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Commite651bcf

Browse files
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Add xmlpath() to evaluate XPath expressions, with namespaces support.
Nikolay Samokhvalov
1 parent4f896da commite651bcf

File tree

6 files changed

+309
-4
lines changed

6 files changed

+309
-4
lines changed

‎src/backend/utils/adt/xml.c

Lines changed: 249 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $PostgreSQL: pgsql/src/backend/utils/adt/xml.c,v 1.35 2007/03/15 23:12:06 tgl Exp $
10+
* $PostgreSQL: pgsql/src/backend/utils/adt/xml.c,v 1.36 2007/03/22 20:14:58 momjian Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -47,6 +47,8 @@
4747
#include<libxml/uri.h>
4848
#include<libxml/xmlerror.h>
4949
#include<libxml/xmlwriter.h>
50+
#include<libxml/xpath.h>
51+
#include<libxml/xpathInternals.h>
5052
#endif/* USE_LIBXML */
5153

5254
#include"catalog/namespace.h"
@@ -67,6 +69,7 @@
6769
#include"utils/datetime.h"
6870
#include"utils/lsyscache.h"
6971
#include"utils/memutils.h"
72+
#include"access/tupmacs.h"
7073
#include"utils/xml.h"
7174

7275

@@ -88,6 +91,7 @@ static xmlChar *xml_text2xmlChar(text *in);
8891
staticintparse_xml_decl(constxmlChar*str,size_t*lenp,xmlChar**version,xmlChar**encoding,int*standalone);
8992
staticboolprint_xml_decl(StringInfobuf,constxmlChar*version,pg_encencoding,intstandalone);
9093
staticxmlDocPtrxml_parse(text*data,XmlOptionTypexmloption_arg,boolpreserve_whitespace,xmlChar*encoding);
94+
statictext*xml_xmlnodetotext(xmlNodePtrcur);
9195

9296
#endif/* USE_LIBXML */
9397

@@ -1463,7 +1467,6 @@ map_xml_name_to_sql_identifier(char *name)
14631467
returnbuf.data;
14641468
}
14651469

1466-
14671470
/*
14681471
* Map SQL value to XML value; see SQL/XML:2003 section 9.16.
14691472
*/
@@ -2403,3 +2406,247 @@ SPI_sql_row_to_xmlelement(int rownum, StringInfo result, char *tablename, bool n
24032406
else
24042407
appendStringInfoString(result,"</row>\n\n");
24052408
}
2409+
2410+
2411+
/*
2412+
* XPath related functions
2413+
*/
2414+
2415+
#ifdefUSE_LIBXML
2416+
/*
2417+
* Convert XML node to text (return value only, it's not dumping)
2418+
*/
2419+
text*
2420+
xml_xmlnodetotext(xmlNodePtrcur)
2421+
{
2422+
xmlChar*str;
2423+
text*result;
2424+
size_tlen;
2425+
2426+
str=xmlXPathCastNodeToString(cur);
2427+
len=strlen((char*)str);
2428+
result= (text*)palloc(len+VARHDRSZ);
2429+
SET_VARSIZE(result,len+VARHDRSZ);
2430+
memcpy(VARDATA(result),str,len);
2431+
2432+
returnresult;
2433+
}
2434+
#endif
2435+
2436+
/*
2437+
* Evaluate XPath expression and return array of XML values.
2438+
* As we have no support of XQuery sequences yet, this functions seems
2439+
* to be the most useful one (array of XML functions plays a role of
2440+
* some kind of substritution for XQuery sequences).
2441+
2442+
* Workaround here: we parse XML data in different way to allow XPath for
2443+
* fragments (see "XPath for fragment" TODO comment inside).
2444+
*/
2445+
Datum
2446+
xmlpath(PG_FUNCTION_ARGS)
2447+
{
2448+
#ifdefUSE_LIBXML
2449+
ArrayBuildState*astate=NULL;
2450+
xmlParserCtxtPtrctxt=NULL;
2451+
xmlDocPtrdoc=NULL;
2452+
xmlXPathContextPtrxpathctx=NULL;
2453+
xmlXPathCompExprPtrxpathcomp=NULL;
2454+
xmlXPathObjectPtrxpathobj=NULL;
2455+
int32len,xpath_len;
2456+
xmlChar*string,*xpath_expr;
2457+
boolres_is_null= FALSE;
2458+
inti;
2459+
xmltype*data;
2460+
text*xpath_expr_text;
2461+
ArrayType*namespaces;
2462+
int*dims,ndims,ns_count=0,bitmask=1;
2463+
char*ptr;
2464+
bits8*bitmap;
2465+
char**ns_names=NULL,**ns_uris=NULL;
2466+
int16typlen;
2467+
booltypbyval;
2468+
chartypalign;
2469+
2470+
/* the function is not strict, we must check first two args */
2471+
if (PG_ARGISNULL(0)||PG_ARGISNULL(1))
2472+
PG_RETURN_NULL();
2473+
2474+
xpath_expr_text=PG_GETARG_TEXT_P(0);
2475+
data=PG_GETARG_XML_P(1);
2476+
2477+
/* Namespace mappings passed as text[].
2478+
* Assume that 2-dimensional array has been passed,
2479+
* the 1st subarray is array of names, the 2nd -- array of URIs,
2480+
* example: ARRAY[ARRAY['myns', 'myns2'], ARRAY['http://example.com', 'http://example2.com']].
2481+
*/
2482+
if (!PG_ARGISNULL(2))
2483+
{
2484+
namespaces=PG_GETARG_ARRAYTYPE_P(2);
2485+
ndims=ARR_NDIM(namespaces);
2486+
dims=ARR_DIMS(namespaces);
2487+
2488+
/* Sanity check */
2489+
if (ndims!=2)
2490+
ereport(ERROR, (errmsg("invalid array passed for namespace mappings"),
2491+
errdetail("Only 2-dimensional array may be used for namespace mappings.")));
2492+
2493+
Assert(ARR_ELEMTYPE(namespaces)==TEXTOID);
2494+
2495+
ns_count=ArrayGetNItems(ndims,dims) /2;
2496+
get_typlenbyvalalign(ARR_ELEMTYPE(namespaces),
2497+
&typlen,&typbyval,&typalign);
2498+
ns_names= (char**)palloc(ns_count*sizeof(char*));
2499+
ns_uris= (char**)palloc(ns_count*sizeof(char*));
2500+
ptr=ARR_DATA_PTR(namespaces);
2501+
bitmap=ARR_NULLBITMAP(namespaces);
2502+
bitmask=1;
2503+
2504+
for (i=0;i<ns_count*2;i++)
2505+
{
2506+
if (bitmap&& (*bitmap&bitmask)==0)
2507+
ereport(ERROR, (errmsg("neither namespace nor URI may be NULL")));/* TODO: better message */
2508+
else
2509+
{
2510+
if (i<ns_count)
2511+
ns_names[i]=DatumGetCString(DirectFunctionCall1(textout,
2512+
PointerGetDatum(ptr)));
2513+
else
2514+
ns_uris[i-ns_count]=DatumGetCString(DirectFunctionCall1(textout,
2515+
PointerGetDatum(ptr)));
2516+
ptr=att_addlength(ptr,typlen,PointerGetDatum(ptr));
2517+
ptr= (char*)att_align(ptr,typalign);
2518+
}
2519+
2520+
/* advance bitmap pointer if any */
2521+
if (bitmap)
2522+
{
2523+
bitmask <<=1;
2524+
if (bitmask==0x100)
2525+
{
2526+
bitmap++;
2527+
bitmask=1;
2528+
}
2529+
}
2530+
}
2531+
}
2532+
2533+
len=VARSIZE(data)-VARHDRSZ;
2534+
xpath_len=VARSIZE(xpath_expr_text)-VARHDRSZ;
2535+
if (xpath_len==0)
2536+
ereport(ERROR, (errmsg("empty XPath expression")));
2537+
2538+
if (xmlStrncmp((xmlChar*)VARDATA(data), (xmlChar*)"<?xml",5)==0)
2539+
{
2540+
string=palloc(len+1);
2541+
memcpy(string,VARDATA(data),len);
2542+
string[len]='\0';
2543+
xpath_expr=palloc(xpath_len+1);
2544+
memcpy(xpath_expr,VARDATA(xpath_expr_text),xpath_len);
2545+
xpath_expr[xpath_len]='\0';
2546+
}
2547+
else
2548+
{
2549+
/* use "<x>...</x>" as dummy root element to enable XPath for fragments */
2550+
/* TODO: (XPath for fragment) find better solution to work with XML fragment! */
2551+
string=xmlStrncatNew((xmlChar*)"<x>", (xmlChar*)VARDATA(data),len);
2552+
string=xmlStrncat(string, (xmlChar*)"</x>",5);
2553+
len+=7;
2554+
xpath_expr=xmlStrncatNew((xmlChar*)"/x", (xmlChar*)VARDATA(xpath_expr_text),xpath_len);
2555+
len+=2;
2556+
}
2557+
2558+
xml_init();
2559+
2560+
PG_TRY();
2561+
{
2562+
/* redundant XML parsing (two parsings for the same value in the same session are possible) */
2563+
ctxt=xmlNewParserCtxt();
2564+
if (ctxt==NULL)
2565+
xml_ereport(ERROR,ERRCODE_INTERNAL_ERROR,
2566+
"could not allocate parser context");
2567+
doc=xmlCtxtReadMemory(ctxt, (char*)string,len,NULL,NULL,0);
2568+
if (doc==NULL)
2569+
xml_ereport(ERROR,ERRCODE_INVALID_XML_DOCUMENT,
2570+
"could not parse XML data");
2571+
xpathctx=xmlXPathNewContext(doc);
2572+
if (xpathctx==NULL)
2573+
xml_ereport(ERROR,ERRCODE_INTERNAL_ERROR,
2574+
"could not allocate XPath context");
2575+
xpathctx->node=xmlDocGetRootElement(doc);
2576+
if (xpathctx->node==NULL)
2577+
xml_ereport(ERROR,ERRCODE_INTERNAL_ERROR,
2578+
"could not find root XML element");
2579+
2580+
/* register namespaces, if any */
2581+
if ((ns_count>0)&&ns_names&&ns_uris)
2582+
for (i=0;i<ns_count;i++)
2583+
if (0!=xmlXPathRegisterNs(xpathctx, (xmlChar*)ns_names[i], (xmlChar*)ns_uris[i]))
2584+
ereport(ERROR,
2585+
(errmsg("could not register XML namespace with prefix=\"%s\" and href=\"%s\"",ns_names[i],ns_uris[i])));
2586+
2587+
xpathcomp=xmlXPathCompile(xpath_expr);
2588+
if (xpathcomp==NULL)
2589+
xml_ereport(ERROR,ERRCODE_INTERNAL_ERROR,
2590+
"invalid XPath expression");/* TODO: show proper XPath error details */
2591+
2592+
xpathobj=xmlXPathCompiledEval(xpathcomp,xpathctx);
2593+
xmlXPathFreeCompExpr(xpathcomp);
2594+
if (xpathobj==NULL)
2595+
ereport(ERROR, (errmsg("could not create XPath object")));
2596+
2597+
if (xpathobj->nodesetval==NULL)
2598+
res_is_null= TRUE;
2599+
2600+
if (!res_is_null&&xpathobj->nodesetval->nodeNr==0)
2601+
/* TODO maybe empty array should be here, not NULL? (if so -- fix segfault) */
2602+
/*PG_RETURN_ARRAYTYPE_P(makeArrayResult(astate, CurrentMemoryContext));*/
2603+
res_is_null= TRUE;
2604+
2605+
if (!res_is_null)
2606+
for (i=0;i<xpathobj->nodesetval->nodeNr;i++)
2607+
{
2608+
Datumelem;
2609+
boolelemisnull= false;
2610+
elem=PointerGetDatum(xml_xmlnodetotext(xpathobj->nodesetval->nodeTab[i]));
2611+
astate=accumArrayResult(astate,elem,
2612+
elemisnull,XMLOID,
2613+
CurrentMemoryContext);
2614+
}
2615+
2616+
xmlXPathFreeObject(xpathobj);
2617+
xmlXPathFreeContext(xpathctx);
2618+
xmlFreeParserCtxt(ctxt);
2619+
xmlFreeDoc(doc);
2620+
xmlCleanupParser();
2621+
}
2622+
PG_CATCH();
2623+
{
2624+
if (xpathcomp)
2625+
xmlXPathFreeCompExpr(xpathcomp);
2626+
if (xpathobj)
2627+
xmlXPathFreeObject(xpathobj);
2628+
if (xpathctx)
2629+
xmlXPathFreeContext(xpathctx);
2630+
if (doc)
2631+
xmlFreeDoc(doc);
2632+
if (ctxt)
2633+
xmlFreeParserCtxt(ctxt);
2634+
xmlCleanupParser();
2635+
2636+
PG_RE_THROW();
2637+
}
2638+
PG_END_TRY();
2639+
2640+
if (res_is_null)
2641+
{
2642+
PG_RETURN_NULL();
2643+
}
2644+
else
2645+
{
2646+
PG_RETURN_ARRAYTYPE_P(makeArrayResult(astate,CurrentMemoryContext));
2647+
}
2648+
#else
2649+
NO_XML_SUPPORT();
2650+
return0;
2651+
#endif
2652+
}

‎src/include/catalog/pg_proc.h

Lines changed: 5 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $PostgreSQL: pgsql/src/include/catalog/pg_proc.h,v 1.449 2007/03/20 05:45:00 neilc Exp $
10+
* $PostgreSQL: pgsql/src/include/catalog/pg_proc.h,v 1.450 2007/03/22 20:14:58 momjian Exp $
1111
*
1212
* NOTES
1313
* The script catalog/genbki.sh reads this file and generates .bki
@@ -4095,6 +4095,10 @@ DESCR("map table contents and structure to XML and XML Schema");
40954095
DATA(insertOID=2930 (query_to_xml_and_xmlschemaPGNSPPGUID121000fftfs4142"25 16 16 25"_null__null_"{query,nulls,tableforest,targetns}"query_to_xml_and_xmlschema-_null_ ));
40964096
DESCR("map query result and structure to XML and XML Schema");
40974097

4098+
DATA(insertOID=2931 (xmlpathPGNSPPGUID1210ffffi3143"25 142 1009"_null__null__null_xmlpath-_null_ ));
4099+
DESCR("evaluate XPath expression, with namespaces support");
4100+
DATA(insertOID=2932 (xmlpathPGNSPPGUID1410ffffi2143"25 142"_null__null__null_"select pg_catalog.xmlpath($1, $2, NULL)"-_null_ ));
4101+
DESCR("evaluate XPath expression");
40984102

40994103
/* uuid */
41004104
DATA(insertOID=2952 (uuid_inPGNSPPGUID1210fftfi12950"2275"_null__null__null_uuid_in-_null_ ));

‎src/include/utils/xml.h

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $PostgreSQL: pgsql/src/include/utils/xml.h,v 1.16 2007/02/16 07:46:55 petere Exp $
10+
* $PostgreSQL: pgsql/src/include/utils/xml.h,v 1.17 2007/03/22 20:14:58 momjian Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -36,6 +36,7 @@ extern Datum xmlconcat2(PG_FUNCTION_ARGS);
3636
externDatumtexttoxml(PG_FUNCTION_ARGS);
3737
externDatumxmltotext(PG_FUNCTION_ARGS);
3838
externDatumxmlvalidate(PG_FUNCTION_ARGS);
39+
externDatumxmlpath(PG_FUNCTION_ARGS);
3940

4041
externDatumtable_to_xml(PG_FUNCTION_ARGS);
4142
externDatumquery_to_xml(PG_FUNCTION_ARGS);

‎src/test/regress/expected/xml.out

Lines changed: 30 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -401,3 +401,33 @@ SELECT table_name, view_definition FROM information_schema.views
401401
xmlview9 | SELECT XMLSERIALIZE(CONTENT 'good'::"xml" AS text) AS "xmlserialize";
402402
(9 rows)
403403

404+
-- Text XPath expressions evaluation
405+
SELECT xmlpath('/value', data) FROM xmltest;
406+
xmlpath
407+
---------
408+
{one}
409+
{two}
410+
(2 rows)
411+
412+
SELECT xmlpath(NULL, NULL) IS NULL FROM xmltest;
413+
?column?
414+
----------
415+
t
416+
t
417+
(2 rows)
418+
419+
SELECT xmlpath('', '<!-- error -->');
420+
ERROR: empty XPath expression
421+
CONTEXT: SQL function "xmlpath" statement 1
422+
SELECT xmlpath('//text()', '<local:data xmlns:local="http://127.0.0.1"><local:piece id="1">number one</local:piece><local:piece id="2" /></local:data>');
423+
xmlpath
424+
----------------
425+
{"number one"}
426+
(1 row)
427+
428+
SELECT xmlpath('//loc:piece/@id', '<local:data xmlns:local="http://127.0.0.1"><local:piece id="1">number one</local:piece><local:piece id="2" /></local:data>', ARRAY[ARRAY['loc'], ARRAY['http://127.0.0.1']]);
429+
xmlpath
430+
---------
431+
{1,2}
432+
(1 row)
433+

‎src/test/regress/expected/xml_1.out

Lines changed: 15 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -197,3 +197,18 @@ SELECT table_name, view_definition FROM information_schema.views
197197
xmlview5 | SELECT XMLPARSE(CONTENT '<abc>x</abc>'::text STRIP WHITESPACE) AS "xmlparse";
198198
(2 rows)
199199

200+
-- Text XPath expressions evaluation
201+
SELECT xmlpath('/value', data) FROM xmltest;
202+
xmlpath
203+
---------
204+
(0 rows)
205+
206+
SELECT xmlpath(NULL, NULL) IS NULL FROM xmltest;
207+
ERROR: no XML support in this installation
208+
CONTEXT: SQL function "xmlpath" statement 1
209+
SELECT xmlpath('', '<!-- error -->');
210+
ERROR: no XML support in this installation
211+
SELECT xmlpath('//text()', '<local:data xmlns:local="http://127.0.0.1"><local:piece id="1">number one</local:piece><local:piece id="2" /></local:data>');
212+
ERROR: no XML support in this installation
213+
SELECT xmlpath('//loc:piece/@id', '<local:data xmlns:local="http://127.0.0.1"><local:piece id="1">number one</local:piece><local:piece id="2" /></local:data>', ARRAY[ARRAY['loc'], ARRAY['http://127.0.0.1']]);
214+
ERROR: no XML support in this installation

‎src/test/regress/sql/xml.sql

Lines changed: 8 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -144,3 +144,11 @@ CREATE VIEW xmlview9 AS SELECT xmlserialize(content 'good' as text);
144144

145145
SELECT table_name, view_definitionFROMinformation_schema.views
146146
WHERE table_nameLIKE'xmlview%'ORDER BY1;
147+
148+
-- Text XPath expressions evaluation
149+
150+
SELECT xmlpath('/value', data)FROM xmltest;
151+
SELECT xmlpath(NULL,NULL) ISNULLFROM xmltest;
152+
SELECT xmlpath('','<!-- error -->');
153+
SELECT xmlpath('//text()','<local:data xmlns:local="http://127.0.0.1"><local:piece id="1">number one</local:piece><local:piece id="2" /></local:data>');
154+
SELECT xmlpath('//loc:piece/@id','<local:data xmlns:local="http://127.0.0.1"><local:piece id="1">number one</local:piece><local:piece id="2" /></local:data>', ARRAY[ARRAY['loc'], ARRAY['http://127.0.0.1']]);

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