[patches] [PATCH 6/7] iproto: send SQL column meta on SELECT

[Kirill Yukhin]

Hello Vlad,

On 28 фев 22:36, Vladislav Shpilevoy wrote:
> JDBC driver is a Java driver to connect to various databases and
> communicate with them using SQL. It requires some meta
> information on a SELECT from a server about each returned column:
> https://docs.oracle.com/javase/6/docs/api/java/sql/ResultSetMetaData.html
> 
> Introduce new IPROTO codes in IPROTO_METADATA map with the needed
> meta and fetch it from SQL statement.
> 
> Closes #2620
> 
> Signed-off-by: Vladislav Shpilevoy <v.shpilevoy at tarantool.org>
> ---
>  src/box/execute.c          | 127 ++++++++++++++++++++++++++++++++++++++-------
>  src/box/iproto_constants.h |  23 ++++++++
>  src/box/lua/net_box.lua    |  29 +++++++++--
>  test/sql/iproto.result     |  59 ++++++++++++++++++---
>  test/sql/iproto.test.lua   |   9 ++++
>  5 files changed, 220 insertions(+), 27 deletions(-)
> 
> diff --git a/src/box/execute.c b/src/box/execute.c
> index 48d166b5b..859bd10ae 100644
> --- a/src/box/execute.c
> +++ b/src/box/execute.c
> @@ -506,6 +507,108 @@ sql_bind(const struct sql_request *request, struct sqlite3_stmt *stmt)
>  	return 0;
>  }
>  
> +/**
> + * Binary encoded MessagePack map. It is used to avoid multiple
> + * mp_sizeof_...() + mp_encode_uint() during column meta building.
> + * Select can contain very big amount of columns, so column meta
> + * building speed is important.
> + */
> +struct PACKED iproto_sql_column_meta_bin {
> +	/** MP_MAP with key count. */
> +	uint8_t m_header;
> +	/** IPROTO_FIELD_FLAGS: MP_UINT8. */
> +	uint8_t k_flags;
> +	uint8_t m_flags;
> +};
> +
> +/** 0x80 - MessagePack map with 0 keys. */
> +static const struct iproto_sql_column_meta_bin iproto_sql_column_meta_bin = {
> +	0x80, IPROTO_FIELD_FLAGS, 0
> +};
> +
> +/**
> + * Encode meta information about a non-table column represented in
> + * a SELECT column list by a constant, or by a complex expression.
> + * It does not have any meta except an alias.
> + * @param out Output buffer.
> + * @param column Column meta.
> + *
> + * @retval  0 Success.
> + * @retval -1 Memory error.
> + */
> +static inline int
> +sql_ephemeral_column_meta_encode(struct obuf *out,
> +				 const struct sql_column_meta *column)
I think reference to artificial column as `ephemeral` is confusing,
since we recently introduced ephemeral spaces. Maybe use other word?

> +static inline int
> +sql_table_column_meta_encode(struct obuf *out,
> +			     const struct sql_column_meta *column)
> +{
> +	assert(column->alias != NULL);
> +	assert(column->name != NULL);
> +	int alias_len = strlen(column->alias);
> +	int name_len = strlen(column->name);
> +	bool is_alias_eq_name =
> +		alias_len == name_len &&
> +		memcmp(column->name, column->alias, name_len) == 0;
> +	struct iproto_sql_column_meta_bin header = iproto_sql_column_meta_bin;
> +	size_t size = sizeof(header) + mp_sizeof_uint(IPROTO_FIELD_COLUMN) +
> +		      mp_sizeof_str(name_len);
> +	if (! is_alias_eq_name) {
> +		size += mp_sizeof_uint(IPROTO_FIELD_NAME) +
> +			mp_sizeof_str(alias_len);
> +		/* @Sa mp_encode_map(). */
I might be out of context, but what is @Sa?

--
Regard, Kirill Yukhin