[Tarantool-patches] [PATCH 1/3] tuple: make update operation tokens consumable
Sergey Ostanevich
sergos at tarantool.org
Fri Dec 27 17:59:28 MSK 2019
Hi!
> So I added a flag to xrow_update_op.
Thanks, this is something that I had in my mind.
LGTM.
Sergos.
On 27 Dec 16:00, Vladislav Shpilevoy wrote:
> Hi! Thanks for the review!
>
> On 26/12/2019 13:07, Sergey Ostanevich wrote:
> > Hi!
> >
> > Thanks for the patch!
> > Just one comment below, otherwise LGTM.
> >
> > Sergos
> >
> > On 23 Dec 23:41, Vladislav Shpilevoy wrote:
> >> There is a case: [1][2][3][4] = 100. It is not a problem when it
> >> is a single operation, not intersecting with anything. It is an
> >> isolated update then, and works ok. But the next patch allows
> >> several update operations have the same prefix, and the path
> >> [1][2][3][4] can become a tree of updated arrays. For example, a
> >> trivial tree like this:
> >>
> >> root: [ [1] ]
> >> |
> >> [ [1] [2] ]
> >> |
> >> [ [1] [2] [3] ]
> >> |
> >> [ [1] [2] [3] [4] ]
> >> =100
> >>
> >> When the update is applied to root, the JSON path [1][2][3][4]
> >> is decoded one part by one. And the operation goes down the tree
> >> until reaches the leaf, where [4] = 100 is applied. Each time when
> >> the update goes one level down, somebody should update
> >> xrow_update_op.field_no so as on the first level it would be 1,
> >> then 2, 3, 4.
> >>
> >> Does it mean that each level of the update [1][2][3][4] should
> >> prepare field_no for the next child? No, because then they would
> >> need to check type of the child if it is an array or map, or
> >> whatever expects a valid field_no/key in xrow_update_op, and
> >> ensure that map-child gets a key, array-child gets a field_no.
> >> That would complicate the code to a totally unreadable
> >> state, and would break encapsulation between
> >> xrow_update_array/map/bar... . Each array update operation would
> >> check a child for all existing types to ensure that the next token
> >> matches it. The same would happen to map updates.
> >>
> >> This patch goes another way - let each level of update check if
> >> its field_no/key is already prepared by the caller. And if not,
> >> extract a next token from the operation path. So the map update
> >> will ensure that it has a valid key, an array update will ensure
> >> that it has a valid field no.
> >>
> >> Part of #1261
> >> ---
> >> src/box/xrow_update_array.c | 47 +++++++++++++++++++++++++++++++++++--
> >> src/box/xrow_update_field.c | 22 +++++++++++++++++
> >> src/box/xrow_update_field.h | 25 ++++++++++++++++++--
> >> 3 files changed, 90 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/src/box/xrow_update_array.c b/src/box/xrow_update_array.c
> >> index 57427e39c..6a7ce09ff 100644
> >> --- a/src/box/xrow_update_array.c
> >> +++ b/src/box/xrow_update_array.c
> >> @@ -32,6 +32,31 @@
> >> #include "msgpuck.h"
> >> #include "fiber.h"
> >>
> >> +/**
> >> + * Make sure @a op contains a valid field number to where the
> >> + * operation should be applied next. Field number may be not
> >> + * known, if the array's parent didn't propagate operation's
> >> + * lexer. In fact, the parent fills fieldno only in some rare
> >> + * cases like branching. Generally, an array should care about
> >> + * fieldno by itself.
> >> + */
> >> +static inline int
> >> +xrow_update_op_prepare_num_token(struct xrow_update_op *op)
> >> +{
> >> + /*
> >> + * Token type END is a special value meaning that the
> >> + * current token needs to be parsed.
> >> + */
> >
> > I really don't like reuse of entities introduced for some purpose. If
> > one will read this code, then it will be hard to understand why out of
> > nowhere Lexer forced to come to an end at
> > xrow_update_op_do_array_insert() for example. More that that - if lexer
> > in a state of 'reached the end' it forced to parse.
> >
> > If we introduce some more functionality for JSON later - I expect we
> > will face even more logic to hang on this 'special value'. Then
> > contexts of these functionalities may intersect... oh my...
> >
> > Can we introduce a new type with some self-explanatory name instead and
> > leave the JSON_TOKEN_END on its own?
>
> Agree. But I don't know how to justify introduction of a new token
> type to the json library. I was thinking about something like
> JSON_TOKEN_INVALID, but 1) json library reports an error via return
> values, not via token types, 2) 'invalid' token assumes an error,
> not an already parsed token, like I need in my patch.
>
> A value like JSON_TOKEN_CONSUMED/USED looks too specific for my case
> to be added to the core lib.
>
> So I added a flag to xrow_update_op. See diff below, and the whole
> patch in the end.
>
> ================================================================================
>
> diff --git a/src/box/xrow_update_array.c b/src/box/xrow_update_array.c
> index 2eb98e8e9..e6b9ed89f 100644
> --- a/src/box/xrow_update_array.c
> +++ b/src/box/xrow_update_array.c
> @@ -43,13 +43,8 @@
> static inline int
> xrow_update_op_prepare_num_token(struct xrow_update_op *op)
> {
> - /*
> - * Token type END is a special value meaning that the
> - * current token needs to be parsed.
> - */
> - if (op->token_type == JSON_TOKEN_END &&
> - xrow_update_op_consume_token(op) != 0)
> - return -1;
> + if (op->is_token_consumed && xrow_update_op_next_token(op) != 0)
> + return -1;
> if (op->token_type != JSON_TOKEN_NUM) {
> return xrow_update_err(op, "can't update an array by a "\
> "non-numeric index");
> @@ -64,7 +59,7 @@ xrow_update_op_prepare_num_token(struct xrow_update_op *op)
> static inline int
> xrow_update_op_adjust_field_no(struct xrow_update_op *op, int32_t field_count)
> {
> - assert(op->token_type == JSON_TOKEN_NUM);
> + assert(op->token_type == JSON_TOKEN_NUM && !op->is_token_consumed);
> if (op->field_no >= 0) {
> if (op->field_no < field_count)
> return 0;
> @@ -254,7 +249,7 @@ xrow_update_op_do_array_insert(struct xrow_update_op *op,
> item = xrow_update_array_extract_item(field, op);
> if (item == NULL)
> return -1;
> - op->token_type = JSON_TOKEN_END;
> + op->is_token_consumed = true;
> return xrow_update_op_do_field_insert(op, &item->field);
> }
>
> @@ -290,7 +285,7 @@ xrow_update_op_do_array_set(struct xrow_update_op *op,
> if (item == NULL)
> return -1;
> if (!xrow_update_op_is_term(op)) {
> - op->token_type = JSON_TOKEN_END;
> + op->is_token_consumed = true;
> return xrow_update_op_do_field_set(op, &item->field);
> }
> op->new_field_len = op->arg.set.length;
> @@ -318,7 +313,7 @@ xrow_update_op_do_array_delete(struct xrow_update_op *op,
> xrow_update_array_extract_item(field, op);
> if (item == NULL)
> return -1;
> - op->token_type = JSON_TOKEN_END;
> + op->is_token_consumed = true;
> return xrow_update_op_do_field_delete(op, &item->field);
> }
>
> @@ -347,7 +342,7 @@ xrow_update_op_do_array_##op_type(struct xrow_update_op *op, \
> if (item == NULL) \
> return -1; \
> if (!xrow_update_op_is_term(op)) { \
> - op->token_type = JSON_TOKEN_END; \
> + op->is_token_consumed = true; \
> return xrow_update_op_do_field_##op_type(op, &item->field); \
> } \
> if (item->field.type != XUPDATE_NOP) \
> diff --git a/src/box/xrow_update_field.c b/src/box/xrow_update_field.c
> index 96fcaf747..460672b4c 100644
> --- a/src/box/xrow_update_field.c
> +++ b/src/box/xrow_update_field.c
> @@ -612,7 +612,7 @@ xrow_update_op_by(char opcode)
> }
>
> int
> -xrow_update_op_consume_token(struct xrow_update_op *op)
> +xrow_update_op_next_token(struct xrow_update_op *op)
> {
> struct json_token token;
> int rc = json_lexer_next_token(&op->lexer, &token);
> @@ -620,6 +620,7 @@ xrow_update_op_consume_token(struct xrow_update_op *op)
> return xrow_update_err_bad_json(op, rc);
> if (token.type == JSON_TOKEN_END)
> return xrow_update_err_no_such_field(op);
> + op->is_token_consumed = false;
> op->token_type = token.type;
> op->key = token.str;
> op->key_len = token.len;
> @@ -661,6 +662,7 @@ xrow_update_op_decode(struct xrow_update_op *op, int index_base,
> * dictionary.
> */
> op->token_type = JSON_TOKEN_NUM;
> + op->is_token_consumed = false;
> int32_t field_no = 0;
> switch(mp_typeof(**expr)) {
> case MP_INT:
> diff --git a/src/box/xrow_update_field.h b/src/box/xrow_update_field.h
> index fbaf45c5d..0b0f608fe 100644
> --- a/src/box/xrow_update_field.h
> +++ b/src/box/xrow_update_field.h
> @@ -179,11 +179,16 @@ struct xrow_update_op {
> const struct xrow_update_op_meta *meta;
> /** Operation arguments. */
> union xrow_update_arg arg;
> + /** Current level token. */
> + enum json_token_type token_type;
> /**
> - * Current level token. END means that it is invalid and
> - * a next token should be extracted from the lexer.
> + * The flag says whether the token is already consumed by
> + * the update operation during its forwarding down the
> + * update tree. When the flag is true, it means that the
> + * next node of the update tree will need to fetch a next
> + * token from the lexer.
> */
> - enum json_token_type token_type;
> + bool is_token_consumed;
> union {
> struct {
> const char *key;
> @@ -212,7 +217,7 @@ struct xrow_update_op {
> * map/array.
> */
> int
> -xrow_update_op_consume_token(struct xrow_update_op *op);
> +xrow_update_op_next_token(struct xrow_update_op *op);
>
> /**
> * Decode an update operation from MessagePack.
>
> ================================================================================
>
> The whole patch:
>
> ================================================================================
>
> tuple: make update operation tokens consumable
>
> There is a case: [1][2][3][4] = 100. It is not a problem when it
> is a single operation, not intersecting with anything. It is an
> isolated update then, and works ok. But the next patch allows
> several update operations have the same prefix, and the path
> [1][2][3][4] can become a tree of updated arrays. For example, a
> trivial tree like this:
>
> root: [ [1] ]
> |
> [ [1] [2] ]
> |
> [ [1] [2] [3] ]
> |
> [ [1] [2] [3] [4] ]
> =100
>
> When the update is applied to root, the JSON path [1][2][3][4]
> is decoded one part by one. And the operation goes down the tree
> until reaches the leaf, where [4] = 100 is applied. Each time when
> the update goes one level down, somebody should update
> xrow_update_op.field_no so as on the first level it would be 1,
> then 2, 3, 4.
>
> Does it mean that each level of the update [1][2][3][4] should
> prepare field_no for the next child? No, because then they would
> need to check type of the child if it is an array or map, or
> whatever expects a valid field_no/key in xrow_update_op, and
> ensure that map-child gets a key, array-child gets a field_no.
> That would complicate the code to a totally unreadable
> state, and would break encapsulation between
> xrow_update_array/map/bar... . Each array update operation would
> check a child for all existing types to ensure that the next token
> matches it. The same would happen to map updates.
>
> This patch goes another way - let each level of update check if
> its field_no/key is already prepared by the caller. And if not,
> extract a next token from the operation path. So the map update
> will ensure that it has a valid key, an array update will ensure
> that it has a valid field no.
>
> Part of #1261
>
> diff --git a/src/box/xrow_update_array.c b/src/box/xrow_update_array.c
> index 57427e39c..e6b9ed89f 100644
> --- a/src/box/xrow_update_array.c
> +++ b/src/box/xrow_update_array.c
> @@ -32,6 +32,26 @@
> #include "msgpuck.h"
> #include "fiber.h"
>
> +/**
> + * Make sure @a op contains a valid field number to where the
> + * operation should be applied next. Field number may be not
> + * known, if the array's parent didn't propagate operation's
> + * lexer. In fact, the parent fills fieldno only in some rare
> + * cases like branching. Generally, an array should care about
> + * fieldno by itself.
> + */
> +static inline int
> +xrow_update_op_prepare_num_token(struct xrow_update_op *op)
> +{
> + if (op->is_token_consumed && xrow_update_op_next_token(op) != 0)
> + return -1;
> + if (op->token_type != JSON_TOKEN_NUM) {
> + return xrow_update_err(op, "can't update an array by a "\
> + "non-numeric index");
> + }
> + return 0;
> +}
> +
> /**
> * Make field index non-negative and check for the field
> * existence.
> @@ -39,6 +59,7 @@
> static inline int
> xrow_update_op_adjust_field_no(struct xrow_update_op *op, int32_t field_count)
> {
> + assert(op->token_type == JSON_TOKEN_NUM && !op->is_token_consumed);
> if (op->field_no >= 0) {
> if (op->field_no < field_count)
> return 0;
> @@ -221,10 +242,14 @@ xrow_update_op_do_array_insert(struct xrow_update_op *op,
> {
> assert(field->type == XUPDATE_ARRAY);
> struct xrow_update_array_item *item;
> + if (xrow_update_op_prepare_num_token(op) != 0)
> + return -1;
> +
> if (!xrow_update_op_is_term(op)) {
> item = xrow_update_array_extract_item(field, op);
> if (item == NULL)
> return -1;
> + op->is_token_consumed = true;
> return xrow_update_op_do_field_insert(op, &item->field);
> }
>
> @@ -248,6 +273,9 @@ xrow_update_op_do_array_set(struct xrow_update_op *op,
> {
> assert(field->type == XUPDATE_ARRAY);
> struct xrow_update_rope *rope = field->array.rope;
> + if (xrow_update_op_prepare_num_token(op) != 0)
> + return -1;
> +
> /* Interpret '=' for n + 1 field as insert. */
> if (op->field_no == (int32_t) xrow_update_rope_size(rope))
> return xrow_update_op_do_array_insert(op, field);
> @@ -256,8 +284,10 @@ xrow_update_op_do_array_set(struct xrow_update_op *op,
> xrow_update_array_extract_item(field, op);
> if (item == NULL)
> return -1;
> - if (!xrow_update_op_is_term(op))
> + if (!xrow_update_op_is_term(op)) {
> + op->is_token_consumed = true;
> return xrow_update_op_do_field_set(op, &item->field);
> + }
> op->new_field_len = op->arg.set.length;
> /*
> * Ignore the previous op, if any. It is not correct,
> @@ -275,11 +305,15 @@ xrow_update_op_do_array_delete(struct xrow_update_op *op,
> struct xrow_update_field *field)
> {
> assert(field->type == XUPDATE_ARRAY);
> + if (xrow_update_op_prepare_num_token(op) != 0)
> + return -1;
> +
> if (!xrow_update_op_is_term(op)) {
> struct xrow_update_array_item *item =
> xrow_update_array_extract_item(field, op);
> if (item == NULL)
> return -1;
> + op->is_token_consumed = true;
> return xrow_update_op_do_field_delete(op, &item->field);
> }
>
> @@ -301,12 +335,16 @@ int \
> xrow_update_op_do_array_##op_type(struct xrow_update_op *op, \
> struct xrow_update_field *field) \
> { \
> + if (xrow_update_op_prepare_num_token(op) != 0) \
> + return -1; \
> struct xrow_update_array_item *item = \
> xrow_update_array_extract_item(field, op); \
> if (item == NULL) \
> return -1; \
> - if (!xrow_update_op_is_term(op)) \
> + if (!xrow_update_op_is_term(op)) { \
> + op->is_token_consumed = true; \
> return xrow_update_op_do_field_##op_type(op, &item->field); \
> + } \
> if (item->field.type != XUPDATE_NOP) \
> return xrow_update_err_double(op); \
> if (xrow_update_op_do_##op_type(op, item->field.data) != 0) \
> diff --git a/src/box/xrow_update_field.c b/src/box/xrow_update_field.c
> index de865a21d..460672b4c 100644
> --- a/src/box/xrow_update_field.c
> +++ b/src/box/xrow_update_field.c
> @@ -611,6 +611,23 @@ xrow_update_op_by(char opcode)
> }
> }
>
> +int
> +xrow_update_op_next_token(struct xrow_update_op *op)
> +{
> + struct json_token token;
> + int rc = json_lexer_next_token(&op->lexer, &token);
> + if (rc != 0)
> + return xrow_update_err_bad_json(op, rc);
> + if (token.type == JSON_TOKEN_END)
> + return xrow_update_err_no_such_field(op);
> + op->is_token_consumed = false;
> + op->token_type = token.type;
> + op->key = token.str;
> + op->key_len = token.len;
> + op->field_no = token.num;
> + return 0;
> +}
> +
> int
> xrow_update_op_decode(struct xrow_update_op *op, int index_base,
> struct tuple_dictionary *dict, const char **expr)
> @@ -639,6 +656,13 @@ xrow_update_op_decode(struct xrow_update_op *op, int index_base,
> diag_set(ClientError, ER_UNKNOWN_UPDATE_OP);
> return -1;
> }
> + /*
> + * First token is always num. Even if a user specified a
> + * field name it is converted to num by the tuple
> + * dictionary.
> + */
> + op->token_type = JSON_TOKEN_NUM;
> + op->is_token_consumed = false;
> int32_t field_no = 0;
> switch(mp_typeof(**expr)) {
> case MP_INT:
> diff --git a/src/box/xrow_update_field.h b/src/box/xrow_update_field.h
> index bda9222cc..0b0f608fe 100644
> --- a/src/box/xrow_update_field.h
> +++ b/src/box/xrow_update_field.h
> @@ -179,8 +179,23 @@ struct xrow_update_op {
> const struct xrow_update_op_meta *meta;
> /** Operation arguments. */
> union xrow_update_arg arg;
> - /** First level field no. */
> - int32_t field_no;
> + /** Current level token. */
> + enum json_token_type token_type;
> + /**
> + * The flag says whether the token is already consumed by
> + * the update operation during its forwarding down the
> + * update tree. When the flag is true, it means that the
> + * next node of the update tree will need to fetch a next
> + * token from the lexer.
> + */
> + bool is_token_consumed;
> + union {
> + struct {
> + const char *key;
> + uint32_t key_len;
> + };
> + int32_t field_no;
> + };
> /** Size of a new field after it is updated. */
> uint32_t new_field_len;
> /** Opcode symbol: = + - / ... */
> @@ -193,6 +208,17 @@ struct xrow_update_op {
> struct json_lexer lexer;
> };
>
> +/**
> + * Extract a next token from the operation path lexer. The result
> + * is used to decide to which child of a current map/array the
> + * operation should be forwarded. It is not just a synonym to
> + * json_lexer_next_token, because fills some fields of @a op,
> + * and should be used only to chose a next child inside a current
> + * map/array.
> + */
> +int
> +xrow_update_op_next_token(struct xrow_update_op *op);
> +
> /**
> * Decode an update operation from MessagePack.
> * @param[out] op Update operation.
>
> ================================================================================
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