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