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Diffstat (limited to 'src/xpath_vtab.cc')
| -rw-r--r-- | src/xpath_vtab.cc | 393 |
1 files changed, 393 insertions, 0 deletions
diff --git a/src/xpath_vtab.cc b/src/xpath_vtab.cc new file mode 100644 index 0000000..f44bde4 --- /dev/null +++ b/src/xpath_vtab.cc @@ -0,0 +1,393 @@ +/** + * Copyright (c) 2020, Timothy Stack + * + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are met: + * + * * Redistributions of source code must retain the above copyright notice, this + * list of conditions and the following disclaimer. + * * Redistributions in binary form must reproduce the above copyright notice, + * this list of conditions and the following disclaimer in the documentation + * and/or other materials provided with the distribution. + * * Neither the name of Timothy Stack nor the names of its contributors + * may be used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ''AS IS'' AND ANY + * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED + * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE + * DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY + * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES + * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; + * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND + * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS + * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + */ + +#include <sstream> +#include <unordered_map> + +#include "base/lnav_log.hh" +#include "config.h" +#include "pugixml/pugixml.hpp" +#include "sql_help.hh" +#include "sql_util.hh" +#include "vtab_module.hh" +#include "xml_util.hh" +#include "yajlpp/yajlpp.hh" + +enum { + XP_COL_RESULT, + XP_COL_NODE_PATH, + XP_COL_NODE_ATTR, + XP_COL_NODE_TEXT, + XP_COL_XPATH, + XP_COL_VALUE, +}; + +static thread_local std::unordered_map<std::string, pugi::xpath_query> + QUERY_CACHE; + +static pugi::xpath_query +checkout_query(const std::string& query) +{ + auto iter = QUERY_CACHE.find(query); + if (iter == QUERY_CACHE.end()) { + auto xquery = pugi::xpath_query(query.c_str()); + + if (!xquery) { + return xquery; + } + + auto pair = QUERY_CACHE.emplace(query, std::move(xquery)); + + iter = pair.first; + } + + auto retval = std::move(iter->second); + + QUERY_CACHE.erase(iter); + + return retval; +} + +static void +checkin_query(const std::string& query_str, pugi::xpath_query query) +{ + if (!query) { + return; + } + + QUERY_CACHE[query_str] = std::move(query); +} + +struct xpath_vtab { + static constexpr const char* NAME = "xpath"; + static constexpr const char* CREATE_STMT = R"( +-- The xpath() table-valued function allows you to execute an xpath expression +CREATE TABLE xpath ( + result text, -- The result of the xpath expression + node_path text, -- The absolute path to the node selected by the expression + node_attr text, -- The node attributes stored in a JSON object + node_text text, -- The text portion of the node selected by the expression + + xpath text HIDDEN, + value text HIDDEN +); +)"; + + struct cursor { + sqlite3_vtab_cursor base; + sqlite3_int64 c_rowid{0}; + std::string c_xpath; + std::string c_value; + bool c_value_as_blob{false}; + pugi::xpath_query c_query; + pugi::xml_document c_doc; + pugi::xpath_node_set c_results; + + cursor(sqlite3_vtab* vt) : base({vt}) {} + + ~cursor() { this->reset(); } + + int reset() + { + this->c_rowid = 0; + checkin_query(this->c_xpath, std::move(this->c_query)); + + return SQLITE_OK; + } + + int next() + { + this->c_rowid += 1; + + return SQLITE_OK; + } + + int eof() { return this->c_rowid >= (int64_t) this->c_results.size(); } + + int get_rowid(sqlite3_int64& rowid_out) + { + rowid_out = this->c_rowid; + + return SQLITE_OK; + } + }; + + int get_column(const cursor& vc, sqlite3_context* ctx, int col) + { + switch (col) { + case XP_COL_RESULT: { + auto& xpath_node = vc.c_results[vc.c_rowid]; + + if (xpath_node.node()) { + std::ostringstream oss; + + // XXX avoid the extra allocs + xpath_node.node().print(oss); + auto node_xml = oss.str(); + sqlite3_result_text(ctx, + node_xml.c_str(), + node_xml.length(), + SQLITE_TRANSIENT); + } else if (xpath_node.attribute()) { + sqlite3_result_text(ctx, + xpath_node.attribute().value(), + -1, + SQLITE_TRANSIENT); + } else { + sqlite3_result_null(ctx); + } + break; + } + case XP_COL_NODE_PATH: { + auto& xpath_node = vc.c_results[vc.c_rowid]; + auto x_node = xpath_node.node(); + auto x_attr = xpath_node.attribute(); + + if (x_node || x_attr) { + if (!x_node) { + x_node = xpath_node.parent(); + } + + auto node_path = lnav::pugixml::get_actual_path(x_node); + if (x_attr) { + node_path += "/@" + std::string(x_attr.name()); + } + sqlite3_result_text(ctx, + node_path.c_str(), + node_path.length(), + SQLITE_TRANSIENT); + } else { + sqlite3_result_null(ctx); + } + break; + } + case XP_COL_NODE_ATTR: { + auto& xpath_node = vc.c_results[vc.c_rowid]; + auto x_node = xpath_node.node(); + auto x_attr = xpath_node.attribute(); + + if (x_node || x_attr) { + if (!x_node) { + x_node = xpath_node.parent(); + } + + yajlpp_gen gen; + + yajl_gen_config(gen, yajl_gen_beautify, false); + + { + yajlpp_map attrs(gen); + + for (const auto& attr : x_node.attributes()) { + attrs.gen(attr.name()); + attrs.gen(attr.value()); + } + } + + auto sf = gen.to_string_fragment(); + + sqlite3_result_text( + ctx, sf.data(), sf.length(), SQLITE_TRANSIENT); + sqlite3_result_subtype(ctx, 'J'); + } else { + sqlite3_result_null(ctx); + } + break; + } + case XP_COL_NODE_TEXT: { + auto& xpath_node = vc.c_results[vc.c_rowid]; + auto x_node = xpath_node.node(); + auto x_attr = xpath_node.attribute(); + + if (x_node || x_attr) { + if (!x_node) { + x_node = xpath_node.parent(); + } + + auto node_text = x_node.text(); + + sqlite3_result_text( + ctx, node_text.get(), -1, SQLITE_TRANSIENT); + } else { + sqlite3_result_null(ctx); + } + break; + } + case XP_COL_XPATH: + sqlite3_result_text(ctx, + vc.c_xpath.c_str(), + vc.c_xpath.length(), + SQLITE_STATIC); + break; + case XP_COL_VALUE: + if (vc.c_value_as_blob) { + sqlite3_result_blob64(ctx, + vc.c_value.c_str(), + vc.c_value.length(), + SQLITE_STATIC); + } else { + sqlite3_result_text(ctx, + vc.c_value.c_str(), + vc.c_value.length(), + SQLITE_STATIC); + } + break; + } + + return SQLITE_OK; + } +}; + +static int +rcBestIndex(sqlite3_vtab* tab, sqlite3_index_info* pIdxInfo) +{ + vtab_index_constraints vic(pIdxInfo); + vtab_index_usage viu(pIdxInfo); + + for (auto iter = vic.begin(); iter != vic.end(); ++iter) { + if (iter->op != SQLITE_INDEX_CONSTRAINT_EQ) { + continue; + } + + switch (iter->iColumn) { + case XP_COL_VALUE: + case XP_COL_XPATH: + viu.column_used(iter); + break; + } + } + + viu.allocate_args(XP_COL_XPATH, XP_COL_VALUE, 2); + return SQLITE_OK; +} + +static int +rcFilter(sqlite3_vtab_cursor* pVtabCursor, + int idxNum, + const char* idxStr, + int argc, + sqlite3_value** argv) +{ + auto* pCur = (xpath_vtab::cursor*) pVtabCursor; + + if (argc != 2) { + pCur->c_xpath.clear(); + pCur->c_value.clear(); + return SQLITE_OK; + } + + pCur->c_value_as_blob = (sqlite3_value_type(argv[1]) == SQLITE_BLOB); + auto byte_count = sqlite3_value_bytes(argv[1]); + + if (byte_count == 0) { + pCur->c_rowid = 0; + return SQLITE_OK; + } + + auto blob = (const char*) sqlite3_value_blob(argv[1]); + pCur->c_value.assign(blob, byte_count); + auto parse_res = pCur->c_doc.load_string(pCur->c_value.c_str()); + if (!parse_res) { + pVtabCursor->pVtab->zErrMsg + = sqlite3_mprintf("Invalid XML document at offset %d: %s", + parse_res.offset, + parse_res.description()); + return SQLITE_ERROR; + } + + pCur->c_xpath = (const char*) sqlite3_value_text(argv[0]); + pCur->c_query = checkout_query(pCur->c_xpath); + if (!pCur->c_query) { + auto& res = pCur->c_query.result(); + pVtabCursor->pVtab->zErrMsg + = sqlite3_mprintf("Invalid XPATH expression at offset %d: %s", + res.offset, + res.description()); + return SQLITE_ERROR; + } + + pCur->c_rowid = 0; + pCur->c_results = pCur->c_doc.select_nodes(pCur->c_query); + + return SQLITE_OK; +} + +int +register_xpath_vtab(sqlite3* db) +{ + static vtab_module<tvt_no_update<xpath_vtab>> XPATH_MODULE; + static help_text xpath_help + = help_text("xpath", + "A table-valued function that executes an xpath expression " + "over an XML " + "string and returns the selected values.") + .sql_table_valued_function() + .with_parameter({ + "xpath", + "The XPATH expression to evaluate over the XML document.", + }) + .with_parameter({"xmldoc", "The XML document as a string."}) + .with_result({"result", "The result of the XPATH expression."}) + .with_result({ + "node_path", + "The absolute path to the node containing the result.", + }) + .with_result( + {"node_attr", "The node's attributes stored in JSON object."}) + .with_result({"node_text", "The node's text value."}) + .with_tags({"string", "xml"}) + .with_example({ + "To select the XML nodes on the path '/abc/def'", + "SELECT * FROM xpath('/abc/def', '<abc><def " + "a=\"b\">Hello</def><def>Bye</def></abc>')", + }) + .with_example({ + "To select all 'a' attributes on the path '/abc/def'", + "SELECT * FROM xpath('/abc/def/@a', '<abc><def " + "a=\"b\">Hello</def><def>Bye</def></abc>')", + }) + .with_example({ + "To select the text nodes on the path '/abc/def'", + "SELECT * FROM xpath('/abc/def/text()', '<abc><def " + "a=\"b\">Hello ★</def></abc>')", + }); + + int rc; + + XPATH_MODULE.vm_module.xBestIndex = rcBestIndex; + XPATH_MODULE.vm_module.xFilter = rcFilter; + + rc = XPATH_MODULE.create(db, "xpath"); + sqlite_function_help.insert(std::make_pair("xpath", &xpath_help)); + xpath_help.index_tags(); + + ensure(rc == SQLITE_OK); + + return rc; +} |