diff options
Diffstat (limited to 'src/backend/utils/adt/varlena.c')
| -rw-r--r-- | src/backend/utils/adt/varlena.c | 54 |
1 files changed, 54 insertions, 0 deletions
diff --git a/src/backend/utils/adt/varlena.c b/src/backend/utils/adt/varlena.c index 479ed9ae54c..0bc345aa4d3 100644 --- a/src/backend/utils/adt/varlena.c +++ b/src/backend/utils/adt/varlena.c @@ -18,6 +18,7 @@ #include <limits.h> #include "access/detoast.h" +#include "access/toast_compression.h" #include "catalog/pg_collation.h" #include "catalog/pg_type.h" #include "common/hashfn.h" @@ -5300,6 +5301,59 @@ pg_column_size(PG_FUNCTION_ARGS) } /* + * Return the compression method stored in the compressed attribute. Return + * NULL for non varlena type or uncompressed data. + */ +Datum +pg_column_compression(PG_FUNCTION_ARGS) +{ + int typlen; + char *result; + ToastCompressionId cmid; + + /* On first call, get the input type's typlen, and save at *fn_extra */ + if (fcinfo->flinfo->fn_extra == NULL) + { + /* Lookup the datatype of the supplied argument */ + Oid argtypeid = get_fn_expr_argtype(fcinfo->flinfo, 0); + + typlen = get_typlen(argtypeid); + if (typlen == 0) /* should not happen */ + elog(ERROR, "cache lookup failed for type %u", argtypeid); + + fcinfo->flinfo->fn_extra = MemoryContextAlloc(fcinfo->flinfo->fn_mcxt, + sizeof(int)); + *((int *) fcinfo->flinfo->fn_extra) = typlen; + } + else + typlen = *((int *) fcinfo->flinfo->fn_extra); + + if (typlen != -1) + PG_RETURN_NULL(); + + /* get the compression method id stored in the compressed varlena */ + cmid = toast_get_compression_id((struct varlena *) + DatumGetPointer(PG_GETARG_DATUM(0))); + if (cmid == TOAST_INVALID_COMPRESSION_ID) + PG_RETURN_NULL(); + + /* convert compression method id to compression method name */ + switch (cmid) + { + case TOAST_PGLZ_COMPRESSION_ID: + result = "pglz"; + break; + case TOAST_LZ4_COMPRESSION_ID: + result = "lz4"; + break; + default: + elog(ERROR, "invalid compression method id %d", cmid); + } + + PG_RETURN_TEXT_P(cstring_to_text(result)); +} + +/* * string_agg - Concatenates values and returns string. * * Syntax: string_agg(value text, delimiter text) RETURNS text |