Hi
This proposal is followup of implementation of XMLTABLE.
Lot of XML documents has assigned document namespace.
<rows xmlns="http://x.y";><row><a>10</a></row></rows>
For these XML document any search path must use schema "http://x.y";. This
is not too intuitive, and from XMLTABLE usage is not too user friendly,
because the default column path (same like column name) cannot be used. A
solution of this issue is default namespace - defined in SQL/XML.
example - related to previous xml
without default namespace:
XMLTABLE(NAMESPACES('http://x.y' AS aux),
'/aux:rows/aux:row' PASSING ...
COLUMNS a int PATH 'aux:a')
with default namespace
XMLTABLE(NAMESPACES(DEFAULT 'http://x.y'),
'/rows/row' PASSING ...
COLUMNS a int);
Unfortunately the libxml2 doesn't support default namespaces in XPath
expressions. Because the libxml2 functionality is frozen, there is not big
chance for support in near future. A implementation is not too hard -
although it requires simple XPath expressions state translator.
The databases with XMLTABLE implementation supports default namespace for
XPath expressions.
The patch for initial implementation is attached.
Regards
Pavel
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 583b3b241a..c2558a33ef 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -10465,8 +10465,7 @@ SELECT xpath_exists('/my:a/text()', '<my:a xmlns:my="http://example.com";>test</m
<para>
The optional <literal>XMLNAMESPACES</> clause is a comma-separated
list of namespaces. It specifies the XML namespaces used in
- the document and their aliases. A default namespace specification
- is not currently supported.
+ the document and their aliases.
</para>
<para>
diff --git a/src/backend/utils/adt/Makefile b/src/backend/utils/adt/Makefile
index 0f512753e4..5a3715cc84 100644
--- a/src/backend/utils/adt/Makefile
+++ b/src/backend/utils/adt/Makefile
@@ -29,7 +29,7 @@ OBJS = acl.o amutils.o arrayfuncs.o array_expanded.o array_selfuncs.o \
tsquery_op.o tsquery_rewrite.o tsquery_util.o tsrank.o \
tsvector.o tsvector_op.o tsvector_parser.o \
txid.o uuid.o varbit.o varchar.o varlena.o version.o \
- windowfuncs.o xid.o xml.o
+ windowfuncs.o xid.o xml.o xpath_parser.o
like.o: like.c like_match.c
diff --git a/src/backend/utils/adt/xml.c b/src/backend/utils/adt/xml.c
index f81cf489d2..d59a76f0b4 100644
--- a/src/backend/utils/adt/xml.c
+++ b/src/backend/utils/adt/xml.c
@@ -91,7 +91,7 @@
#include "utils/rel.h"
#include "utils/syscache.h"
#include "utils/xml.h"
-
+#include "utils/xpath_parser.h"
/* GUC variables */
int xmlbinary;
@@ -184,6 +184,7 @@ typedef struct XmlTableBuilderData
xmlXPathCompExprPtr xpathcomp;
xmlXPathObjectPtr xpathobj;
xmlXPathCompExprPtr *xpathscomp;
+ bool with_default_ns;
} XmlTableBuilderData;
#endif
@@ -4180,6 +4181,7 @@ XmlTableInitOpaque(TableFuncScanState *state, int natts)
xtCxt->magic = XMLTABLE_CONTEXT_MAGIC;
xtCxt->natts = natts;
xtCxt->xpathscomp = palloc0(sizeof(xmlXPathCompExprPtr) * natts);
+ xtCxt->with_default_ns = false;
xmlerrcxt = pg_xml_init(PG_XML_STRICTNESS_ALL);
@@ -4272,6 +4274,8 @@ XmlTableSetDocument(TableFuncScanState *state, Datum value)
#endif /* not USE_LIBXML */
}
+#define DEFAULT_NAMESPACE_NAME "pgdefnamespace"
+
/*
* XmlTableSetNamespace
* Add a namespace declaration
@@ -4282,12 +4286,14 @@ XmlTableSetNamespace(TableFuncScanState *state, char *name, char *uri)
#ifdef USE_LIBXML
XmlTableBuilderData *xtCxt;
- if (name == NULL)
- ereport(ERROR,
- (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
- errmsg("DEFAULT namespace is not supported")));
xtCxt = GetXmlTableBuilderPrivateData(state, "XmlTableSetNamespace");
+ if (name == NULL)
+ {
+ xtCxt->with_default_ns = true;
+ name = DEFAULT_NAMESPACE_NAME;
+ }
+
if (xmlXPathRegisterNs(xtCxt->xpathcxt,
pg_xmlCharStrndup(name, strlen(name)),
pg_xmlCharStrndup(uri, strlen(uri))))
@@ -4316,6 +4322,14 @@ XmlTableSetRowFilter(TableFuncScanState *state, char *path)
(errcode(ERRCODE_DATA_EXCEPTION),
errmsg("row path filter must not be empty string")));
+ if (xtCxt->with_default_ns)
+ {
+ StringInfoData str;
+
+ transformXPath(&str, path, DEFAULT_NAMESPACE_NAME);
+ path = str.data;
+ }
+
xstr = pg_xmlCharStrndup(path, strlen(path));
xtCxt->xpathcomp = xmlXPathCompile(xstr);
@@ -4347,6 +4361,14 @@ XmlTableSetColumnFilter(TableFuncScanState *state, char *path, int colnum)
(errcode(ERRCODE_DATA_EXCEPTION),
errmsg("column path filter must not be empty string")));
+ if (xtCxt->with_default_ns)
+ {
+ StringInfoData str;
+
+ transformXPath(&str, path, DEFAULT_NAMESPACE_NAME);
+ path = str.data;
+ }
+
xstr = pg_xmlCharStrndup(path, strlen(path));
xtCxt->xpathscomp[colnum] = xmlXPathCompile(xstr);
diff --git a/src/backend/utils/adt/xpath_parser.c b/src/backend/utils/adt/xpath_parser.c
new file mode 100644
index 0000000000..7ec2d584c6
--- /dev/null
+++ b/src/backend/utils/adt/xpath_parser.c
@@ -0,0 +1,323 @@
+/*-------------------------------------------------------------------------
+ *
+ * xpath_parser.c
+ * XML XPath parser.
+ *
+ * Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/backend/utils/adt/xpath_parser.c
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "utils/xpath_parser.h"
+
+/*
+ * All PostgreSQL XML related functionality is based on libxml2 library, and
+ * XPath support is not an exception. However, libxml2 doesn't support
+ * default namespace for XPath expressions. Because there are not any API
+ * how to transform or access to parsed XPath expression we have to parse
+ * XPath here.
+ *
+ * Those functionalities are implemented with a simple XPath parser/
+ * preprocessor. This XPath parser transforms a XPath expression to another
+ * XPath expression that can be used by libxml2 XPath evaluation. It doesn't
+ * replace libxml2 XPath parser or libxml2 XPath expression evaluation.
+ */
+
+#ifdef USE_LIBXML
+
+/*
+ * We need to work with XPath expression tokens. When expression starting with
+ * nodename, then we can use prefix. When default namespace is defined, then we
+ * should to enhance any nodename and attribute without namespace by default
+ * namespace.
+ */
+
+typedef enum
+{
+ XPATH_TOKEN_NONE,
+ XPATH_TOKEN_NAME,
+ XPATH_TOKEN_STRING,
+ XPATH_TOKEN_NUMBER,
+ XPATH_TOKEN_OTHER
+} XPathTokenType;
+
+typedef struct XPathTokenInfo
+{
+ XPathTokenType ttype;
+ char *start;
+ int length;
+} XPathTokenInfo;
+
+#define TOKEN_STACK_SIZE 10
+
+typedef struct ParserData
+{
+ char *str;
+ char *cur;
+ XPathTokenInfo stack[TOKEN_STACK_SIZE];
+ int stack_length;
+} XPathParserData;
+
+/* Any high-bit-set character is OK (might be part of a multibyte char) */
+#define NODENAME_FIRSTCHAR(c) ((c) == '_' || (c) == '-' || \
+ ((c) >= 'A' && (c) <= 'Z') || \
+ ((c) >= 'a' && (c) <= 'z') || \
+ (IS_HIGHBIT_SET(c)))
+
+#define IS_NODENAME_CHAR(c) (NODENAME_FIRSTCHAR(c) || (c) == '.' || \
+ ((c) >= '0' && (c) <= '9'))
+
+
+/*
+ * Returns next char after last char of token - XPath lexer
+ */
+static char *
+getXPathToken(char *str, XPathTokenInfo * ti)
+{
+ /* skip initial spaces */
+ while (*str == ' ')
+ str++;
+
+ if (*str != '\0')
+ {
+ char c = *str;
+
+ ti->start = str++;
+
+ if (c >= '0' && c <= '9')
+ {
+ while (*str >= '0' && *str <= '9')
+ str++;
+ if (*str == '.')
+ {
+ str++;
+ while (*str >= '0' && *str <= '9')
+ str++;
+ }
+ ti->ttype = XPATH_TOKEN_NUMBER;
+ }
+ else if (NODENAME_FIRSTCHAR(c))
+ {
+ while (IS_NODENAME_CHAR(*str))
+ str++;
+
+ ti->ttype = XPATH_TOKEN_NAME;
+ }
+ else if (c == '"')
+ {
+ while (*str != '\0')
+ if (*str++ == '"')
+ break;
+
+ ti->ttype = XPATH_TOKEN_STRING;
+ }
+ else
+ ti->ttype = XPATH_TOKEN_OTHER;
+
+ ti->length = str - ti->start;
+ }
+ else
+ {
+ ti->start = NULL;
+ ti->length = 0;
+
+ ti->ttype = XPATH_TOKEN_NONE;
+ }
+
+ return str;
+}
+
+/*
+ * reset XPath parser stack
+ */
+static void
+initXPathParser(XPathParserData * parser, char *str)
+{
+ parser->str = str;
+ parser->cur = str;
+ parser->stack_length = 0;
+}
+
+/*
+ * Returns token from stack or read token
+ */
+static void
+nextXPathToken(XPathParserData * parser, XPathTokenInfo * ti)
+{
+ if (parser->stack_length > 0)
+ memcpy(ti, &parser->stack[--parser->stack_length],
+ sizeof(XPathTokenInfo));
+ else
+ parser->cur = getXPathToken(parser->cur, ti);
+}
+
+/*
+ * Push token to stack
+ */
+static void
+pushXPathToken(XPathParserData * parser, XPathTokenInfo * ti)
+{
+ if (parser->stack_length == TOKEN_STACK_SIZE)
+ elog(ERROR, "internal error");
+ memcpy(&parser->stack[parser->stack_length++], ti,
+ sizeof(XPathTokenInfo));
+}
+
+/*
+ * Write token to output string
+ */
+static void
+writeXPathToken(StringInfo str, XPathTokenInfo * ti)
+{
+ Assert(ti->ttype != XPATH_TOKEN_NONE);
+
+ if (ti->ttype != XPATH_TOKEN_OTHER)
+ appendBinaryStringInfo(str, ti->start, ti->length);
+ else
+ appendStringInfoChar(str, *ti->start);
+}
+
+/*
+ * This is main part of XPath transformation. It can be called recursivly,
+ * when XPath expression contains predicates.
+ */
+static void
+_transformXPath(StringInfo str, XPathParserData * parser,
+ bool inside_predicate,
+ char *def_namespace_name)
+{
+ XPathTokenInfo t1,
+ t2;
+ bool last_token_is_name = false;
+
+ nextXPathToken(parser, &t1);
+
+ while (t1.ttype != XPATH_TOKEN_NONE)
+ {
+ switch (t1.ttype)
+ {
+ case XPATH_TOKEN_NUMBER:
+ case XPATH_TOKEN_STRING:
+ last_token_is_name = false;
+ writeXPathToken(str, &t1);
+ nextXPathToken(parser, &t1);
+ break;
+
+ case XPATH_TOKEN_NAME:
+ {
+ bool is_qual_name = false;
+
+ /* inside predicate ignore keywords "and" "or" */
+ if (inside_predicate)
+ {
+ if ((strncmp(t1.start, "and", 3) == 0 && t1.length == 3) ||
+ (strncmp(t1.start, "or", 2) == 0 && t1.length == 2))
+ {
+ writeXPathToken(str, &t1);
+ nextXPathToken(parser, &t1);
+ break;
+ }
+ }
+
+ last_token_is_name = true;
+ nextXPathToken(parser, &t2);
+ if (t2.ttype == XPATH_TOKEN_OTHER)
+ {
+ if (*t2.start == '(')
+ last_token_is_name = false;
+ else if (*t2.start == ':')
+ is_qual_name = true;
+ }
+
+ if (last_token_is_name && !is_qual_name && def_namespace_name != NULL)
+ appendStringInfo(str, "%s:", def_namespace_name);
+
+ writeXPathToken(str, &t1);
+
+ if (is_qual_name)
+ {
+ writeXPathToken(str, &t2);
+ nextXPathToken(parser, &t1);
+ if (t1.ttype == XPATH_TOKEN_NAME)
+ writeXPathToken(str, &t1);
+ else
+ pushXPathToken(parser, &t1);
+ }
+ else
+ pushXPathToken(parser, &t2);
+
+ nextXPathToken(parser, &t1);
+ }
+ break;
+
+ case XPATH_TOKEN_OTHER:
+ {
+ char c = *t1.start;
+
+ writeXPathToken(str, &t1);
+
+ if (c == '[')
+ _transformXPath(str, parser, true, def_namespace_name);
+ else
+ {
+ last_token_is_name = false;
+
+ if (c == ']' && inside_predicate)
+ return;
+
+ else if (c == '@')
+ {
+ nextXPathToken(parser, &t1);
+ if (t1.ttype == XPATH_TOKEN_NAME)
+ {
+ bool is_qual_name = false;
+
+ nextXPathToken(parser, &t2);
+ if (t2.ttype == XPATH_TOKEN_OTHER && *t2.start == ':')
+ is_qual_name = true;
+
+ if (!is_qual_name && def_namespace_name != NULL)
+ appendStringInfo(str, "%s:", def_namespace_name);
+
+ writeXPathToken(str, &t1);
+ if (is_qual_name)
+ {
+ writeXPathToken(str, &t2);
+ nextXPathToken(parser, &t1);
+ if (t1.ttype == XPATH_TOKEN_NAME)
+ writeXPathToken(str, &t1);
+ else
+ pushXPathToken(parser, &t1);
+ }
+ else
+ pushXPathToken(parser, &t2);
+ }
+ else
+ pushXPathToken(parser, &t1);
+ }
+ }
+ nextXPathToken(parser, &t1);
+ }
+ break;
+
+ case XPATH_TOKEN_NONE:
+ elog(ERROR, "should not be here");
+ }
+ }
+}
+
+void
+transformXPath(StringInfo str, char *xpath,
+ char *def_namespace_name)
+{
+ XPathParserData parser;
+
+ initStringInfo(str);
+ initXPathParser(&parser, xpath);
+ _transformXPath(str, &parser, false, def_namespace_name);
+}
+
+#endif
diff --git a/src/include/utils/xpath_parser.h b/src/include/utils/xpath_parser.h
new file mode 100644
index 0000000000..b2fc239e12
--- /dev/null
+++ b/src/include/utils/xpath_parser.h
@@ -0,0 +1,23 @@
+/*-------------------------------------------------------------------------
+ *
+ * xpath_parser.h
+ * Declarations for XML XPath transformation.
+ *
+ *
+ * Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/utils/xml.h
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#ifndef XPATH_PARSER_H
+#define XPATH_PARSER_H
+
+#include "postgres.h"
+#include "lib/stringinfo.h"
+
+void transformXPath(StringInfo str, char *xpath, char *def_namespace_name);
+
+#endif /* XPATH_PARSER_H */
diff --git a/src/test/regress/expected/xml.out b/src/test/regress/expected/xml.out
index bcc585d427..9c543edad6 100644
--- a/src/test/regress/expected/xml.out
+++ b/src/test/regress/expected/xml.out
@@ -1085,7 +1085,11 @@ SELECT * FROM XMLTABLE(XMLNAMESPACES(DEFAULT 'http://x.y'),
'/rows/row'
PASSING '<rows xmlns="http://x.y";><row><a>10</a></row></rows>'
COLUMNS a int PATH 'a');
-ERROR: DEFAULT namespace is not supported
+ a
+----
+ 10
+(1 row)
+
-- used in prepare statements
PREPARE pp AS
SELECT xmltable.*
--
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