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15 | 15 |
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16 | 16 | #include "postgres.h"
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17 | 17 |
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| 18 | +#include "pageinspect.h" |
| 19 | + |
18 | 20 | #include "access/htup_details.h"
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19 | 21 | #include "catalog/catalog.h"
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20 | 22 | #include "catalog/namespace.h"
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@@ -158,6 +160,42 @@ get_raw_page_internal(text *relname, ForkNumber forknum, BlockNumber blkno)
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158 | 160 | return raw_page;
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159 | 161 | }
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160 | 162 |
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| 163 | + |
| 164 | +/* |
| 165 | + * get_page_from_raw |
| 166 | + * |
| 167 | + * Get a palloc'd, maxalign'ed page image from the result of get_raw_page() |
| 168 | + * |
| 169 | + * On machines with MAXALIGN = 8, the payload of a bytea is not maxaligned, |
| 170 | + * since it will start 4 bytes into a palloc'd value. On alignment-picky |
| 171 | + * machines, this will cause failures in accesses to 8-byte-wide values |
| 172 | + * within the page. We don't need to worry if accessing only 4-byte or |
| 173 | + * smaller fields, but when examining a struct that contains 8-byte fields, |
| 174 | + * use this function for safety. |
| 175 | + */ |
| 176 | +Page |
| 177 | +get_page_from_raw(bytea *raw_page) |
| 178 | +{ |
| 179 | + Page page; |
| 180 | + int raw_page_size; |
| 181 | + |
| 182 | + raw_page_size = VARSIZE(raw_page) - VARHDRSZ; |
| 183 | + |
| 184 | + if (raw_page_size != BLCKSZ) |
| 185 | + ereport(ERROR, |
| 186 | + (errcode(ERRCODE_INVALID_PARAMETER_VALUE), |
| 187 | + errmsg("invalid page size"), |
| 188 | + errdetail("Expected %d bytes, got %d.", |
| 189 | + BLCKSZ, raw_page_size))); |
| 190 | + |
| 191 | + page = palloc(raw_page_size); |
| 192 | + |
| 193 | + memcpy(page, VARDATA(raw_page), raw_page_size); |
| 194 | + |
| 195 | + return page; |
| 196 | +} |
| 197 | + |
| 198 | + |
161 | 199 | /*
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162 | 200 | * page_header
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163 | 201 | *
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