Add an early execution mode for prepared statements

driver/connect.c

@@ -1402,6 +1402,9 @@ SQLRETURN config_dbc(esodbc_dbc_st *dbc, esodbc_dsn_attrs_st *attrs)
 	/* "apply TZ" param for time conversions */
 	dbc->apply_tz = wstr2bool(&attrs->apply_tz);
 	INFOH(dbc, "apply TZ: %s.", dbc->apply_tz ? "true" : "false");
+	/* early execution */
+	dbc->early_exec = wstr2bool(&attrs->early_exec);
+	INFOH(dbc, "early execution: %s.", dbc->early_exec ? "true" : "false");
 
 	/* how to print the floats? */
 	assert(1 <= attrs->sci_floats.cnt); /* default should apply */

driver/defs.h

@@ -173,6 +173,8 @@
 #define ESODBC_DEF_TRACE_LEVEL		"WARN"
 /* default TZ handling */
 #define ESODBC_DEF_APPLY_TZ			"no"
+/* default early execution flag */
+#define ESODBC_DEF_EARLY_EXEC		"yes"
 /* default of scientific floats printing */
 #define ESODBC_DEF_SCI_FLOATS		ESODBC_DSN_FLTS_DEF
 #define ESODBC_PWD_VAL_SUBST		"<redacted>"

driver/dsn.c

@@ -76,6 +76,7 @@ int assign_dsn_attr(esodbc_dsn_attrs_st *attrs,
 		{&MK_WSTR(ESODBC_DSN_MAX_FETCH_SIZE), &attrs->max_fetch_size},
 		{&MK_WSTR(ESODBC_DSN_MAX_BODY_SIZE_MB), &attrs->max_body_size},
 		{&MK_WSTR(ESODBC_DSN_APPLY_TZ), &attrs->apply_tz},
+		{&MK_WSTR(ESODBC_DSN_EARLY_EXEC), &attrs->early_exec},
 		{&MK_WSTR(ESODBC_DSN_SCI_FLOATS), &attrs->sci_floats},
 		{&MK_WSTR(ESODBC_DSN_VERSION_CHECKING), &attrs->version_checking},
 		{&MK_WSTR(ESODBC_DSN_MFIELD_LENIENT), &attrs->mfield_lenient},
@@ -411,6 +412,7 @@ long TEST_API write_00_list(esodbc_dsn_attrs_st *attrs,
 		{&MK_WSTR(ESODBC_DSN_MAX_FETCH_SIZE), &attrs->max_fetch_size},
 		{&MK_WSTR(ESODBC_DSN_MAX_BODY_SIZE_MB), &attrs->max_body_size},
 		{&MK_WSTR(ESODBC_DSN_APPLY_TZ), &attrs->apply_tz},
+		{&MK_WSTR(ESODBC_DSN_EARLY_EXEC), &attrs->early_exec},
 		{&MK_WSTR(ESODBC_DSN_SCI_FLOATS), &attrs->sci_floats},
 		{&MK_WSTR(ESODBC_DSN_VERSION_CHECKING), &attrs->version_checking},
 		{&MK_WSTR(ESODBC_DSN_MFIELD_LENIENT), &attrs->mfield_lenient},
@@ -675,6 +677,10 @@ BOOL write_system_dsn(esodbc_dsn_attrs_st *new_attrs,
 			&MK_WSTR(ESODBC_DSN_APPLY_TZ), &new_attrs->apply_tz,
 			old_attrs ? &old_attrs->apply_tz : NULL
 		},
+		{
+			&MK_WSTR(ESODBC_DSN_EARLY_EXEC), &new_attrs->early_exec,
+			old_attrs ? &old_attrs->early_exec : NULL
+		},
 		{
 			&MK_WSTR(ESODBC_DSN_SCI_FLOATS), &new_attrs->sci_floats,
 			old_attrs ? &old_attrs->sci_floats : NULL
@@ -786,6 +792,7 @@ long TEST_API write_connection_string(esodbc_dsn_attrs_st *attrs,
 		{&attrs->max_fetch_size, &MK_WSTR(ESODBC_DSN_MAX_FETCH_SIZE)},
 		{&attrs->max_body_size, &MK_WSTR(ESODBC_DSN_MAX_BODY_SIZE_MB)},
 		{&attrs->apply_tz, &MK_WSTR(ESODBC_DSN_APPLY_TZ)},
+		{&attrs->early_exec, &MK_WSTR(ESODBC_DSN_EARLY_EXEC)},
 		{&attrs->sci_floats, &MK_WSTR(ESODBC_DSN_SCI_FLOATS)},
 		{&attrs->version_checking, &MK_WSTR(ESODBC_DSN_VERSION_CHECKING)},
 		{&attrs->mfield_lenient, &MK_WSTR(ESODBC_DSN_MFIELD_LENIENT)},
@@ -884,6 +891,9 @@ void assign_dsn_defaults(esodbc_dsn_attrs_st *attrs)
 	res |= assign_dsn_attr(attrs,
 			&MK_WSTR(ESODBC_DSN_APPLY_TZ), &MK_WSTR(ESODBC_DEF_APPLY_TZ),
 			/*overwrite?*/FALSE);
+	res |= assign_dsn_attr(attrs,
+			&MK_WSTR(ESODBC_DSN_EARLY_EXEC), &MK_WSTR(ESODBC_DEF_EARLY_EXEC),
+			/*overwrite?*/FALSE);
 	res |= assign_dsn_attr(attrs,
 			&MK_WSTR(ESODBC_DSN_SCI_FLOATS), &MK_WSTR(ESODBC_DEF_SCI_FLOATS),
 			/*overwrite?*/FALSE);

driver/dsn.h

@@ -35,6 +35,7 @@
 #define ESODBC_DSN_MAX_FETCH_SIZE	"MaxFetchSize"
 #define ESODBC_DSN_MAX_BODY_SIZE_MB	"MaxBodySizeMB"
 #define ESODBC_DSN_APPLY_TZ			"ApplyTZ"
+#define ESODBC_DSN_EARLY_EXEC		"EarlyExecution"
 #define ESODBC_DSN_SCI_FLOATS		"ScientificFloats"
 #define ESODBC_DSN_VERSION_CHECKING	"VersionChecking"
 #define ESODBC_DSN_MFIELD_LENIENT	"MultiFieldLenient"
@@ -78,6 +79,7 @@ typedef struct {
 	wstr_st max_fetch_size;
 	wstr_st max_body_size;
 	wstr_st apply_tz;
+	wstr_st early_exec;
 	wstr_st sci_floats;
 	wstr_st version_checking;
 	wstr_st mfield_lenient;
@@ -86,7 +88,7 @@ typedef struct {
 	wstr_st trace_enabled;
 	wstr_st trace_file;
 	wstr_st trace_level;
-#define ESODBC_DSN_ATTRS_COUNT	28
+#define ESODBC_DSN_ATTRS_COUNT	29
 	SQLWCHAR buff[ESODBC_DSN_ATTRS_COUNT * ESODBC_DSN_MAX_ATTR_LEN];
 	/* DSN reading/writing functions are passed a SQLSMALLINT lenght param */
 #if SHRT_MAX < ESODBC_DSN_ATTRS_COUNT * ESODBC_DSN_MAX_ATTR_LEN

driver/handles.c

@@ -170,6 +170,7 @@ static void init_stmt(esodbc_stmt_st *stmt, SQLHANDLE InputHandle)
 	 * set at connection level. */
 	stmt->metadata_id = DBCH(InputHandle)->metadata_id;
 	stmt->sql2c_conversion = CONVERSION_UNCHECKED;
+	stmt->early_executed = FALSE;
 }
 
 void dump_record(esodbc_rec_st *rec)

driver/handles.h

@@ -161,6 +161,7 @@ typedef struct struct_dbc {
 		ESODBC_CMPSS_AUTO,
 	} compression;
 	BOOL apply_tz; /* should the times be converted from UTC to local TZ? */
+	BOOL early_exec; /* should prepared, non-param queries be exec'd early? */
 	enum {
 		ESODBC_FLTS_DEFAULT = 0,
 		ESODBC_FLTS_SCIENTIFIC,
@@ -391,6 +392,8 @@ typedef struct struct_stmt {
 		CONVERSION_SUPPORTED,
 		CONVERSION_SKIPPED, /* used with driver's meta queries */
 	} sql2c_conversion;
+	/* early execution */
+	BOOL early_executed;
 
 	/* SQLGetData state members */
 	SQLINTEGER gd_col; /* current column to get from, if positive */

driver/queries.c

@@ -39,6 +39,7 @@
 /* fwd decl */
 static SQLRETURN statement_params_len_cbor(esodbc_stmt_st *stmt,
 	size_t *enc_len, size_t *conv_len);
+static SQLRETURN count_param_markers(esodbc_stmt_st *stmt, SQLSMALLINT *p_cnt);
 
 static thread_local cstr_st tz_param;
 static cstr_st version = CSTR_INIT(STR(DRV_VERSION)); /* build-time define */
@@ -1103,6 +1104,7 @@ SQLRETURN TEST_API attach_sql(esodbc_stmt_st *stmt,
 	/* if the app correctly SQL_CLOSE'es the statement, this would not be
 	 * needed. but just in case: re-init counter of total # of rows and sets */
 	STMT_ROW_CNT_RESET(stmt);
+	stmt->early_executed = false;
 
 	return SQL_SUCCESS;
 }
@@ -2407,6 +2409,7 @@ SQLRETURN EsSQLPrepareW
 {
 	esodbc_stmt_st *stmt = STMH(hstmt);
 	SQLRETURN ret;
+	SQLSMALLINT markers;
 
 	if (cchSqlStr == SQL_NTS) {
 		cchSqlStr = (SQLINTEGER)wcslen(szSqlStr);
@@ -2420,7 +2423,29 @@ SQLRETURN EsSQLPrepareW
 	ret = EsSQLFreeStmt(stmt, ESODBC_SQL_CLOSE);
 	assert(SQL_SUCCEEDED(ret)); /* can't return error */
 
-	return attach_sql(stmt, szSqlStr, cchSqlStr);
+	ret = attach_sql(stmt, szSqlStr, cchSqlStr);
+	/* if early execution mode is on and the statement has no parameter
+	 * markers, execute the query right away */
+	if (HDRH(stmt)->dbc->early_exec && SQL_SUCCEEDED(ret)) {
+		assert(! stmt->early_executed); /* cleared by now */
+		if (! SQL_SUCCEEDED(count_param_markers(stmt, &markers))) {
+			ERRH(stmt, "failed to count parameter markers in query. "
+				"Early execution disabled.");
+			/* clear set diagnostic */
+			init_diagnostic(&HDRH(stmt)->diag);
+			return ret;
+		}
+		if (0 < markers) {
+			INFOH(stmt, "query contains %hd parameter markers -- early "
+					"execution disabled.", markers);
+			return ret;
+		}
+		ret = EsSQLExecute(hstmt);
+		if (SQL_SUCCEEDED(ret)) {
+			stmt->early_executed = true;
+		}
+	}
+	return ret;
 }
 
 
@@ -3604,7 +3629,18 @@ SQLRETURN EsSQLExecute(SQLHSTMT hstmt)
 	char buff[ESODBC_BODY_BUF_START_SIZE];
 	cstr_st body = {buff, sizeof(buff)};
 
-	DBGH(stmt, "executing SQL: [%zd] `" LCPDL "`.", stmt->u8sql.cnt,
+	if (stmt->early_executed) {
+		stmt->early_executed = false; /* re-enable subsequent executions */
+		if (STMT_HAS_RESULTSET(stmt)) {
+			DBGH(stmt, "query early executed: [%zd] `" LCPDL "`.",
+				stmt->u8sql.cnt, LCSTR(&stmt->u8sql));
+			return SQL_SUCCESS;
+		} else {
+			WARNH(stmt, "query `" LCPDL "` early executed, but lacking result"
+				" set.", LCSTR(&stmt->u8sql));
+		}
+	}
+	DBGH(stmt, "executing query: [%zd] `" LCPDL "`.", stmt->u8sql.cnt,
 		LCSTR(&stmt->u8sql));
 
 	ret = serialize_statement(stmt, &body);