From: Ian Jackson <ian@liberator.relativity.greenend.org.uk>
Date: Sun, 4 Oct 2009 21:14:19 +0000 (+0100)
Subject: WIP routesearch; New SQL_DISTINCT_{DECL,STEP}
X-Git-Tag: 5.0^2~75
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~yarrgweb/git?p=ypp-sc-tools.db-test.git;a=commitdiff_plain;h=4119041216579a6020e649469037c3088364e214;hp=5f317a6465f48831fd170a745b58763602218421

WIP routesearch; New SQL_DISTINCT_{DECL,STEP}
---

diff --git a/yarrg/rscommon.h b/yarrg/rscommon.h
index f62fd99..5cf25f6 100644
--- a/yarrg/rscommon.h
+++ b/yarrg/rscommon.h
@@ -30,9 +30,34 @@
 
 void sql_fatal(const char *stmt_what, int sqr, const char *act_what) NORET;
 
-#define SQL_STEP(ssh) (sql_step_wrap((ssh), #ssh, __FILE__, __LINE__))
-int sql_step_wrap(sqlite3_stmt *ssh, const char *ssh_string,
-		  const char *file, int line);
+#define SQL_STEP(ssh) (sql_step((ssh), #ssh, __FILE__, __LINE__))
+int sql_step(sqlite3_stmt *ssh, const char *ssh_string,
+	     const char *file, int line);
+
+#define SQL_DISTINCT_DECL(cols, nintcols)	\
+  int cols[nintcols];				\
+  cols[0]= -1;
+#define SQL_DISTINCT_STEP(ssh, cols, nkeycols)				 \
+  (sql_step_distinct((ssh), #ssh, __FILE__, __LINE__,			 \
+		     (cols), sizeof((cols))/sizeof((cols)[0]), nkeycols))
+int sql_step_distinct(sqlite3_stmt *ssh, const char *ssh_string,
+		      const char *file, int line,
+		      int *cols, int ncols, int nkeycols);
+   /* These work if we're making a query whose columns consist of:
+    *  - keys: integer column(s) on which the results are sorted by the query
+    *  - consequences: zero or more integer cols strictly dependent on the keys
+    *  - extra: zero or more further (possibly non-integer) columns
+    *
+    * Call SQL_DISTINCT_DECL, passing intcols = the total number of keys and
+    * consequences; it will declare  int cols[intfields];
+    *
+    * Then each SQL_DISTINCT_STEP is like SQL_STEP only you have to
+    * pass the number of key columns and it only returns rows with
+    * distinct keys.  Rows with all-identical keys are asserted to
+    * have identical consequences.  After each call to
+    * SQL_DISTINCT_STEP the keys and consequences will be stored in
+    * cols.
+    */
 
 int sql_single_int(const char *stmt);
 
diff --git a/yarrg/rssql.c b/yarrg/rssql.c
index 898ac3b..bfe60d6 100644
--- a/yarrg/rssql.c
+++ b/yarrg/rssql.c
@@ -57,8 +57,28 @@ sqlite3_stmt *sql_prepare(const char *stmt, const char *what) {
   return ssr;
 }
 
-int sql_step_wrap(sqlite3_stmt *ssh, const char *ssh_string,
-		  const char *file, int line) {
+int sql_step_distinct(sqlite3_stmt *ssh, const char *ssh_string,
+		      const char *file, int line,
+		      int *cols, int ncols, int nkeycols) {
+  for (;;) {
+    if (!sql_step(ssh, ssh_string, file, line)) return 0;
+
+    int i;
+    for (i=0; i<ncols; i++) {
+      int v= sqlite3_column_int(ssh, i);
+      if (v == cols[i]) continue;
+      
+      assert(i<nkeycols);
+      cols[i++]= v;
+      for ( ; i<ncols; i++)
+	cols[i]= sqlite3_column_int(ssh, i);
+      return 1;
+    }
+  }
+}
+
+int sql_step(sqlite3_stmt *ssh, const char *ssh_string,
+	     const char *file, int line) {
   for (;;) {
     int sqr;
     sqr= sqlite3_step((ssh));