postgresql/contrib/xml2/xpath.c

/* Parser interface for DOM-based parser (libxml) rather than
   stream-based SAX-type parser */

#include "postgres.h"
#include "fmgr.h"
#include "executor/spi.h"
#include "funcapi.h"
#include "miscadmin.h"
#include "lib/stringinfo.h"

/* libxml includes */

#include <libxml/xpath.h>
#include <libxml/tree.h>
#include <libxml/xmlmemory.h>
#include <libxml/xmlerror.h>
#include <libxml/parserInternals.h>

/* declarations */

static void *pgxml_palloc(size_t size);
static void *pgxml_repalloc(void *ptr, size_t size);
static void pgxml_pfree(void *ptr);
static char *pgxml_pstrdup(const char *string);
static void pgxml_errorHandler (void * ctxt, const char *msg, ...);

void elog_error(int level, char *explain, int force);
void pgxml_parser_init(void);

static xmlChar *pgxmlNodeSetToText(xmlNodeSetPtr nodeset,
				   xmlChar * toptagname, xmlChar * septagname,
				   xmlChar * plainsep);

text *pgxml_result_to_text(xmlXPathObjectPtr res, xmlChar *toptag, 
			   xmlChar *septag, xmlChar *plainsep);

xmlChar *pgxml_texttoxmlchar(text *textstring);

static xmlXPathObjectPtr pgxml_xpath(text *document, xmlChar* xpath);


Datum		pgxml_parse(PG_FUNCTION_ARGS);
Datum           xpath_nodeset(PG_FUNCTION_ARGS);
Datum		xpath_string(PG_FUNCTION_ARGS);
Datum		xpath_number(PG_FUNCTION_ARGS);
Datum           xpath_bool(PG_FUNCTION_ARGS);
Datum           xpath_list(PG_FUNCTION_ARGS);
Datum           xpath_table(PG_FUNCTION_ARGS);

/* Global variables */
char *errbuf; /* per line error buffer */
char *pgxml_errorMsg = NULL; /* overall error message */

/* Convenience macros */

#define GET_TEXT(cstrp) DatumGetTextP(DirectFunctionCall1(textin, CStringGetDatum(cstrp)))
#define GET_STR(textp) DatumGetCString(DirectFunctionCall1(textout, PointerGetDatum(textp)))

#define ERRBUF_SIZE 200

/* memory handling passthrough functions (e.g. palloc, pstrdup are
   currently macros, and the others might become so...) */

static void *
pgxml_palloc(size_t size)
{
/*	elog(DEBUG1,"Alloc %d in CMC %x",size,CurrentMemoryContext); */
	return palloc(size);
}

static void *
pgxml_repalloc(void *ptr, size_t size)
{
/*	elog(DEBUG1,"ReAlloc in CMC %x",CurrentMemoryContext);*/
	return repalloc(ptr, size);
}

static void
pgxml_pfree(void *ptr)
{
/*	elog(DEBUG1,"Free in CMC %x",CurrentMemoryContext); */
	return pfree(ptr);
}

static char *
pgxml_pstrdup(const char *string)
{
	return pstrdup(string);
}

/* The error handling function. This formats an error message and sets
 * a flag - an ereport will be issued prior to return
 */

static void
pgxml_errorHandler (void * ctxt, const char *msg, ...)
{
  va_list args;

  va_start(args, msg);
  vsnprintf(errbuf, ERRBUF_SIZE, msg, args);
  va_end(args);
  /* Now copy the argument across */
  if (pgxml_errorMsg == NULL)
    {
      pgxml_errorMsg = pstrdup(errbuf);
    }
else
  {
    int32 xsize = strlen(pgxml_errorMsg);
    pgxml_errorMsg = repalloc(pgxml_errorMsg, 
		       (size_t) (xsize + strlen(errbuf) + 1));
    strncpy(&pgxml_errorMsg[xsize-1],errbuf,strlen(errbuf));
    pgxml_errorMsg[xsize+strlen(errbuf)-1]='\0';

  }
    memset(errbuf,0,ERRBUF_SIZE);
}

/* This function reports the current message at the level specified */
void elog_error(int level, char *explain, int force)
{
  if (force || (pgxml_errorMsg != NULL))
    {
      if (pgxml_errorMsg == NULL) 
	{
	  ereport(level,(errcode(ERRCODE_EXTERNAL_ROUTINE_EXCEPTION),
					 errmsg(explain)));
	}
      else
	{
	  ereport(level,(errcode(ERRCODE_EXTERNAL_ROUTINE_EXCEPTION),
					 errmsg("%s:%s",explain,pgxml_errorMsg)));
	  pfree(pgxml_errorMsg);
	}
    }
}

void
pgxml_parser_init()
{
	/*
	 * This code could also set parser settings from  user-supplied info.
	 * Quite how these settings are made is another matter :)
	 */

	xmlMemSetup(pgxml_pfree, pgxml_palloc, pgxml_repalloc, pgxml_pstrdup);
	xmlInitParser();

	xmlSetGenericErrorFunc(NULL, pgxml_errorHandler);

	xmlSubstituteEntitiesDefault(1);
	xmlLoadExtDtdDefaultValue = 1;

	pgxml_errorMsg = NULL;

	errbuf = palloc(200);
	memset(errbuf,0,200);

}


/* Returns true if document is well-formed */

PG_FUNCTION_INFO_V1(pgxml_parse);

Datum
pgxml_parse(PG_FUNCTION_ARGS)
{
	/* called as pgxml_parse(document) */
	xmlDocPtr	doctree;
	text	   *t = PG_GETARG_TEXT_P(0);		/* document buffer */
	int32		docsize = VARSIZE(t) - VARHDRSZ;

	pgxml_parser_init();

	doctree = xmlParseMemory((char *) VARDATA(t), docsize);
	if (doctree == NULL)
	{
		xmlCleanupParser();
		PG_RETURN_BOOL(false);	/* i.e. not well-formed */
	}
	xmlCleanupParser();
	xmlFreeDoc(doctree);
	PG_RETURN_BOOL(true);
}


static xmlChar
*
pgxmlNodeSetToText(xmlNodeSetPtr nodeset,
				   xmlChar * toptagname,
				   xmlChar * septagname,
		                   xmlChar * plainsep)
{
	/* Function translates a nodeset into a text representation */

	/*
	 * iterates over each node in the set and calls xmlNodeDump to write
	 * it to an xmlBuffer -from which an xmlChar * string is returned.
	 */

	/* each representation is surrounded by <tagname> ... </tagname> */
	/* plainsep is an ordinary (not tag) seperator - if used, then
	* nodes are cast to string as output method */
        

	xmlBufferPtr buf;
	xmlChar    *result;
	int			i;

	buf = xmlBufferCreate();

	if ((toptagname != NULL) && (xmlStrlen(toptagname) > 0))
	{
		xmlBufferWriteChar(buf, "<");
		xmlBufferWriteCHAR(buf, toptagname);
		xmlBufferWriteChar(buf, ">");
	}
	if (nodeset != NULL)
	{
		for (i = 0; i < nodeset->nodeNr; i++)
		{

		  if (plainsep != NULL) {
		    xmlBufferWriteCHAR(buf,
			  xmlXPathCastNodeToString(nodeset->nodeTab[i]));
			 
			/* If this isn't the last entry, write the plain sep. */
		    if (i < (nodeset->nodeNr)-1) {
			  xmlBufferWriteChar(buf, plainsep);
			}
		  } else {


			if ((septagname != NULL) && (xmlStrlen(septagname) > 0))
			{
				xmlBufferWriteChar(buf, "<");
				xmlBufferWriteCHAR(buf, septagname);
				xmlBufferWriteChar(buf, ">");
			}
						xmlNodeDump(buf, 
				    nodeset->nodeTab[i]->doc, 
				    nodeset->nodeTab[i], 
				    1, 0);

			if ((septagname != NULL) && (xmlStrlen(septagname) > 0))
			{
				xmlBufferWriteChar(buf, "</");
				xmlBufferWriteCHAR(buf, septagname);
				xmlBufferWriteChar(buf, ">");
			}
		  }
		}
	}

	if ((toptagname != NULL) && (xmlStrlen(toptagname) > 0))
	{
		xmlBufferWriteChar(buf, "</");
		xmlBufferWriteCHAR(buf, toptagname);
		xmlBufferWriteChar(buf, ">");
	}
	result = xmlStrdup(buf->content);
	xmlBufferFree(buf);
	return result;
}


/* Translate a PostgreSQL "varlena" -i.e. a variable length parameter
 * into the libxml2 representation
 */

xmlChar *
pgxml_texttoxmlchar(text *textstring)
{
	xmlChar    *res;
	int32		txsize;

	txsize = VARSIZE(textstring) - VARHDRSZ;
	res = (xmlChar *) palloc(txsize + 1);
	memcpy((char *) res, VARDATA(textstring), txsize);
	res[txsize] = '\0';
	return res;
}

/* Public visible XPath functions */

/* This is a "raw" xpath function. Check that it returns child elements
 * properly
 */

PG_FUNCTION_INFO_V1(xpath_nodeset);

Datum
xpath_nodeset(PG_FUNCTION_ARGS)
{
  xmlChar    *xpath, *toptag, *septag;
  int32 pathsize;
	text	   
	           *xpathsupp,
		   *xpres;

	/* PG_GETARG_TEXT_P(0) is document buffer */
	xpathsupp = PG_GETARG_TEXT_P(1);	/* XPath expression */

	toptag = pgxml_texttoxmlchar(PG_GETARG_TEXT_P(2));
	septag = pgxml_texttoxmlchar(PG_GETARG_TEXT_P(3));

	pathsize = VARSIZE(xpathsupp) - VARHDRSZ;

	xpath = pgxml_texttoxmlchar(xpathsupp);

	xpres = pgxml_result_to_text(
				     pgxml_xpath(PG_GETARG_TEXT_P(0),xpath),
				     toptag,septag,NULL);

	/* xmlCleanupParser(); done by result_to_text routine */
	pfree((void *) xpath);

	if (xpres == NULL) 
	  {
	    PG_RETURN_NULL();
	  }
	PG_RETURN_TEXT_P(xpres);
}

// The following function is almost identical, but returns the elements in
// a list.

PG_FUNCTION_INFO_V1(xpath_list);

Datum
xpath_list(PG_FUNCTION_ARGS)
{
  xmlChar    *xpath, *plainsep;
  int32 pathsize;
	text	   
	           *xpathsupp,
		   *xpres;

	/* PG_GETARG_TEXT_P(0) is document buffer */
	xpathsupp = PG_GETARG_TEXT_P(1);	/* XPath expression */

	plainsep = pgxml_texttoxmlchar(PG_GETARG_TEXT_P(2));

	pathsize = VARSIZE(xpathsupp) - VARHDRSZ;

	xpath = pgxml_texttoxmlchar(xpathsupp);

	xpres = pgxml_result_to_text(
				     pgxml_xpath(PG_GETARG_TEXT_P(0),xpath),
				     NULL,NULL,plainsep);

	/* xmlCleanupParser(); done by result_to_text routine */
	pfree((void *) xpath);

	if (xpres == NULL) 
	  {
	    PG_RETURN_NULL();
	  }
	PG_RETURN_TEXT_P(xpres);
}


PG_FUNCTION_INFO_V1(xpath_string);

Datum
xpath_string(PG_FUNCTION_ARGS)
{
  xmlChar    *xpath;
  int32 pathsize;
	text	   
	           *xpathsupp,
		   *xpres;

	/* PG_GETARG_TEXT_P(0) is document buffer */
	xpathsupp = PG_GETARG_TEXT_P(1);	/* XPath expression */

	pathsize = VARSIZE(xpathsupp) - VARHDRSZ;

	/* We encapsulate the supplied path with "string()"
	 * = 8 chars + 1 for NUL at end */
	/* We could try casting to string using the libxml function? */

	xpath =(xmlChar *) palloc(pathsize + 9);
	memcpy((char *) (xpath+7), VARDATA(xpathsupp), pathsize);
	strncpy((char *) xpath, "string(",7);
	xpath[pathsize+7] = ')';
	xpath[pathsize+8] = '\0';

	xpres = pgxml_result_to_text(
				     pgxml_xpath(PG_GETARG_TEXT_P(0),xpath),
				     NULL,NULL,NULL);

	xmlCleanupParser();
	pfree((void *) xpath);

	if (xpres == NULL) 
	  {
	    PG_RETURN_NULL();
	  }
	PG_RETURN_TEXT_P(xpres);
}


PG_FUNCTION_INFO_V1(xpath_number);

Datum
xpath_number(PG_FUNCTION_ARGS)
{
  xmlChar    *xpath;
  int32 pathsize;
	text	   
	  *xpathsupp;
		   
	float4 fRes;

	xmlXPathObjectPtr res;

	/* PG_GETARG_TEXT_P(0) is document buffer */
	xpathsupp = PG_GETARG_TEXT_P(1);	/* XPath expression */

	pathsize = VARSIZE(xpathsupp) - VARHDRSZ;

	xpath = pgxml_texttoxmlchar(xpathsupp);

	res = pgxml_xpath(PG_GETARG_TEXT_P(0),xpath);
	pfree((void *) xpath);

	if (res == NULL)
	  {
	    xmlCleanupParser();
	    PG_RETURN_NULL();
	  }

	fRes = xmlXPathCastToNumber(res);
	xmlCleanupParser();
	if (xmlXPathIsNaN(fRes))
	  {
	    PG_RETURN_NULL();
	  }

	PG_RETURN_FLOAT4(fRes);

}


PG_FUNCTION_INFO_V1(xpath_bool);

Datum
xpath_bool(PG_FUNCTION_ARGS)
{
  xmlChar    *xpath;
  int32 pathsize;
	text	   
	  *xpathsupp;
		   
	int bRes;

	xmlXPathObjectPtr res;

	/* PG_GETARG_TEXT_P(0) is document buffer */
	xpathsupp = PG_GETARG_TEXT_P(1);	/* XPath expression */

	pathsize = VARSIZE(xpathsupp) - VARHDRSZ;

	xpath = pgxml_texttoxmlchar(xpathsupp);

	res = pgxml_xpath(PG_GETARG_TEXT_P(0),xpath);
	pfree((void *) xpath);

	if (res == NULL)
	  {
	    xmlCleanupParser();
	    PG_RETURN_BOOL(false);
	  }

	bRes = xmlXPathCastToBoolean(res);
	xmlCleanupParser();
	PG_RETURN_BOOL(bRes);

}



/* Core function to evaluate XPath query */

xmlXPathObjectPtr
  pgxml_xpath(text *document, xmlChar *xpath)
  {

	xmlDocPtr	doctree;
	xmlXPathContextPtr ctxt;
	xmlXPathObjectPtr res;

	xmlXPathCompExprPtr comppath;

	int32		docsize;

    
	docsize = VARSIZE(document) - VARHDRSZ;

	pgxml_parser_init();

	doctree = xmlParseMemory((char *) VARDATA(document), docsize);
	if (doctree == NULL)
	{					/* not well-formed */
		return NULL;
	}

	ctxt = xmlXPathNewContext(doctree);
	ctxt->node = xmlDocGetRootElement(doctree);


	/* compile the path */
	comppath = xmlXPathCompile(xpath);
	if (comppath == NULL)
	{
		xmlCleanupParser();
		xmlFreeDoc(doctree);
		elog_error(ERROR,"XPath Syntax Error",1);

	        return NULL;
	}

	/* Now evaluate the path expression. */
	res = xmlXPathCompiledEval(comppath, ctxt);
	xmlXPathFreeCompExpr(comppath);

	if (res == NULL)
	{
	  xmlXPathFreeContext(ctxt);
	  // xmlCleanupParser();
		xmlFreeDoc(doctree);

		return NULL;
	}
	/* xmlFreeDoc(doctree); */
	return res;
  }

text 
*pgxml_result_to_text(xmlXPathObjectPtr res, 
		      xmlChar *toptag, 
		      xmlChar *septag,
		      xmlChar *plainsep)
{
	xmlChar *xpresstr;
	int32 ressize;
	text *xpres;

  if (res == NULL)
    {
      return NULL;
    }
	switch (res->type)
	{
		case XPATH_NODESET:
			xpresstr = pgxmlNodeSetToText(res->nodesetval,
						      toptag,
						      septag, plainsep);
			break;

		case XPATH_STRING:
			xpresstr = xmlStrdup(res->stringval);
			break;

		default:
			elog(NOTICE, "Unsupported XQuery result: %d", res->type);
			xpresstr = xmlStrdup("<unsupported/>");
	}


	/* Now convert this result back to text */
	ressize = strlen(xpresstr);
	xpres = (text *) palloc(ressize + VARHDRSZ);
	memcpy(VARDATA(xpres), xpresstr, ressize);
	VARATT_SIZEP(xpres) = ressize + VARHDRSZ;

	/* Free various storage */
	xmlCleanupParser();
	/* xmlFreeDoc(doctree);  -- will die at end of tuple anyway */

	xmlFree(xpresstr);

	elog_error(ERROR,"XPath error",0);


	return xpres;
}

/* xpath_table is a table function. It needs some tidying (as do the
 * other functions here!
 */

PG_FUNCTION_INFO_V1(xpath_table);

Datum xpath_table(PG_FUNCTION_ARGS)
{
/* SPI (input tuple) support */
  SPITupleTable *tuptable;
  HeapTuple  spi_tuple;
  TupleDesc  spi_tupdesc;

/* Output tuple (tuplestore) support */
  Tuplestorestate *tupstore = NULL;
  TupleDesc ret_tupdesc;
  HeapTuple  ret_tuple;

  ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
  AttInMetadata *attinmeta;
  MemoryContext per_query_ctx;
  MemoryContext oldcontext;

/* Function parameters */              
  char *pkeyfield = GET_STR(PG_GETARG_TEXT_P(0));
  char *xmlfield = GET_STR(PG_GETARG_TEXT_P(1));
  char *relname = GET_STR(PG_GETARG_TEXT_P(2));
  char *xpathset = GET_STR(PG_GETARG_TEXT_P(3));
  char *condition = GET_STR(PG_GETARG_TEXT_P(4));

  char **values;
  xmlChar **xpaths; 
  xmlChar *pos;
  xmlChar *pathsep= "|";

  int numpaths;
  int ret;
  int proc;
  int i;
  int j;
  int rownr; /* For issuing multiple rows from one original document */
  int had_values; /* To determine end of nodeset results */

  StringInfo querysql;

/* We only have a valid tuple description in table function mode */
  if (rsinfo->expectedDesc == NULL) {
	  ereport(ERROR,(errcode(ERRCODE_SYNTAX_ERROR),
					 errmsg("xpath_table must be called as a table function")));
  }
 
/* The tuplestore must exist in a higher context than 
 * this function call (per_query_ctx is used) */

  per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
  oldcontext = MemoryContextSwitchTo(per_query_ctx);

/* Create the tuplestore - SortMem is the max in-memory size before it is
 * shipped to a disk heap file. Just like ... SortMem!
 */

  tupstore = tuplestore_begin_heap(true, false, SortMem);

  MemoryContextSwitchTo(oldcontext);

  /* get the requested return tuple description */
  ret_tupdesc = CreateTupleDescCopy(rsinfo->expectedDesc);

  /* At the moment we assume that the returned attributes make sense
   * for the XPath specififed (i.e. we trust the caller). 
   * It's not fatal if they get it wrong - the input function for the
   * column type will raise an error if the path result can't be converted
   * into the correct binary representation.
   */

  attinmeta = TupleDescGetAttInMetadata(ret_tupdesc);

  /* We want to materialise because it means that we don't have to
   * carry libxml2 parser state between invocations of this function
   */

  /* check to see if caller supports us returning a tuplestore */
  if (!rsinfo || !(rsinfo->allowedModes & SFRM_Materialize))
	  ereport(ERROR, (errcode(ERRCODE_SYNTAX_ERROR),
					  errmsg("xpath_table requires Materialize mode, but it is not "
							 "allowed in this context")));

  // Set return mode and allocate value space.
  rsinfo->returnMode = SFRM_Materialize;
  rsinfo->setDesc = ret_tupdesc;
  
  values = (char **) palloc(ret_tupdesc->natts * sizeof(char *));

  xpaths = (xmlChar **) palloc(ret_tupdesc->natts * sizeof(xmlChar *));

  /* Split XPaths. xpathset is a writable CString. */

  /* Note that we stop splitting once we've done all needed for tupdesc */

  numpaths=0;
  pos = xpathset;
  do {
    xpaths[numpaths] = pos;
    pos = strstr(pos,pathsep);
    if (pos != NULL) {
      *pos = '\0';
      pos++;
    }
    numpaths++;
  } while ((pos != NULL) && (numpaths < (ret_tupdesc->natts - 1) ));

  /* Now build query */

  querysql = makeStringInfo();

  /* Build initial sql statement */
  appendStringInfo(querysql, "SELECT %s, %s FROM %s WHERE %s",
		   pkeyfield,
		   xmlfield,
		   relname,
		   condition
		   );


  if ((ret = SPI_connect()) < 0) {
    elog(ERROR, "xpath_table: SPI_connect returned %d", ret);
  }

  if ((ret = SPI_exec(querysql->data,0)) != SPI_OK_SELECT) {
    elog(ERROR,"xpath_table: SPI execution failed for query %s",querysql->data);
  }

  proc= SPI_processed;
  /*  elog(DEBUG1,"xpath_table: SPI returned %d rows",proc); */
  tuptable = SPI_tuptable;
  spi_tupdesc = tuptable->tupdesc;

/* Switch out of SPI context */
  MemoryContextSwitchTo(oldcontext);


/* Check that SPI returned correct result. If you put a comma into one of
 * the function parameters, this will catch it when the SPI query returns
 * e.g. 3 columns. 
 */

  if (spi_tupdesc->natts != 2) {
    ereport(ERROR,(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
				   errmsg("Expression returning multiple columns is not valid in parameter list"),
				   errdetail("Expected two columns in SPI result, got %d",spi_tupdesc->natts)));
  }

/* Setup the parser. Beware that this must happen in the same context as the
 * cleanup - which means that any error from here on must do cleanup to
 * ensure that the entity table doesn't get freed by being out of context.
 */
  pgxml_parser_init();

   /* For each row i.e. document returned from SPI */
  for (i=0; i < proc; i++) {
	  char *pkey;
	  char *xmldoc;

	  xmlDocPtr	doctree;
	  xmlXPathContextPtr ctxt;
	  xmlXPathObjectPtr res;
	  xmlChar *resstr;

    
	  xmlXPathCompExprPtr comppath;

	  /* Extract the row data as C Strings */
	  
	  spi_tuple = tuptable->vals[i]; 
	  pkey = SPI_getvalue(spi_tuple, spi_tupdesc,1);
	  xmldoc = SPI_getvalue(spi_tuple, spi_tupdesc,2);


	  /* Clear the values array, so that not-well-formed documents
	   * return NULL in all columns.
	   */
    
	  /* Note that this also means that spare columns will be NULL. */
	  for (j=0; j < ret_tupdesc->natts; j++) {
		  values[j]= NULL;
	  }
    
	  /* Insert primary key */
	  values[0]=pkey;
    
	  /* Parse the document */
	  doctree = xmlParseMemory(xmldoc, strlen(xmldoc));

	  if (doctree == NULL)
      {					/* not well-formed, so output all-NULL tuple */
	
		  ret_tuple = BuildTupleFromCStrings(attinmeta, values);
		  oldcontext = MemoryContextSwitchTo(per_query_ctx);
		  tuplestore_puttuple(tupstore, ret_tuple);
		  MemoryContextSwitchTo(oldcontext);
		  heap_freetuple(ret_tuple);
      }
	  else 
      {
		  /* New loop here - we have to deal with nodeset results */
		  rownr=0;
		  
		  do {
			  /* Now evaluate the set of xpaths. */
			  had_values=0;
			  for (j=0; j < numpaths; j++) {
				  
				  ctxt = xmlXPathNewContext(doctree);
				  ctxt->node = xmlDocGetRootElement(doctree);
				  xmlSetGenericErrorFunc(ctxt, pgxml_errorHandler);
				  
				  /* compile the path */
				  comppath = xmlXPathCompile(xpaths[j]);
				  if (comppath == NULL)
				  {
					  xmlCleanupParser();
					  xmlFreeDoc(doctree);
					  
					  elog_error(ERROR,"XPath Syntax Error",1);
					  
					  PG_RETURN_NULL();  /* Keep compiler happy */
				  }
				  
				  /* Now evaluate the path expression. */
				  res = xmlXPathCompiledEval(comppath, ctxt);
				  xmlXPathFreeCompExpr(comppath);
				  
				  if (res != NULL) 
				  {
					  switch (res->type)
					  {
					  case XPATH_NODESET:
						  /* We see if this nodeset has enough nodes */
						  if ((res->nodesetval != NULL) && (rownr < res->nodesetval->nodeNr)) {
							  resstr = 
								  xmlXPathCastNodeToString(res->nodesetval->nodeTab[rownr]);
							  had_values=1;
						  } else {
							  resstr = NULL;
						  }
						  
						  break;
						  
					  case XPATH_STRING:
						  resstr = xmlStrdup(res->stringval);
						  break;
						  
					  default:
						  elog(NOTICE, "Unsupported XQuery result: %d", res->type);
						  resstr = xmlStrdup("<unsupported/>");
					  }
					  
					  
					  // Insert this into the appropriate column in the result tuple.
					  values[j+1] = resstr;
				  }
				  xmlXPathFreeContext(ctxt);
			  }
			  // Now add the tuple to the output, if there is one.
			  if (had_values) {
				  ret_tuple = BuildTupleFromCStrings(attinmeta, values);
				  oldcontext = MemoryContextSwitchTo(per_query_ctx);
				  tuplestore_puttuple(tupstore, ret_tuple);
				  MemoryContextSwitchTo(oldcontext);
				  heap_freetuple(ret_tuple);
			  }
			  
			  rownr++;
			  
		  } while (had_values);
		  
      }
	  
    xmlFreeDoc(doctree);    
    
    pfree(pkey);
    pfree(xmldoc);
  }

  xmlCleanupParser();
/* Needed to flag completeness in 7.3.1. 7.4 defines it as a no-op. */
  tuplestore_donestoring(tupstore);

  SPI_finish();

  rsinfo->setResult=tupstore;
  
  /*
   * SFRM_Materialize mode expects us to return a NULL Datum. The actual
   * tuples are in our tuplestore and passed back through
   * rsinfo->setResult. rsinfo->setDesc is set to the tuple description
   * that we actually used to build our tuples with, so the caller can
   * verify we did what it was expecting.
   */
  return (Datum) 0;
  
}