db_unixodbc: fix query result handling and improve performance

Until now, query rows were incrementally stored in a list with
separately allocated length and string buffers, along with a great deal
of useless pointer dereferencing, effectively wasting CPU cycles and pkg
mem usage.

This patch eliminates the linked list logic with a global buffer of
pointers (doubling in size when required) meant to hold each result column.
Each column is transparently freed by the DB backend. This completes
commit d63ee19.
(cherry picked from commit 683dfaa)

modules/db_unixodbc/con.h

@@ -60,7 +60,6 @@ struct my_con
 	SQLHSTMT stmt_handle;			  /* Actual result */
 	SQLHDBC dbc;					  /* Connection representation */
 	char** row;						  /* Actual row in the result */
-	void *data;
 	time_t timestamp;				  /* Timestamp of last query */
 };
 
@@ -73,7 +72,6 @@ struct my_con
 #define CON_TIMESTAMP(db_con)  (((struct my_con*)((db_con)->tail))->timestamp)
 #define CON_ID(db_con) 		(((struct my_con*)((db_con)->tail))->id)
 #define CON_ENV(db_con)		(((struct my_con*)((db_con)->tail))->env)
-#define CON_DATA(db_con)	(((struct my_con*)((db_con)->tail))->data)
 
 #define MAX_CONN_STR_LEN 2048
 

modules/db_unixodbc/dbase.c

@@ -38,7 +38,6 @@
 #include "../../dprint.h"
 #include "../../db/db_query.h"
 #include "val.h"
-#include "list.h"
 #include "con.h"
 #include "res.h"
 #include "db_unixodbc.h"
@@ -247,12 +246,9 @@ int db_unixodbc_free_result(db_con_t* _h, db_res_t* _r)
 		return -1;
 	}
 
-	/* free the duplicated list of results */
-	if (CON_DATA(_h))
-		db_unixodbc_list_destroy((list *)CON_DATA(_h));
-
 	SQLFreeHandle(SQL_HANDLE_STMT, CON_RESULT(_h));
-	CON_RESULT(_h) = 0;
+	CON_RESULT(_h) = NULL;
+
 	return 0;
 }
 

modules/db_unixodbc/res.c

@@ -36,7 +36,6 @@
 #include "../../db/db_res.h"
 #include "con.h"
 #include "res.h"
-#include "list.h"
 #include <stdlib.h>
 #include <string.h>
 
@@ -160,9 +159,8 @@ static inline int db_unixodbc_convert_rows(const db_con_t* _h, db_res_t* _r)
 {
 	int row_n = 0, i = 0, ret = 0;
 	SQLSMALLINT columns;
-	list* rows = NULL;
-	list* rowstart = NULL;
 	strn* temp_row = NULL;
+	str *rows = NULL;
 
 	if((!_h) || (!_r)) {
 		LM_ERR("invalid parameter\n");
@@ -173,10 +171,10 @@ static inline int db_unixodbc_convert_rows(const db_con_t* _h, db_res_t* _r)
 	temp_row = (strn*)pkg_malloc( columns*sizeof(strn) );
 	if(!temp_row) {
 		LM_ERR("no private memory left\n");
-		return -1;
+		return E_OUT_OF_MEM;
 	}
 
-	while(SQL_SUCCEEDED(ret = SQLFetch(CON_RESULT(_h))))
+	while (SQL_SUCCEEDED(ret = SQLFetch(CON_RESULT(_h))))
 	{
 		for(i=0; i < columns; i++)
 		{
@@ -192,52 +190,39 @@ static inline int db_unixodbc_convert_rows(const db_con_t* _h, db_res_t* _r)
 			}
 		}
 
-		if (db_unixodbc_list_insert(&rowstart, &rows, columns, temp_row) < 0) {
-			LM_ERR("insert failed\n");
-			pkg_free(temp_row);
-			temp_row= NULL;
-			return -5;
+		rows = db_unixodbc_dup_row(temp_row, row_n, columns);
+		if (!rows) {
+			LM_ERR("no more pkg mem\n");
+			return E_OUT_OF_MEM;
 		}
+
 		row_n++;
 	}
+
 	/* free temporary row data */
 	pkg_free(temp_row);
 	CON_ROW(_h) = NULL;
 
 	RES_ROW_N(_r) = row_n;
-	if (!row_n) {
-		RES_ROWS(_r) = 0;
+	if (row_n == 0) {
+		RES_ROWS(_r) = NULL;
 		return 0;
 	}
 
-	if (db_allocate_rows( _r, row_n)!=0) {
+	if (db_allocate_rows(_r, row_n) != 0) {
 		LM_ERR("no private memory left\n");
-		return -2;
+		return E_OUT_OF_MEM;
 	}
 
-	i = 0;
-	rows = rowstart;
-	while(rows)
-	{
-		CON_ROW(_h) = rows->data;
-		if (!CON_ROW(_h))
-		{
-			LM_ERR("string null\n");
-			RES_ROW_N(_r) = row_n;
-			db_free_rows(_r);
-			return -3;
-		}
-		if (db_unixodbc_convert_row(_h, _r, &(RES_ROWS(_r)[i]), rows->lengths) < 0) {
+	for (i = 0; i < row_n; i++) {
+		if (db_unixodbc_convert_row(&rows[i * columns], _r, &RES_ROWS(_r)[i]) < 0) {
 			LM_ERR("converting row failed #%d\n", i);
-			RES_ROW_N(_r) = i;
+			RES_ROW_N(_r) = 0;
 			db_free_rows(_r);
 			return -4;
 		}
-		i++;
-		rows = rows->next;
 	}
 
-	CON_DATA(_h) = rowstart ? rowstart : NULL;
 	return 0;
 }