[sql] do not dump the log on an empty SQL result

Related to #466

src/command_executor.cc

@@ -914,7 +914,7 @@ execute_init_commands(
                 wait_for_pipers(deadline);
                 rebuild_indexes_repeatedly();
             }
-            if (dls.dls_rows.size() > 1 && lnav_data.ld_view_stack.size() == 1)
+            if (!dls.dls_headers.empty() && lnav_data.ld_view_stack.size() == 1)
             {
                 lnav_data.ld_views[LNV_DB].reload_data();
                 ensure_view(LNV_DB);
@@ -951,36 +951,38 @@ execute_init_commands(
 int
 sql_callback(exec_context& ec, sqlite3_stmt* stmt)
 {
+    const auto& vc = view_colors::singleton();
     auto& dls = *(ec.ec_label_source_stack.back());
+    int ncols = sqlite3_column_count(stmt);
 
     if (!sqlite3_stmt_busy(stmt)) {
         dls.clear();
 
+        for (int lpc = 0; lpc < ncols; lpc++) {
+            const int type = sqlite3_column_type(stmt, lpc);
+            std::string colname = sqlite3_column_name(stmt, lpc);
+
+            dls.push_header(colname, type, false);
+        }
         return 0;
     }
 
-    auto& vc = view_colors::singleton();
+    int retval = 0;
-    int ncols = sqlite3_column_count(stmt);
+    auto set_vars = dls.dls_rows.empty();
-    int row_number;
-    int lpc, retval = 0;
-    auto set_vars = false;
 
-    row_number = dls.dls_rows.size();
+    if (dls.dls_rows.empty()) {
-    dls.dls_rows.resize(row_number + 1);
+        for (int lpc = 0; lpc < ncols; lpc++) {
-    if (dls.dls_headers.empty()) {
-        for (lpc = 0; lpc < ncols; lpc++) {
             int type = sqlite3_column_type(stmt, lpc);
             std::string colname = sqlite3_column_name(stmt, lpc);
-            bool graphable;
 
-            graphable = ((type == SQLITE_INTEGER || type == SQLITE_FLOAT)
+            bool graphable = (type == SQLITE_INTEGER || type == SQLITE_FLOAT)
-                         && !binary_search(lnav_data.ld_db_key_names.begin(),
+                && !binary_search(lnav_data.ld_db_key_names.begin(),
-                                           lnav_data.ld_db_key_names.end(),
+                                  lnav_data.ld_db_key_names.end(),
-                                           colname));
+                                  colname);
-
+            auto& hm = dls.dls_headers[lpc];
-            dls.push_header(colname, type, graphable);
+            hm.hm_column_type = type;
+            hm.hm_graphable = graphable;
             if (graphable) {
-                auto& hm = dls.dls_headers.back();
                 auto name_for_ident_attrs = colname;
                 auto attrs = vc.attrs_for_ident(name_for_ident_attrs);
                 for (size_t attempt = 0;
@@ -991,14 +993,17 @@ sql_callback(exec_context& ec, sqlite3_stmt* stmt)
                     attrs = vc.attrs_for_ident(name_for_ident_attrs);
                 }
                 hm.hm_chart.with_attrs_for_ident(colname, attrs);
-                dls.dls_headers.back().hm_title_attrs = attrs;
+                hm.hm_title_attrs = attrs;
+                hm.hm_column_size = std::max(hm.hm_column_size, size_t{10});
             }
         }
-        set_vars = true;
     }
-    for (lpc = 0; lpc < ncols; lpc++) {
+
+    auto row_number = dls.dls_rows.size();
+    dls.dls_rows.resize(row_number + 1);
+    for (int lpc = 0; lpc < ncols; lpc++) {
         auto* raw_value = sqlite3_column_value(stmt, lpc);
-        auto value_type = sqlite3_value_type(raw_value);
+        const auto value_type = sqlite3_value_type(raw_value);
         scoped_value_t value;
         auto& hm = dls.dls_headers[lpc];
 

src/internals/sql-ref.rst

@@ -337,6 +337,7 @@ SELECT *result-column* FROM *table* WHERE *\[cond\]* GROUP BY *grouping-expr* OR
     .. code-block::  custsqlite
 
       ;SELECT * FROM syslog_log
+      log_line log_time log_level log_hostname log_msgid log_pid log_pri log_procname log_struct log_syslog_tag syslog_version log_part log_idle_msecs log_mark log_comment log_tags log_annotations log_filters 
 
 
 ----

src/lnav_commands.cc

@@ -4397,6 +4397,7 @@ com_summarize(exec_context& ec,
         } else {
             bool done = false;
 
+            ec.ec_sql_callback(ec, stmt.in());
             while (!done) {
                 retcode = sqlite3_step(stmt.in());
 

src/textfile_sub_source.cc

@@ -52,6 +52,20 @@
 
 using namespace lnav::roles::literals;
 
+static bool
+file_needs_reformatting(const std::shared_ptr<logfile> lf)
+{
+    switch (lf->get_text_format()) {
+        case text_format_t::TF_DIFF:
+            return false;
+        default:
+            if (lf->get_longest_line_length() > 240) {
+                return true;
+            }
+            return false;
+    }
+}
+
 size_t
 textfile_sub_source::text_line_count()
 {
@@ -990,7 +1004,7 @@ textfile_sub_source::rescan_files(textfile_sub_source::scan_callback& callback,
                               lf->get_filename().c_str(),
                               read_res.unwrapErr().c_str());
                 }
-            } else if (lf->get_longest_line_length() > 240) {
+            } else if (file_needs_reformatting(lf)) {
                 auto rend_iter
                     = this->tss_rendered_files.find(lf->get_filename());
                 if (rend_iter != this->tss_rendered_files.end()) {

test/Makefile.am

@@ -296,6 +296,7 @@ dist_noinst_DATA = \
 	datafile_xml.0 \
 	dhcp.pcapng \
 	dhcp-trunc.pcapng \
+	empty-result.lnav \
 	example.patch \
 	example.toml \
 	expected_help.txt \

test/empty-result.lnav

@@ -0,0 +1 @@
+;SELECT * FROM syslog_log LIMIT 0

test/test_sql.sh

@@ -161,12 +161,13 @@ Wed May 19 12:00:04 +0000 2021 line 4
 EOF
 
 
-run_test ${lnav_test} -n \
+run_cap_test ${lnav_test} -n \
     -c ";SELECT * FROM access_log LIMIT 0" \
     ${test_dir}/logfile_access_log.0
 
-check_output "output generated for empty result set?" <<EOF
+run_cap_test ${lnav_test} -n \
-EOF
+    -c "|${test_dir}/empty-result.lnav" \
+    ${test_dir}/logfile_access_log.0
 
 run_cap_test ${lnav_test} -n \
     -c ":goto 2" \
@@ -389,6 +390,7 @@ run_test ${lnav_test} -n \
     ${test_dir}/logfile_syslog.0
 
 check_output "log_time collation failed on null" <<EOF
+log_line,log_time,log_level,log_hostname,log_msgid,log_pid,log_pri,log_procname,log_struct,log_syslog_tag,syslog_version,log_part,log_idle_msecs,log_mark,log_comment,log_tags,log_annotations,log_filters
 EOF
 
 
@@ -549,6 +551,7 @@ run_test ${lnav_test} -n \
     ${test_dir}/logfile_access_log.0
 
 check_output "delete from environ table does not work" <<EOF
+name,value
 EOF
 
 
@@ -559,6 +562,7 @@ run_test ${lnav_test} -n \
     ${test_dir}/logfile_access_log.0
 
 check_output "delete environ table does not work" <<EOF
+name,value
 EOF
 
 
@@ -777,6 +781,9 @@ run_test ${lnav_test} -n \
     ${test_dir}/logfile_multiline.0
 
 check_output "able to select a continued line?" <<EOF
+[
+
+]
 EOF