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Add xmlpath() to evaluate XPath expressions, with namespaces support.

Browse Source 
Nikolay Samokhvalov
This commit is contained in:
Bruce Momjian 2007-03-22 20:14:58 +00:00
parent 4f896dac17
commit e651bcf3f6
6 changed files with 309 additions and 4 deletions
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251
src/backend/utils/adt/xml.c
View File

@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/backend/utils/adt/xml.c,v 1.35 2007/03/15 23:12:06 tgl Exp $
* $PostgreSQL: pgsql/src/backend/utils/adt/xml.c,v 1.36 2007/03/22 20:14:58 momjian Exp $
*
*-------------------------------------------------------------------------
*/
@ -47,6 +47,8 @@
#include <libxml/uri.h>
#include <libxml/xmlerror.h>
#include <libxml/xmlwriter.h>
#include <libxml/xpath.h>
#include <libxml/xpathInternals.h>
#endif /* USE_LIBXML */
#include "catalog/namespace.h"
@ -67,6 +69,7 @@
#include "utils/datetime.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "access/tupmacs.h"
#include "utils/xml.h"
@ -88,6 +91,7 @@ static xmlChar *xml_text2xmlChar(text *in);
static int parse_xml_decl(const xmlChar *str, size_t *lenp, xmlChar **version, xmlChar **encoding, int *standalone);
static bool print_xml_decl(StringInfo buf, const xmlChar *version, pg_enc encoding, int standalone);
static xmlDocPtr xml_parse(text *data, XmlOptionType xmloption_arg, bool preserve_whitespace, xmlChar *encoding);
static text *xml_xmlnodetotext(xmlNodePtr cur);
#endif /* USE_LIBXML */
@ -1463,7 +1467,6 @@ map_xml_name_to_sql_identifier(char *name)
return buf.data;
}
/*
* Map SQL value to XML value; see SQL/XML:2003 section 9.16.
*/
@ -2403,3 +2406,247 @@ SPI_sql_row_to_xmlelement(int rownum, StringInfo result, char *tablename, bool n
else
appendStringInfoString(result, "</row>\n\n");
}
/*
* XPath related functions
*/
#ifdef USE_LIBXML
/*
* Convert XML node to text (return value only, it's not dumping)
*/
text *
xml_xmlnodetotext(xmlNodePtr cur)
{
xmlChar *str;
text *result;
size_t len;
str = xmlXPathCastNodeToString(cur);
len = strlen((char *) str);
result = (text *) palloc(len + VARHDRSZ);
SET_VARSIZE(result, len + VARHDRSZ);
memcpy(VARDATA(result), str, len);
return result;
}
#endif
/*
* Evaluate XPath expression and return array of XML values.
* As we have no support of XQuery sequences yet, this functions seems
* to be the most useful one (array of XML functions plays a role of
* some kind of substritution for XQuery sequences).
* Workaround here: we parse XML data in different way to allow XPath for
* fragments (see "XPath for fragment" TODO comment inside).
*/
Datum
xmlpath(PG_FUNCTION_ARGS)
{
#ifdef USE_LIBXML
ArrayBuildState *astate = NULL;
xmlParserCtxtPtr ctxt = NULL;
xmlDocPtr doc = NULL;
xmlXPathContextPtr xpathctx = NULL;
xmlXPathCompExprPtr xpathcomp = NULL;
xmlXPathObjectPtr xpathobj = NULL;
int32 len, xpath_len;
xmlChar *string, *xpath_expr;
bool res_is_null = FALSE;
int i;
xmltype *data;
text *xpath_expr_text;
ArrayType *namespaces;
int *dims, ndims, ns_count = 0, bitmask = 1;
char *ptr;
bits8 *bitmap;
char **ns_names = NULL, **ns_uris = NULL;
int16 typlen;
bool typbyval;
char typalign;
/* the function is not strict, we must check first two args */
if (PG_ARGISNULL(0) || PG_ARGISNULL(1))
PG_RETURN_NULL();
xpath_expr_text = PG_GETARG_TEXT_P(0);
data = PG_GETARG_XML_P(1);
/* Namespace mappings passed as text[].
* Assume that 2-dimensional array has been passed,
* the 1st subarray is array of names, the 2nd -- array of URIs,
* example: ARRAY[ARRAY['myns', 'myns2'], ARRAY['http://example.com', 'http://example2.com']].
*/
if (!PG_ARGISNULL(2))
{
namespaces = PG_GETARG_ARRAYTYPE_P(2);
ndims = ARR_NDIM(namespaces);
dims = ARR_DIMS(namespaces);
/* Sanity check */
if (ndims != 2)
ereport(ERROR, (errmsg("invalid array passed for namespace mappings"),
errdetail("Only 2-dimensional array may be used for namespace mappings.")));
Assert(ARR_ELEMTYPE(namespaces) == TEXTOID);
ns_count = ArrayGetNItems(ndims, dims) / 2;
get_typlenbyvalalign(ARR_ELEMTYPE(namespaces),
&typlen, &typbyval, &typalign);
ns_names = (char **) palloc(ns_count * sizeof(char *));
ns_uris = (char **) palloc(ns_count * sizeof(char *));
ptr = ARR_DATA_PTR(namespaces);
bitmap = ARR_NULLBITMAP(namespaces);
bitmask = 1;
for (i = 0; i < ns_count * 2; i++)
{
if (bitmap && (*bitmap & bitmask) == 0)
ereport(ERROR, (errmsg("neither namespace nor URI may be NULL"))); /* TODO: better message */
else
{
if (i < ns_count)
ns_names[i] = DatumGetCString(DirectFunctionCall1(textout,
PointerGetDatum(ptr)));
else
ns_uris[i - ns_count] = DatumGetCString(DirectFunctionCall1(textout,
PointerGetDatum(ptr)));
ptr = att_addlength(ptr, typlen, PointerGetDatum(ptr));
ptr = (char *) att_align(ptr, typalign);
}
/* advance bitmap pointer if any */
if (bitmap)
{
bitmask <<= 1;
if (bitmask == 0x100)
{
bitmap++;
bitmask = 1;
}
}
}
}
len = VARSIZE(data) - VARHDRSZ;
xpath_len = VARSIZE(xpath_expr_text) - VARHDRSZ;
if (xpath_len == 0)
ereport(ERROR, (errmsg("empty XPath expression")));
if (xmlStrncmp((xmlChar *) VARDATA(data), (xmlChar *) "<?xml", 5) == 0)
{
string = palloc(len + 1);
memcpy(string, VARDATA(data), len);
string[len] = '\0';
xpath_expr = palloc(xpath_len + 1);
memcpy(xpath_expr, VARDATA(xpath_expr_text), xpath_len);
xpath_expr[xpath_len] = '\0';
}
else
{
/* use "<x>...</x>" as dummy root element to enable XPath for fragments */
/* TODO: (XPath for fragment) find better solution to work with XML fragment! */
string = xmlStrncatNew((xmlChar *) "<x>", (xmlChar *) VARDATA(data), len);
string = xmlStrncat(string, (xmlChar *) "</x>", 5);
len += 7;
xpath_expr = xmlStrncatNew((xmlChar *) "/x", (xmlChar *) VARDATA(xpath_expr_text), xpath_len);
len += 2;
}
xml_init();
PG_TRY();
{
/* redundant XML parsing (two parsings for the same value in the same session are possible) */
ctxt = xmlNewParserCtxt();
if (ctxt == NULL)
xml_ereport(ERROR, ERRCODE_INTERNAL_ERROR,
"could not allocate parser context");
doc = xmlCtxtReadMemory(ctxt, (char *) string, len, NULL, NULL, 0);
if (doc == NULL)
xml_ereport(ERROR, ERRCODE_INVALID_XML_DOCUMENT,
"could not parse XML data");
xpathctx = xmlXPathNewContext(doc);
if (xpathctx == NULL)
xml_ereport(ERROR, ERRCODE_INTERNAL_ERROR,
"could not allocate XPath context");
xpathctx->node = xmlDocGetRootElement(doc);
if (xpathctx->node == NULL)
xml_ereport(ERROR, ERRCODE_INTERNAL_ERROR,
"could not find root XML element");
/* register namespaces, if any */
if ((ns_count > 0) && ns_names && ns_uris)
for (i = 0; i < ns_count; i++)
if (0 != xmlXPathRegisterNs(xpathctx, (xmlChar *) ns_names[i], (xmlChar *) ns_uris[i]))
ereport(ERROR,
(errmsg("could not register XML namespace with prefix=\"%s\" and href=\"%s\"", ns_names[i], ns_uris[i])));
xpathcomp = xmlXPathCompile(xpath_expr);
if (xpathcomp == NULL)
xml_ereport(ERROR, ERRCODE_INTERNAL_ERROR,
"invalid XPath expression"); /* TODO: show proper XPath error details */
xpathobj = xmlXPathCompiledEval(xpathcomp, xpathctx);
xmlXPathFreeCompExpr(xpathcomp);
if (xpathobj == NULL)
ereport(ERROR, (errmsg("could not create XPath object")));
if (xpathobj->nodesetval == NULL)
res_is_null = TRUE;
if (!res_is_null && xpathobj->nodesetval->nodeNr == 0)
/* TODO maybe empty array should be here, not NULL? (if so -- fix segfault) */
/*PG_RETURN_ARRAYTYPE_P(makeArrayResult(astate, CurrentMemoryContext));*/
res_is_null = TRUE;
if (!res_is_null)
for (i = 0; i < xpathobj->nodesetval->nodeNr; i++)
{
Datum elem;
bool elemisnull = false;
elem = PointerGetDatum(xml_xmlnodetotext(xpathobj->nodesetval->nodeTab[i]));
astate = accumArrayResult(astate, elem,
elemisnull, XMLOID,
CurrentMemoryContext);
}
xmlXPathFreeObject(xpathobj);
xmlXPathFreeContext(xpathctx);
xmlFreeParserCtxt(ctxt);
xmlFreeDoc(doc);
xmlCleanupParser();
}
PG_CATCH();
{
if (xpathcomp)
xmlXPathFreeCompExpr(xpathcomp);
if (xpathobj)
xmlXPathFreeObject(xpathobj);
if (xpathctx)
xmlXPathFreeContext(xpathctx);
if (doc)
xmlFreeDoc(doc);
if (ctxt)
xmlFreeParserCtxt(ctxt);
xmlCleanupParser();
PG_RE_THROW();
}
PG_END_TRY();
if (res_is_null)
{
PG_RETURN_NULL();
}
else
{
PG_RETURN_ARRAYTYPE_P(makeArrayResult(astate, CurrentMemoryContext));
}
#else
NO_XML_SUPPORT();
return 0;
#endif
}

6
src/include/catalog/pg_proc.h
View File

@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/catalog/pg_proc.h,v 1.449 2007/03/20 05:45:00 neilc Exp $
* $PostgreSQL: pgsql/src/include/catalog/pg_proc.h,v 1.450 2007/03/22 20:14:58 momjian Exp $
*
* NOTES
* 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");
DATA(insert OID = 2930 ( query_to_xml_and_xmlschema PGNSP PGUID 12 100 0 f f t f s 4 142 "25 16 16 25" _null_ _null_ "{query,nulls,tableforest,targetns}" query_to_xml_and_xmlschema - _null_ ));
DESCR("map query result and structure to XML and XML Schema");
DATA(insert OID = 2931 ( xmlpath PGNSP PGUID 12 1 0 f f f f i 3 143 "25 142 1009" _null_ _null_ _null_ xmlpath - _null_ ));
DESCR("evaluate XPath expression, with namespaces support");
DATA(insert OID = 2932 ( xmlpath PGNSP PGUID 14 1 0 f f f f i 2 143 "25 142" _null_ _null_ _null_ "select pg_catalog.xmlpath($1, $2, NULL)" - _null_ ));
DESCR("evaluate XPath expression");
/* uuid */
DATA(insert OID = 2952 ( uuid_in PGNSP PGUID 12 1 0 f f t f i 1 2950 "2275" _null_ _null_ _null_ uuid_in - _null_ ));

3
src/include/utils/xml.h
View File

@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/utils/xml.h,v 1.16 2007/02/16 07:46:55 petere Exp $
* $PostgreSQL: pgsql/src/include/utils/xml.h,v 1.17 2007/03/22 20:14:58 momjian Exp $
*
*-------------------------------------------------------------------------
*/
@ -36,6 +36,7 @@ extern Datum xmlconcat2(PG_FUNCTION_ARGS);
extern Datum texttoxml(PG_FUNCTION_ARGS);
extern Datum xmltotext(PG_FUNCTION_ARGS);
extern Datum xmlvalidate(PG_FUNCTION_ARGS);
extern Datum xmlpath(PG_FUNCTION_ARGS);
extern Datum table_to_xml(PG_FUNCTION_ARGS);
extern Datum query_to_xml(PG_FUNCTION_ARGS);

30
src/test/regress/expected/xml.out
View File

@ -401,3 +401,33 @@ SELECT table_name, view_definition FROM information_schema.views
xmlview9 | SELECT XMLSERIALIZE(CONTENT 'good'::"xml" AS text) AS "xmlserialize";
(9 rows)
-- Text XPath expressions evaluation
SELECT xmlpath('/value', data) FROM xmltest;
xmlpath
---------
{one}
{two}
(2 rows)
SELECT xmlpath(NULL, NULL) IS NULL FROM xmltest;
?column?
----------
t
t
(2 rows)
SELECT xmlpath('', '<!-- error -->');
ERROR: empty XPath expression
CONTEXT: SQL function "xmlpath" statement 1
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>');
xmlpath
----------------
{"number one"}
(1 row)
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']]);
xmlpath
---------
{1,2}
(1 row)

15
src/test/regress/expected/xml_1.out
View File

@ -197,3 +197,18 @@ SELECT table_name, view_definition FROM information_schema.views
xmlview5 | SELECT XMLPARSE(CONTENT '<abc>x</abc>'::text STRIP WHITESPACE) AS "xmlparse";
(2 rows)
-- Text XPath expressions evaluation
SELECT xmlpath('/value', data) FROM xmltest;
xmlpath
---------
(0 rows)
SELECT xmlpath(NULL, NULL) IS NULL FROM xmltest;
ERROR: no XML support in this installation
CONTEXT: SQL function "xmlpath" statement 1
SELECT xmlpath('', '<!-- error -->');
ERROR: no XML support in this installation
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>');
ERROR: no XML support in this installation
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']]);
ERROR: no XML support in this installation

8
src/test/regress/sql/xml.sql
View File

@ -144,3 +144,11 @@ CREATE VIEW xmlview9 AS SELECT xmlserialize(content 'good' as text);
SELECT table_name, view_definition FROM information_schema.views
WHERE table_name LIKE 'xmlview%' ORDER BY 1;
-- Text XPath expressions evaluation
SELECT xmlpath('/value', data) FROM xmltest;
SELECT xmlpath(NULL, NULL) IS NULL FROM xmltest;
SELECT xmlpath('', '<!-- error -->');
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>');
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']]);