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-rw-r--r--contrib/xml2/xpath.c746
1 files changed, 746 insertions, 0 deletions
diff --git a/contrib/xml2/xpath.c b/contrib/xml2/xpath.c
new file mode 100644
index 0000000..a692dc6
--- /dev/null
+++ b/contrib/xml2/xpath.c
@@ -0,0 +1,746 @@
+/*
+ * contrib/xml2/xpath.c
+ *
+ * Parser interface for DOM-based parser (libxml) rather than
+ * stream-based SAX-type parser
+ */
+#include "postgres.h"
+
+#include "access/htup_details.h"
+#include "executor/spi.h"
+#include "fmgr.h"
+#include "funcapi.h"
+#include "lib/stringinfo.h"
+#include "miscadmin.h"
+#include "utils/builtins.h"
+#include "utils/xml.h"
+
+/* libxml includes */
+
+#include <libxml/xpath.h>
+#include <libxml/tree.h>
+#include <libxml/xmlmemory.h>
+#include <libxml/xmlerror.h>
+#include <libxml/parserInternals.h>
+
+PG_MODULE_MAGIC;
+
+/* exported for use by xslt_proc.c */
+
+PgXmlErrorContext *pgxml_parser_init(PgXmlStrictness strictness);
+
+/* workspace for pgxml_xpath() */
+
+typedef struct
+{
+ xmlDocPtr doctree;
+ xmlXPathContextPtr ctxt;
+ xmlXPathObjectPtr res;
+} xpath_workspace;
+
+/* local declarations */
+
+static xmlChar *pgxmlNodeSetToText(xmlNodeSetPtr nodeset,
+ xmlChar *toptagname, xmlChar *septagname,
+ xmlChar *plainsep);
+
+static text *pgxml_result_to_text(xmlXPathObjectPtr res, xmlChar *toptag,
+ xmlChar *septag, xmlChar *plainsep);
+
+static xmlChar *pgxml_texttoxmlchar(text *textstring);
+
+static xmlXPathObjectPtr pgxml_xpath(text *document, xmlChar *xpath,
+ xpath_workspace *workspace);
+
+static void cleanup_workspace(xpath_workspace *workspace);
+
+
+/*
+ * Initialize for xml parsing.
+ *
+ * As with the underlying pg_xml_init function, calls to this MUST be followed
+ * by a PG_TRY block that guarantees that pg_xml_done is called.
+ */
+PgXmlErrorContext *
+pgxml_parser_init(PgXmlStrictness strictness)
+{
+ PgXmlErrorContext *xmlerrcxt;
+
+ /* Set up error handling (we share the core's error handler) */
+ xmlerrcxt = pg_xml_init(strictness);
+
+ /* Note: we're assuming an elog cannot be thrown by the following calls */
+
+ /* Initialize libxml */
+ xmlInitParser();
+
+ xmlSubstituteEntitiesDefault(1);
+ xmlLoadExtDtdDefaultValue = 1;
+
+ return xmlerrcxt;
+}
+
+
+/* Encodes special characters (<, >, &, " and \r) as XML entities */
+
+PG_FUNCTION_INFO_V1(xml_encode_special_chars);
+
+Datum
+xml_encode_special_chars(PG_FUNCTION_ARGS)
+{
+ text *tin = PG_GETARG_TEXT_PP(0);
+ text *tout;
+ xmlChar *ts,
+ *tt;
+
+ ts = pgxml_texttoxmlchar(tin);
+
+ tt = xmlEncodeSpecialChars(NULL, ts);
+
+ pfree(ts);
+
+ tout = cstring_to_text((char *) tt);
+
+ xmlFree(tt);
+
+ PG_RETURN_TEXT_P(tout);
+}
+
+/*
+ * 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) separator - if used, then nodes are
+ * cast to string as output method
+ */
+static xmlChar *
+pgxmlNodeSetToText(xmlNodeSetPtr nodeset,
+ xmlChar *toptagname,
+ xmlChar *septagname,
+ xmlChar *plainsep)
+{
+ 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, (char *) 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
+ */
+static xmlChar *
+pgxml_texttoxmlchar(text *textstring)
+{
+ return (xmlChar *) text_to_cstring(textstring);
+}
+
+/* Publicly 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)
+{
+ text *document = PG_GETARG_TEXT_PP(0);
+ text *xpathsupp = PG_GETARG_TEXT_PP(1); /* XPath expression */
+ xmlChar *toptag = pgxml_texttoxmlchar(PG_GETARG_TEXT_PP(2));
+ xmlChar *septag = pgxml_texttoxmlchar(PG_GETARG_TEXT_PP(3));
+ xmlChar *xpath;
+ text *xpres;
+ xmlXPathObjectPtr res;
+ xpath_workspace workspace;
+
+ xpath = pgxml_texttoxmlchar(xpathsupp);
+
+ res = pgxml_xpath(document, xpath, &workspace);
+
+ xpres = pgxml_result_to_text(res, toptag, septag, NULL);
+
+ cleanup_workspace(&workspace);
+
+ pfree(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)
+{
+ text *document = PG_GETARG_TEXT_PP(0);
+ text *xpathsupp = PG_GETARG_TEXT_PP(1); /* XPath expression */
+ xmlChar *plainsep = pgxml_texttoxmlchar(PG_GETARG_TEXT_PP(2));
+ xmlChar *xpath;
+ text *xpres;
+ xmlXPathObjectPtr res;
+ xpath_workspace workspace;
+
+ xpath = pgxml_texttoxmlchar(xpathsupp);
+
+ res = pgxml_xpath(document, xpath, &workspace);
+
+ xpres = pgxml_result_to_text(res, NULL, NULL, plainsep);
+
+ cleanup_workspace(&workspace);
+
+ pfree(xpath);
+
+ if (xpres == NULL)
+ PG_RETURN_NULL();
+ PG_RETURN_TEXT_P(xpres);
+}
+
+
+PG_FUNCTION_INFO_V1(xpath_string);
+
+Datum
+xpath_string(PG_FUNCTION_ARGS)
+{
+ text *document = PG_GETARG_TEXT_PP(0);
+ text *xpathsupp = PG_GETARG_TEXT_PP(1); /* XPath expression */
+ xmlChar *xpath;
+ int32 pathsize;
+ text *xpres;
+ xmlXPathObjectPtr res;
+ xpath_workspace workspace;
+
+ pathsize = VARSIZE_ANY_EXHDR(xpathsupp);
+
+ /*
+ * 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, "string(", 7);
+ memcpy((char *) (xpath + 7), VARDATA_ANY(xpathsupp), pathsize);
+ xpath[pathsize + 7] = ')';
+ xpath[pathsize + 8] = '\0';
+
+ res = pgxml_xpath(document, xpath, &workspace);
+
+ xpres = pgxml_result_to_text(res, NULL, NULL, NULL);
+
+ cleanup_workspace(&workspace);
+
+ pfree(xpath);
+
+ if (xpres == NULL)
+ PG_RETURN_NULL();
+ PG_RETURN_TEXT_P(xpres);
+}
+
+
+PG_FUNCTION_INFO_V1(xpath_number);
+
+Datum
+xpath_number(PG_FUNCTION_ARGS)
+{
+ text *document = PG_GETARG_TEXT_PP(0);
+ text *xpathsupp = PG_GETARG_TEXT_PP(1); /* XPath expression */
+ xmlChar *xpath;
+ float4 fRes;
+ xmlXPathObjectPtr res;
+ xpath_workspace workspace;
+
+ xpath = pgxml_texttoxmlchar(xpathsupp);
+
+ res = pgxml_xpath(document, xpath, &workspace);
+
+ pfree(xpath);
+
+ if (res == NULL)
+ PG_RETURN_NULL();
+
+ fRes = xmlXPathCastToNumber(res);
+
+ cleanup_workspace(&workspace);
+
+ if (xmlXPathIsNaN(fRes))
+ PG_RETURN_NULL();
+
+ PG_RETURN_FLOAT4(fRes);
+}
+
+
+PG_FUNCTION_INFO_V1(xpath_bool);
+
+Datum
+xpath_bool(PG_FUNCTION_ARGS)
+{
+ text *document = PG_GETARG_TEXT_PP(0);
+ text *xpathsupp = PG_GETARG_TEXT_PP(1); /* XPath expression */
+ xmlChar *xpath;
+ int bRes;
+ xmlXPathObjectPtr res;
+ xpath_workspace workspace;
+
+ xpath = pgxml_texttoxmlchar(xpathsupp);
+
+ res = pgxml_xpath(document, xpath, &workspace);
+
+ pfree(xpath);
+
+ if (res == NULL)
+ PG_RETURN_BOOL(false);
+
+ bRes = xmlXPathCastToBoolean(res);
+
+ cleanup_workspace(&workspace);
+
+ PG_RETURN_BOOL(bRes);
+}
+
+
+
+/* Core function to evaluate XPath query */
+
+static xmlXPathObjectPtr
+pgxml_xpath(text *document, xmlChar *xpath, xpath_workspace *workspace)
+{
+ int32 docsize = VARSIZE_ANY_EXHDR(document);
+ PgXmlErrorContext *xmlerrcxt;
+ xmlXPathCompExprPtr comppath;
+
+ workspace->doctree = NULL;
+ workspace->ctxt = NULL;
+ workspace->res = NULL;
+
+ xmlerrcxt = pgxml_parser_init(PG_XML_STRICTNESS_LEGACY);
+
+ PG_TRY();
+ {
+ workspace->doctree = xmlParseMemory((char *) VARDATA_ANY(document),
+ docsize);
+ if (workspace->doctree != NULL)
+ {
+ workspace->ctxt = xmlXPathNewContext(workspace->doctree);
+ workspace->ctxt->node = xmlDocGetRootElement(workspace->doctree);
+
+ /* compile the path */
+ comppath = xmlXPathCompile(xpath);
+ if (comppath == NULL)
+ xml_ereport(xmlerrcxt, ERROR, ERRCODE_EXTERNAL_ROUTINE_EXCEPTION,
+ "XPath Syntax Error");
+
+ /* Now evaluate the path expression. */
+ workspace->res = xmlXPathCompiledEval(comppath, workspace->ctxt);
+
+ xmlXPathFreeCompExpr(comppath);
+ }
+ }
+ PG_CATCH();
+ {
+ cleanup_workspace(workspace);
+
+ pg_xml_done(xmlerrcxt, true);
+
+ PG_RE_THROW();
+ }
+ PG_END_TRY();
+
+ if (workspace->res == NULL)
+ cleanup_workspace(workspace);
+
+ pg_xml_done(xmlerrcxt, false);
+
+ return workspace->res;
+}
+
+/* Clean up after processing the result of pgxml_xpath() */
+static void
+cleanup_workspace(xpath_workspace *workspace)
+{
+ if (workspace->res)
+ xmlXPathFreeObject(workspace->res);
+ workspace->res = NULL;
+ if (workspace->ctxt)
+ xmlXPathFreeContext(workspace->ctxt);
+ workspace->ctxt = NULL;
+ if (workspace->doctree)
+ xmlFreeDoc(workspace->doctree);
+ workspace->doctree = NULL;
+}
+
+static text *
+pgxml_result_to_text(xmlXPathObjectPtr res,
+ xmlChar *toptag,
+ xmlChar *septag,
+ xmlChar *plainsep)
+{
+ xmlChar *xpresstr;
+ 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((const xmlChar *) "<unsupported/>");
+ }
+
+ /* Now convert this result back to text */
+ xpres = cstring_to_text((char *) xpresstr);
+
+ /* Free various storage */
+ xmlFree(xpresstr);
+
+ 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)
+{
+ /* Function parameters */
+ char *pkeyfield = text_to_cstring(PG_GETARG_TEXT_PP(0));
+ char *xmlfield = text_to_cstring(PG_GETARG_TEXT_PP(1));
+ char *relname = text_to_cstring(PG_GETARG_TEXT_PP(2));
+ char *xpathset = text_to_cstring(PG_GETARG_TEXT_PP(3));
+ char *condition = text_to_cstring(PG_GETARG_TEXT_PP(4));
+
+ /* SPI (input tuple) support */
+ SPITupleTable *tuptable;
+ HeapTuple spi_tuple;
+ TupleDesc spi_tupdesc;
+
+
+ ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+ AttInMetadata *attinmeta;
+
+ char **values;
+ xmlChar **xpaths;
+ char *pos;
+ const char *pathsep = "|";
+
+ int numpaths;
+ int ret;
+ uint64 proc;
+ int j;
+ int rownr; /* For issuing multiple rows from one original
+ * document */
+ bool had_values; /* To determine end of nodeset results */
+ StringInfoData query_buf;
+ PgXmlErrorContext *xmlerrcxt;
+ volatile xmlDocPtr doctree = NULL;
+
+ InitMaterializedSRF(fcinfo, MAT_SRF_USE_EXPECTED_DESC);
+
+ /* must have at least one output column (for the pkey) */
+ if (rsinfo->setDesc->natts < 1)
+ ereport(ERROR,
+ (errcode(ERRCODE_SYNTAX_ERROR),
+ errmsg("xpath_table must have at least one output column")));
+
+ /*
+ * At the moment we assume that the returned attributes make sense for the
+ * XPath specified (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(rsinfo->setDesc);
+
+ values = (char **) palloc(rsinfo->setDesc->natts * sizeof(char *));
+ xpaths = (xmlChar **) palloc(rsinfo->setDesc->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;
+ while (numpaths < (rsinfo->setDesc->natts - 1))
+ {
+ xpaths[numpaths++] = (xmlChar *) pos;
+ pos = strstr(pos, pathsep);
+ if (pos != NULL)
+ {
+ *pos = '\0';
+ pos++;
+ }
+ else
+ break;
+ }
+
+ /* Now build query */
+ initStringInfo(&query_buf);
+
+ /* Build initial sql statement */
+ appendStringInfo(&query_buf, "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(query_buf.data, 0)) != SPI_OK_SELECT)
+ elog(ERROR, "xpath_table: SPI execution failed for query %s",
+ query_buf.data);
+
+ proc = SPI_processed;
+ tuptable = SPI_tuptable;
+ spi_tupdesc = tuptable->tupdesc;
+
+ /*
+ * 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. This should happen after we are done evaluating the
+ * query, in case it calls functions that set up libxml differently.
+ */
+ xmlerrcxt = pgxml_parser_init(PG_XML_STRICTNESS_LEGACY);
+
+ PG_TRY();
+ {
+ /* For each row i.e. document returned from SPI */
+ uint64 i;
+
+ for (i = 0; i < proc; i++)
+ {
+ char *pkey;
+ char *xmldoc;
+ xmlXPathContextPtr ctxt;
+ xmlXPathObjectPtr res;
+ xmlChar *resstr;
+ xmlXPathCompExprPtr comppath;
+ HeapTuple ret_tuple;
+
+ /* 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 < rsinfo->setDesc->natts; j++)
+ values[j] = NULL;
+
+ /* Insert primary key */
+ values[0] = pkey;
+
+ /* Parse the document */
+ if (xmldoc)
+ doctree = xmlParseMemory(xmldoc, strlen(xmldoc));
+ else /* treat NULL as not well-formed */
+ doctree = NULL;
+
+ if (doctree == NULL)
+ {
+ /* not well-formed, so output all-NULL tuple */
+ ret_tuple = BuildTupleFromCStrings(attinmeta, values);
+ tuplestore_puttuple(rsinfo->setResult, ret_tuple);
+ 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 = false;
+ for (j = 0; j < numpaths; j++)
+ {
+ ctxt = xmlXPathNewContext(doctree);
+ ctxt->node = xmlDocGetRootElement(doctree);
+
+ /* compile the path */
+ comppath = xmlXPathCompile(xpaths[j]);
+ if (comppath == NULL)
+ xml_ereport(xmlerrcxt, ERROR,
+ ERRCODE_EXTERNAL_ROUTINE_EXCEPTION,
+ "XPath Syntax Error");
+
+ /* 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 = true;
+ }
+ else
+ resstr = NULL;
+
+ break;
+
+ case XPATH_STRING:
+ resstr = xmlStrdup(res->stringval);
+ break;
+
+ default:
+ elog(NOTICE, "unsupported XQuery result: %d", res->type);
+ resstr = xmlStrdup((const xmlChar *) "<unsupported/>");
+ }
+
+ /*
+ * Insert this into the appropriate column in the
+ * result tuple.
+ */
+ values[j + 1] = (char *) resstr;
+ }
+ xmlXPathFreeContext(ctxt);
+ }
+
+ /* Now add the tuple to the output, if there is one. */
+ if (had_values)
+ {
+ ret_tuple = BuildTupleFromCStrings(attinmeta, values);
+ tuplestore_puttuple(rsinfo->setResult, ret_tuple);
+ heap_freetuple(ret_tuple);
+ }
+
+ rownr++;
+ } while (had_values);
+ }
+
+ if (doctree != NULL)
+ xmlFreeDoc(doctree);
+ doctree = NULL;
+
+ if (pkey)
+ pfree(pkey);
+ if (xmldoc)
+ pfree(xmldoc);
+ }
+ }
+ PG_CATCH();
+ {
+ if (doctree != NULL)
+ xmlFreeDoc(doctree);
+
+ pg_xml_done(xmlerrcxt, true);
+
+ PG_RE_THROW();
+ }
+ PG_END_TRY();
+
+ if (doctree != NULL)
+ xmlFreeDoc(doctree);
+
+ pg_xml_done(xmlerrcxt, false);
+
+ SPI_finish();
+
+ /*
+ * 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;
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-02 04:01:18 +0000