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c4810d9ae0
in versions >= 8.3). The core code is more robust and efficient than what was there before, and this also reduces risks involved in swapping different libxml error handler settings. Before 8.3, there is still some risk of problems if add-on modules such as Perl invoke libxml without setting their own error handler. Given the lack of reports I'm not sure there's a risk in practice, so I didn't take the step of actually duplicating the core code into older contrib/xml2 branches. Instead I just tweaked the existing code to ensure it didn't leave a dangling pointer to short-lived memory when throwing an error.
860 lines
20 KiB
C
860 lines
20 KiB
C
/* Parser interface for DOM-based parser (libxml) rather than
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stream-based SAX-type parser */
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#include "postgres.h"
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#include "fmgr.h"
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#include "executor/spi.h"
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#include "funcapi.h"
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#include "miscadmin.h"
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#include "lib/stringinfo.h"
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/* libxml includes */
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#include <libxml/xpath.h>
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#include <libxml/tree.h>
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#include <libxml/xmlmemory.h>
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#include <libxml/xmlerror.h>
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#include <libxml/parserInternals.h>
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PG_MODULE_MAGIC;
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/* externally accessible functions */
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Datum xml_is_well_formed(PG_FUNCTION_ARGS);
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Datum xml_encode_special_chars(PG_FUNCTION_ARGS);
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Datum xpath_nodeset(PG_FUNCTION_ARGS);
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Datum xpath_string(PG_FUNCTION_ARGS);
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Datum xpath_number(PG_FUNCTION_ARGS);
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Datum xpath_bool(PG_FUNCTION_ARGS);
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Datum xpath_list(PG_FUNCTION_ARGS);
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Datum xpath_table(PG_FUNCTION_ARGS);
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/* these are exported for use by xslt_proc.c */
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void elog_error(const char *explain, bool force);
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void pgxml_parser_init(void);
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/* local declarations */
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static void pgxml_errorHandler(void *ctxt, const char *msg,...);
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static xmlChar *pgxmlNodeSetToText(xmlNodeSetPtr nodeset,
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xmlChar *toptagname, xmlChar *septagname,
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xmlChar *plainsep);
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static text *pgxml_result_to_text(xmlXPathObjectPtr res, xmlChar *toptag,
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xmlChar *septag, xmlChar *plainsep);
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static xmlChar *pgxml_texttoxmlchar(text *textstring);
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static xmlXPathObjectPtr pgxml_xpath(text *document, xmlChar *xpath);
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/* Global variables */
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static char *pgxml_errorMsg = NULL; /* overall error message */
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#define GET_STR(textp) DatumGetCString(DirectFunctionCall1(textout, PointerGetDatum(textp)))
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/*
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* The error handling function. This formats an error message and sets
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* a flag - an ereport will be issued prior to return
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*/
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static void
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pgxml_errorHandler(void *ctxt, const char *msg,...)
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{
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char errbuf[1024]; /* per line error buffer */
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va_list args;
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/* Format the message */
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va_start(args, msg);
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vsnprintf(errbuf, sizeof(errbuf), msg, args);
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va_end(args);
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/* Store in, or append to, pgxml_errorMsg */
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if (pgxml_errorMsg == NULL)
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pgxml_errorMsg = pstrdup(errbuf);
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else
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{
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size_t oldsize = strlen(pgxml_errorMsg);
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size_t newsize = strlen(errbuf);
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/*
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* We intentionally discard the last char of the existing message,
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* which should be a carriage return. (XXX wouldn't it be saner
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* to keep it?)
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*/
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pgxml_errorMsg = repalloc(pgxml_errorMsg, oldsize + newsize);
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memcpy(&pgxml_errorMsg[oldsize - 1], errbuf, newsize);
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pgxml_errorMsg[oldsize + newsize - 1] = '\0';
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}
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}
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/*
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* This function ereports the current message if any. If force is true
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* then an error is thrown even if pgxml_errorMsg hasn't been set.
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*/
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void
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elog_error(const char *explain, bool force)
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{
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if (force || pgxml_errorMsg != NULL)
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{
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if (pgxml_errorMsg == NULL)
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ereport(ERROR,
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(errcode(ERRCODE_EXTERNAL_ROUTINE_EXCEPTION),
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errmsg("%s", explain)));
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else
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{
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/*
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* Ensure pgxml_errorMsg is reset to null before we give up
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* control. This provides some protection against crashes if
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* pgxml_errorHandler is invoked again later, perhaps as a
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* result of other modules' use of libxml.
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*/
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char *msg = pgxml_errorMsg;
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pgxml_errorMsg = NULL;
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ereport(ERROR,
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(errcode(ERRCODE_EXTERNAL_ROUTINE_EXCEPTION),
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errmsg("%s: %s", explain, msg)));
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}
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}
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}
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/*
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* Initialize for xml parsing.
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*/
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void
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pgxml_parser_init(void)
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{
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/* Set up error handling */
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pgxml_errorMsg = NULL;
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xmlSetGenericErrorFunc(NULL, pgxml_errorHandler);
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/* Initialize libxml */
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xmlInitParser();
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xmlSubstituteEntitiesDefault(1);
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xmlLoadExtDtdDefaultValue = 1;
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}
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/* Returns true if document is well-formed */
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PG_FUNCTION_INFO_V1(xml_is_well_formed);
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Datum
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xml_is_well_formed(PG_FUNCTION_ARGS)
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{
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text *t = PG_GETARG_TEXT_P(0); /* document buffer */
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int32 docsize = VARSIZE(t) - VARHDRSZ;
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xmlDocPtr doctree;
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pgxml_parser_init();
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doctree = xmlParseMemory((char *) VARDATA(t), docsize);
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if (doctree == NULL)
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PG_RETURN_BOOL(false); /* i.e. not well-formed */
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xmlFreeDoc(doctree);
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PG_RETURN_BOOL(true);
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}
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/* Encodes special characters (<, >, &, " and \r) as XML entities */
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PG_FUNCTION_INFO_V1(xml_encode_special_chars);
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Datum
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xml_encode_special_chars(PG_FUNCTION_ARGS)
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{
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text *tin = PG_GETARG_TEXT_P(0);
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text *tout;
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int32 ressize;
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xmlChar *ts,
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*tt;
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ts = pgxml_texttoxmlchar(tin);
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tt = xmlEncodeSpecialChars(NULL, ts);
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pfree(ts);
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ressize = strlen(tt);
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tout = (text *) palloc(ressize + VARHDRSZ);
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memcpy(VARDATA(tout), tt, ressize);
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VARATT_SIZEP(tout) = ressize + VARHDRSZ;
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xmlFree(tt);
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PG_RETURN_TEXT_P(tout);
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}
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/*
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* Function translates a nodeset into a text representation
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*
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* iterates over each node in the set and calls xmlNodeDump to write it to
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* an xmlBuffer -from which an xmlChar * string is returned.
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*
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* each representation is surrounded by <tagname> ... </tagname>
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*
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* plainsep is an ordinary (not tag) separator - if used, then nodes are
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* cast to string as output method
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*/
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static xmlChar *
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pgxmlNodeSetToText(xmlNodeSetPtr nodeset,
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xmlChar *toptagname,
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xmlChar *septagname,
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xmlChar *plainsep)
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{
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xmlBufferPtr buf;
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xmlChar *result;
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int i;
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buf = xmlBufferCreate();
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if ((toptagname != NULL) && (xmlStrlen(toptagname) > 0))
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{
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xmlBufferWriteChar(buf, "<");
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xmlBufferWriteCHAR(buf, toptagname);
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xmlBufferWriteChar(buf, ">");
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}
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if (nodeset != NULL)
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{
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for (i = 0; i < nodeset->nodeNr; i++)
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{
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if (plainsep != NULL)
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{
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xmlBufferWriteCHAR(buf,
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xmlXPathCastNodeToString(nodeset->nodeTab[i]));
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/* If this isn't the last entry, write the plain sep. */
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if (i < (nodeset->nodeNr) - 1)
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xmlBufferWriteChar(buf, plainsep);
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}
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else
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{
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if ((septagname != NULL) && (xmlStrlen(septagname) > 0))
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{
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xmlBufferWriteChar(buf, "<");
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xmlBufferWriteCHAR(buf, septagname);
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xmlBufferWriteChar(buf, ">");
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}
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xmlNodeDump(buf,
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nodeset->nodeTab[i]->doc,
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nodeset->nodeTab[i],
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1, 0);
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if ((septagname != NULL) && (xmlStrlen(septagname) > 0))
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{
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xmlBufferWriteChar(buf, "</");
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xmlBufferWriteCHAR(buf, septagname);
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xmlBufferWriteChar(buf, ">");
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}
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}
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}
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}
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if ((toptagname != NULL) && (xmlStrlen(toptagname) > 0))
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{
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xmlBufferWriteChar(buf, "</");
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xmlBufferWriteCHAR(buf, toptagname);
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xmlBufferWriteChar(buf, ">");
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}
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result = xmlStrdup(buf->content);
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xmlBufferFree(buf);
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return result;
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}
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/* Translate a PostgreSQL "varlena" -i.e. a variable length parameter
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* into the libxml2 representation
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*/
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static xmlChar *
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pgxml_texttoxmlchar(text *textstring)
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{
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xmlChar *res;
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int32 txsize;
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txsize = VARSIZE(textstring) - VARHDRSZ;
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res = (xmlChar *) palloc(txsize + 1);
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memcpy((char *) res, VARDATA(textstring), txsize);
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res[txsize] = '\0';
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return res;
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}
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/* Publicly visible XPath functions */
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/*
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* This is a "raw" xpath function. Check that it returns child elements
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* properly
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*/
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PG_FUNCTION_INFO_V1(xpath_nodeset);
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Datum
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xpath_nodeset(PG_FUNCTION_ARGS)
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{
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xmlChar *xpath,
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*toptag,
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*septag;
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int32 pathsize;
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text *xpathsupp,
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*xpres;
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/* PG_GETARG_TEXT_P(0) is document buffer */
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xpathsupp = PG_GETARG_TEXT_P(1); /* XPath expression */
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toptag = pgxml_texttoxmlchar(PG_GETARG_TEXT_P(2));
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septag = pgxml_texttoxmlchar(PG_GETARG_TEXT_P(3));
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pathsize = VARSIZE(xpathsupp) - VARHDRSZ;
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xpath = pgxml_texttoxmlchar(xpathsupp);
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xpres = pgxml_result_to_text(pgxml_xpath(PG_GETARG_TEXT_P(0), xpath),
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toptag, septag, NULL);
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pfree(xpath);
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if (xpres == NULL)
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PG_RETURN_NULL();
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PG_RETURN_TEXT_P(xpres);
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}
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/*
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* The following function is almost identical, but returns the elements in
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* a list.
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*/
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PG_FUNCTION_INFO_V1(xpath_list);
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Datum
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xpath_list(PG_FUNCTION_ARGS)
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{
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xmlChar *xpath,
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*plainsep;
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int32 pathsize;
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text *xpathsupp,
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*xpres;
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/* PG_GETARG_TEXT_P(0) is document buffer */
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xpathsupp = PG_GETARG_TEXT_P(1); /* XPath expression */
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plainsep = pgxml_texttoxmlchar(PG_GETARG_TEXT_P(2));
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pathsize = VARSIZE(xpathsupp) - VARHDRSZ;
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xpath = pgxml_texttoxmlchar(xpathsupp);
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xpres = pgxml_result_to_text(pgxml_xpath(PG_GETARG_TEXT_P(0), xpath),
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NULL, NULL, plainsep);
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pfree(xpath);
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if (xpres == NULL)
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PG_RETURN_NULL();
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PG_RETURN_TEXT_P(xpres);
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}
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PG_FUNCTION_INFO_V1(xpath_string);
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Datum
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xpath_string(PG_FUNCTION_ARGS)
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{
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xmlChar *xpath;
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int32 pathsize;
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text *xpathsupp,
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*xpres;
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/* PG_GETARG_TEXT_P(0) is document buffer */
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xpathsupp = PG_GETARG_TEXT_P(1); /* XPath expression */
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pathsize = VARSIZE(xpathsupp) - VARHDRSZ;
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/*
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* We encapsulate the supplied path with "string()" = 8 chars + 1 for NUL
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* at end
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*/
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/* We could try casting to string using the libxml function? */
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xpath = (xmlChar *) palloc(pathsize + 9);
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memcpy((char *) (xpath + 7), VARDATA(xpathsupp), pathsize);
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strncpy((char *) xpath, "string(", 7);
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xpath[pathsize + 7] = ')';
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xpath[pathsize + 8] = '\0';
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xpres = pgxml_result_to_text(pgxml_xpath(PG_GETARG_TEXT_P(0), xpath),
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NULL, NULL, NULL);
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pfree(xpath);
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if (xpres == NULL)
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PG_RETURN_NULL();
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PG_RETURN_TEXT_P(xpres);
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}
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PG_FUNCTION_INFO_V1(xpath_number);
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Datum
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xpath_number(PG_FUNCTION_ARGS)
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{
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xmlChar *xpath;
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int32 pathsize;
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text *xpathsupp;
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float4 fRes;
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xmlXPathObjectPtr res;
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/* PG_GETARG_TEXT_P(0) is document buffer */
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xpathsupp = PG_GETARG_TEXT_P(1); /* XPath expression */
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pathsize = VARSIZE(xpathsupp) - VARHDRSZ;
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xpath = pgxml_texttoxmlchar(xpathsupp);
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res = pgxml_xpath(PG_GETARG_TEXT_P(0), xpath);
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pfree(xpath);
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if (res == NULL)
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PG_RETURN_NULL();
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fRes = xmlXPathCastToNumber(res);
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if (xmlXPathIsNaN(fRes))
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PG_RETURN_NULL();
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PG_RETURN_FLOAT4(fRes);
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}
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PG_FUNCTION_INFO_V1(xpath_bool);
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Datum
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xpath_bool(PG_FUNCTION_ARGS)
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{
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xmlChar *xpath;
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int32 pathsize;
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text *xpathsupp;
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int bRes;
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xmlXPathObjectPtr res;
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/* PG_GETARG_TEXT_P(0) is document buffer */
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xpathsupp = PG_GETARG_TEXT_P(1); /* XPath expression */
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pathsize = VARSIZE(xpathsupp) - VARHDRSZ;
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xpath = pgxml_texttoxmlchar(xpathsupp);
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res = pgxml_xpath(PG_GETARG_TEXT_P(0), xpath);
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pfree(xpath);
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if (res == NULL)
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PG_RETURN_BOOL(false);
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bRes = xmlXPathCastToBoolean(res);
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PG_RETURN_BOOL(bRes);
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}
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/* Core function to evaluate XPath query */
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static xmlXPathObjectPtr
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pgxml_xpath(text *document, xmlChar *xpath)
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{
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xmlDocPtr doctree;
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xmlXPathContextPtr ctxt;
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xmlXPathObjectPtr res;
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xmlXPathCompExprPtr comppath;
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int32 docsize;
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docsize = VARSIZE(document) - VARHDRSZ;
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pgxml_parser_init();
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doctree = xmlParseMemory((char *) VARDATA(document), docsize);
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if (doctree == NULL)
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return NULL; /* not well-formed */
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ctxt = xmlXPathNewContext(doctree);
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ctxt->node = xmlDocGetRootElement(doctree);
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/* compile the path */
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comppath = xmlXPathCompile(xpath);
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if (comppath == NULL)
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{
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xmlFreeDoc(doctree);
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elog_error("XPath Syntax Error", true);
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}
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/* Now evaluate the path expression. */
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res = xmlXPathCompiledEval(comppath, ctxt);
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xmlXPathFreeCompExpr(comppath);
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if (res == NULL)
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{
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xmlXPathFreeContext(ctxt);
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xmlFreeDoc(doctree);
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return NULL;
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}
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/* xmlFreeDoc(doctree); */
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return res;
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}
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static text *
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pgxml_result_to_text(xmlXPathObjectPtr res,
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xmlChar *toptag,
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xmlChar *septag,
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xmlChar *plainsep)
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{
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xmlChar *xpresstr;
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int32 ressize;
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text *xpres;
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if (res == NULL)
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return NULL;
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switch (res->type)
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{
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case XPATH_NODESET:
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xpresstr = pgxmlNodeSetToText(res->nodesetval,
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toptag,
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septag, plainsep);
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break;
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case XPATH_STRING:
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xpresstr = xmlStrdup(res->stringval);
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break;
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default:
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elog(NOTICE, "unsupported XQuery result: %d", res->type);
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xpresstr = xmlStrdup("<unsupported/>");
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}
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/* Now convert this result back to text */
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ressize = strlen(xpresstr);
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xpres = (text *) palloc(ressize + VARHDRSZ);
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memcpy(VARDATA(xpres), xpresstr, ressize);
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VARATT_SIZEP(xpres) = ressize + VARHDRSZ;
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/* Free various storage */
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xmlFree(xpresstr);
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elog_error("XPath error", false);
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return xpres;
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}
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/*
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* xpath_table is a table function. It needs some tidying (as do the
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* other functions here!
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*/
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PG_FUNCTION_INFO_V1(xpath_table);
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Datum
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xpath_table(PG_FUNCTION_ARGS)
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{
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/* Function parameters */
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char *pkeyfield = GET_STR(PG_GETARG_TEXT_P(0));
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char *xmlfield = GET_STR(PG_GETARG_TEXT_P(1));
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char *relname = GET_STR(PG_GETARG_TEXT_P(2));
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char *xpathset = GET_STR(PG_GETARG_TEXT_P(3));
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char *condition = GET_STR(PG_GETARG_TEXT_P(4));
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/* SPI (input tuple) support */
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SPITupleTable *tuptable;
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HeapTuple spi_tuple;
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TupleDesc spi_tupdesc;
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/* Output tuple (tuplestore) support */
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Tuplestorestate *tupstore = NULL;
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TupleDesc ret_tupdesc;
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HeapTuple ret_tuple;
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ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
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AttInMetadata *attinmeta;
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MemoryContext per_query_ctx;
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MemoryContext oldcontext;
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char **values;
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xmlChar **xpaths;
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xmlChar *pos;
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xmlChar *pathsep = "|";
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int numpaths;
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int ret;
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int proc;
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int i;
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int j;
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int rownr; /* For issuing multiple rows from one original
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* document */
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bool had_values; /* To determine end of nodeset results */
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StringInfoData query_buf;
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/* We only have a valid tuple description in table function mode */
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if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
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ereport(ERROR,
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(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
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errmsg("set-valued function called in context that cannot accept a set")));
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if (rsinfo->expectedDesc == NULL)
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ereport(ERROR,
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(errcode(ERRCODE_SYNTAX_ERROR),
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errmsg("xpath_table must be called as a table function")));
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/*
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* We want to materialise because it means that we don't have to carry
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* libxml2 parser state between invocations of this function
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*/
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if (!(rsinfo->allowedModes & SFRM_Materialize))
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ereport(ERROR,
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(errcode(ERRCODE_SYNTAX_ERROR),
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errmsg("xpath_table requires Materialize mode, but it is not "
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"allowed in this context")));
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/*
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* The tuplestore must exist in a higher context than this function call
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* (per_query_ctx is used)
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*/
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per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
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oldcontext = MemoryContextSwitchTo(per_query_ctx);
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/*
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* Create the tuplestore - work_mem is the max in-memory size before a
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* file is created on disk to hold it.
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*/
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tupstore = tuplestore_begin_heap(true, false, work_mem);
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MemoryContextSwitchTo(oldcontext);
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/* get the requested return tuple description */
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ret_tupdesc = CreateTupleDescCopy(rsinfo->expectedDesc);
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/* must have at least one output column (for the pkey) */
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if (ret_tupdesc->natts < 1)
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ereport(ERROR,
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(errcode(ERRCODE_SYNTAX_ERROR),
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errmsg("xpath_table must have at least one output column")));
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/*
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* At the moment we assume that the returned attributes make sense for the
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* XPath specififed (i.e. we trust the caller). It's not fatal if they get
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* it wrong - the input function for the column type will raise an error
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* if the path result can't be converted into the correct binary
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* representation.
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*/
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attinmeta = TupleDescGetAttInMetadata(ret_tupdesc);
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/* Set return mode and allocate value space. */
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rsinfo->returnMode = SFRM_Materialize;
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rsinfo->setDesc = ret_tupdesc;
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values = (char **) palloc(ret_tupdesc->natts * sizeof(char *));
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xpaths = (xmlChar **) palloc(ret_tupdesc->natts * sizeof(xmlChar *));
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/*
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* Split XPaths. xpathset is a writable CString.
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*
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* Note that we stop splitting once we've done all needed for tupdesc
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*/
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numpaths = 0;
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pos = xpathset;
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while (numpaths < (ret_tupdesc->natts - 1))
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{
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xpaths[numpaths++] = (xmlChar *) pos;
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pos = strstr(pos, pathsep);
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if (pos != NULL)
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{
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*pos = '\0';
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pos++;
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}
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else
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break;
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}
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/* Now build query */
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initStringInfo(&query_buf);
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/* Build initial sql statement */
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appendStringInfo(&query_buf, "SELECT %s, %s FROM %s WHERE %s",
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pkeyfield,
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xmlfield,
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relname,
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condition);
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if ((ret = SPI_connect()) < 0)
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elog(ERROR, "xpath_table: SPI_connect returned %d", ret);
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if ((ret = SPI_exec(query_buf.data, 0)) != SPI_OK_SELECT)
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elog(ERROR, "xpath_table: SPI execution failed for query %s",
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query_buf.data);
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proc = SPI_processed;
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/* elog(DEBUG1,"xpath_table: SPI returned %d rows",proc); */
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tuptable = SPI_tuptable;
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spi_tupdesc = tuptable->tupdesc;
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/* Switch out of SPI context */
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MemoryContextSwitchTo(oldcontext);
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/*
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* Check that SPI returned correct result. If you put a comma into one of
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* the function parameters, this will catch it when the SPI query returns
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* e.g. 3 columns.
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*/
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if (spi_tupdesc->natts != 2)
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{
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ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
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errmsg("expression returning multiple columns is not valid in parameter list"),
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errdetail("Expected two columns in SPI result, got %d.", spi_tupdesc->natts)));
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}
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/*
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* Setup the parser. Beware that this must happen in the same context as
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* the cleanup - which means that any error from here on must do cleanup
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* to ensure that the entity table doesn't get freed by being out of
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* context.
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*/
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pgxml_parser_init();
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/* For each row i.e. document returned from SPI */
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for (i = 0; i < proc; i++)
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{
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char *pkey;
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char *xmldoc;
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xmlDocPtr doctree;
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xmlXPathContextPtr ctxt;
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xmlXPathObjectPtr res;
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xmlChar *resstr;
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xmlXPathCompExprPtr comppath;
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/* Extract the row data as C Strings */
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spi_tuple = tuptable->vals[i];
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pkey = SPI_getvalue(spi_tuple, spi_tupdesc, 1);
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xmldoc = SPI_getvalue(spi_tuple, spi_tupdesc, 2);
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/*
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* Clear the values array, so that not-well-formed documents return
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* NULL in all columns. Note that this also means that spare columns
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* will be NULL.
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*/
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for (j = 0; j < ret_tupdesc->natts; j++)
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values[j] = NULL;
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/* Insert primary key */
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values[0] = pkey;
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/* Parse the document */
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if (xmldoc)
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doctree = xmlParseMemory(xmldoc, strlen(xmldoc));
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else /* treat NULL as not well-formed */
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doctree = NULL;
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if (doctree == NULL)
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{
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/* not well-formed, so output all-NULL tuple */
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ret_tuple = BuildTupleFromCStrings(attinmeta, values);
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tuplestore_puttuple(tupstore, ret_tuple);
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heap_freetuple(ret_tuple);
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}
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else
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{
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/* New loop here - we have to deal with nodeset results */
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rownr = 0;
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do
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{
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/* Now evaluate the set of xpaths. */
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had_values = false;
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for (j = 0; j < numpaths; j++)
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{
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ctxt = xmlXPathNewContext(doctree);
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ctxt->node = xmlDocGetRootElement(doctree);
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xmlSetGenericErrorFunc(ctxt, pgxml_errorHandler);
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/* compile the path */
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comppath = xmlXPathCompile(xpaths[j]);
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if (comppath == NULL)
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{
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xmlFreeDoc(doctree);
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elog_error("XPath Syntax Error", true);
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}
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/* Now evaluate the path expression. */
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res = xmlXPathCompiledEval(comppath, ctxt);
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xmlXPathFreeCompExpr(comppath);
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if (res != NULL)
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{
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switch (res->type)
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{
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case XPATH_NODESET:
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/* We see if this nodeset has enough nodes */
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if (res->nodesetval != NULL &&
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rownr < res->nodesetval->nodeNr)
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{
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resstr =
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xmlXPathCastNodeToString(res->nodesetval->nodeTab[rownr]);
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had_values = true;
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}
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else
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resstr = NULL;
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break;
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case XPATH_STRING:
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resstr = xmlStrdup(res->stringval);
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break;
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default:
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elog(NOTICE, "unsupported XQuery result: %d", res->type);
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resstr = xmlStrdup("<unsupported/>");
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}
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/*
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* Insert this into the appropriate column in the
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* result tuple.
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*/
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values[j + 1] = resstr;
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}
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xmlXPathFreeContext(ctxt);
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}
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/* Now add the tuple to the output, if there is one. */
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if (had_values)
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{
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ret_tuple = BuildTupleFromCStrings(attinmeta, values);
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tuplestore_puttuple(tupstore, ret_tuple);
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heap_freetuple(ret_tuple);
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}
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rownr++;
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} while (had_values);
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}
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xmlFreeDoc(doctree);
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if (pkey)
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pfree(pkey);
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if (xmldoc)
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pfree(xmldoc);
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}
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tuplestore_donestoring(tupstore);
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SPI_finish();
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rsinfo->setResult = tupstore;
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/*
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* SFRM_Materialize mode expects us to return a NULL Datum. The actual
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* tuples are in our tuplestore and passed back through rsinfo->setResult.
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* rsinfo->setDesc is set to the tuple description that we actually used
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* to build our tuples with, so the caller can verify we did what it was
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* expecting.
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*/
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return (Datum) 0;
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}
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