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MXS-1364 Provide function field usage information

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Only API change, implementations follow.
This commit is contained in:
Johan Wikman 2017-08-17 13:48:17 +03:00
parent 655f8b9170
commit 365371e7b5
1 changed files with 21 additions and 2 deletions
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23
include/maxscale/query_classifier.h
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@ -144,6 +144,16 @@ typedef enum qc_field_usage
QC_USED_IN_GROUP_BY = 0x10, /*< ... GROUP BY fld */
} qc_field_usage_t;
/**
* QC_FIELD_NAME contains information about the name of a field used in a statement.
*/
typedef struct qc_field_name
{
char* database; /** Present if the field is of the form "a.b.c", NULL otherwise. */
char* table; /** Present if the field is of the form "a.b", NULL otherwise. */
char* column; /** Always present. */
} QC_FIELD_NAME;
/**
* QC_FIELD_INFO contains information about a field used in a statement.
*/
@ -160,8 +170,10 @@ typedef struct qc_field_info
*/
typedef struct qc_function_info
{
char* name; /** Name of function. */
uint32_t usage; /** Bitfield denoting where the column appears. */
char* name; /** Name of function. */
uint32_t usage; /** Bitfield denoting where the column appears. */
QC_FIELD_NAME* fields; /** What fields the function accesses. */
uint32_t n_fields; /** The number of fields in @c fields. */
} QC_FUNCTION_INFO;
/**
@ -603,6 +615,13 @@ void qc_get_field_info(GWBUF* stmt, const QC_FIELD_INFO** infos, size_t* n_infos
* @note The returned array belongs to the GWBUF and remains valid for as
* long as the GWBUF is valid. If the data is needed for longer than
* that, it must be copied.
*
* @note For each function, only the fields that any invocation of it directly
* accesses will be returned. For instance:
*
* select length(a), length(concat(b, length(a))) from t
*
* will for @length return the field @a and for @c concat the field @b.
*/
void qc_get_function_info(GWBUF* stmt, const QC_FUNCTION_INFO** infos, size_t* n_infos);