mirror of https://github.com/postgres/postgres
This new header contains all the variable-length data types support (TOAST support) from postgres.h, which isn't needed by large parts of the backend code. Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> Discussion: https://www.postgresql.org/message-id/flat/ddcce239-0f29-6e62-4b47-1f8ca742addf%40enterprisedb.compull/113/head
Peter Eisentraut
3 years ago
parent
cd06ccd78f
commit
d952373a98
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/*-------------------------------------------------------------------------
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* |
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* varatt.h |
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* variable-length datatypes (TOAST support) |
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* |
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* |
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* Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group |
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* Portions Copyright (c) 1995, Regents of the University of California |
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* |
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* src/include/varatt.h |
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* |
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*------------------------------------------------------------------------- |
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*/ |
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#ifndef VARATT_H |
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#define VARATT_H |
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/*
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* struct varatt_external is a traditional "TOAST pointer", that is, the |
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* information needed to fetch a Datum stored out-of-line in a TOAST table. |
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* The data is compressed if and only if the external size stored in |
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* va_extinfo is less than va_rawsize - VARHDRSZ. |
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* |
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* This struct must not contain any padding, because we sometimes compare |
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* these pointers using memcmp. |
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* |
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* Note that this information is stored unaligned within actual tuples, so |
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* you need to memcpy from the tuple into a local struct variable before |
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* you can look at these fields! (The reason we use memcmp is to avoid |
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* having to do that just to detect equality of two TOAST pointers...) |
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*/ |
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typedef struct varatt_external |
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{ |
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int32 va_rawsize; /* Original data size (includes header) */ |
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uint32 va_extinfo; /* External saved size (without header) and
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* compression method */ |
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Oid va_valueid; /* Unique ID of value within TOAST table */ |
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Oid va_toastrelid; /* RelID of TOAST table containing it */ |
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} varatt_external; |
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/*
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* These macros define the "saved size" portion of va_extinfo. Its remaining |
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* two high-order bits identify the compression method. |
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*/ |
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#define VARLENA_EXTSIZE_BITS 30 |
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#define VARLENA_EXTSIZE_MASK ((1U << VARLENA_EXTSIZE_BITS) - 1) |
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/*
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* struct varatt_indirect is a "TOAST pointer" representing an out-of-line |
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* Datum that's stored in memory, not in an external toast relation. |
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* The creator of such a Datum is entirely responsible that the referenced |
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* storage survives for as long as referencing pointer Datums can exist. |
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* |
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* Note that just as for struct varatt_external, this struct is stored |
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* unaligned within any containing tuple. |
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*/ |
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typedef struct varatt_indirect |
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{ |
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struct varlena *pointer; /* Pointer to in-memory varlena */ |
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} varatt_indirect; |
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/*
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* struct varatt_expanded is a "TOAST pointer" representing an out-of-line |
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* Datum that is stored in memory, in some type-specific, not necessarily |
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* physically contiguous format that is convenient for computation not |
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* storage. APIs for this, in particular the definition of struct |
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* ExpandedObjectHeader, are in src/include/utils/expandeddatum.h. |
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* |
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* Note that just as for struct varatt_external, this struct is stored |
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* unaligned within any containing tuple. |
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*/ |
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typedef struct ExpandedObjectHeader ExpandedObjectHeader; |
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typedef struct varatt_expanded |
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{ |
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ExpandedObjectHeader *eohptr; |
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} varatt_expanded; |
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/*
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* Type tag for the various sorts of "TOAST pointer" datums. The peculiar |
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* value for VARTAG_ONDISK comes from a requirement for on-disk compatibility |
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* with a previous notion that the tag field was the pointer datum's length. |
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*/ |
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typedef enum vartag_external |
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{ |
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VARTAG_INDIRECT = 1, |
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VARTAG_EXPANDED_RO = 2, |
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VARTAG_EXPANDED_RW = 3, |
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VARTAG_ONDISK = 18 |
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} vartag_external; |
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/* this test relies on the specific tag values above */ |
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#define VARTAG_IS_EXPANDED(tag) \ |
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(((tag) & ~1) == VARTAG_EXPANDED_RO) |
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#define VARTAG_SIZE(tag) \ |
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((tag) == VARTAG_INDIRECT ? sizeof(varatt_indirect) : \
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VARTAG_IS_EXPANDED(tag) ? sizeof(varatt_expanded) : \
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(tag) == VARTAG_ONDISK ? sizeof(varatt_external) : \
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(AssertMacro(false), 0)) |
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/*
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* These structs describe the header of a varlena object that may have been |
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* TOASTed. Generally, don't reference these structs directly, but use the |
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* macros below. |
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* |
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* We use separate structs for the aligned and unaligned cases because the |
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* compiler might otherwise think it could generate code that assumes |
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* alignment while touching fields of a 1-byte-header varlena. |
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*/ |
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typedef union |
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{ |
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struct /* Normal varlena (4-byte length) */ |
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{ |
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uint32 va_header; |
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char va_data[FLEXIBLE_ARRAY_MEMBER]; |
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} va_4byte; |
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struct /* Compressed-in-line format */ |
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{ |
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uint32 va_header; |
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uint32 va_tcinfo; /* Original data size (excludes header) and
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* compression method; see va_extinfo */ |
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char va_data[FLEXIBLE_ARRAY_MEMBER]; /* Compressed data */ |
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} va_compressed; |
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} varattrib_4b; |
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typedef struct |
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{ |
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uint8 va_header; |
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char va_data[FLEXIBLE_ARRAY_MEMBER]; /* Data begins here */ |
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} varattrib_1b; |
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/* TOAST pointers are a subset of varattrib_1b with an identifying tag byte */ |
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typedef struct |
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{ |
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uint8 va_header; /* Always 0x80 or 0x01 */ |
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uint8 va_tag; /* Type of datum */ |
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char va_data[FLEXIBLE_ARRAY_MEMBER]; /* Type-specific data */ |
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} varattrib_1b_e; |
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/*
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* Bit layouts for varlena headers on big-endian machines: |
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* |
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* 00xxxxxx 4-byte length word, aligned, uncompressed data (up to 1G) |
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* 01xxxxxx 4-byte length word, aligned, *compressed* data (up to 1G) |
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* 10000000 1-byte length word, unaligned, TOAST pointer |
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* 1xxxxxxx 1-byte length word, unaligned, uncompressed data (up to 126b) |
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* |
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* Bit layouts for varlena headers on little-endian machines: |
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* |
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* xxxxxx00 4-byte length word, aligned, uncompressed data (up to 1G) |
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* xxxxxx10 4-byte length word, aligned, *compressed* data (up to 1G) |
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* 00000001 1-byte length word, unaligned, TOAST pointer |
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* xxxxxxx1 1-byte length word, unaligned, uncompressed data (up to 126b) |
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* |
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* The "xxx" bits are the length field (which includes itself in all cases). |
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* In the big-endian case we mask to extract the length, in the little-endian |
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* case we shift. Note that in both cases the flag bits are in the physically |
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* first byte. Also, it is not possible for a 1-byte length word to be zero; |
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* this lets us disambiguate alignment padding bytes from the start of an |
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* unaligned datum. (We now *require* pad bytes to be filled with zero!) |
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* |
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* In TOAST pointers the va_tag field (see varattrib_1b_e) is used to discern |
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* the specific type and length of the pointer datum. |
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*/ |
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/*
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* Endian-dependent macros. These are considered internal --- use the |
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* external macros below instead of using these directly. |
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* |
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* Note: IS_1B is true for external toast records but VARSIZE_1B will return 0 |
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* for such records. Hence you should usually check for IS_EXTERNAL before |
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* checking for IS_1B. |
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*/ |
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#ifdef WORDS_BIGENDIAN |
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#define VARATT_IS_4B(PTR) \ |
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((((varattrib_1b *) (PTR))->va_header & 0x80) == 0x00) |
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#define VARATT_IS_4B_U(PTR) \ |
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((((varattrib_1b *) (PTR))->va_header & 0xC0) == 0x00) |
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#define VARATT_IS_4B_C(PTR) \ |
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((((varattrib_1b *) (PTR))->va_header & 0xC0) == 0x40) |
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#define VARATT_IS_1B(PTR) \ |
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((((varattrib_1b *) (PTR))->va_header & 0x80) == 0x80) |
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#define VARATT_IS_1B_E(PTR) \ |
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((((varattrib_1b *) (PTR))->va_header) == 0x80) |
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#define VARATT_NOT_PAD_BYTE(PTR) \ |
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(*((uint8 *) (PTR)) != 0) |
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/* VARSIZE_4B() should only be used on known-aligned data */ |
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#define VARSIZE_4B(PTR) \ |
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(((varattrib_4b *) (PTR))->va_4byte.va_header & 0x3FFFFFFF) |
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#define VARSIZE_1B(PTR) \ |
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(((varattrib_1b *) (PTR))->va_header & 0x7F) |
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#define VARTAG_1B_E(PTR) \ |
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(((varattrib_1b_e *) (PTR))->va_tag) |
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#define SET_VARSIZE_4B(PTR,len) \ |
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(((varattrib_4b *) (PTR))->va_4byte.va_header = (len) & 0x3FFFFFFF) |
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#define SET_VARSIZE_4B_C(PTR,len) \ |
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(((varattrib_4b *) (PTR))->va_4byte.va_header = ((len) & 0x3FFFFFFF) | 0x40000000) |
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#define SET_VARSIZE_1B(PTR,len) \ |
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(((varattrib_1b *) (PTR))->va_header = (len) | 0x80) |
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#define SET_VARTAG_1B_E(PTR,tag) \ |
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(((varattrib_1b_e *) (PTR))->va_header = 0x80, \
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((varattrib_1b_e *) (PTR))->va_tag = (tag)) |
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#else /* !WORDS_BIGENDIAN */ |
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#define VARATT_IS_4B(PTR) \ |
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((((varattrib_1b *) (PTR))->va_header & 0x01) == 0x00) |
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#define VARATT_IS_4B_U(PTR) \ |
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((((varattrib_1b *) (PTR))->va_header & 0x03) == 0x00) |
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#define VARATT_IS_4B_C(PTR) \ |
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((((varattrib_1b *) (PTR))->va_header & 0x03) == 0x02) |
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#define VARATT_IS_1B(PTR) \ |
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((((varattrib_1b *) (PTR))->va_header & 0x01) == 0x01) |
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#define VARATT_IS_1B_E(PTR) \ |
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((((varattrib_1b *) (PTR))->va_header) == 0x01) |
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#define VARATT_NOT_PAD_BYTE(PTR) \ |
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(*((uint8 *) (PTR)) != 0) |
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/* VARSIZE_4B() should only be used on known-aligned data */ |
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#define VARSIZE_4B(PTR) \ |
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((((varattrib_4b *) (PTR))->va_4byte.va_header >> 2) & 0x3FFFFFFF) |
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#define VARSIZE_1B(PTR) \ |
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((((varattrib_1b *) (PTR))->va_header >> 1) & 0x7F) |
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#define VARTAG_1B_E(PTR) \ |
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(((varattrib_1b_e *) (PTR))->va_tag) |
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#define SET_VARSIZE_4B(PTR,len) \ |
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(((varattrib_4b *) (PTR))->va_4byte.va_header = (((uint32) (len)) << 2)) |
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#define SET_VARSIZE_4B_C(PTR,len) \ |
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(((varattrib_4b *) (PTR))->va_4byte.va_header = (((uint32) (len)) << 2) | 0x02) |
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#define SET_VARSIZE_1B(PTR,len) \ |
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(((varattrib_1b *) (PTR))->va_header = (((uint8) (len)) << 1) | 0x01) |
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#define SET_VARTAG_1B_E(PTR,tag) \ |
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(((varattrib_1b_e *) (PTR))->va_header = 0x01, \
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((varattrib_1b_e *) (PTR))->va_tag = (tag)) |
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#endif /* WORDS_BIGENDIAN */ |
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#define VARDATA_4B(PTR) (((varattrib_4b *) (PTR))->va_4byte.va_data) |
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#define VARDATA_4B_C(PTR) (((varattrib_4b *) (PTR))->va_compressed.va_data) |
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#define VARDATA_1B(PTR) (((varattrib_1b *) (PTR))->va_data) |
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#define VARDATA_1B_E(PTR) (((varattrib_1b_e *) (PTR))->va_data) |
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/*
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* Externally visible TOAST macros begin here. |
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*/ |
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#define VARHDRSZ_EXTERNAL offsetof(varattrib_1b_e, va_data) |
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#define VARHDRSZ_COMPRESSED offsetof(varattrib_4b, va_compressed.va_data) |
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#define VARHDRSZ_SHORT offsetof(varattrib_1b, va_data) |
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#define VARATT_SHORT_MAX 0x7F |
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#define VARATT_CAN_MAKE_SHORT(PTR) \ |
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(VARATT_IS_4B_U(PTR) && \
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(VARSIZE(PTR) - VARHDRSZ + VARHDRSZ_SHORT) <= VARATT_SHORT_MAX) |
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#define VARATT_CONVERTED_SHORT_SIZE(PTR) \ |
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(VARSIZE(PTR) - VARHDRSZ + VARHDRSZ_SHORT) |
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/*
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* In consumers oblivious to data alignment, call PG_DETOAST_DATUM_PACKED(), |
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* VARDATA_ANY(), VARSIZE_ANY() and VARSIZE_ANY_EXHDR(). Elsewhere, call |
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* PG_DETOAST_DATUM(), VARDATA() and VARSIZE(). Directly fetching an int16, |
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* int32 or wider field in the struct representing the datum layout requires |
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* aligned data. memcpy() is alignment-oblivious, as are most operations on |
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* datatypes, such as text, whose layout struct contains only char fields. |
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* |
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* Code assembling a new datum should call VARDATA() and SET_VARSIZE(). |
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* (Datums begin life untoasted.) |
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* |
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* Other macros here should usually be used only by tuple assembly/disassembly |
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* code and code that specifically wants to work with still-toasted Datums. |
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*/ |
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#define VARDATA(PTR) VARDATA_4B(PTR) |
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#define VARSIZE(PTR) VARSIZE_4B(PTR) |
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#define VARSIZE_SHORT(PTR) VARSIZE_1B(PTR) |
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#define VARDATA_SHORT(PTR) VARDATA_1B(PTR) |
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#define VARTAG_EXTERNAL(PTR) VARTAG_1B_E(PTR) |
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#define VARSIZE_EXTERNAL(PTR) (VARHDRSZ_EXTERNAL + VARTAG_SIZE(VARTAG_EXTERNAL(PTR))) |
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#define VARDATA_EXTERNAL(PTR) VARDATA_1B_E(PTR) |
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#define VARATT_IS_COMPRESSED(PTR) VARATT_IS_4B_C(PTR) |
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#define VARATT_IS_EXTERNAL(PTR) VARATT_IS_1B_E(PTR) |
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#define VARATT_IS_EXTERNAL_ONDISK(PTR) \ |
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(VARATT_IS_EXTERNAL(PTR) && VARTAG_EXTERNAL(PTR) == VARTAG_ONDISK) |
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#define VARATT_IS_EXTERNAL_INDIRECT(PTR) \ |
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(VARATT_IS_EXTERNAL(PTR) && VARTAG_EXTERNAL(PTR) == VARTAG_INDIRECT) |
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#define VARATT_IS_EXTERNAL_EXPANDED_RO(PTR) \ |
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(VARATT_IS_EXTERNAL(PTR) && VARTAG_EXTERNAL(PTR) == VARTAG_EXPANDED_RO) |
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#define VARATT_IS_EXTERNAL_EXPANDED_RW(PTR) \ |
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(VARATT_IS_EXTERNAL(PTR) && VARTAG_EXTERNAL(PTR) == VARTAG_EXPANDED_RW) |
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#define VARATT_IS_EXTERNAL_EXPANDED(PTR) \ |
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(VARATT_IS_EXTERNAL(PTR) && VARTAG_IS_EXPANDED(VARTAG_EXTERNAL(PTR))) |
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#define VARATT_IS_EXTERNAL_NON_EXPANDED(PTR) \ |
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(VARATT_IS_EXTERNAL(PTR) && !VARTAG_IS_EXPANDED(VARTAG_EXTERNAL(PTR))) |
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#define VARATT_IS_SHORT(PTR) VARATT_IS_1B(PTR) |
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#define VARATT_IS_EXTENDED(PTR) (!VARATT_IS_4B_U(PTR)) |
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#define SET_VARSIZE(PTR, len) SET_VARSIZE_4B(PTR, len) |
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#define SET_VARSIZE_SHORT(PTR, len) SET_VARSIZE_1B(PTR, len) |
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#define SET_VARSIZE_COMPRESSED(PTR, len) SET_VARSIZE_4B_C(PTR, len) |
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#define SET_VARTAG_EXTERNAL(PTR, tag) SET_VARTAG_1B_E(PTR, tag) |
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#define VARSIZE_ANY(PTR) \ |
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(VARATT_IS_1B_E(PTR) ? VARSIZE_EXTERNAL(PTR) : \
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(VARATT_IS_1B(PTR) ? VARSIZE_1B(PTR) : \
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VARSIZE_4B(PTR))) |
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/* Size of a varlena data, excluding header */ |
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#define VARSIZE_ANY_EXHDR(PTR) \ |
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(VARATT_IS_1B_E(PTR) ? VARSIZE_EXTERNAL(PTR)-VARHDRSZ_EXTERNAL : \
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(VARATT_IS_1B(PTR) ? VARSIZE_1B(PTR)-VARHDRSZ_SHORT : \
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VARSIZE_4B(PTR)-VARHDRSZ)) |
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/* caution: this will not work on an external or compressed-in-line Datum */ |
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/* caution: this will return a possibly unaligned pointer */ |
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#define VARDATA_ANY(PTR) \ |
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(VARATT_IS_1B(PTR) ? VARDATA_1B(PTR) : VARDATA_4B(PTR)) |
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/* Decompressed size and compression method of a compressed-in-line Datum */ |
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#define VARDATA_COMPRESSED_GET_EXTSIZE(PTR) \ |
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(((varattrib_4b *) (PTR))->va_compressed.va_tcinfo & VARLENA_EXTSIZE_MASK) |
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#define VARDATA_COMPRESSED_GET_COMPRESS_METHOD(PTR) \ |
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(((varattrib_4b *) (PTR))->va_compressed.va_tcinfo >> VARLENA_EXTSIZE_BITS) |
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/* Same for external Datums; but note argument is a struct varatt_external */ |
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#define VARATT_EXTERNAL_GET_EXTSIZE(toast_pointer) \ |
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((toast_pointer).va_extinfo & VARLENA_EXTSIZE_MASK) |
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#define VARATT_EXTERNAL_GET_COMPRESS_METHOD(toast_pointer) \ |
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((toast_pointer).va_extinfo >> VARLENA_EXTSIZE_BITS) |
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#define VARATT_EXTERNAL_SET_SIZE_AND_COMPRESS_METHOD(toast_pointer, len, cm) \ |
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do { \
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Assert((cm) == TOAST_PGLZ_COMPRESSION_ID || \
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(cm) == TOAST_LZ4_COMPRESSION_ID); \
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((toast_pointer).va_extinfo = \
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(len) | ((uint32) (cm) << VARLENA_EXTSIZE_BITS)); \
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} while (0) |
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/*
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* Testing whether an externally-stored value is compressed now requires |
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* comparing size stored in va_extinfo (the actual length of the external data) |
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* to rawsize (the original uncompressed datum's size). The latter includes |
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* VARHDRSZ overhead, the former doesn't. We never use compression unless it |
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* actually saves space, so we expect either equality or less-than. |
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*/ |
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#define VARATT_EXTERNAL_IS_COMPRESSED(toast_pointer) \ |
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(VARATT_EXTERNAL_GET_EXTSIZE(toast_pointer) < \
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(toast_pointer).va_rawsize - VARHDRSZ) |
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#endif |
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Reference in new issue