Feature #1095 - LOCAL TEMPORARY TABLE #8860
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| ### Temporary storage in read-only databases | ||
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| Since LTT definitions are not stored in the database, they can be created and used in read-only databases. This is not | ||
| possible with Global Temporary Tables, which require metadata modifications. |
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For GTT "created" and "used" is different - while it really can't be created in RO database, it can be used there.
| | Metadata storage | System tables (`RDB$RELATIONS`, etc.)| Connection memory only | | ||
| | Visibility of definition | All connections | Creating connection only | | ||
| | Persistence of definition | Permanent (until explicitly dropped) | Until connection ends | | ||
| | Read-only database support | No | Yes | |
| | Indexes | Full support | Basic support (no expression/partial) | | ||
| | DDL triggers | Fire on CREATE/DROP/ALTER | Do not fire | | ||
| | DML triggers support | Yes | Not supported | | ||
| | Constraints (PK, FK, CHECK) | Supported | Not supported | |
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Field level NOT NULL constraint is supported by LTT, so I offer to split this row by two:
"Field level NOT NULL constraints" and "Other constraints (PK, FK, CHECK)"
| { | ||
| ERR_post(Arg::Gds(isc_imp_exc) << | ||
| Arg::Gds(isc_random) << | ||
| Arg::Str("Local temporary table limit exceeded")); |
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It is not clear which limit is exceeded, imho. Maybe "Too many local temporary tables exists already" or so on...
| MET_dsql_cache_release(tdbb, SYM_relation, name); | ||
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| if (!(relation->rel_flags & REL_ltt_created)) | ||
| MET_dsql_cache_release(tdbb, SYM_relation, name); |
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Looks like LTT can't be here. See above at line 8282
| { | ||
| const auto ltt = lttEntry.second; | ||
| if (ltt->relationId == id && ltt->relation) | ||
| return ltt->relation; |
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Is it possible to call MET_relation() with id of being created LTT ?
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| // LTT not found - unlike normal relations, LTTs are not auto-created by this function | ||
| fb_assert(false); | ||
| status_exception::raise(Arg::PrivateDyn(61)); |
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Put in comments content of unnamed error message (DYN 61), please.
Also, usage of DYN error code in MET looks weird.
| if (relation->rel_flags & REL_blocking) | ||
| if ((relation->rel_flags & REL_blocking) && | ||
| !(relation->rel_flags & REL_temp_ltt) && | ||
| relation->rel_existence_lock) |
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Is it required to check for both conditions (REL_temp_ltt and rel_existence_lock) of just one enough ?
| return &rel_pages_base; | ||
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| return getPagesInternal(tdbb, tran, allocPages); | ||
| } |
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AFAIU, getPages() for LTT should return rel_pages_base - as DFW/make_ltt_version() uses getBasePages() for newly created relation.
| inline bool jrd_rel::isTemporary() const noexcept | ||
| { | ||
| return (rel_flags & (REL_temp_tran | REL_temp_conn)); | ||
| } |
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Maybe add also isLTT() or isLocalTemporary() ?
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