2525
#include "miscadmin.h"
26+
#include "nodes/extensible.h"
2627
#include "nodes/plannodes.h"
2728
#include "nodes/relation.h"
2829
#include "utils/datum.h"
@@ -4165,6 +4166,27 @@ _copyList(const List *from)
41654166
return new;
41664167
}
41674168

4169+
/* ****************************************************************
4170+
* extensible.h copy functions
4171+
* ****************************************************************
4172+
*/
4173+
static ExtensibleNode *
4174+
_copyExtensibleNode(const ExtensibleNode *from)
4175+
{
4176+
ExtensibleNode *newnode;
4177+
const ExtensibleNodeMethods *methods;
4178+
4179+
methods = GetExtensibleNodeMethods(from->extnodename, false);
4180+
newnode = (ExtensibleNode *) newNode(methods->node_size,
4181+
T_ExtensibleNode);
4182+
COPY_STRING_FIELD(extnodename);
4183+
4184+
/* copy the private fields */
4185+
methods->nodeCopy(newnode, from);
4186+
4187+
return newnode;
4188+
}
4189+
41684190
/* ****************************************************************
41694191
* value.h copy functions
41704192
* ****************************************************************
@@ -4544,6 +4566,13 @@ copyObject(const void *from)
45444566
retval 57AE = list_copy(from);
45454567
break;
45464568

4569+
/*
4570+
* EXTENSIBLE NODES
4571+
*/
4572+
case T_ExtensibleNode:
4573+
retval = _copyExtensibleNode(from);
4574+
break;
4575+
45474576
/*
45484577
* PARSE NODES
45494578
*/

‎src/backend/nodes/equalfuncs.c

Lines changed: 27 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -29,6 +29,7 @@
2929

3030
#include "postgres.h"
3131

32+
#include "nodes/extensible.h"
3233
#include "nodes/relation.h"
3334
#include "utils/datum.h"
3435

@@ -871,6 +872,25 @@ _equalPlaceHolderInfo(const PlaceHolderInfo *a, const PlaceHolderInfo *b)
871872
return true;
872873
}
873874

875+
/*
876+
* Stuff from extensible.h
877+
*/
878+
static bool
879+
_equalExtensibleNode(const ExtensibleNode *a, const ExtensibleNode *b)
880+
{
881+
const ExtensibleNodeMethods *methods;
882+
883+
COMPARE_STRING_FIELD(extnodename);
884+
885+
/* At this point, we know extnodename is the same for both nodes. */
886+
methods = GetExtensibleNodeMethods(a->extnodename, false);
887+
888+
/* compare the private fields */
889+
if (!methods->nodeEqual(a, b))
890+
return false;
891+
892+
return true;
893+
}
874894

875895
/*
876896
* Stuff from parsenodes.h
@@ -2873,6 +2893,13 @@ equal(const void *a, const void *b)
28732893
retval = _equalValue(a, b);
28742894
break;
28752895

2896+
/*
2897+
* EXTENSIBLE NODES
2898+
*/
2899+
case T_ExtensibleNode:
2900+
retval = _equalExtensibleNode(a, b);
2901+
break;
2902+
28762903
/*
28772904
* PARSE NODES
28782905
*/

‎src/backend/nodes/extensible.c

Lines changed: 92 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,92 @@
1+
/*-------------------------------------------------------------------------
2+
*
3+
* extensible.c
4+
* Support for extensible node types
5+
*
6+
* Loadable modules can define what are in effect new types of nodes using
7+
* the routines in this file. All such nodes are flagged T_ExtensibleNode,
8+
* with the extnodename field distinguishing the specific type. Use
9+
* RegisterExtensibleNodeMethods to register a new type of extensible node,
10+
* and GetExtensibleNodeMethods to get information about a previously
11+
* registered type of extensible node.
12+
*
13+
* Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
14+
* Portions Copyright (c) 1994, Regents of the University of California
15+
*
16+
* IDENTIFICATION
17+
* src/backend/nodes/extensible.c
18+
*
19+
*-------------------------------------------------------------------------
20+
*/
21+
#include "postgres.h"
22+
23+
#include "nodes/extensible.h"
24+
#include "utils/hsearch.h"
25+
26+
static HTAB *extensible_node_methods = NULL;
27+
28+
typedef struct
29+
{
30+
char extnodename[EXTNODENAME_MAX_LEN];
31+
const ExtensibleNodeMethods *methods;
32+
} ExtensibleNodeEntry;
33+
34+
/*
35+
* Register a new type of extensible node.
36+
*/
37+
void
38+
RegisterExtensibleNodeMethods(const ExtensibleNodeMethods *methods)
39+
{
40+
ExtensibleNodeEntry *entry;
41+
bool found;
42+
43+
if (extensible_node_methods == NULL)
44+
{
45+
HASHCTL ctl;
46+
47+
memset(&ctl, 0, sizeof(HASHCTL));
48+
ctl.keysize = NAMEDATALEN;
49+
ctl.entrysize = sizeof(ExtensibleNodeEntry);
50+
extensible_node_methods = hash_create("Extensible Node Methods",
51+
100, &ctl, HASH_ELEM);
52+
}
53+
54+
Assert(strlen(methods->extnodename) <= EXTNODENAME_MAX_LEN);
55+
56+
entry = (ExtensibleNodeEntry *) hash_search(extensible_node_methods,
57+
methods->extnodename,
58+
HASH_ENTER, &found);
59+
if (found)
60+
ereport(ERROR,
61+
(errcode(ERRCODE_DUPLICATE_OBJECT),
62+
errmsg("extensible node type \"%s\" already exists",
63+
methods->extnodename)));
64+
65+
entry->methods = methods;
66+
}
67+
68+
/*
69+
* Get the methods for a given type of extensible node.
70+
*/
71+
const ExtensibleNodeMethods *
72+
GetExtensibleNodeMethods(const char *extnodename, bool missing_ok)
73+
{
74+
ExtensibleNodeEntry *entry = NULL;
75+
76+
if (extensible_node_methods != NULL)
77+
entry = (ExtensibleNodeEntry *) hash_search(extensible_node_methods,
78+
extnodename,
79+
HASH_FIND, NULL);
80+
81+
if (!entry)
82+
{
83+
if (missing_ok)
84+
return NULL;
85+
ereport(ERROR,
86+
(errcode(ERRCODE_UNDEFINED_OBJECT),
87+
errmsg("ExtensibleNodeMethods \"%s\" was not registered",
88+
extnodename)));
89+
}
90+
91+
return entry->methods;
92+
}

‎src/backend/nodes/outfuncs.c

Lines changed: 40 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -26,6 +26,7 @@
2626
#include <ctype.h>
2727

2828
#include "lib/stringinfo.h"
29+
#include "nodes/extensible.h"
2930
#include "nodes/plannodes.h"
3031
#include "nodes/relation.h"
3132
#include "utils/datum.h"
@@ -140,6 +141,13 @@ _outToken(StringInfo str, const char *s)
140141
}
141142
}
142143

144+
/* for use by extensions which define extensible nodes */
145+
void
146+
outToken(StringInfo str, const char *s)
147+
{
148+
_outToken(str, s);
149+
}
150+
143151
static void
144152
_outList(StringInfo str, const List *node)
145153
{
@@ -196,6 +204,13 @@ _outBitmapset(StringInfo str, const Bitmapset *bms)
196204
appendStringInfoChar(str, ')');
197205
}
198206

207+
/* for use by extensions which define extensible nodes */
208+
void
209+
outBitmapset(StringInfo str, const Bitmapset *bms)
210+
{
211+
_outBitmapset(str, bms);
212+
}
213+
199214
/*
200215
* Print the value of a Datum given its type.
201216
*/
@@ -2112,6 +2127,27 @@ _outPlannerParamItem(StringInfo str, const PlannerParamItem *node)
21122127
WRITE_INT_FIELD(paramId);
21132128
}
21142129

2130+
/*****************************************************************************
2131+
*
2132+
* Stuff from extensible.h
2133+
*
2134+
*****************************************************************************/
2135+
2136+
static void
2137+
_outExtensibleNode(StringInfo str, const ExtensibleNode *node)
2138+
{
2139+
const ExtensibleNodeMethods *methods;
2140+
2141+
methods = GetExtensibleNodeMethods(node->extnodename, false);
2142+
2143+
WRITE_NODE_TYPE("EXTENSIBLENODE");
2144+
2145+
WRITE_STRING_FIELD(extnodename);
2146+
2147+
/* serialize the private fields */
2148+
methods->nodeOut(str, node);
2149+
}
2150+
21152151
/*****************************************************************************
21162152
*
21172153
* Stuff from parsenodes.h.
@@ -3367,6 +3403,10 @@ _outNode(StringInfo str, const void *obj)
33673403
_outPlannerParamItem(str, obj);
33683404
break;
33693405

3406+
case T_ExtensibleNode:
3407+
_outExtensibleNode(str, obj);
3408+
break;
3409+
33703410
case T_CreateStmt:
33713411
_outCreateStmt(str, obj);
33723412
break;

‎src/backend/nodes/readfuncs.c

Lines changed: 40 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -29,6 +29,7 @@
2929
#include <math.h>
3030

3131
#include "fmgr.h"
32+
#include "nodes/extensible.h"
3233
#include "nodes/parsenodes.h"
3334
#include "nodes/plannodes.h"
3435
#include "nodes/readfuncs.h"
@@ -218,6 +219,14 @@ _readBitmapset(void)
218219
return result;
219220
}
220221

222+
/*
223+
* for use by extensions which define extensible nodes
224+
*/
225+
Bitmapset *
226+
readBitmapset(void)
227+
{
228+
return _readBitmapset();
229+
}
221230

222231
/*
223232
* _readQuery
@@ -2219,6 +2228,35 @@ _readAlternativeSubPlan(void)
22192228
READ_DONE();
22202229
}
22212230

2231+
/*
2232+
* _readExtensibleNode
2233+
*/
2234+
static ExtensibleNode *
2235+
_readExtensibleNode(void)
2236+
{
2237+
const ExtensibleNodeMethods *methods;
2238+
ExtensibleNode *local_node;
2239+
const char *extnodename;
2240+
READ_TEMP_LOCALS();
2241+
2242+
token = pg_strtok(&length); /* skip: extnodename */
2243+
token = pg_strtok(&length); /* get extnodename */
2244+
2245+
extnodename = nullable_string(token, length);
2246+
if (!extnodename)
2247+
elog(ERROR, "extnodename has to be supplied");
2248+
methods = GetExtensibleNodeMethods(extnodename, false);
2249+
2250+
local_node = (ExtensibleNode *) newNode(methods->node_size,
2251+
T_ExtensibleNode);
2252+
local_node->extnodename = extnodename;
2253+
2254+
/* deserialize the private fields */
2255+
methods->nodeRead(local_node);
2256+
2257+
READ_DONE();
2258+
}
2259+
22222260
/*
22232261
* parseNodeString
22242262
*
@@ -2447,6 +2485,8 @@ parseNodeString(void)
24472485
return_value = _readSubPlan();
24482486
else if (MATCH("ALTERNATIVESUBPLAN", 18))
24492487
return_value = _readAlternativeSubPlan();
2488+
else if (MATCH("EXTENSIBLENODE", 14))
2489+
return_value = _readExtensibleNode();
24502490
else
24512491
{
24522492
elog(ERROR, "badly formatted node string \"%.32s\"...", token);

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