MDEV-37886 PAGE_COMPRESSED ALTER TABLE operations inconsistent with innodb_file_per_table setting

[Thirunarayanan]

Problem:

InnoDB DDL does ALTER TABLE PAGE_COMPRESSED=1 because:

1. check_if_supported_inplace_alter() reads srv_file_per_table during precheck and does allow INSTANT operation.
2. User does change innodb_file_per_table later. But prepare phase read srv_file_per_table again during execution.
3. If the global variable changed between these phases, causes server abort for page_compressed tables.

Solution:

• Add a file_per_table member to Alter_inplace_info to capture the innodb_file_per_table value during the precheck phase and use that consistent value throughout the entire ALTER TABLE operation.

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[dr-m]

There should be no need for the reserved field nor for the struct encapsulation.

Could the ignore flag be part of the same bit-field? Could we move this bit-field next to uint index_altered_ignorability_count in order to reduce the alignment loss? Check the output of ptype/o Alter_inplace_info in GDB.

[Thirunarayanan]

{code}

Before:
======
(gdb) ptype /o ha_alter_info
type = class Alter_inplace_info {
                             public:
/*      0      |       8 */    HA_CREATE_INFO *create_info;
/*      8      |       8 */    Alter_info *alter_info;
/*     16      |       8 */    KEY *key_info_buffer;
/*     24      |       4 */    uint key_count;
/*     28      |       4 */    uint index_drop_count;
/*     32      |       8 */    KEY **index_drop_buffer;
/*     40      |       4 */    uint index_add_count;
/* XXX  4-byte hole      */
/*     48      |       8 */    uint *index_add_buffer;
/*     56      |       8 */    KEY_PAIR *index_altered_ignorability_buffer;
/*     64      |       4 */    uint index_altered_ignorability_count;
/* XXX  4-byte hole      */
/*     72      |      32 */    Rename_keys_vector rename_keys;
/*    104      |       8 */    inplace_alter_handler_ctx *handler_ctx;
/*    112      |       8 */    inplace_alter_handler_ctx **group_commit_ctx;
/*    120      |       8 */    alter_table_operations handler_flags;
/*    128      |       8 */    ulong partition_flags;
/*    136      |       8 */    partition_info * const modified_part_info;
/*    144      |       1 */    const bool ignore;
/*    145      |       1 */    bool online;
/* XXX  6-byte hole      */
/*    152      |       8 */    inplace_alter_table_commit_callback *inplace_alter_table_committed;
/*    160      |       8 */    void *inplace_alter_table_committed_argument;
/*    168      |       4 */    enum_alter_inplace_result inplace_supported;
/* XXX  4-byte hole      */
/*    176      |       8 */    const char *unsupported_reason;
/*    184      |       1 */    const bool error_if_not_empty;
/*    185      |       1 */    bool mdl_exclusive_after_prepare;
/* XXX  6-byte padding   */

                               /* total size (bytes):  192 */
                             } *
After:
=====
(gdb) ptype/o ha_alter_info
type = class Alter_inplace_info {
                             public:
/*      0      |       8 */    HA_CREATE_INFO *create_info;
/*      8      |       8 */    Alter_info *alter_info;
/*     16      |       8 */    KEY *key_info_buffer;
/*     24      |       8 */    KEY **index_drop_buffer;
/*     32      |       8 */    uint *index_add_buffer;
/*     40      |       8 */    KEY_PAIR *index_altered_ignorability_buffer;
/*     48      |       8 */    inplace_alter_handler_ctx *handler_ctx;
/*     56      |       8 */    inplace_alter_handler_ctx **group_commit_ctx;
/*     64      |       8 */    alter_table_operations handler_flags;
/*     72      |       8 */    partition_info * const modified_part_info;
/*     80      |       8 */    inplace_alter_table_commit_callback *inplace_alter_table_committed;
/*     88      |       8 */    void *inplace_alter_table_committed_argument;
/*     96      |       8 */    const char *unsupported_reason;
/*    104      |       8 */    ulong partition_flags;
/*    112      |      32 */    Rename_keys_vector rename_keys;
/*    144      |       4 */    uint key_count;
/*    148      |       4 */    uint index_drop_count;
/*    152      |       4 */    uint index_add_count;
/*    156      |       4 */    uint index_altered_ignorability_count;
/*    160      |       4 */    enum_alter_inplace_result inplace_supported;
/*    164: 0   |       4 */    unsigned int online : 1;
/*    164: 1   |       4 */    unsigned int file_per_table : 1;
/*    164: 2   |       4 */    unsigned int ignore : 1;
/*    164: 3   |       4 */    unsigned int error_if_not_empty : 1;
/*    164: 4   |       4 */    unsigned int mdl_exclusive_after_prepare : 1;
/* XXX  3-bit padding    */
/* XXX  3-byte padding   */

                               /* total size (bytes):  168 */
                             } *