Tom Lane wrote:
Robert Haas <robertmh...@gmail.com> writes:
On Tue, May 25, 2010 at 1:09 PM, Mike Fowler <m...@mlfowler.com> wrote:
We're unlikely to accept this patch if it changes the minimum version
of libxml2 required to compile PostgreSQL
Why? 2.6.27 is almost 4 years old.
At a minimum, I think it's fair to say that the burden is on you to
justify what it's worth bumping the version number.
Yes. Increasing the minimum required version of some library is a Big
Deal, we don't do it on a whim. And we definitely don't do it just
because it's old.
regards, tom lane
OK, I consider myself suitably educated/chastised. I now understand why
a version bump is such a big deal. Your objections are all reasonable, I
suppose I'm just used to living on the bleeding edge of everything.
Consequently I have changed the code to produce the same result in a
different way without using the new function. I've down-graded my
version to 2.6.26 and it all compiles cleanly. Please find attached my
revised patch, and thanks all for your advise.
Regards,
--
Mike Fowler
Registered Linux user: 379787
Index: src/backend/utils/adt/xml.c
===================================================================
RCS file: /home/mfowler/cvsrepo/pgrepo/pgsql/src/backend/utils/adt/xml.c,v
retrieving revision 1.97
diff -c -r1.97 xml.c
*** src/backend/utils/adt/xml.c 3 Mar 2010 17:29:45 -0000 1.97
--- src/backend/utils/adt/xml.c 26 May 2010 09:36:50 -0000
***************
*** 3495,3497 ****
--- 3495,3678 ----
return 0;
#endif
}
+
+ /*
+ * Determines if the node specified by the supplied XPath exists
+ * in a given XML document, returning a boolean.
+ *
+ * It is up to the user to ensure that the XML passed is in fact
+ * an XML document - XPath doesn't work easily on fragments without
+ * a context node being known.
+ */
+ Datum
+ xmlexists(PG_FUNCTION_ARGS)
+ {
+ #ifdef USE_LIBXML
+ text *xpath_expr_text = PG_GETARG_TEXT_P(0);
+ xmltype *data = PG_GETARG_XML_P(1);
+ ArrayType *namespaces = PG_GETARG_ARRAYTYPE_P(2);
+ xmlParserCtxtPtr ctxt = NULL;
+ xmlDocPtr doc = NULL;
+ xmlXPathContextPtr xpathctx = NULL;
+ xmlXPathCompExprPtr xpathcomp = NULL;
+ xmlXPathObjectPtr xpathobj = NULL;
+ char *datastr;
+ int32 len;
+ int32 xpath_len;
+ xmlChar *string;
+ xmlChar *xpath_expr;
+ int i;
+ int ndim;
+ Datum *ns_names_uris;
+ bool *ns_names_uris_nulls;
+ int ns_count;
+ int result;
+
+ /*
+ * Namespace mappings are passed as text[]. If an empty array is passed
+ * (ndim = 0, "0-dimensional"), then there are no namespace mappings.
+ * Else, a 2-dimensional array with length of the second axis being equal
+ * to 2 should be passed, i.e., every subarray contains 2 elements, the
+ * first element defining the name, the second one the URI. Example:
+ * ARRAY[ARRAY['myns', 'http://example.com'], ARRAY['myns2',
+ * 'http://example2.com']].
+ */
+ ndim = ARR_NDIM(namespaces);
+ if (ndim != 0)
+ {
+ int *dims;
+
+ dims = ARR_DIMS(namespaces);
+
+ if (ndim != 2 || dims[1] != 2)
+ ereport(ERROR,
+ (errcode(ERRCODE_DATA_EXCEPTION),
+ errmsg("invalid array for XML namespace mapping"),
+ errdetail("The array must be two-dimensional with length of the second axis equal to 2.")));
+
+ Assert(ARR_ELEMTYPE(namespaces) == TEXTOID);
+
+ deconstruct_array(namespaces, TEXTOID, -1, false, 'i',
+ &ns_names_uris, &ns_names_uris_nulls,
+ &ns_count);
+
+ Assert((ns_count % 2) == 0); /* checked above */
+ ns_count /= 2; /* count pairs only */
+ }
+ else
+ {
+ ns_names_uris = NULL;
+ ns_names_uris_nulls = NULL;
+ ns_count = 0;
+ }
+
+ datastr = VARDATA(data);
+ len = VARSIZE(data) - VARHDRSZ;
+ xpath_len = VARSIZE(xpath_expr_text) - VARHDRSZ;
+ if (xpath_len == 0)
+ ereport(ERROR,
+ (errcode(ERRCODE_DATA_EXCEPTION),
+ errmsg("empty XPath expression")));
+
+ string = (xmlChar *) palloc((len + 1) * sizeof(xmlChar));
+ memcpy(string, datastr, len);
+ string[len] = '\0';
+
+ xpath_expr = (xmlChar *) palloc((xpath_len + 1) * sizeof(xmlChar));
+ memcpy(xpath_expr, VARDATA(xpath_expr_text), xpath_len);
+ xpath_expr[xpath_len] = '\0';
+
+ pg_xml_init();
+ xmlInitParser();
+
+ PG_TRY();
+ {
+ /*
+ * redundant XML parsing (two parsings for the same value during one
+ * command execution are possible)
+ */
+ ctxt = xmlNewParserCtxt();
+ if (ctxt == NULL)
+ xml_ereport(ERROR, ERRCODE_OUT_OF_MEMORY,
+ "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 document");
+ xpathctx = xmlXPathNewContext(doc);
+ if (xpathctx == NULL)
+ xml_ereport(ERROR, ERRCODE_OUT_OF_MEMORY,
+ "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)
+ {
+ for (i = 0; i < ns_count; i++)
+ {
+ char *ns_name;
+ char *ns_uri;
+
+ if (ns_names_uris_nulls[i * 2] ||
+ ns_names_uris_nulls[i * 2 + 1])
+ ereport(ERROR,
+ (errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
+ errmsg("neither namespace name nor URI may be null")));
+ ns_name = TextDatumGetCString(ns_names_uris[i * 2]);
+ ns_uri = TextDatumGetCString(ns_names_uris[i * 2 + 1]);
+ if (xmlXPathRegisterNs(xpathctx,
+ (xmlChar *) ns_name,
+ (xmlChar *) ns_uri) != 0)
+ ereport(ERROR, /* is this an internal error??? */
+ (errmsg("could not register XML namespace with name \"%s\" and URI \"%s\"",
+ ns_name, ns_uri)));
+ }
+ }
+
+ xpathcomp = xmlXPathCompile(xpath_expr);
+ if (xpathcomp == NULL) /* TODO: show proper XPath error details */
+ xml_ereport(ERROR, ERRCODE_INTERNAL_ERROR,
+ "invalid XPath expression");
+
+ xpathobj = xmlXPathCompiledEval(xpathcomp, xpathctx);
+ if (xpathobj == NULL) /* TODO: reason? */
+ xml_ereport(ERROR, ERRCODE_INTERNAL_ERROR,
+ "could not create XPath object");
+
+ /* return empty array in cases when nothing is found */
+ if (xpathobj->nodesetval == NULL)
+ result = 0;
+ else
+ result = xpathobj->nodesetval->nodeNr;
+ }
+ PG_CATCH();
+ {
+ if (xpathobj)
+ xmlXPathFreeObject(xpathobj);
+ if (xpathcomp)
+ xmlXPathFreeCompExpr(xpathcomp);
+ if (xpathctx)
+ xmlXPathFreeContext(xpathctx);
+ if (doc)
+ xmlFreeDoc(doc);
+ if (ctxt)
+ xmlFreeParserCtxt(ctxt);
+ PG_RE_THROW();
+ }
+ PG_END_TRY();
+
+ xmlXPathFreeObject(xpathobj);
+ xmlXPathFreeCompExpr(xpathcomp);
+ xmlXPathFreeContext(xpathctx);
+ xmlFreeDoc(doc);
+ xmlFreeParserCtxt(ctxt);
+
+ PG_RETURN_BOOL(result);
+ #else
+ NO_XML_SUPPORT();
+ return 0;
+ #endif
+ }
Index: src/include/catalog/pg_proc.h
===================================================================
RCS file: /home/mfowler/cvsrepo/pgrepo/pgsql/src/include/catalog/pg_proc.h,v
retrieving revision 1.570
diff -c -r1.570 pg_proc.h
*** src/include/catalog/pg_proc.h 26 Feb 2010 02:01:21 -0000 1.570
--- src/include/catalog/pg_proc.h 25 May 2010 14:04:27 -0000
***************
*** 4385,4390 ****
--- 4385,4396 ----
DATA(insert OID = 2932 ( xpath PGNSP PGUID 14 1 0 0 f f f t f i 2 0 143 "25 142" _null_ _null_ _null_ _null_ "select pg_catalog.xpath($1, $2, ''{}''::pg_catalog.text[])" _null_ _null_ _null_ ));
DESCR("evaluate XPath expression");
+ DATA(insert OID = 3037 ( xmlexists PGNSP PGUID 12 1 0 0 f f f t f i 3 0 16 "25 142 1009" _null_ _null_ _null_ _null_ xmlexists _null_ _null_ _null_ ));
+ DESCR("evaluate XPath expression in a boolean context, with namespaces support");
+ DATA(insert OID = 3038 ( xmlexists PGNSP PGUID 14 1 0 0 f f f t f i 2 0 16 "25 142" _null_ _null_ _null_ _null_ "select pg_catalog.xmlexists($1, $2, ''{}''::pg_catalog.text[])" _null_ _null_ _null_ ));
+ DESCR("evaluate XPath expression in a boolean context");
+
+
/* uuid */
DATA(insert OID = 2952 ( uuid_in PGNSP PGUID 12 1 0 0 f f f t f i 1 0 2950 "2275" _null_ _null_ _null_ _null_ uuid_in _null_ _null_ _null_ ));
DESCR("I/O");
Index: src/include/utils/xml.h
===================================================================
RCS file: /home/mfowler/cvsrepo/pgrepo/pgsql/src/include/utils/xml.h,v
retrieving revision 1.31
diff -c -r1.31 xml.h
*** src/include/utils/xml.h 3 Mar 2010 17:29:45 -0000 1.31
--- src/include/utils/xml.h 25 May 2010 13:45:32 -0000
***************
*** 37,42 ****
--- 37,43 ----
extern Datum xmltotext(PG_FUNCTION_ARGS);
extern Datum xmlvalidate(PG_FUNCTION_ARGS);
extern Datum xpath(PG_FUNCTION_ARGS);
+ extern Datum xmlexists(PG_FUNCTION_ARGS);
extern Datum table_to_xml(PG_FUNCTION_ARGS);
extern Datum query_to_xml(PG_FUNCTION_ARGS);
Index: src/test/regress/expected/xml.out
===================================================================
RCS file: /home/mfowler/cvsrepo/pgrepo/pgsql/src/test/regress/expected/xml.out,v
retrieving revision 1.25
diff -c -r1.25 xml.out
*** src/test/regress/expected/xml.out 9 Jun 2009 22:00:57 -0000 1.25
--- src/test/regress/expected/xml.out 25 May 2010 14:12:04 -0000
***************
*** 502,504 ****
--- 502,545 ----
{<b>two</b>,<b>etc</b>}
(1 row)
+ -- Text xmlexists evalutation
+ INSERT INTO xmltest VALUES (4, '<menu><beers><name>Budvar</name><cost>free</cost><name>Carling</name><cost>lots</cost></beers></menu>'::xml);
+ INSERT INTO xmltest VALUES (5, '<menu><beers><name>Molson</name><cost>free</cost><name>Carling</name><cost>lots</cost></beers></menu>'::xml);
+ INSERT INTO xmltest VALUES (6, '<myns:menu xmlns:myns="http://myns.com";><myns:beers><myns:name>Budvar</myns:name><myns:cost>free</myns:cost><myns:name>Carling</myns:name><myns:cost>lots</myns:cost></myns:beers></myns:menu>'::xml);
+ INSERT INTO xmltest VALUES (7, '<myns:menu xmlns:myns="http://myns.com";><myns:beers><myns:name>Molson</myns:name><myns:cost>free</myns:cost><myns:name>Carling</myns:name><myns:cost>lots</myns:cost></myns:beers></myns:menu>'::xml);
+ SELECT COUNT(id) FROM xmltest WHERE xmlexists('/menu/beer',data);
+ count
+ -------
+ 0
+ (1 row)
+
+ SELECT COUNT(id) FROM xmltest WHERE xmlexists('/menu/beers',data);
+ count
+ -------
+ 2
+ (1 row)
+
+ SELECT COUNT(id) FROM xmltest WHERE xmlexists('/menu/beers/name[text() = ''Molson'']',data);
+ count
+ -------
+ 1
+ (1 row)
+
+ SELECT COUNT(id) FROM xmltest WHERE xmlexists('/myns:menu/myns:beer',data,ARRAY[ARRAY['myns','http://myns.com']]);
+ count
+ -------
+ 0
+ (1 row)
+
+ SELECT COUNT(id) FROM xmltest WHERE xmlexists('/myns:menu/myns:beers',data,ARRAY[ARRAY['myns','http://myns.com']]);
+ count
+ -------
+ 2
+ (1 row)
+
+ SELECT COUNT(id) FROM xmltest WHERE xmlexists('/myns:menu/myns:beers/myns:name[text() = ''Molson'']',data,ARRAY[ARRAY['myns','http://myns.com']]);
+ count
+ -------
+ 1
+ (1 row)
+
Index: src/test/regress/sql/xml.sql
===================================================================
RCS file: /home/mfowler/cvsrepo/pgrepo/pgsql/src/test/regress/sql/xml.sql,v
retrieving revision 1.19
diff -c -r1.19 xml.sql
*** src/test/regress/sql/xml.sql 9 Jun 2009 22:00:57 -0000 1.19
--- src/test/regress/sql/xml.sql 25 May 2010 14:09:02 -0000
***************
*** 163,165 ****
--- 163,178 ----
SELECT xpath('//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 xpath('//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', 'http://127.0.0.1']]);
SELECT xpath('//b', '<a>one <b>two</b> three <b>etc</b></a>');
+
+ -- Text xmlexists evalutation
+ INSERT INTO xmltest VALUES (4, '<menu><beers><name>Budvar</name><cost>free</cost><name>Carling</name><cost>lots</cost></beers></menu>'::xml);
+ INSERT INTO xmltest VALUES (5, '<menu><beers><name>Molson</name><cost>free</cost><name>Carling</name><cost>lots</cost></beers></menu>'::xml);
+ INSERT INTO xmltest VALUES (6, '<myns:menu xmlns:myns="http://myns.com";><myns:beers><myns:name>Budvar</myns:name><myns:cost>free</myns:cost><myns:name>Carling</myns:name><myns:cost>lots</myns:cost></myns:beers></myns:menu>'::xml);
+ INSERT INTO xmltest VALUES (7, '<myns:menu xmlns:myns="http://myns.com";><myns:beers><myns:name>Molson</myns:name><myns:cost>free</myns:cost><myns:name>Carling</myns:name><myns:cost>lots</myns:cost></myns:beers></myns:menu>'::xml);
+
+ SELECT COUNT(id) FROM xmltest WHERE xmlexists('/menu/beer',data);
+ SELECT COUNT(id) FROM xmltest WHERE xmlexists('/menu/beers',data);
+ SELECT COUNT(id) FROM xmltest WHERE xmlexists('/menu/beers/name[text() = ''Molson'']',data);
+ SELECT COUNT(id) FROM xmltest WHERE xmlexists('/myns:menu/myns:beer',data,ARRAY[ARRAY['myns','http://myns.com']]);
+ SELECT COUNT(id) FROM xmltest WHERE xmlexists('/myns:menu/myns:beers',data,ARRAY[ARRAY['myns','http://myns.com']]);
+ SELECT COUNT(id) FROM xmltest WHERE xmlexists('/myns:menu/myns:beers/myns:name[text() = ''Molson'']',data,ARRAY[ARRAY['myns','http://myns.com']]);
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