pgsql: Fix interaction of TOAST compression with expression indexes.

Fix interaction of TOAST compression with expression indexes.

Before, trying to compress a value for insertion into an expression
index would crash.

Dilip Kumar, with some editing by me. Report by Jaime Casanova.

Discussion: http://postgr.es/m/CAJKUy5gcs0zGOp6JXU2mMVdthYhuQpFk=S3V8DOKT=LZC1L36Q@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/5db1fd7823a1a12e2bdad98abc8e102fd71ffbda

Modified Files
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src/backend/access/brin/brin_tuple.c        |  8 +++++---
src/backend/access/common/indextuple.c      | 15 +++++++++++++--
src/backend/catalog/index.c                 | 10 ++++++++++
src/test/regress/expected/compression.out   |  6 ++++++
src/test/regress/expected/compression_1.out | 13 +++++++++++++
src/test/regress/sql/compression.sql        |  7 +++++++
6 files changed, 54 insertions(+), 5 deletions(-)